Advanced Strength and Conditioning Becoming an effective strength and conditioning practitioner requires the development of a professional skills set and a thorough understanding of the scientific basis of best practice. Aimed at advanced students and novice-toexpert practitioners, in this book the authors explore the latest scientific evidence and apply it to exercise selection and programming choices across the full range of areas in strength and conditioning, from strength and power, speed and agility, to aerobic conditioning. Since the first edition of this text was written extensive research has expanded the supporting evidence base that provides the theoretical foundation for each chapter. In addition, some areas that were previously under-researched have now been expanded and some key concepts have been further challenged. Each chapter is written by experts with experience in a wide variety of sports, including both applied and research experience, ensuring this concise but sophisticated textbook is the perfect bridge from introductory study to effective professional practice. While advanced concepts are explored within the book, the coach must not forget that consistency in the application of the basic principles of strength and conditioning is the foundation of athletic development. Advanced Strength and Conditioning: An Evidence-based Approach is a valuable resource for all advanced students and practitioners of strength and conditioning and fitness training. Anthony N. Turner is Associate Professor in Strength and Conditioning and the Director of Programmes for postgraduate studies in sport at the London Sport Institute, Middlesex University. Anthony is a consultant to numerous sports teams as well as the British Military. Anthony is Associate Editor for the Strength and Conditioning Journal, has published over 100 peer-reviewed journal articles and numerous book chapters, and has edited two textbooks. Paul Comfort is Reader in Strength and Conditioning at the University of Salford (UK), where he leads the master’s degree in Strength and Conditioning. He is Adjunct Professor at Edith Cowan University (Australia) and an honorary research fellow at Leeds Beckett University (UK). He regularly consults with numerous professional rugby and soccer teams and is a founder member and accredited member of the United Kingdom Strength and Conditioning Association (UKSCA). Paul is an editorial board member for the European Journal of Sport Science and Sports Biomechanics, Associate Editor for the Strength and Conditioning Journal, Senior Associate Editor of the Journal of Strength and Conditioning Research, and has edited three textbooks. “Advanced Strength and Conditioning: An Evidence-based Approach is a fantastic core text which students in particular should read. It covers all the key areas relating to developing your athlete, programming and monitoring your athletes and of course, coaching your athlete, which provides a great blend of theory and practice with a fantastic author line-up adding to the credibility of this book. ”Chris Bishop, Programme Leader: MSc in Strength and Conditioning, Middlesex University, UK Advanced Strength and Conditioning An Evidence-based Approach Second Edition Edited by Anthony N. Turner and Paul Comfort Cover image credit: vm / Getty Images Second edition published 2022 by Routledge 605 Third Avenue, New York, NY 10158 and by Routledge 2 Park Square, Milton Park, Abingdon, Oxon, OX14 4RN Routledge is an imprint of the Taylor & Francis Group, an informa business © 2022 Taylor & Francis The right of Anthony N. Turner and Paul Comfort to be identified as the authors of the editorial material, and of the authors for their individual chapters, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. First edition published by Routledge 2017 Library of Congress Cataloging-in-Publication Data Names: Turner, Anthony (Anthony N.), editor. | Comfort, Paul, editor. Title: Advanced strength and conditioning : an evidence-based approach / edited by Anthony Turner and Paul Comfort. Description: Second edition. | New York, N.Y. : Routledge, 2022. | Includes bibliographical references and index. Identifiers: LCCN 2021045906 (print) | LCCN 2021045907 (ebook) | ISBN 9780367491369 (hardback) | ISBN 9780367491352 (paperback) | ISBN 9781003044734 (ebook) Subjects: LCSH: Physical education and training. | Muscle strength. | Physical fitness–Physiological aspects. Classification: LCC GV711.5 .A37 2022 (print) | LCC GV711.5 (ebook) | DDC 613.7/13–dc23 LC record available at https://lccn.loc.gov/2021045906 LC ebook record available at https://lccn.loc.gov/2021045907 ISBN: 978-0-367-49136-9 (hbk) ISBN: 978-0-367-49135-2 (pbk) ISBN: 978-1-003-04473-4 (ebk) DOI: 10.4324/9781003044734 Typeset in Baskerville by Newgen Publishing UK Access the Support Material: www.routledge.com/9780367491352 Contents List of figures List of tables List of contributors Introduction 1 Strength and conditioning: coach or scientist? PERRY STEWART, PAUL COMFORT AND ANTHONY N. TURNER PART I Developing your athlete 2 Developing muscular strength and power TIMOTHY J. SUCHOMEL AND PAUL COMFORT 3 Stretch-shortening cycle and muscle–tendon stiffness JOHN J. MCMAHON 4 Understanding and developing aerobic fitness RICHARD C. BLAGROVE 5 Repeat sprint ability: physiological basis and implications for training ANTHONY N. TURNER AND DAVID BISHOP 6 Concurrent training RODRIGO ASPE, RICHARD CLARKE, GARETH HARRIS AND JONATHAN HUGHES PART II Programming and monitoring for your athlete 7 Periodisation SHYAM CHAVDA, ANTHONY N. TURNER AND PAUL COMFORT 8 Strategies to enhance athlete recovery VINCENT KELLY, PATRICK HOLMBERG AND DAVID JENKINS 9 Priming match-day performance: strategies for team sports players MARK RUSSELL, NATALIE BROWN, SAMUEL P. HILLS AND LIAM P. KILDUFF 10 Fitness testing and data analysis JOHN J. MCMAHON, PAUL COMFORT AND ANTHONY N. TURNER 11 Analysis and presentation of fitness test results JOHN J. MCMAHON, ANTHONY N. TURNER AND PAUL COMFORT 12 Eccentric training: scientific background and practical applications MELLISSA HARDEN, PAUL COMFORT AND G. GREGORY HAFF 13 Cluster sets: scientific background and practical applications G. GREGORY HAFF AND MELLISSA HARDEN PART III Coaching your athlete 14 Movement screening: a systematic approach to assessing movement quality LOUIS HOWE AND CHRIS BISHOP 15 Technical demands of strength training TIMOTHY J. SUCHOMEL AND PAUL COMFORT 16 Weightlifting for sports performance TIMOTHY J. SUCHOMEL AND PAUL COMFORT 17 Plyometric training CHRISTOPHER J. SOLE, CHRISTOPHER R. BELLON AND GEORGE K. BECKHAM 18 Training for change of direction and agility THOMAS DOS’SANTOS AND PAUL JONES 19 Speed and acceleration training PEDRO JIMÉNEZ-REYES AND JEAN-BENOÎT MORIN 20 Applied coaching science NICK WINKELMAN 21 Developing as a coach: leadership, culture, and purpose BRIAN GEARITY AND CHRISTOPH SZEDLAK Index Figures 1.1 2.1 2.2 2.3 2.4 2.5 2.6 2.7 3.1 3.2 3.3 3.4 Integration of coaching and applied science principles. S&C, strength and conditioning; TL, training load Comparison of countermovement jump kinetic and temporal variables between stronger and weaker athletes. RFD, rate of force development Medial gastrocnemius (MG) fascicle length (dashed line) and MG pennation angle (θ), as measured between the superficial (A) and deep (B) MG aponeuroses Four sarcomeres in parallel Four sarcomeres in series Example emphasis change during a periodised training programme (phase potentiation). 1RM, one repetition maximum Back squat exercise using variable resistance with chains Bench press exercise using variable resistance with elastic bands An example of an object that obeys Hooke’s law and the equation to calculate stiffness (k), where ∆F = change in force and ∆x = change in length An example of the torsional spring model and how it corresponds to the human body An example of the joint moment–joint angular displacement relationship during loaded flexion and extension An example of how joint touchdown angles influence leg and joint stiffness values 3.5 An example of the spring–mass model and how it corresponds to the human body 3.6 A schematic illustrating how the legs change from being more compliant (opposite of stiff) to more stiff for a range of stretchshortening cycle tasks. DJ, drop jump 4.1 Relationship between intensity and oxygen uptake response during an incremental test 4.2 Maximal oxygen uptake values for male and female elite endurance athletes, elite athletes from selected intermittent sports, and healthy individuals (20–40 years old) from the population (50th-percentile values from several studies shown; Kaminsky, Arena, and Myers, 2016) Factors that influence an athlete’s exercise economy with examples Physiological profile and training zones for an elite male endurance runner Oxygen uptake kinetics during moderate- (dotted line), heavy(dashed line), and severe-intensity (hatched-line) exercise Training strategies and recommended exercise prescription to develop aerobic fitness components for various categories of sports. %HRmax, percentage of maximum heart rate; V̇O2max, maximal oxygen uptake Endurance training intensity distribution for three common approaches adopted by endurance sport athletes How modes of training differ between moderate-intensity continuous training (MICT), high-intensity interval training (HIIT) and sprint interval training (SIT). HR max, maximum heart rate; V̇O2max, maximal oxygen uptake Putative adaptive pathways in response to the concurrent programming of endurance and resistance exercises in a training program 4.3 4.4 4.5 4.6 4.7 5.1 6.1 6.2 The recommended decision-making process during periods of concurrent training. SIT, sprint interval training 7.1 (a) Distribution of training load; (b) distribution of training modes in Olympic fencers Relationship between volume, intensity and training specificity over the three main phases of training. GPT, general physical training; SSPT, sport-specific physical training; Comp, competition Basic components of a periodised plan. GPT, general physical training; SSPT, sport-specific physical training 7.2 7.3 7.4 Soon ripe, soon rotten. Training intensity is inversely correlated with: (1) the time a performance peak can be maintained; (2) the height of that performance peak; and (3) the rate of detraining 7.5 7.6 The 3:1 loading paradigm, illustrating the increase and then dissipation of excessive fatigue The general adaptation syndrome (GAS) model 7.7 7.8 The stimulus–fatigue–recovery–adaptation (SFRA) concept. The fitness–fatigue paradigm 7.9 Athlete preparedness based on the specific form of fatigue 7.10 The principle of diminishing returns 7.11 Basic model of periodisation entailing little variation and relatively flat workloads 7.12 The traditional, undulating approach to the design of periodised training, which is attributed to the work of Matveyev (1977). Note the 3:1 loading method within each mesocycle 7.13 The conjugate sequence system pioneered by Yuri Verkhoshansky (1986) 7.14 Schematic representation of the three principal tapering strategies 7.15 Schematic representation of the two-phase taper 8.1 Flow chart detailing factors to consider when determining the implementation of recovery methods 9.1 10.1 11.1 11.2 11.3 11.4 11.5 12.1 Model of implementing the performance-enhancing strategies Example of correctly identifying the unweighting, braking and propulsive phases of a countermovement jump force–time curve (solid grey line) by overlaying the velocity–time curve (dotted black line). The dotted grey line represents zero centre of mass velocity A typical normal data distribution curve with z-scores and the corresponding percentage of data that they comprise A typical normal data distribution curve with z-scores, corresponding standard ten (STEN), t-score and percentile values and integrated traffic-light system example Example results of a pre-season fitness-testing battery conducted within rugby league and presented as a radar chart using a standardised t-score scale and integrated traffic-light system Example results from force platform assessments that were conducted as part of a pre-season fitness-testing battery within rugby league presented as a radar chart using a standardised t-score scale and an integrated traffic-light system Example results from a countermovement jump assessment that was conducted using a force platform as part of a pre-season fitnesstesting battery within rugby league presented as a radar chart using a standardised t-score scale and an integrated traffic-light system Schematic diagram illustrating an approach to tempo training 12.2 Schematic diagram illustrating augmented eccentric training using weight releasers, with a total of 80% 1RM as an example 12.3 Schematic diagram illustrating augmented eccentric training during back squats using weight releasers, with a total of 80% 1RM as an example Schematic diagram illustrating accentuated eccentric training using weight releasers 12.4 12.5 Schematic diagram illustrating accentuated eccentric training using weight releasers 12.6 Schematic diagram illustrating accentuated eccentric training using weight releasers 12.7 Schematic diagram illustrating accentuated eccentric training using weight releasers 13.1 Example set structures used in resistance training 13.2 13.3 Example undulating, wave, ascending, and descending cluster sets Example cluster set repetition modifications 13.4 Suggested exercise alignments for cluster sets 13.5 Suggested training target / goal set type alignments 13.6 13.7 Cluster sets: set and repetition examples Inter-repetition and intra-set rest interval alignments with training phase 13.8 13.9 Partner cluster sets Set alignments with phases of a periodised training plan 14.1 Model to establish the cause(s) of movement fault(s) 15.1 Ground reaction forces (orange arrow) and local coordinate frames (blue arrows) during a sprint acceleration 15.2 Scenario requiring weightlifting alternatives for the snatch: (a) range of motion must be reduced and the bar raised for the start of the lift; (b) if planning to use a catching variation in subsequent phases a catching variation at 80–95% 1RM may be advantageous to reinforce technique; (c) if the athlete cannot catch (e.g. due to injury or limited range of motion) and/or higher loads (≥100% 1RM power snatch) are desired pulling derivatives may be advantageous Scenario requiring weightlifting alternatives for the hang power clean 15.3 16.1 Hook grip – (a) thumb wraps under the bar with (b) the fingers wrapped around the thumb and bar 16.2 16.3 Clean (top) and snatch (bottom) grip spacing Starting position for (left) the snatch and (right) clean 16.4 The end of the first pull for (left) the snatch and (right) clean 16.5 Mid-thigh position side view for (left) the snatch and (right) clean 16.6 16.7 Second pull of (left) the snatch and (right) clean Catch position of the snatch (left) and clean (right) 16.8 Power snatch (left) and power clean (right) catch positions 16.9 Recovery position for the snatch (left) and clean (right) 16.10 Starting position for a jerk variation 16.11 Completion of the dip phase of the jerk 16.12 The drive phase of the jerk 16.13 Split jerk receiving position 16.14 Power jerk receiving position 16.15 Jerk recovery 16.16 Force–velocity curve for weightlifting exercises. 1RM, one repetition maximum; HPC, hang power clean; PC, power clean 16.17 Sequenced progressions of speed and strength-power development with the weightlifting derivatives that may be used within each phase. CM, countermovement 17.1 17.2 17.3 18.1 18.2 (a) Mechanical and (b) neurophysiological models of stretchshortening cycle potentiation. SEC, series elastic component; CC, contractile component; PEC, parallel elastic component; MS, muscle spindles; EF, extrafusal fibers The force–time histories of two 40-centimeter drop jumps performed by the same athlete within the same training session: the athlete was instructed to perform a compliant or “soft” landing (dashed line) or a stiff “spring-like” landing (solid line) Plyometric tier progression with example exercises. CMJ, countermovement jump; COD, change of direction Model summarizing factors that underpin successful agility performance Braking strategy and technique requirements for different directional changes. FFC, final-foot contact; PFC, penultimate-foot contact; XOC, crossover cut 18.3 Summary of the biomechanical differences between side-step, crossover, and split-step cutting techniques. Side-step manoeuvres present higher knee joint loads and thus, potential knee injury risk, but can be performed from a faster approach compared to a split step and are effective for sharp directional changes. Crossover cuts are ideal when velocity maintenance is required to shallow cutting angles. Split-steps are ideal to avoid opponents and can achieve sharp directional changes, but from relatively slow approaches. GCT, ground contact time; VM, vastus medius; GM, gluteus medius; XOC, crossover cut 18.4 Change of direction (COD) underpinned by the interaction between velocity, deceleration, mechanics, and physical capacity. PFC, penultimate-foot contact 18.5 Summary of biomechanical factors associated with peak knee abduction moments based on literature. GRF, ground reaction force 18.6 Side-step cutting model to mediate the performance–injury conflict. PFC, penultimate-foot contact Important physical preparation considerations for change-of-direction (COD) actions: developing physical capacity for load tolerance 18.7 18.8 Mixed multicomponent programmes for change-of-direction (COD) speed and agility development. SSGs, small-sided games 18.9 Change-of-direction (COD) speed and agility development framework. XOC, crossover cut The resultant or “total” ground reaction force (FTot) during sprinting support phase can be split and illustrated as the vectorial sum of antero-posterior horizontal (FH) and vertical (VH) components. FV, force–velocity; RF, ratio of forces 19.1 19.2 Ratio of forces (RF) and decrease in the ratio of forces (DRF). In this typical example (sprinter performing a maximal acceleration over 60 m from the starting blocks) ground reaction force was assessed at each step on a force plate instrumented track (Morin et al., 2019). The DRF is −7.42%, which means that the athlete’s mechanical effectiveness (RF) decreases on average by 7.42% for each meter per second of speed increase. The dashed black and grey lines illustrate a more and less efficient athlete, with similar first-step RF. Range of DRF values reported is ~−5 to −14%, from elite sprinters to nonspecialists 19.3 Force–velocity–power profile of Usain Bolt’s world record. The input data used are the athlete’s body mass and running speed–time data 20.1 Newell (1986) Interacting Constraints Model Tables 1.1 2.1 2.2 2.3 3.1 5.1 5.2 5.3 5.4 6.1 6.2 6.3 7.1 The definition of scientific disciplines in relation to potential strength and conditioning (S&C) coach roles Muscle architectural adaptations in response to different training stimuli Neurological adaptations in response to different training stimuli Relative power outputs for male athletes during various exercises Summary of studies that have determined the effects of training interventions on global lower-limb stiffness measures Comparison of SIT vs HIIT vs. MICT protocols on peripheral muscle adaptations and central adaptations Effective training systems to enhance aerobic fitness (Helgerud, Hoydal, Wang, Karlsen, Berg, & Bjerkaas, 2007): * significantly (p < 0.001) different from pre- to post-training Interval distances for high-intensity interval training using maximal aerobic speed (MAS), and calculated using a 1.5-mile run time of 10 min (Baker, 2011) High-intensity interval training (HIIT) based on each energy system Typical training week Programming for concurrent training over an 8-week block Mean (±SD) values for performance measures conducted in elite women’s rugby players pre- and post-8 weeks of concurrent training interventions The main phases and sub-phases of periodisation 7.2 Exercise deletion and representation 7.3 Example sessions used as part of a basic periodised model 7.4 Two example strength sessions and two example power sessions, which can be implemented as part of an intermediate periodised programme A practical example for applying and adapting the conjugate system 7.5 7.6 7.7 7.8 8.1 8.2 8.3 8.4 11.1 11.2 11.3 12.1 12.2 12.3 Example microcycle completed as part of a non-traditional periodisation strategy Summary of performance gains following a taper Effect of training variables on the effect size of taper-induced performance adaptations Practical recommendations for recovery strategies Example of a 12-week periodized training plan for college soccer and recommendations for use of water immersion therapy Example of an in-season week for American football and recommendations for use of water immersion therapy Practical recommendations to improve sleep Example performance test results, corresponding z-scores and total score of athleticism Corresponding percentile, standard ten (STEN) and t-score values for a given z-score Example performance test results and corresponding individual and average percentiles Four eccentric training modalities and specificities underpinning each modality Summary of the physiological responses to eccentric training regimes and the role of these responses in developing muscle hypertrophy, strength, and power output Examples of different isoweight eccentric training methods and application examples for different-level athletes 13.1 13.2 Traditional training emphasis alignments with repetition ranges Example training session employing cluster sets 13.3 14.1 Example loading patterns for cluster sets Example movement screens, including standardisation procedures 14.2 Performance criteria for each example screen, including a brief underpinning rationale Key considerations to improve reliability when screening movement quality 14.3 14.4 Example task manipulations for an overhead squat screen that can be applied at stage 3 of the investigation process 14.5 14.6 Isolated assessments for mobility testing Movement screen findings and associated investigatory process for an international distance runner 15.1 15.2 15.3 Potential training effects of partial and deep squat variations Rest interval length to achieve specific training goals Cluster set rest interval length to achieve specific training goals 17.1 17.2 Plyometric focus within a periodized annual training plan Plyometric tiers 17.3 17.4 Athlete A Athlete B 18.1 A technical framework for a side-step cutting manoeuvre from a running approach A technical framework for a 180° pivot from a running approach 18.2 18.3 18.4 18.5 Summary of important physical qualities for successful change-ofdirection performance Side-step cutting technique checklist Example multi-component training programme to reduce change-ofdirection (COD) biomechanical characteristics associated with increased anterior cruciate ligament (ACL) injury risk 19.1 21.1 Sprint running phase mechanics, corresponding key muscle actions and suggestions for training. These are indicative points (not exhaustive rules) based on published research evidence Summary of coaching philosophies and applied suggestions to promote servant (SL) and transformational leadership (TL) behaviours in strength and conditioning coaching Contributors Rodrigo Aspe is Lecturer in Applied Sport and Exercise Science at Robert Gordon University. He previously held academic posts at Abertay University, University of Gloucestershire, and Hartpury University. He obtained an MSc in Strength and Conditioning at the University of Edinburgh and is an accredited strength and conditioning coach with the United Kingdom Strength and Conditioning Association (UKSCA). In addition to his academic career, Rodrigo continues to work as an applied coach with Aberdeen Grammar Rugby in the Scottish Premiership. He previously held positions with Scottish Hockey and the Talented Athlete Scholarship Scheme (TASS). George K. Beckham is Assistant Professor at California State University, Monterey Bay. He holds a PhD in Sports Physiology and Performance from East Tennessee State University. Christopher R. Bellon is Assistant Professor in the Department of Health and Human Performance at The Citadel, Military College of South Carolina. He earned his doctoral degree in Sport Physiology and Performance at East Tennessee State University. He is also a certified strength and conditioning specialist with the National Strength and Conditioning Association (NSCA). Chris Bishop is Senior Lecturer in Strength and Conditioning at the London Sport Institute, Middlesex University, where he is also the Programme Leader for the MSc Strength and Conditioning degree. Chris has been accredited with the UKSCA since 2011 and served on the Board of Directors for the association from 2017 to 2021, with the last three years as Chair of the Board. Chris has published extensively, with over 140 peer-reviewed journal articles and three book chapters to date; his main areas of research are focused on inter-limb asymmetry and athlete profiling through fitness testing and movement screening. David Bishop has more than 20 years of experience as both a researcher and an applied sport scientist working with elite athletes. He was the inaugural research leader at the Institute of Health and Sport (iHeS), Victoria University, Australia, and also leads the skeletal muscle and training research group. His team is interested in optimising skeletal muscle adaptation to exercise training, so as to improve health and performance. He is known for his many highly cited articles on repeated sprint ability. A more recent focus of his research group is to examine how diet, exercise, and genes interact to regulate skeletal muscle mitochondrial content and function. Professor Bishop has written more than 280 peer-reviewed articles and ten book chapters in the area of exercise and sport science. His research is currently funded by the Australian Research Council (ARC), the National Health and Medicine Research Council (NHMRC), and the Australian Defence Force. He is also the past president of Exercise and Sport Science Australia (ESSA), and Assistant Editor of Medicine and Science in Sports and Exercise (MSSE). In the three years prior to the 2000 Sydney Olympics, he worked with Australian hockey, water polo, netball, beach volleyball, and kayak teams. Professor Bishop has also gained invaluable experience consulting with professional teams such as the Fremantle Football Club. Richard C. Blagrove is Lecturer in Physiology and the Programme Leader for the MSc in Strength and Conditioning at Loughborough University. He previously worked at Birmingham City University as Senior Lecturer in Sport and Exercise Science and at St Mary’s University as Programme Director for the BSc Strength and Conditioning Science course, where he also managed the sport science support to The Royal Ballet Company in London. Richard’s research investigates the physiological factors that underpin performance in endurance running and how strength-training exercise can be used as a tool to improve the metabolic cost of exercise. He is also interested in health-related issues associated with endurance sports, particularly the consequences of low energy availability on bone health. Richard is an accredited strength and conditioning coach and previously a director of the UKSCA. He has provided strength and conditioning coaching support to numerous athletes over the last 12 years, including endurance runners who have competed in finals at the last three Olympic Games. Natalie Brown is a research assistant for the Welsh Institute of Performance Science working in collaboration with Sport Wales. Shyam Chavda is the programme lead for the MSc in Strength and Conditioning distance education at the London Sport Institute, Middlesex University. He is also the performance scientist for British Weightlifting and the head coach at Middlesex University Weightlifting Club. Richard Clarke is an accredited strength and conditioning coach with the UKSCA, having served as a director of the association. Richard has a strong history of athletic performance delivery to elite athletes working in professional football, rugby, and basketball. Richard has also had a track record of working in higher education, previously leading and teaching on degrees at undergraduate and postgraduate level at the University of Gloucestershire and Birmingham City University. Thomas Dos’Santos is Lecturer in Strength and Conditioning at Manchester Metropolitan University. He was awarded his bachelor’s degree, master’s degree, and PhD from the University of Salford. Brian T. Gearity is Director and Associate Professor of Sport Coaching and online sport graduate certificate programmes at the University of Denver. In addition to over 50 peer-reviewed publications, he coedited the book, Coach Education and Development in Sport: Instructional Strategies and co-authored Understanding Strength and Conditioning as Sport Coaching: Bridging the Biophysical, Pedagogical and Sociocultural Foundations of Practice. He is Editorin-Chief for the NSCA practitioner journal NSCA Coach, a fellow of the NSCA, and is on the editorial board for Sport Coaching Review, International Sport Coaching Journal, Qualitative Research in Sport, Exercise, and Health, and Strength & Conditioning Journal. G. Gregory Haff is Professor of Strength and Conditioning at Edith Cowan University (Perth, Western Australia) and an honorary professor at the University of Salford, UK. He is a past president of the NSCA (2015– 2018). Professor Haff was the 2021 NSCA Impact Award winner for his contributions to the strength and conditioning profession. In 2014, he was named the UKSCA Strength & Conditioning Coach of the Year – Education and Research. Additionally, Professor Haff was the 2011 NSCA’s William J. Kraemer Sport Scientist of the Year award winner. He is also a Certified Strength and Conditioning Specialist with Distinction, a Fellow of the NSCA, and an accredited member of the UKSCA. Mellissa Harden is a teaching and learning fellow at the University of Salford, UK. She completed her PhD in eccentric training at Northumbria University, funded by Great Britain Cycling, while working as a strength coach with the cyclists. Gareth Harris is Head of Athletic Performance at Bristol Bears Women’s Rugby Club. He has an extensive applied background, having worked with athletes across the performance spectrum from junior golfers to university scholars and elite international athletes. Gareth completed his education at the University of Gloucestershire, achieving an MSc in Sports Strength and Conditioning with distinction. Samuel P. Hills is Lecturer in Sports Science at Bournemouth University, having achieved his PhD from Leeds Trinity University in 2020. He has contributed to more than 20 peer-reviewed publications and presented internationally on the topic of team sports preparation. Patrick Holmberg has over 15 years of experience working as a collegiate strength and conditioning coach and athletics administrator. He holds an EdD in Higher Education Leadership. Patrick is a certified strength and conditioning specialist and registered strength and conditioning coach with distinction through the NSCA. He has worked with multiple National Collegiate Athletic Association (NCAA) team and individual national champions across a range of sports. Patrick is currently a PhD student at Queensland University of Technology. Louis Howe has been a strength and conditioning coach since 2007, having helped prepare numerous athletes for the British Athletics Championships, European Athletics Championships, Pan American Games, Commonwealth Games, and Olympic Games. Louis currently lectures at the University of Essex, having previously held positions at Edge Hill University, University of Cumbria, and St Mary’s University. Louis is an accredited strength and conditioning coach with the UKSCA, and has a PhD in investigating compensatory movement strategies derived from ankle dorsiflexion range of motion restrictions. Jonathan Hughes is Academic Course Leader for the MSc in Sports Strength and Conditioning at the University of Gloucestershire, UK. Jonathan has applied experience of delivery across both team and individual sports spanning 20 years; he is currently Head of Physical Performance for the Italian Lacrosse National team. having fulfilled a similar role for the Great Britain Women’s Ice Hockey team. Jonathan is an accredited strength and conditioning coach with the UKSCA and serves on its Research and Community Grants Panel. Jonathan has published over 35 peer-reviewed journal articles and is currently supervising six PhD students, all linked to high-performance sport research. David Jenkins is Professor of Sport and Exercise Science in the School of Health and Behavioural Sciences at The University of the Sunshine Coast. He also holds an adjunct appointment at The University of Queensland, where he worked for 30 years prior to 2020. Professor Jenkins is an exercise physiologist with an international reputation in researching physiological responses to acute and chronic high-intensity intermittent exercise. Many of his 180 peer-reviewed published papers have described the acute and chronic responses to sprint, multiple sprint, and interval exercise across different populations and groups. Pedro Jiménez-Reyes is Lecturer at the Faculty of Sport of the Catholic University of San Antonio, USA. Paul Jones is Lecturer in Sports Biomechanics & Strength and Conditioning at the University of Salford, UK. Paul earned a BSc(Hons) and MSc in Sports Science, both from Liverpool John Moores University, and a PhD in Sports Biomechanics at the University of Salford. He is a certified strength and conditioning specialist, recertified with distinction (CSCS*D) with the NSCA, an accredited sports and exercise scientist with the British Association of Sports and Exercise Sciences (BASES), and a chartered scientist (CSci) with The Science Council. Paul has over 20 years’ experience in biomechanics and strength and conditioning support to athletes and teams, working in sports such as athletics, football, and rugby, and was a former sports science support coordinator for UK disability athletics (2002–2006). Paul has authored/co-authored over 90 peer-reviewed journal articles, mainly in the areas of change-of-direction biomechanics, assessment and development of speed, change-of-direction speed, and agility and strength diagnostics. Paul has co-edited a book, Performance Assessment in Strength and Conditioning, published by Routledge, and is a member of the BASES accreditation committee. Vincent Kelly is Associate Professor of Strength and Conditioning and Sport Science at the School of Exercise and Nutrition Sciences, Queensland University of Technology. His areas of research interest include fatigue and recovery in athletes, strength and conditioning in high-performance sport, mental fatigue in sport and exercise, resistance-training priming, quantification and management of athlete training load, the neuromuscular and hormonal adaptations to exercise, and ergogenic aids and sport nutrition supplementation. He has over 20 years’ experience in elite sport, working in high-performance, sport science, and strength and conditioning roles with professional football teams, the Queensland Academy of Sport, and individual athletes. He is a member of the National Rugby League (NRL) Research Committee and a member of several committees with Exercise and Sport Science Australia. Liam P. Kilduff obtained his PhD from Glasgow University examining the effects of creatine supplementation in sport, health, and disease. He has worked for the last 18 years as Professor of Performance Science at Swansea University, where his research interests focus on elite athlete preparation strategies. He is currently Head of the Applied Sports, Technology, Exercise and Medicine Research Centre (ASTEM) and chairs both the Research Steering Group and Strategic Management Board of the Welsh Institute of Performance Science. He has published in excess of 180 peer-reviewed papers and has secured over £3m in research income. He sits on the editorial board of three sports science journals. John J. McMahon is Lecturer in Sports Biomechanics and Strength and Conditioning at the University of Salford. He received his PhD in sports biomechanics from the University of Salford in 2015 following his research into dynamic muscle–tendon stiffness and stretchshortening cycle function. John has been an accredited strength and conditioning coach with both the NSCA and UKSCA since 2010 and has worked as a strength and conditioning coach across several team sports. He has also co-authored 70 peer-reviewed journal articles relating to athletic performance assessment and is currently researching how to develop force plate-testing batteries across different sports to help inform athletes’ training priorities. John is also a co-editor of a book titled, Performance Assessment in Strength and Conditioning, published by Routledge. Jean-Benoît (JB) Morin is Full Professor at the University of Saint-Etienne (France), and a member of the Interuniversity Laboratory of Human Movement Biology (LIBM). He is also associate researcher with the Sports Research Institute New Zealand (SPRINZ) at Auckland University of Technology, and visiting Professor in Locomotion Biomechanics at the School of Sport, Exercise and Health Science at Loughborough University. He obtained a Track and Field Coach National Diploma in 1998 and a PhD in Human Locomotion and Performance in 2004 under the joint supervision of Professor Alain Belli (University of Saint-Etienne, France) and Professor Pietro di Prampero (University of Udine, Italy). JB’s field of research is mainly human locomotion and performance, with specific interest in running biomechanics and maximal-power movements (sprint, jumps). He has edited a textbook (Biomechanics of Training and Testing, published by Springer in 2018) and published over 150 peer-reviewed scientific papers. He is also a consultant for professional sports groups in soccer, rugby, sprint, and other power-speed sports. He practised soccer for ten years, practised and coached track and field (middle distance and 400m hurdles) for eight years, and he now enjoys trail running and triathlon. Mark Russell is Professor of Performance Nutrition and Applied Exercise Physiology at Leeds Trinity University. As a result of his research, Professor Russell has published over 90 peer-reviewed articles and book chapters, presented at international conferences, and led multiple industry-funded contract research projects from inception to completion. Professor Russell currently leads the Enhancing Human Performance research theme at Leeds Trinity University and has a special interest in team sport performance enhancement strategies. Professor Russell works with a range of professional rugby and football teams and has consulted for a number of English Premier League football clubs and national and international rugby squads. Christopher J. Sole PhD is Assistant Professor in the Department of Health and Human Performance at The Citadel, Military College of South Carolina. He earned his doctoral degree in Sport Physiology and Performance at East Tennessee State University. He is also a certified strength and conditioning specialist with the NSC. Perry Stewart is a lead academy strength and conditioning coach at Arsenal Football Club and a visiting lecturer at the London Sport Institute, Middlesex University. He is an accredited strength and conditioning coach and chartered sport scientist who has worked with athletes from a range of sports, including football, tennis, fencing, taekwondo, judo, karate, and athletics. Perry is currently studying for a PhD at Loughborough University and was the winner of the UKSCA Strength and Conditioning Coach of the Year award for Youth Sport in 2020. Timothy J. Suchomel is Associate Professor of Exercise Science and the Program Director for the Sport Physiology and Performance Coaching masters programme at Carroll University. He also serves as the Director of the Carroll University Sport Performance Institute (CUSPI) and works as a human performance coach at the university. He has published over 85 peer-reviewed journal articles on strength and power development, weightlifting movements and their derivatives, and athlete monitoring. He is a certified strength and conditioning specialist (recertified with distinction) and registered strength and conditioning coach through the NSCA. Christoph Szedlak is an academic, researcher, and the lead strength and conditioning coach at the University of Southampton. He has worked with a variety of different-level athletes, including Olympic and world champions, for over 13 years. His research focuses on examining the psychological and social aspects of coaching and their impact on the development of the athlete. With a specific emphasis on innovative qualitative methods to present and disseminate findings, his research has gained international recognition within strength and conditioning coach development and education. Nick Winkelman is Head of Athletic Performance and Science for the Irish Rugby Football Union. His primary role is to oversee the delivery and development of strength and conditioning and sports science across all national (Men and Women, XVs, and sevens) and provincial teams (Leinster, Munster, Connacht, and Ulster). Prior to working for Irish Rugby, Nick was the director of education and training systems for EXOS (formerly Athletes’ Performance), located in Phoenix, AZ. As the director of education, Nick oversaw the development and execution of all internal and external educational initiatives. As a performance coach, Nick oversaw the speed and assessment component of the EXOS National Football League (NFL) Combine Development Program, and supported many athletes across the NFL, Major League Baseball (MLB), National Basketball Association (NBA), national sport organizations, and Military. Nick completed his PhD through Rocky Mountain University of Health Professions with a dissertation focus on motor skill learning and sprinting. Nick is an internationally recognized speaker on human performance and coaching science and has multiple peer-reviewed publications and book chapters alongside his own book, The Language of Coaching: The Art & Science of Teaching Movement. Introduction DOI: 10.4324/9781003044734-1 Becoming an effective strength and conditioning practitioner requires the development of a professional skills set and a thorough understanding of the scientific basis of best practice. Aimed at advanced students and practitioners (from novice to expert), the authors explore the latest scientific evidence and apply it to exercise selection and programming choices across the full range of areas in strength and conditioning, from strength and power, speed and agility, to aerobic conditioning. With coverage of data analysis and feedback on performance assessments to key stakeholders, both vital skills for the contemporary strength and conditioning coach, this concise but sophisticated textbook is the perfect bridge from introductory study to effective professional practice. Written by experts with experience in a wide variety of sports, including both applied and research experience, the chapters are enhanced with new illustrations and address key topics such as: fitness testing data analysis and interpretation weightlifting for sports performance applied coaching science strategies for competition priming eccentric training the use of cluster sets. Advanced Strength and Conditioning: An Evidence-based Approach is a valuable resource for all advanced students and practitioners of strength and conditioning and fitness training. While advanced concepts are explored within the book, the coach must not forget that consistency in the application of the basic principles of strength and conditioning is the foundation of athletic development. Since the first edition of this text was written extensive research has expanded the supporting evidence base that provides the theoretical foundation for the majority of the chapters. In addition, some areas that were previously under-researched have now been expanded and some key concepts further challenged. Research within the area on the use of weightlifting to enhance sports performance has expanded noticeably, and as a result, some of the theoretical concepts and original figures are now out of date. Similarly, research relating to change-of-direction and agility performance has expanded substantially since the first edition of this book, with the chapter now being re-written by two new authors who are currently at the forefront of research in this area. Fitness testing and data analysis and interpretation have been divided into two chapters, to permit more detailed and focused content on this important area. Some training practices that are seen as being more advanced have received much more attention by researchers, resulting in the need for specific chapters to explore these research findings and the appropriate application: the two new chapters are ‘Eccentric training: scientific background and practical applications’ and ‘Cluster sets: scientific background and practical applications’. To complement the ‘Applied coaching science’ chapter, which has been updated, a further chapter on ‘Developing as a coach’ has also been included, exploring the art of applying the underpinning science. 1 Strength and conditioning: coach or scientist? Perry Stewart, Paul Comfort and Anthony N. Turner DOI: 10.4324/9781003044734-2 Introduction With sport playing an increasingly important role in the rapidly changing economic, political, cultural and social world, the demand for elite sports organizations to be successful and profitable is unprecedented. A result of the growing demand is a rise in the medicalization and scientization of organizations in the pursuit of a competitive advantage. Subsequently, there has been an increased presence and reliance on sophisticated sport medicine and sport science (SM&SS) staff and systems being employed. The support network for an athlete and/or team has increased exponentially and now often includes a complex team of support staff, including coaches, assistant coaches, strength and conditioning (S&C) coaches, physiotherapists, doctors, sports rehabilitators, soft-tissue therapists, psychologists, physiologists, biomechanists, nutritionists and performance analysts. Such support personnel are appointed in the majority of sports and across all sectors, including government-funded (e.g. national institutes of sport), educational establishments (e.g. schools, colleges and universities), professional sport clubs, commercial performance facilities and by individual athletes (Dawson et al., 2013). S&C coaches have become a common feature of the modern support network, especially within elite sport organizations. Fundamentally, the role of an S&C coach is to test, monitor and enhance athleticism, by typically utilizing periodized programme designs that include strength, power, speed, agility and flexibility strategies as part of a holistic model of athletic development (Ebben and Blackard, 2001; Ebben et al., 2004; Simenz et al., 2005). However, in reality, the specification of each S&C job role will likely depend on a number of factors, including specific context (e.g. competition level, age of athlete), the organizational structure (e.g. centralized vs. decentralized, hierarchical structure), the financial resources of the organization (e.g. S&C roles may be merged with other roles to save money) and the organization’s vision, objectives and training philosophy. It is also likely that boundaries become blurred as S&C coaches engage in activities unrelated to their specific discipline, for example, helping with logistics and operations. Despite some inconsistencies existing in role specification, one central requirement for most S&C coaches is the need to integrate and interact with multiple stakeholders such as athletes, coaches, support staff and management. It is evident that although S&C is a discipline grounded in the physical preparation of athletes, the role of the S&C coach is multifaceted with responsibilities extending far beyond that of designing and implementing training programmes. It is valuable for all current and aspiring S&C coaches to appreciate the breadth and depth of knowledge and skills that are typically required to effectively work in, and excel in, the discipline of S&C. Arguably the role now is very different to the one carried out as little as 10 years ago, and we must appreciate its evolution towards a practitioner who is just as much a scientist as a coach. Therefore, the aim of this introductory chapter is to review the attributes required to be an effective S&C practitioner within today’s industry. It is the intention that this will in turn set the context and significance of each chapter that follows, where all these components are discussed in far greater detail. The coach It is prudent to start this chapter by addressing the foundation of the role, the (S&C) coach. The role of any coach is simply to improve athletes’ physical, mental and emotional performance, in preparation for sporting competition (Dorgo, 2009). Previous conceptual models of coaching have emerged from different theoretical perspectives, including leadership, expertise, coach–athlete relationships, motivation and education, highlighting the complexity of a coach’s role – all of which are important. Cote and Gilbert (2009) define coaching effectiveness as: The consistent application of integrated professional, interpersonal and intrapersonal knowledge to improve athletes’ competence, confidence, connection, and character in specific coaching contexts. This definition can be better understood when the three components of this model (knowledge, outcomes and contexts) are considered in more detail. The coach’s skills, attitudes and behaviours – collectively referred to as ‘knowledge’ – are separated into three interrelated categories. 1. Professional knowledge. Expert knowledge of subject-specific matter. For example, an S&C coach is likely to have knowledge of competition demands, applied physiology and biomechanics, principles of planning and periodizing, dynamic correspondence and testing/monitoring. 2. Interpersonal knowledge. To be successful, coaches have to successfully interact with their athletes and head and assistant coaches, as well as other key stakeholders. This refers to the soft skills (sometimes referred to as emotional intelligence) required to identify, use, understand and manage interactions. 3. Intrapersonal knowledge. Described as self-awareness and introspection, this is the ability of a coach to critically reflect. Gilbert and Trudel’s (2001) research examined good coaches and how they translate experience into knowledge and skills through reflection. In summary, for an S&C coach to maximize athletes’ outcomes they must possess comprehensive professional knowledge and effective interpersonal skills and also practise continuous introspection, review and revision of their practice (Cote and Gilbert, 2009). Despite S&C coaches focusing most of their attention, time and energy towards developing professional knowledge, it is the aggregate of professional knowledge, the ability to connect with others (interpersonal skills) and the willingness to engage in continued learning and self-reflection (intrapersonal skills) that will determine how effective and successful an S&C coach will be. Previous research has reported that stressful and dysfunctional relationships between technical coaches and sport science personnel exist (Soanes and Williams, 2019), and that technical coaches’ perceptions of the relevance, applicability and language associated with sport science teams vary (Martindale and Nash, 2013). Martindale and Nash (2013) highlight the need to practically apply professional knowledge, build effective working relationships, efficiently disseminate information and apply user-friendly language. The second component of effective coaching focuses on ‘athlete outcomes’, which typically relate to performance improvements (successful performances and player development) and positive psychological responses (high level of self-esteem, intrinsic motivation, enjoyment and satisfaction). Cote and Gilbert (2009) identified four athlete outcomes, namely: competence, confidence, connection and character/caring. It is believed that the coach responsible for designing appropriate training conditions can enhance all of these. These are explained in relation to the S&C industry below. Competence. Optimizing an athlete’s physical performance in relation to their sport. Confidence. Improved sense of overall positive self-worth. A coach and athlete should agree achievable objectives and the coach should design programmes that balance challenge and success. Connection. Facilitating positive social relationships inside and outside sport. A coach can encourage communication between athlete and staff, parents and non-sporting peers. Character. Encouraging moral attributes such as respect, integrity, empathy and responsibility. Encourage athletes to take responsibility for their own environment, personal standards and development. The third and final component of effective coaching is ‘coaching contexts’, which refers to the unique settings in which coaches work. Cote and Gilbert (2009) describe coaching effectiveness and expertise as context-specific, identifying three classifications: (1) recreational; (2) developmental; and (3) elite sport. Further to this, the following situational factors should be considered: (1) context (individual athlete or team sport, male or female, senior or youth populations); (2) employment type (full- or part-time); (3) the role (senior position or intern); and (4) the employer (amateur/professional organization, state-funded or education). The context alters the focus and attention of the coach and requires a high level of specificity related to programme design and delivery. For example, an S&C coach working with a developmental team athlete with a low training age will plan, deliver and evaluate outcomes differently than if working with an elite individual athlete in a highly demanding performance environment. The scientist It is clear from criteria detailed in job specifications that the responsibilities of an S&C coach have evolved to include roles from other sport science disciplines. Before exploring the application of sport science we consider the definition of science: pursuit and application of knowledge and understanding, following systematic methodologies based on evidence (Science Council, 2021) Therefore, sport science can be thought of as a scientific process used to guide the practice of sport, with the ultimate aim of improving sporting performance (Bishop et al., 2006). The British Association of Sport and Exercise Sciences (BASES) recognizes that the application of scientific principles in sport is principally achieved through one of the three branches of science or through interdisciplinary approaches: biomechanics, physiology and psychology (Table 1.1). The importance of nutrition in sport and exercise science is evident and now recognized as an integral role within the multidisciplinary team, hence its inclusion in this chapter. The discipline of S&C is fundamentally embedded in sport science with, for example, the knowledge of programming being underpinned by the understanding of how the anatomy will adapt (physiology), how changing movement patterns can impact the kinetic chain and kinematics (biomechanics), goal setting and motivation (psychology) and advising an athlete what and when to eat to maximize performance or recovery (nutrition). As previously mentioned, S&C job roles and responsibilities are likely to vary based on various constraints (e.g. organizational structure, working environment, level of athlete); however, it is common to observe that in addition to the underpinning knowledge that allows S&C professionals to perform their primary role, coaches are progressively being expected to perform additional services such as postural, gait and movement screening, testing using laboratory-based equipment (e.g. force plates, isokinetic dynamometry, body composition analysis) and monitoring of physical and physiological responses (e.g. vertical jumps, heart rate, GPS, rate of perceived exertion, subjective questionnaires, blood and saliva analyses). Table 1.1 The definition of scientific disciplines in relation to potential strength and conditioning (S&C) coach roles Definition Source: www.bases.org.uk/About-Sport-and-Exercise-Science. Relation to S&C Biomechanics An examination of the causes and consequences of human movement Movement analysis Athlete performance testing/profiling Monitoring external training responses Physiology An examination of the way the body responds to exercise and training Athlete performance testing/profiling Monitoring internal training responses Recovery modalities Psychology An examination of human behaviour within exercise science Profiling Monitoring (questionnaires, e.g. Profile of Mood States (POMS)) Nutrition An examination and practice of nutrition to enhance wellbeing and athletic performance Fuelling Hydration Recovery Supplementation Source: www.bases.org.uk/About-Sport-and-Exercise-Science. It is not suggested that S&C coaches should fill the roles of biomechanists, physiologists, psychologists or nutritionists; however, it appears that S&C coaches are expected to have a working understanding of, or at times even embrace the role of, these professions. This may be a result of the limited financial and physical resources dedicated by some sporting organizations. In effect, the role of an S&C coach is like that of an interdisciplinary sport and exercise scientist who attempts to utilize and integrate more than one area of sport science to solve real-world problems (Burwitz et al., 1994). The majority of S&C coaches within the UK hold a minimum of an undergraduate-level degree within an exercise science discipline (Hartsthorn et al., 2016), and within the USA, it is essential to possess a degree for job roles and relevant industry certifications. Therefore, it is perhaps unsurprising that S&C coaches are expected to extend themselves to these roles. It is also hard to say whether these growing responsibilities were academia-led (noting that degrees in S&C teach would-be coaches these skills as though it is a requirement to succeed) or a reflection of the economic status of the organization. However, it is important that S&C coaches recognize their limitations and only work within their scope of practice. In addition to having professional knowledge of a broad range of scientific areas and their practical application, the S&C coach is commonly expected to perform data analysis. Due to the evidence-based environments in which S&C coaches work, the ability to run data and statistical analyses using appropriate platforms (Excel, SPSS, R, etc.), is becoming increasingly important. Such skills enable the S&C coach to identify the success or failure of an intervention, to detect meaningful changes and trends, and to develop models that inform performance. Furthermore, this information must be interpreted, filtered and communicated to technical coaches, support staff, athletes and parents in a way that is relevant and meaningful. This requires the S&C coach to, firstly, be competent at completing the required analysis and, secondly, have adequate interpersonal knowledge to communicate the results within the correct sporting context. Performance lifestyle: non-contact coaching Since the dawn of professionalization within elite sport, and the subsequent increased commercial attention and financial incentives (for both athlete and organization), performance outcomes (success of team/individual, win/loss ratio, player development) have become of paramount importance. At any level, athlete development and performance are undeniably multidimensional components that require dedicated, individualized approaches. It is now expected that professionals such as S&C coaches influence performance through the education of athletes, to capitalize on the non-contact hours; in essence, there is now a need for non-contact coaching (i.e. the ability to influence athletes’ behaviours and subsequently their performance when they are away from the training environment). A term that embraces this concept is ‘marginal gains’. This was coined and popularized by Sir Dave Brailsford, who sums it up as ‘put simply … how small improvements in a number of different aspects of what we do can have a huge impact on the performance of the team’ (Slater, 2012). Similarly, Clive Woodward describes using a strategy to improve ‘critical non-essentials’ (CNe). Again, this approach focused on improving the small details of everything in the preparation for performance. Whilst such approaches have yielded great success for some athletes and teams, it is worth noting that such an approach should be reserved for highly developed athletes who have maximized basic performance-enhancing methods. Although many of the approaches used within elite sport are outside the control of S&C coaches (for example, development of technology, organizational culture, competition schedule, travel arrangements, etc.), many alterations to daily lifestyle can be prescribed or controlled. These may include recovery modalities, sleep hygiene, strategies to reduce risk of infection, ergonomics of equipment and travel, dealing with travelling across time zones, etc. The aforementioned are concepts rooted in scientific rationale and are designed and implemented to gain small advantages. The S&C coach must now be constantly investigating ways to improve physical outcomes, positive psychology, training environment and performance lifestyle for athletes to truly gain a competitive edge. However, to reiterate, the minor advantages achieved via these small modifications are only meaningful if the S&C coach has successfully implemented key concepts, such as appropriate analysis, planning, coaching, monitoring and recovery. Considerations for a modern-day S&C coach An S&C coach must consider a multitude of factors before commencing a working relationship with an athlete. Crudely, these can be categorized into analysis, planning, coaching, monitoring performance, readiness and recovery (before returning to analysis). Below is a non-exhaustive list of some of the elements that may need to be considered when working with athletes. Analysis (and re-analysis) Athlete background/objective. Short-, medium-, long-term objectives? How to monitor success or failure? Injury history? Training age/history? Biological age? Preferences? Sport/competition demands. How many games/tournaments? Frequency of competition? Priority games/tournaments? How long is the season? Travel demands? Physical demands (how far and fast, etc.)? Injury prevalence within sport/population, including common mechanisms of injury? Postural and movement screening. What type of movement screen? For what reason are you screening? Are the results meaningful or confounded by subjectivity? What are the movement dysfunctions? What drives movement dysfunction? Implications on transfer of force through the kinetic chain and injury prevalence? Physical performance testing. Determining successful athletic factors in the sport? Strength/power/speed/agility/endurance tests? Laboratory or field-based testing? Reliability and measurement error? Validity of test? How to interpret and present results? Planning (within context) Periodization: block or undulating? How to structure macro-, mesoand micro-cycles? Knowing when to overload and when to taper and when to rest? How to structure technical sessions? Exercise programming. Training methods? Associated adaptations? Exercise selection? Exercise sequence (concurrent or single stimulus)? Prescription of training loads? Rehabilitation/prehabilitation. Methods and exercises to tackle highrisk groups/muscles/joints? When to apply prehabilitation strategies? Return to play/competition strategies? Remedial/preparatory exercise? Non-contact coaching. Nutritional guidance? Sleep hygiene? Strategies to reduce the risk of infection? How to prepare for different time zones, climates, surfaces? Coaching Professional knowledge. How to apply fundamental training principles? Dynamic correspondence of training? Understanding of sport/competition rules, regulations and physical demands? Knowledge of skill acquisition and pedagogical theory? Which method of training and coaching style induces optimal physical and psychological response (might be different at different times)? Interpersonal knowledge. How do you communicate with athletes, coaches and other stakeholders? Awareness of verbal cues (internal vs. external) and non-verbal communication? How do athletes best retain information? Are you able to adapt the programme in relation to how the athlete is feeling? Intrapersonal knowledge. Do you evaluate sessions? How do you evaluate? Does it inform future practice? Open and willing to try new ideas? Confidence, connection, character. Do you understand what motivates your athlete/s? How to instil confidence? How to be a role model and leader? How can you instil good habits that transfer into wider society? How to create a performance environment? Monitoring Monitor training load (TL) and responses to TL. Internal methods? External methods? Methods to assess response to training? Performance tests? Physiological markers? Psychological assessments? Wellbeing? Are the metrics/markers/questions sensitive enough to detect meaningful changes? Determining differences between functional overreaching (FO), non-functional overreaching (NFO), overtraining (OT)? Data analysis? What, how and to whom to report the information? What actions are required as a result? Recovery Do we need to use recovery strategies at this point? What is the aim of a recovery strategy? What are the best strategies? When to apply? Should everyone use the same recovery strategy? Are they proactively planned or reactive to environment? Physiological and pschosocial response? Then return to analysis. Conclusion The role of an S&C coach is multifaceted and fundamentally requires the individual to effectively interact and communicate with relevant stakeholders as well as apply scientific principles in the pursuit of optimizing sporting performance. Additional skills deemed integral to the role include organization, administration, athlete motivation, education and public relations (Kraemer, 1990). In an era when substantial financial investments and the adoption of strategic approaches to enhancing performance are commonplace, it is unsurprising that a largely evidencebased culture has evolved. S&C coaches must analyse, interpret and influence decision making using facts and figures. Hunches and instincts are becoming increasingly more difficult to justify to technical coaches and managers, and can rarely promote change. Although traditionally a coach may value professional knowledge above all else, it is recommended that equal attention be applied to both the development of interpersonal skills and reflective practices. In summary, the discipline of S&C requires the individual to be both an effective coach and an interdisciplinary sport scientist. (See Figure 1.1 for a non-exhaustive list of coaching and applied science principles.) These required skill sets should be embraced and seen as essential if the S&C coach is to truly be effective. Therefore, due to the breadth and depth of knowledge and skills required it may be suggested that S&C coaches should strive to be excellent ‘generalists’ and consider being a ‘specialist’ in a specific area of expertise once the basics have been mastered. The following chapters provide a greater in-depth analysis of these areas and are an important part of appreciating the role of the contemporary S&C coach. Integration of coaching and applied science principles. S&C, strength and conditioning; TL, training load. The chapters will be principally structured in two sections: (1) an objective and concise review of pertinent literature in the specific subject area; and (2) a discussion (including applied examples) of context-specific real-world practical applications. References Bishop, D., Burnett, A., Farrow, D., Gabbett, T., & Newton, R. 2006. Sports-science roundtable: Does sports-science research influence practice? International Journal of Sports Physiology and Performance, 1(2), 161–168. Burwitz, L., Moore, P.M., & Wilkinson, D.M. 1994. Future directions for performance-related sports science research: An interdisciplinary approach. Journal of Sports Sciences, 12(1), 93–109. Côté, J., & Gilbert, W. 2009. An integrative definition of coaching effectiveness and expertise. International Journal of Sports Science & Coaching, 4(3), 307–323. Dawson, A.J., Leonard, Z.M., Wehner, K.A., & Gastin, P.B. 2013. Building without a plan: The career experiences of Australian strength and conditioning coaches. The Journal of Strength & Conditioning Research, 27(5), 1423–1434. Dorgo, S. 2009. Unfolding the practical knowledge of an expert strength and conditioning coach. International Journal of Sports Science & Coaching, 4(1), 17–30. 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Suchomel and Paul Comfort DOI: 10.4324/9781003044734-4 Introduction In this chapter we explore the importance of muscular strength and power to sport performance, discuss the physiological underpinnings, and consider various methods of improving these qualities in athletes. While basic concepts of periodisation and programming for improving strength and power characteristics will be mentioned within this chapter, more thorough discussions can be found in Chapter 7, as well as Stone et al. (1982), Bompa and Haff (2009), and DeWeese et al. (2015a, 2015b). SECTION 1 The importance of muscular strength and power for athletes Muscular strength is defined as the ability to exert force on an external resistance (Stone, 1993). Based on the demands of a sport or an event, an athlete may have to manipulate (e.g., accelerate/decelerate) their own body mass against gravity (e.g., sprinting, gymnastics, etc.), both their body mass and an opponent’s body mass (e.g., rugby, wrestling, etc.), or an external object (e.g., soccer, weightlifting, etc.). Ultimately, the force exerted and the duration over which it is applied (impulse = force × time) will change the motion of a body in space. This concept is based on Newton’s second law (i.e., the law of acceleration), whereby force is equal to the product of mass and acceleration (force = mass × acceleration). Based on this principle, the acceleration of a given mass is directly proportional to, and in the same direction as, the force applied and the duration over which it is applied. Thus, it appears that muscular strength is the primary factor for producing an effective and efficient movement of an athlete’s body or an external object. This concept has been supported throughout the literature as muscular strength (maximal force production) has been correlated to greater rate of force development (RFD), power output, jump height, sprinting speed, change-of-direction performance, sport-specific skills, and postactivation potentiation (PAP) magnitude (Suchomel et al., 2016b). Previous researchers and practitioners have indicated that RFD and power output are two of the most important characteristics regarding an athlete’s performance (Morrissey et al., 1995; Baker, 2001b; Stone et al., 2002). Given that muscular strength serves as the foundation upon which other abilities can be enhanced, it should come as no surprise that greater magnitudes of RFD and power output are by-products of increased strength. However, it should be noted that when assessing power, changes in technique alone (e.g., jump strategy during a countermovement jump) can alter the power output. Ultimately, it is the relative net impulse that determines acceleration, therefore both the force and time over which it is generated are key to enhancing performance in athletic tasks. Rate of force development RFD may be defined as the change in force divided by the change in time, with the ability to rapidly produce force being critical given the time constraints of various tasks. For example, during high-velocity sprinting, ground contact times are <250 ms, with a progressive decline in contact time as velocity increases (Weyand et al., 2000; Morin et al., 2012; Haugen et al., 2018), reaching contact times as low as 80 ms when running at velocities >11 m·s−1 (Tidow, 1990). The importance of rapid force production is further supported by the fact that it takes a longer duration (>300 ms) to produce a maximum force (Aagaard et al., 2002a; Andersen et al., 2003) compared to the duration of jumping and ground contact time during sprinting (Andersen and Aagaard, 2006). As mentioned above, increases in muscular strength enhance an athlete’s ability to increase their magnitude and RFD. The results of previous research, albeit assessing force production via single-joint tasks, has demonstrated that resistance training may enhance an athlete’s RFD characteristics, which may lead to improved performance (Häkkinen et al., 1985; Aagaard et al., 2002a, 2010). In a review, Taber et al. (2016) provided evidence that RFD, along with greater muscular strength, may underpin the development of greater power output (Figure 2.1). Interestingly, the results of a recent training intervention indicate that high-load (80–90% 1RM, where 1RM = one repetition maximum), multi-joint resistance training, which follows moderate-load training (60–82.5% 1RM), results in superior increases in early multi-joint force production (force at 50, 100, 150, 200, and 250 ms) assessed via the isometric mid-thigh pull, compared to the changes observed after moderateload resistance training (Comfort et al., 2020). Comparison of countermovement jump kinetic and temporal variables between stronger and weaker athletes. RFD, rate of force development. Power output As mentioned above, alongside RFD, power output is considered one of the most important characteristics regarding an athlete’s performance. Power output may be defined as the rate of performing work, with any sport task requiring the completion of a given amount of mechanical work. While the work performed is important, athletes have limited time to perform these tasks and, thus, it would seem beneficial to complete the work in the shortest duration possible. For example, an athlete who completes the required work of a given task more quickly may be given a competitive edge compared to their opponent (e.g., rebound in basketball) or may win the overall competition (e.g., 100-m sprint). The findings of previous research indicate that power output differs between the playing level of athletes (Fry and Kraemer, 1991; Baker, 2001a; Hansen et al., 2011) and between starters and non-starters in various sports . Furthermore, researchers have noted strong relationships between power output and performance characteristics such as sprinting (Weyand et al., 2000, 2010), jumping (Newton et al., 1999; Hori et al., 2008), change of direction (Nimphius et al., 2010; Spiteri et al., 2012), and throwing velocity (McEvoy and Newton, 1998; Marques et al., 2011). Given the importance of power output to an athlete’s success, many strength and conditioning practitioners have sought to improve these qualities through various training strategies. Common training strategies that have been used to enhance power output will be discussed in the second half of this chapter. Impulse Impulse may be defined as the amount of force produced over a given time period (impulse = force × time). This characteristic has been deemed important due to the fact that relative net impulse ultimately determines vertical jump performance (Kirby et al., 2011) and may influence weightlifting performance (Garhammer and Gregor, 1992). Due to its influence on movement, it is important to understand how muscular strength characteristics influence the shape of an athlete’s relative net impulse. For example, McMahon et al. (2017) indicated that senior-level rugby athletes applied greater relative impulses during the braking and propulsive phases of a countermovement jump compared to academy-level athletes, resulting in greater jump heights in the senior athletes. While the shape of an athlete’s applied impulse may be affected by their jumping strategy (e.g., shallow versus deep countermovement), it should be noted that the ability to rapidly apply force during both the braking and propulsive phases also plays a role. If an athlete is strong enough to tolerate a rapid countermovement, it is likely that the shape of their impulse will be taller (higher-force) and skinnier (reduced-duration); however, a weaker athlete who cannot decelerate momentum as effectively may produce a shorter (lower-force) and wider impulse (longer-duration) (McMahon et al., 2018). The component pieces of force production and time are important given the constraint of time within sports. Morphological factors affecting strength and power Cross-sectional area Researchers have indicated that an increase in an athlete’s muscle crosssectional area (CSA) and work capacity (i.e., force production capacity) may lead to an enhanced ability to increase their muscular strength (Stone et al., 1982; Minetti, 2002; Zamparo et al., 2002). Typically, this is achieved via a resistance-training phase that includes a high volume of work completed with moderate to moderately high intensity (60–80% 1RM). Greater detail will be provided in the second half of this chapter. An increase in muscle fibre CSA results in an increased size of the overall muscle (hypertrophy). From a physiological perspective, increases in muscle CSA lead to improved force production capacity due to an increased number of newly formed sarcomeres (i.e., the smallest contractile units within muscle cells). Simply put, an increase in the number of sarcomeres increases the number of potential interactions between actin and myosin microfilaments (i.e., cross-bridges) which ultimately increases the force-generating capacity of a muscle. This is supported by research from Kawakami et al. (1993) indicating that muscle fibre pennation angles are greater in hypertrophied muscles. A greater pennation angle permits a greater number of cross-bridge interactions to occur within a given area of the muscle, due to the packing of muscle fascicles within the area (Figure 2.2). Medial gastrocnemius (MG) fascicle length (dashed line) and MG pennation angle (θ), as measured between the superficial (A) and deep (B) MG aponeuroses. Another influence on the CSA of muscle fibres is the ratio of type II fibres to type I fibres. The results of previous research indicated that an increased CSA following resistance training coincided with a greater type II:I ratio due to a greater rate of hypertrophy of type II muscle fibres compared to type I fibres (Campos et al., 2002). Additional research findings demonstrate that a greater percentage change in type II:I ratio following 8 weeks of resistance training strongly correlated with the percentage change of squat jump power (Häkkinen et al., 1981). Thus, it appears that an increased CSA coinciding with a greater type II:I ratio may increase the ability to generate power by altering the force–velocity characteristics of the muscle. However, it should be noted that the training method will greatly impact which motor units will be recruited and thus affect which muscle fibres (e.g., type I, IIa, IIx) adapt to the training stimulus. This concept is discussed in greater detail below (see the section ‘Neuromuscular factors affecting strength and power’). The training method may also affect how additional sarcomeres are added. For example, high-force training (i.e., resistance training) may result in increases in a muscle’s CSA by adding sarcomeres in parallel (Figure 2.3), which may increase the overall force produced by the muscle given that each sarcomere acts independently. In contrast, high-velocity training (e.g., plyometrics, discussed in detail in Chapter 17) may add sarcomeres in series (Figure 2.4), which may increase shortening velocity at the expense of force production given that the sarcomeres in series pull against each other (Suchomel et al., 2019b). This concept is important to consider given the demands of athletes in various sports. Four sarcomeres in parallel. (Adapted from Stone et al., 2007.) Four sarcomeres in series. (Adapted from Stone et al., 2007.) Muscle architecture While the overall size of the muscle may affect the magnitude of force produced, additional muscle architecture characteristics may affect muscle tension. A muscle’s pennation angle may be defined as the angle in which the fascicles (i.e., bundle of muscle fibres) attach to the superficial or deep aponeurosis (Figure 2.2). The muscle’s pennation angle will determine the force–velocity characteristics of the muscle. For example, a greater pennation angle will allow the muscle to place a greater emphasis on force due to the ability to pack more muscle fascicles into a given area, leading to a greater number of cross-bridge interactions and enhanced force production (Huxley, 1974). In contrast, a smaller pennation angle will place a greater emphasis on velocity due to the position of the fascicles being more parallel in relation to the muscle’s aponeuroses, leading to a greater shortening velocity due to the combined shortening of sarcomeres across the area of the muscle belly. Researchers have assessed longitudinal changes in muscle architecture (i.e., muscle thickness, pennation angle, and fascicle length) following various resistance-training programmes, illustrating that changes in muscle architecture may affect performance outcomes. For example, Nimphius et al. (2012) indicated that moderate increases in fascicle length following resistance training were strongly correlated with sprint times to first and second base from home plate in elite softball players. In addition, Kawakami et al. (1995) and Aagaard et al. (2001) observed increases in muscle thickness and pennation angles following heavy strength training. Such adaptations may be favourable when it comes to producing greater overall magnitudes of force within the muscle. Further research findings indicated that training with relatively high movement velocity and lighter loads (<60% 1RM) may produce increases in fascicle length with no changes in pennation angle (Blazevich et al., 2003; Alegre et al., 2006). From a practical standpoint, architectural changes of this nature may increase the overall shortening velocity of the muscle, likely leading to greater increases in power output. Based on the results of previous literature, it appears that muscle architectural changes may be specific to the muscle actions performed (Table 2.1). Additional research comparing eccentric and concentric muscle action training supports this notion (Blazevich et al., 2007; Franchi et al., 2014). Table 2.1 Training stimulus Muscle architectural adaptations in response to different training stimuli CSA Pennation Fascicle Fascicle ↑ ↑ angle length thickness Sarcomeres Sarcomeres in series in parallel Hypertrophy ↑ ↑ ↓ ↑ No Yes Strength ↑ ↑ ↓ ↑ No Yes Power – ↓ ↑ – Yes No Eccentric focus – ↓ ↑ – Yes No CSA, cross-sectional area; ↑ = increase; ↓ = decrease; – = minimal change. It should be noted that the changes in muscle size and pennation angle may not be uniform throughout an entire muscle belly (Ema et al., 2013; Wells et al., 2014). Given the demands of various sport tasks, non-uniform hypertrophy may result in greater growth proximally or distally depending on the activation of musculature during training (Wakahara et al., 2012). For example, the quadriceps muscles of track and field sprinters may hypertrophy more proximally than track cyclists due to the lower-limb mechanics required. This idea becomes important when selecting exercises with the intent of increasing the probability that training-induced adaptations will transfer to an athlete’s performance. Neuromuscular factors affecting strength and power Motor unit recruitment A motor unit may be defined as an alpha motor neuron and all the muscle fibres it innervates. The magnitude and rate of force produced coincide with the number and type of motor units recruited. Classic work from Henneman and colleagues (1965) indicates that motor units are recruited in a sequenced manner based on their size (Henneman’s size principle). Motor units are recruited in order from smallest to largest based on the neuromuscular requirements of the activity. For example, smaller motor units that include slow-twitch type I fibres are recruited at low force magnitudes and are followed by larger motor units that include fast-twitch type IIa and IIx fibres if higher force and RFD are required. While the size principle appears to hold true during slow, graded actions as well as isometric actions (Milner-Brown and Stein, 1975) and ballistic actions (Desmedt and Godaux, 1977, 1978), it should be noted that motor unit recruitment thresholds may be lowered during ballistic-type movements due to a greater RFD demand (van Cutsem et al., 1998). Thus, the ability to recruit high-threshold motor units during training would be beneficial to the improvement of muscular strength, RFD, and power. For a motor unit to be trained, it must be recruited. As mentioned above, the nature of the activity will directly affect what motor units are recruited and how they will respond to training. For example, a distance runner repeatedly recruits low-threshold, slow-fatiguing (type I) motor units due to the low/moderate forces that are produced during each stride. Due to the nature of the task, high-threshold (type II) motor units may not need to be recruited until the type I motor units fatigue and additional force production is needed to sustain the activity. In contrast, weightlifters performing the snatch require high magnitudes and rates of force production during a task that lasts less than 5 seconds. In this case, both low- and high-threshold motor units are recruited due to the order of recruitment. However, it appears that the preferential recruitment of high-threshold motor units would be beneficial for the weightlifter in order to enhance muscular power (Kraemer et al., 1996; Duchateau and Hainaut, 2003). Seminal work by van Cutsem et al. (1998) demonstrated that while the orderly recruitment of motor units existed during both slow, ramp and ballistic actions following ballistic-type training, motor units were recruited at lower force thresholds. From a practical standpoint, training methods that are ballistic in nature will allow recruitment of larger, type II motor units at lower thresholds, thus allowing for positive strength and power adaptations to occur, even without near-maximal loads. Firing frequency (rate coding) Firing frequency may be defined as the frequency at which neural impulses are transmitted from the α-motoneuron to the muscle fibres of recruited motor units. Following the recruitment of specific motor units, force production properties may be modified in two ways by the firing frequency. Enoka (1995) indicated that force production magnitude may increase upwards to 300–1500% when the firing frequency of recruited motor units increases from its minimum to its maximum. In addition, RFD may be impacted by the firing frequency of motor units due to high initial firing frequencies being linked to an increase in doublet discharges (i.e., two consecutive motor unit discharges in ≤5 ms) (van Cutsem et al., 1998). Both the increase in magnitude and RFD, as the result of an increased firing frequency, may ultimately contribute to positive strength and power adaptations. Practically speaking, certain training methods may lead to improvements in the firing frequency of recruited motor units. Previous research findings demonstrate that ballistic-type training may enhance motor unit firing frequency within 12 weeks (van Cutsem et al., 1998). Additional researchers suggest that other ballistic training methods, such as weightlifting movements (Leong et al., 1999) and sprinting (Saplinskas et al., 1980), may enhance motor unit firing frequency, leading to enhanced strength-power characteristics. Motor unit synchronisation Motor unit synchronisation refers to the simultaneous activation of two or more motor units resulting in increased force production. While the physiological underpinnings are not fully understood, some literature indicates that motor unit synchronisation is more related to RFD compared to the magnitude of force produced (Semmler, 2002). Milner-Brown and Lee (1975) indicated that 6 weeks of strength training led to an increase in motor unit synchronisation. Results of another study indicated that motor unit synchronisation strength was largest in the dominant and non-dominant hands of weightlifters compared to musicians and untrained individuals (Semmler and Nordstrom, 1998). Although van Cutsem et al. (1998) found that motor unit synchronisation did not appear to change following ballistictype training, another study indicated that motor unit synchronisation was enhanced during tasks that require movement, especially those involving rapid muscle actions (Semmler et al., 2000). Finally, Aagaard et al. (2000) suggested that heavy strength training (~6RM loads) may result in an increase in motor unit synchronisation, possibly contributing to force production. Neuromuscular inhibition Neuromuscular inhibition, which refers to a reduction in the voluntary neural drive of a given muscle group during voluntary muscle actions, may negatively affect force production due to neural feedback received from muscle and joint receptors (Gabriel et al., 2006). Undoubtedly, neural mechanisms that negatively affect the development of force and power may alter potential adaptations. However, Aagaard et al. (2000) indicated that heavy strength training (~6RM loads) may down-regulate Ib afferent feedback to the spinal motoneuron pool, ultimately reducing neuromuscular inhibition and increasing force production. Results of additional studies highlighted an enhanced neural drive from the spinal and supraspinal levels following strength training that coincided with a decrease in neuromuscular inhibition (Aagaard et al., 2002b) and enhanced RFD (Aagaard et al., 2002a; Table 2.2). Taking the above into account, heavy resistance training may lead to an enhanced neural drive, increased RFD, and decreased neuromuscular inhibition, creating potential enhancements in the strengthpower characteristics of athletes. Table 2.2 Neurological adaptations in response to different training stimuli Training stimulus MU Firing recruitment frequency MU Neuromuscular synchronisation inhibition Hypertrophy ↑ ↓ ↓ ↑ Strength ↑ ↑ ↑ ↓ Power ↑ ↑ ↑ ↓ Eccentric focus ↑ ↑ ↑ ↓ MU, motor unit; ↑ = increase; ↓ = decrease; – = minimal change. SECTION 2 Training considerations for improving muscular strength and power In addition to understanding the physiological underpinnings that affect both strength and power, practitioners must select a periodisation model, exercises and/or training methods, the movement intent (i.e., ballistic or non-ballistic), and loads for each exercise, all while implementing each factor in a sequenced progression. Moreover, the athlete’s training status must be considered, as certain training methods may be more appropriate for those who are more/less well trained. Readers are directed to Suchomel et al. (2018a) and Cormie et al. (2011) for more thorough reviews on developing muscular strength and neuromuscular power, respectively. Periodisation model An abundance of periodisation models exist within the strength and conditioning field. Much of the extant literature supports the notion that block periodisation may provide superior results compared to other models, as discussed by DeWeese and colleagues (2015a). This model is based on the idea that a concentrated load may be used to emphasise the development of one specific characteristic during each training phase, while maintaining the previously developed characteristic(s) (Figure 2.5). This appears to be advantageous considering that researchers and practitioners have indicated that it may be difficult, and potentially less productive, to develop multiple physiological characteristics or motor abilities simultaneously (Stone et al., 2007; Issurin, 2008, 2010). It should be noted that other models of periodisation may still provide an effective blueprint for developing an athlete’s strength-power characteristics (e.g., traditional, undulating, conjugate, etc.). However, further research comparing periodisation models with different athletic populations, with different competition schedules, is still needed to determine their effectiveness. Periodisation and the effectiveness of various periodisation models for athletic performance are explored in greater detail in Chapter 7. Example emphasis change during a periodised training programme (phase potentiation). 1RM, one repetition maximum. Resistance-training methods The type of training method may provide a vastly different stimulus that may affect gains in muscle CSA, strength, or power. As discussed in Chapters 7 and 15, the training mode and exercises should be selected based on their ability to achieve the goals of each training phase. For example, exercises may be selected based on their power characteristics. Because power is the product of force and velocity, certain exercises may emphasise one or both characteristics. Simply put, force–velocity, force–velocity or force–velocity are all combinations of exercise types used in training. Table 2.3 displays relative power outputs of a variety of exercises discussed within the literature. Table 2.3 Relative power outputs for male athletes during various exercises Exercise Relative power outputs: Force–velocity male (W kg−1) characteristics Clean 33–80 Hang power clean 22–47 Jerk 44–80 Jerk drive 28–56 Power clean 25–80 Snatch 34–80 Clean pull from floor 33–80 Hang high pull 47–54 Hexagonal barbell jump 45–80 Jump shrug 57–87 Mid-thigh clean pull from dead stop 35–67 Mid-thigh snatch pull from dead stop 35–48 Snatch pull from floor 30–80 Countermovement jump squat 64–75 Static jump squat 58–69 Bench press 0.3–8.3 Deadlift 11–13 Squat 11–30 High-force and high-velocity movements Moderate–high-force and moderate– high-velocity movements Low-force and high-velocity movements High-force and low-velocity movements Notes: The relative power outputs displayed may vary based on the level of the athlete, load lifted, technical efficiency of the athlete, and method used to quantify power output. The data presented represent the ranges of averages across various loads within the literature. (Adapted from Garhammer (1980, 1985, 1991, 1993), Haff et al. (1997, 2001, 2012, 2015), McBride et al. (1999), Driss et al. (2001), Kawamori et al. (2005), Cormie et al. (2008), Stone et al. (2008), Thompson et al. (2010), Comfort et al. (2012, 2015) and Suchomel et al. (2013, 2014, 2015, 2019a).) Bodyweight exercise Bodyweight exercise is one of the most basic forms of resistance training that has been used for decades. Some of the most common bodyweight exercises, such as bodyweight weight squats, push-ups, pull-ups, and situps, are still implemented in resistance-training programmes to this day as a training exercise, progression, or regression. Bodyweight exercises have several advantages, including being specific to the individual’s anthropometrics and muscle/tendon insertion, the inclusion of closed-chain exercises, the ability to train multiple muscle groups simultaneously, and its accessibility and versatility compared to other training methods (Harrison, 2010). Like any training method, bodyweight exercise has its limitations. The most obvious limitation of bodyweight exercises is the inability to continue to provide an overload stimulus to the athlete, preventing a significant transfer to absolute strength measures (Harrison, 2010). For example, practitioners may continue to prescribe a greater number of repetitions or modify the movement (e.g., bilateral squat → split squat → single-leg [unilateral] squat, etc.) in order to progress each bodyweight exercise. However, a continual increase in repetitions would lead to an emphasis on strength-endurance characteristics instead of the development of strengthpower characteristics necessary for enhanced sport performance. Based on their advantages and limitations, it is suggested that bodyweight exercises should be prescribed to enhance basic strength and movement characteristics before progressing to other training methods that may result in greater strength and power adaptations. Machine vs. free-weight training When prescribing either machine or free-weight exercises, practitioners should note that each method has its limitations. For example, machinebased exercises allow for the isolation of specific muscle groups, which may be important from a rehabilitation standpoint. However, utilising machine-based exercises for sport performance may be questionable. Researchers have indicated that athletic movements rarely include muscle actions performed in an isolated manner (Behm and Anderson, 2006), with the transfer from isolation (single-joint) exercises to athletic performance being somewhat limited (Augustsson et al., 1998; Blackburn and Morrissey, 1998; Östenberg et al., 1998). Thus, it appears that exercises that incorporate multiple muscle groups may provide a superior training alternative (Bobbert and Van Soest, 1994; Anderson and Behm, 2005). Furthermore, it is been noted that free-weight exercises may recruit muscle stabilisers to a greater extent than machine-based exercises (Haff, 2000). Collectively, it appears that the movement similarities with athletic movements and the recruitment of muscle stabilisers of free-weight exercises may produce greater strength-power adaptations as they relate to sport performance. Training with weightlifting movements Weightlifting exercises produce some of the greatest power outputs compared to other types of exercise (Table 2.3). Given the importance of muscular strength and power in sport, it is not surprising that many practitioners implement the weightlifting movements and their derivatives within resistance-training programmes. Weightlifting movements are unique in that they exploit both the force and velocity aspects of power output by moving moderate–heavy loads with ballistic intent. In fact, weightlifting pulling derivatives (i.e., those that remove the catch phase) may expand the force and velocity spectrum of weightlifting exercises and produce superior strength, sprint, jump, and change-of-direction training adaptations compared to weightlifting catching derivatives alone (Suchomel et al., 2017, 2020a, 2020b). One key advantage of the ballistic nature is the fact that the athlete aims to accelerate throughout the propulsive phase, whereas exercises such as the bench press and squat result in deceleration during the later stages of the propulsive phase (Newton et al., 1996; Lake et al., 2012b). Previous researchers have demonstrated that weightlifting movements may provide a superior strength-power training stimulus compared to jump training (Tricoli et al., 2005; Teo et al., 2016), traditional resistance training (Hoffman et al., 2004; Channell and Barfield, 2008; Arabatzi and Kellis, 2012; Chaouachi et al., 2014), and kettlebell training (Otto III et al., 2012). Greater detail regarding the use of weightlifting movements during resistance training will be provided in Chapter 16. Plyometric training While a thorough discussion of plyometric exercises will be provided in Chapter 17, this chapter will provide a brief discussion on their effectiveness as a strength-power training stimulus. Plyometric movements may be defined as quick, power-based movements that utilise a prestretch/countermovement that includes the stretch-shortening cycle (SSC). Specifically, plyometrics refer to a concentric muscle action that is enhanced by a rapid preceding eccentric muscle action, generally with a movement time of <250 ms. Their ballistic nature, combined with an emphasis on power development, has led to their use within strength and conditioning programmes for athletes. The authors of a meta-analysis concluded that training with plyometric exercises may produce similar improvements in jump height compared to training with weightlifting exercises (Hackett et al., 2016), demonstrating that plyometrics may be an effective training stimulus for athletes. When it comes to designing a plyometric training programme, practitioners should consider the fact that plyometric exercises are a form of resistance training and should therefore be periodised. Previous research findings demonstrate the effectiveness of programming plyometric exercises in a periodised fashion during 6-week training programmes by decreasing the volume of foot contacts and increasing the intensity of the plyometric exercises during the final 4 weeks of the training (Ebben et al., 2010, 2014). Practitioners should also consider the frequency of training sessions, length of programme, and recovery time between repetitions, sets, and training sessions. Typical training frequencies range from 1 to 3 sessions per week, while the length of most programmes ranges from 6 to 10 weeks (Allerheiligen and Rogers, 1995). Most plyometric exercises are implemented using the athlete’s body mass as the resistance to ensure a short movement duration and rapid prestretch of the muscle to stimulate the SSC. However, using only the athlete’s body mass as a resistance may be limited in terms of strengthpower development. Practitioners may be able to prescribe small additional loads to increase the loading stimulus on the athlete; however, a more sensible method would be to increase plyometric exercise intensity, while simultaneously adjusting the volume to meet the needs of each athlete. See Chapter 17 for a detailed discussion of plyometric training. Eccentric training Eccentric muscle actions are those that lengthen the muscle as a result of a greater force being applied to a muscle than the muscle itself can produce. Although not well understood, eccentric muscle actions result in unique molecular and neural characteristics that may contribute to a variety of adaptations (Douglas et al., 2017b; Suchomel et al., 2019b). Douglas et al. (2017a) indicated that eccentric training may produce similar or greater adaptations in muscle mechanical function (e.g., muscular strength, muscular power, RFD, and stiffness), morphological adaptations (e.g., tendon and muscle fibre CSA), neuromuscular adaptations (e.g., motor unit recruitment and firing frequency) and performance (e.g., vertical jumping, sprint speed, and change of direction) compared to concentric, isometric, and traditional (eccentric/concentric) training. Due to the potential adaptations listed above, it is not surprising that eccentric exercise has received growing interest as a training stimulus. Although interest in utilising eccentric training has grown, less is known about how to effectively implement this type of training. Recent reviews highlighted some of the most common methods of eccentric training (e.g., tempo, flywheel inertial training, accentuated eccentric loading [AEL], and plyometric training) and provided some insight on how these methods may be implemented within an athlete’s resistance-training programme (Suchomel et al., 2019b, 2019c). It should be noted that researchers have indicated that adaptations from eccentric exercise are based on their intensity (Malliaras et al., 2013; English et al., 2014) and eccentric phase speed (Farthing and Chilibeck, 2003; Isner-Horobeti et al., 2013; Stasinaki et al., 2019). It is worth noting, however, that performing the lowering phase of an exercise rapidly initially results in a reduction in force, to permit gravitational acceleration, with a higher force required during the braking phase, to permit deceleration over a shorter duration. Taking this into account, higher eccentric loads may produce favourable adaptations compared to lighter loads. Interestingly, practitioners have the opportunity with eccentric-type training to prescribe loads in excess of what the athlete can lift concentrically (i.e., > 1RM). This concept will be explored in greater detail in Chapter 12. Another aspect to consider with eccentric training is the type of movement(s) the athlete can perform. For example, much of the previously discussed literature within this section has focused on eccentric-only movements. However, AEL is becoming increasingly popular amongst practitioners and researchers. Training with AEL involves performing the eccentric phase of a lift with a heavier load than the concentric phase as a result of a portion of the load being removed by a weight release system (Ojasto and Häkkinen, 2009; Wagle et al., 2018; Lates et al., 2020), spotters (Brandenburg and Docherty, 2002), or the athlete dropping it (Sheppard et al., 2008) at the end of the eccentric phase. Collectively, the results of the previous studies provide evidence that AEL may produce greater adaptations in explosive performance characteristics (i.e., jumping, sprinting, and concentric power). Although a limited body of literature exists, it appears that AEL may provide an effective training stimulus to improve an athlete’s strength-power performance. A further discussion of AEL and its benefits may be found in Chapter 12 and within a review by Wagle et al. (2017). Complex training and strength-power potentiation complexes Complex training (CT) is a training method that involves completing a resistance-training exercise prior to performing a ballistic exercise that is biomechanically similar (Robbins, 2005). For example, back squats may be paired with countermovement jumps, while the bench press may be paired with bench press throws. CT may allow athletes to perform high-force or power exercises at a higher intensity compared to traditional training (Verkhoshansky, 1986; Ebben et al., 2000), ultimately creating a superior training stimulus. In theory, CT may result in greater strength and speed adaptations compared to traditional resistance-training methods longitudinally by providing a broader range of training stimuli (Ebben and Watts, 1998; Jones and Lees, 2003). A topic of frequent research that uses CT principles is PAP. PAP is defined as an acute enhancement in performance as a result of the muscle’s contractile history (Robbins, 2005). Training complexes designed to produce a potentiated state are termed strength-power-potentiating complexes (SPPCs) (Robbins, 2005; Stone et al., 2008). SPPCs involve performing a high-force or high-power movement to potentiate the performance of a subsequent high-velocity or power movement. While several studies have demonstrated that various potentiation stimuli may acutely enhance strength-power performance (Gullich and Schmidtbleicher, 1996; Young et al., 1998; Bullock and Comfort, 2011), a number of factors within the SPPC or the athlete’s characteristics may affect the magnitude of potentiation produced (Suchomel et al., 2016a). Thus, it is not surprising that similar SPPCs resulted in no change or a decrease in subsequent performances in other studies (Jensen and Ebben, 2003; Till and Cooke, 2009; Tsolakis and Bogdanis, 2011). While the concept of using implementing SPPCs within an athlete’s resistance-training programme is appealing, limited research has examined the longitudinal effects of training with SPPCs (Docherty and Hodgson, 2007). In addition, practitioners should note that SPPCs may not be as appropriate for weaker individuals as greater muscular strength may lead to faster and greater potentiation (Miyamoto et al., 2013; Seitz et al., 2014; Suchomel et al., 2016d). Finally, it should be noted that the long-term use of SPPCs may not be appropriate given the goals of specific resistance-training phases. For example, implementing SPPCs may be specific to the goals of a strength-speed phase, but counterproductive during a strength-endurance phase. Unilateral vs. bilateral training Some practitioners may argue that unilateral exercises may be more sportspecific given the unilateral weight-bearing phase of various sport tasks (e.g., sprinting, cutting tasks, etc.). Thus, a frequent topic of discussion within the strength and conditioning field is the use of unilateral exercises compared to bilateral exercises. Unilateral/partial unilateral movements may be defined as those where the resistance is unevenly distributed between an individual’s limbs, whereas bilateral movements are those where the resistance is distributed evenly, for the most part, between an individual’s limbs (McCurdy et al., 2005). The majority of resistancetraining programmes implement predominantly bilateral exercises for strength and power development. This is not surprising given that strong relationships exist between bilateral strength and sprinting, jump height and peak power, and change-of-direction performance (Suchomel et al., 2016b). However, in order to provide practitioners with a variety of options for exercise prescription, further discussion on unilateral exercise is needed. Several studies have compared the training effects of unilateral and bilateral training. McCurdy et al. (2005) examined the strength and power adaptation differences following 8 weeks of unilateral or bilateral strength training and plyometric exercise in untrained subjects. Their results indicated that both groups improved to a similar extent, suggesting that either mode of training may be equally as effective. Makaruk et al. (2011) indicated that both unilateral and bilateral plyometric training improved both countermovement jump and alternate leg-bounding performance in previously untrained females. However, the authors also noted that only the bilateral training group retained their training adaptations following a 4week detraining period. Another study indicated that similar improvements in unilateral and bilateral strength, sprint speed, and agility were displayed by academy rugby players following 5 weeks of either training with the rear foot elevated split-squat or traditional back-squat exercise (Speirs et al., 2016). Although no difference was seen in sprint adaptations, Appleby and colleagues (2020) showed that greater change-of-direction adaptations may occur following bilateral training compared to unilateral training. In addition, Appleby et al. (2019) indicated that both unilateral and bilateral movements may improve strength characteristics in movement-specific tasks, but may also transfer these improvements to other non-trained movements. Collectively, the previous studies indicate that training with unilateral exercises may be an effective alternative to bilateral exercises when it comes to improving various performance parameters. However, practitioners should focus on the physiological stimulus rather than movement specificity when selecting exercises in order to maximise training results (Appleby et al., 2020). Previously, researchers indicated that gluteus medius, hamstring, and quadriceps activation was greater during a modified split squat compared to a traditional bilateral squat (McCurdy et al., 2010), which should not be overly surprising given the decreased stability of unilateral exercises. However, decreased stability may be viewed as a limitation because it is difficult to prescribe heavy loads with unilateral exercises. Given that greater stability within a movement may lead to a greater potential to express force (Behm and Anderson, 2006), it appears that bilateral exercises may serve as a better foundation for improving an athlete’s strength-power characteristics. However, that is not to say that unilateral exercises should not be programmed; rather, they should be implemented as assistance exercises to bilateral movements (Ramirez-Campillo et al., 2018), especially during the general preparatory phase of training. Variable-resistance training Traditional resistance-training methods typically involve performing exercises with an eccentric and concentric component in which the external load remains constant throughout the entire range of motion. While this type of training has become an essential addition to training programmes, it is not without its limitations. For example, an athlete performing a back squat may be limited at the lowest point of the squat due to a decreased capacity to produce force in that position. As a result, athletes may experience a ‘sticking point’ when they begin to ascend, due to mechanical disadvantages being present within the active musculature. In contrast, muscle force production continues to increase and peaks during the top portion of the squat. Based on this description of the back squat, a method of training that trains each portion of the lift based on its mechanical advantage/disadvantage would be beneficial. Variable-resistance training refers to a training method that alters external resistance during the exercise in order to maximise muscle force throughout the range of motion (Fleck and Kraemer, 2014). Traditionally, this method of training involves the use of chains or elastic bands during exercises such as the back squat (Figure 2.6) or bench press (Figure 2.7). The addition of chains or elastic bands may alter the loading profile of an exercise (Israetel et al., 2010; Figures 2.6 and 2.7), which may allow the athlete to match changes in joint leverage (Zatsiorsky, 1995) and overcome mechanical disadvantages at various joint angles (Ebben and Jensen, 2002; Wallace et al., 2006). Swinton et al. (2011) indicated that the addition of chains equal to 20 and 40% of an individual’s 1RM deadlift may increase the length of the acceleration phase of the overall movement, allowing for greater peak force and impulse to be achieved at the end of the concentric motion. Further support for this method of training comes from a metaanalysis that indicated that greater strength gains were produced during the bench press exercise following variable-resistance training compared to traditional methods (Soria-Gila et al., 2015). While additional training studies are needed, it appears that variable resistance training may be used as an effective training tool for developing muscular strength and power. Back squat exercise using variable resistance with chains. Bench press exercise using variable resistance with elastic bands. Kettlebell training Another form of resistance training that has gained popularity is the use of kettlebell exercises. Kettlebells consist of a weighted ball and handle (Cotter, 2014). Among other movements, individuals have used kettlebells in a variety of ways, including swings, goblet squats, accelerated swings, and modified weightlifting exercises such as a snatch for the purposes of developing strength and power. Previous research has indicated that kettlebell training may improve various measures of muscular strength (Jay et al., 2011, 2013; Lake and Lauder, 2012; Otto III et al., 2012; Manocchia et al., 2013) and explosive performance as measured by vertical jumping (Lake and Lauder, 2012; Otto III et al., 2012) and clean and jerk 3RM (Manocchia et al., 2013). However, it should be noted that two other studies indicated that vertical jump (Jay et al., 2013) and sprint performance (Holmstrup et al., 2016) were not enhanced following kettlebell training when compared to a control group, indicating that not all research supports the use of kettlebells as a strength-training method. Research findings suggest that kettlebell training may provide an effective strength-power-training stimulus. However, it should be noted that more traditional methods of training, such as weightlifting, may provide superior adaptations when it comes to improving maximal strength and explosiveness (Otto III et al., 2012). This may in part be due to overload placed on the body. For example, athletes training with weightlifting movements may be able to clean and jerk 100 kg; however, it may be difficult to perform a kettlebell swing with the same load using proper technique. Further research examining kettlebell training is needed to determine its role within strength and conditioning programmes. Ballistic vs. non-ballistic The intent of performing an exercise may alter a given training stimulus. Ballistic exercises (i.e., those that accelerate throughout the entire concentric movement) may lower the recruitment threshold for motor units (Desmedt and Godaux, 1977; van Cutsem et al., 1998) and allow the entire motor neuron pool to be activated within a few milliseconds (Duchateau and Hainaut, 2003). Based on the discussion earlier in this chapter, recruiting a greater number of motor units will ultimately lead to greater magnitudes and rates of force production. This notion is supported by previous research findings that indicated that ballistic exercises produced greater force, velocity, power, and muscle activation compared to the same exercises performed quickly (Newton et al., 1996; Lake et al., 2012b; Suchomel et al., 2018b). The results of additional research indicate that ballistic movements using 90% of an individual’s 1RM concentric-only half-squat may also produce superior potentiation effects compared to nonballistic exercises (Suchomel et al., 2016c). Due to the potential training benefits of ballistic-type exercises, it should come as no surprise that practitioners often implement these exercises throughout the training year. However, it should be noted that the goals of each training phase will often dictate which exercises are prescribed. Loading considerations Training to failure Training with heavy loads will ultimately lead to increases in muscular strength. A method of training that supports this idea is training with loads that result in failure on the final repetition. The theory behind this method is that training with RM loads (e.g., 3RM, 5RM, etc.) will lead to greater overall adaptations in strength compared to training with submaximal loads. While it seems plausible that training to failure may stimulate the recruitment of high-threshold motor units, Sundstrup et al. (2012) indicated that there was no difference in motor unit recruitment following training to failure compared to heavy-load training. However, the findings of existing literature appear to be mixed as the results of previous meta-analyses indicated that training to failure does not elicit greater strength gains compared to not training to failure (Peterson et al., 2005) or produces similar effects (Davies et al., 2016). It should be noted that training to failure may increase the time needed to recover neuromuscular function and metabolic and hormonal homeostasis (Morán-Navarro et al., 2017). The fatigue that results from training to failure may decrease force and the nervous system’s ability to voluntarily activate muscles (Häkkinen, 1993), which could also negatively impact rapid force production, movement velocity, and power output (Häkkinen and Kauhanen, 1989). Furthermore, additional research findings suggest that training to failure may improve muscle endurance characteristics rather than power development compared to not training to failure (Izquierdo et al., 2006). Due to the use of consistently heavy loads, athletes may not be able to sustain training to failure for long periods of time, or during periods of intensive competition/fixture congestion. While there are training periods when the primary emphasis may be lifting very heavy loads (90–95% 1RM) to improve maximal strength qualities (Suchomel et al., 2018a), it does not appear that training to failure is a required element in an athlete’s resistance-training programme (Davies et al., 2016). For example, Carroll et al. (2019) indicated that not training to failure may produce greater improvements in vertical jump, RFD, and maximal strength compared to training to failure. The authors also noted that the build-up of residual neuromuscular fatigue from training to failure may prevent continual improvements in strength-power characteristics from occurring. Therefore, it is important to include variation in the training stimulus to avoid a plateau (Thompson et al., 2010). Due to the accumulation of fatigue and potential decrements in strength-power characteristics, it is important to note that if training to failure is incorporated into training programmes, it should be used sparingly in order to limit the risks of injuries and overtraining (Davies et al., 2016). Combining heavy and light loads Training for maximal strength and power requires the use of a variety of loads. Specific to strength gains, heavier loads will likely provide a training stimulus that will enhance the magnitude and rate of force production of an athlete. In contrast, training to enhance maximal power production requires the use of a range of loads that train the entire force–velocity curve (Haff and Nimphius, 2012). The training loads implemented with various exercises should complement the exercises that are being used. For example, heavier loads may be used with core exercises (e.g., squats, presses, and pulls) and certain weightlifting movements (e.g., power clean, pull from the floor, mid-thigh pull) that emphasise high-force production, while lighter loads may be prescribed for more ballistic movements that emphasise high velocities (e.g., jump squat, jump shrug, bench press throws). However, as mentioned above, combination loading may also be achieved through the implementation of both weight training (high force) and plyometrics (high velocity). Suchomel et al. (2017) discussed this concept using weightlifting derivatives (also discussed in more detail in Chapter 16). It should be noted that a combination loading stimulus may also be achieved across each microcycle (e.g., week of training) and session of training. Over the course of an individual microcycle, the same exercises may be implemented throughout the week; however, the exercises are prescribed using a ‘heavy day/light day’ loading concept. One review discussed this method of programming for track and field athletes (DeWeese et al., 2015b). In addition, Harris et al. (2000) displayed that a combination loading group performed back squats at 80% 1RM on their heavy day and back squats at 60% 1RM on their light day. Similarly, achieving a combined loading stimulus within a single training session is realised through the combination of working sets as well as warm-up and warm-down sets of each exercise. Optimal loads Some literature supports the idea of training at or near the load that maximises power production, termed the ‘optimal load’ (Kawamori & Haff, 2004). In theory, optimal loads provide an ideal combination of force and velocity magnitudes that produce high-power outputs. However, it should be noted that a number of factors may affect optimal loads. For example, research findings indicated that the optimal load or range of loads for the greatest power output is exercise-specific for both upper- (Soriano et al., 2017) and lower-body exercises (Soriano et al., 2015). Additional research findings suggest that the load that maximises power may be specific to the method that is used to assess power output (e.g., force platform, linear position transducer, etc.) (Cormie et al., 2007; Hori et al., 2007; McBride et al., 2011; Lake et al., 2012a), further indicating that it may be necessary to train with a range of loads, especially as an athlete gets stronger (Stone et al., 2003). Collectively, it appears that training near or at optimal loads may be beneficial from a power development standpoint. However, the extant literature supports the notion that practitioners should prescribe a range of loads instead of a single load in order to train both low- and high-force power characteristics during different exercises (Haff and Nimphius, 2012). Training status An athlete’s training status may dictate: (1) what exercises and loads the individual can tolerate; and (2) what their training emphasis should be. As with any type of training, practitioners should be mindful of an athlete’s abilities as exercise competency will dictate whether it is appropriate to implement certain exercises or progress using various training methods. Because muscular strength serves as a foundation for a number of other abilities (Suchomel et al., 2016b), the training emphasis for weaker and/or less well-trained athletes should focus on increasing maximal strength. Too often practitioners place an emphasis on high-velocity or power training without developing the necessary strength characteristics that will allow the athletes to exploit power-type training more extensively. That is not to say that power-type exercises such as weightlifting movements and plyometrics should not be prescribed to a weaker athlete, but they may not be featured as exclusively until an athlete increases their baseline strength levels using core movements such as squats, presses, and pulls, and improves their technique during power exercises. While the emphasis of training for weaker and/or less well-trained individuals may be on gaining maximal strength, the emphasis of training for stronger/well-trained athletes may be modified. Previous literature indicated that although strength influences an athlete’s performance, the degree of this influence may diminish when athletes maintain high levels of strength (Kraemer and Newton, 2000). Therefore, the window of adaptation for greater strength gains is reduced while an athlete increases their maximal strength. As a result, additional literature has indicated that after achieving specific standards of strength (e.g., parallel back squat ≥ 2 × body weight as the barbell load), an athlete’s training emphasis may shift towards power-type or RFD training while maintaining or increasing their strength levels (Stone et al., 2007; DeWeese et al., 2015b). Specifically, achieving a high baseline level of strength may allow an athlete to maximise the benefits of incorporating training methods such as plyometrics, ballistic exercises, and CT. Summary Muscular strength is defined as the ability to exert force on an external object and is considered to be the primary underpinning factor for greater RFD and power. It is important that adequate strength development is the primary, although not exclusive, focus of training initially, before progressing to power-type training once an athlete’s strength increases. By achieving a high level of muscular strength, athletes may increase their RFD, power, and athletic performance, while decreasing the risk of injury (Suchomel et al., 2016b). Both morphological and neuromuscular factors may affect the development of muscular strength and power. Morphological factors include muscle CSA and architecture while neuromuscular factors include motor unit recruitment, rate coding, motor unit synchronisation, and neuromuscular inhibition. From a practical standpoint, the periodisation model, method of resistance training, prescribed loads, and training status may directly affect muscular strength and power adaptations and training emphases. 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Champaign, IL: Human Kinetics. 3 Stretch-shortening cycle and muscle–tendon stiffness John J. McMahon DOI: 10.4324/9781003044734-5 What is the stretch-shortening cycle? Early research findings revealed that when isolated skeletal muscle fibres were tetanically stimulated (i.e. maximally activated by a nerve stimulator), stretched and then immediately allowed to shorten, they performed a far greater amount of positive mechanical work than when compared to being shortened alone (Cavagna et al., 1965, 1968). This sequential combination of eccentric (lengthening) and concentric (shortening) muscle actions was later termed the stretch-shortening cycle (SSC) (Cavanagh and Komi, 1979). The apparent ‘performance-enhancing’ effect of the SSC was also demonstrated during a range of SSC actions involving the entire lower limb(s), such as those involved during running, jumping and hopping (Asmussen and Bonde-Petersen, 1974; Luhtanen and Komi, 1978; Fukashiro and Komi, 1987). Whilst it is important to note the SSC is common to upper-limb movements too, such as when throwing (Newton et al., 1997), the majority of researchers have explored the SSC of the lower limb(s) and so this will comprise the focus of this chapter. Due to its aforementioned prevalence in key athletic actions such as running, jumping and hopping, the SSC forms the most common type of lower-limb muscle function (Van Ingen Schenau et al., 1997a). In recent years, there has been much debate over the proposed mechanisms that cause the potentiating effect (e.g. increased positive work) of the SSC; however, stimulation of muscle stretch reflexes (e.g. muscle spindles) and storage and re-utilisation of elastic energy within the involved muscle–tendon units (MTUs) are the two primary mechanisms that have been agreed upon by researchers (Van Ingen Schenau et al., 1997a, 1997b; Cormie et al., 2011; Turner and Jeffreys, 2011). During the SSC, stretch reflexes act to increase muscle stiffness (Taube et al., 2012) while tendon stiffness influences the storage and re-utilisation of elastic energy (Farris et al., 2011), thus it can be deduced that MTS has a profound influence on lower-limb SSC function. What is stiffness? Simply stated, stiffness describes the relationship between force and lengthening, or stress and strain, of an object or body (Butler et al., 2003; Brughelli and Cronin, 2008a; McMahon et al., 2012). When applied to the MTU, the object or body of reference could be the muscle, the tendon or both. The term ‘stiffness’ is based on Hooke’s law, which has been described in detail elsewhere (Butler et al., 2003; Brughelli and Cronin, 2008a). Hooke’s law describes the stiffness of an ideal spring–mass system (Butler et al., 2003). When an object that obeys Hooke’s law deforms (i.e. stretches, such as tendon), its change in length will be directly proportional to the force acting upon it (Alexander, 1997) (Figure 3.1). During this deformation (e.g. during the eccentric phase of an SSC action), the object will store elastic energy, which will be re-utilised as the object shortens (e.g. during the concentric phase of an SSC action) and returns to its original resting length (Butler et al., 2003). It is worth pointing out at this stage that activated muscle does not always adhere to Hooke’s law and the reasons for this will be discussed in later sections of this chapter. Nevertheless, during the performance of lower-limb SSC actions, stiffness can be described at a broad range of levels, from an individual MTU, to modelling the entire body as a simple spring–mass system (Butler et al., 2003; Brughelli and Cronin, 2008a). An example of an object that obeys Hooke’s law and the equation to calculate stiffness (k), where ∆F = change in force and ∆x = change in length. Muscle–tendon stiffness (MTS) When considering stiffness in the context of the various MTUs that surround the primary lower-limb joints (e.g. ankles, knees and hips), it is known that there are both passive components (tendon, connective tissue, etc., commonly referred to as the series and parallel elastic components) and active components (muscle, commonly referred to as the contractile component). Due to this, the MTU is considered to be a variably stiff system because whilst tendon possesses a fairly linear relationship (due to it demonstrating mainly elastic behaviour) between force and deformation (Lichtwark and Wilson, 2005; Farris et al., 2011), muscle can vary its stiffness through both feedforward (e.g. pre-programmed) and feedback (e.g. reflex) activation mechanisms (Taube et al., 2012). It must also be noted that the tendon is known to possess viscous as well as elastic properties (Pearson and McMahon, 2012) and so the amount of tendon stretch (and thus storage of elastic energy) experienced during SSC actions will be somewhat affected by tendon-loading rate (McMahon et al., 2014). Muscle activation is, therefore, the primary modulator of MTS during SSC actions, as this will influence both muscle stiffness (i.e. the resultant muscle length changes) and tendon stiffness (i.e. by affecting load rate) alike. Therefore, it is important to note that when discussing whole lower-limb SSC actions it may be seen that the involved muscle components of the MTUs do not always lengthen and shorten during the ‘eccentric’ and ‘concentric’ phases, respectively, of the movement, thus ‘braking’ and ‘propulsion’ phases may be more appropriate terms. As mentioned earlier, both pre-programmed and reflex muscle activation strategies largely dictate the muscle stiffness attained during SSC tasks (Taube et al., 2012). The pre-programmed aspect of muscle activation relates to both muscle pre-activation, which acts to provide sufficient stiffness to the MTU at initial ground contact (Taube et al., 2012), and variable activation during ground contact, which helps to maintain stiffness (i.e. prevent muscle lengthening) during the braking phase and then facilitate the controlled release of high forces (produced in the braking phase) in the subsequent propulsion phase (Komi, 2003). The reflex aspect of muscle activation relates primarily to the stimulation of a stretch reflex called short-latency response (SLR), although when muscle is pre-activated prior to stretching (as is the case during SSC tasks) there are mediumlatency responses (MLR) and long-latency responses (LLR) involved too (Taube et al., 2012). These reflex responses simply relate to their timecourse of stimulation with time epochs of 30–60, 60–90 and 90–120 ms typically relating to the SLR, MLR and LLR, respectively. It has been suggested, however, that stretch reflex contributions to muscle stiffness are more apparent when the muscle is not fully activated, e.g. during submaximal SSC tasks: Cronin et al., 2011), in order to help prevent sudden muscle yielding during the braking phase (Taube et al., 2012). Calculating individual MTS contributions to the total stiffness attained by a given MTU during SSC tasks is a relatively complex process which requires the simultaneous collection of ultrasound, electromyography, force platform and motion analysis data, followed by a lengthy data analysis process which makes this discrete level of analysis difficult to perform in a competitive sport setting. Thus, in the applied strength and conditioning research and practice setting, it is more common to see ‘global’ measures of lower-limb MTS assessed, such as joint stiffness (Kjoint) and leg stiffness (Kleg), as these measures are easier to attain, require less processing time and can still provide valuable insight into how MTS influences SSC function during a variety of athletic tasks (e.g. running, jumping, hopping). Joint stiffness Lower-limb Kjoint is typically calculated using the torsional-spring model (Figure 3.2), as the ratio of the peak sagittal plane joint moment (i.e. the joint rotatory force) to peak sagittal plane joint angular displacement (Figure 3.3), between the instants of ground contact and maximum joint flexion (Farley et al., 1998). An alternative method of quantifying Kjoint has also been described in the literature, as the ratio of negative mechanical work to change in joint angle between the instants of ground contact and maximum joint flexion (Arampatzis et al., 1999); however, this method was later critiqued (Gunther and Blickhan, 2002) and, to the author’s knowledge, has not been reported in any other studies. Despite the method used, however, Kjoint calculations require access to both a force platform and either two- or three-dimensional motion capture, so this equipment may be more accessible to strength and conditioning researchers and practitioners than the addition of ultrasound and electromyography equipment needed to calculate MTS. The torsional-spring model assumes that the lower limbs can be represented by multiple spring-like joints (i.e. the ankles, knees and hips) during SSC actions, which flex and extend during the ground contact period, thus storing and releasing energy (Figure 3.2). An example of the torsional spring model and how it corresponds to the human body. An example of the joint moment–joint angular displacement relationship during loaded flexion and extension. It has been suggested that Kjoint only provides a measure of ‘quasistiffness’, as one stiffness value is used to describe all contributing components to Kjoint, such as muscles, tendons, ligaments, cartilage and bone (Latash and Zatsiorsky, 1993). Nevertheless, Kjoint during SSC tasks is mainly influenced by the magnitude of agonist muscle activation, in addition to the magnitude of antagonist muscle coactivation, immediately prior to and during ground contact (Farley et al., 1998; Arampatzis et al., 2001a, 2001b). Therefore, Kjoint is mainly controlled by muscle stiffness through the muscle activation mechanisms mentioned in the previous section. Another point to consider is that Kjoint attained during SSC tasks is also influenced by limb geometry at touchdown (Devita and Skelly, 1992; Farley et al., 1998; Moritz and Farley, 2004). This can be reasoned by the understanding of the joint moment–angle relationship, in that as the lower limb becomes more extended at touchdown, the moment about the joint decreases for any given external ground reaction force (Figure 3.4), resulting in decreased joint flexion for any given level of extensor muscle activation (Moritz and Farley, 2004). Therefore, athletes can be cued to contact the ground with their limbs orientated in such a manner to either increase or decrease Kjoint depending on the desired outcome. An example of how joint touchdown angles influence leg and joint stiffness values. Leg stiffness It has been shown in several studies that Kjoint is the primary determinant of Kleg during SSC actions (Farley et al., 1998; Arampatzis et al., 1999; Kuitunen et al., 2002) and so although the predominant joint that regulates Kleg depends on the type of SSC task being performed, this most ‘global’ measure of lower-limb stiffness provides valuable information pertaining to SSC function and is the easiest of the lower-limb stiffness hierarchy to measure in both laboratory and field settings. The Kleg measurement is based on the human body acting as a simple spring–mass system during SSC tasks (Geyer et al., 2006; Brughelli and Cronin, 2008b). The spring–mass model (Figure 3.5) is comprised of a point mass (equal to body mass), which is supported by a single massless Hookean spring (representing the leg or legs depending upon whether a unilateral or bilateral task is being performed) (Blickhan, 1989; McMahon and Cheng, 1990). When the spring is not compressed (i.e. during the flight phase of SSC tasks), it does not store any energy and thus no force is developed; however, energy is stored when the spring is compressed (i.e. during the braking phase of SSC tasks) and force is produced and the majority of this energy is re-utilised when the spring subsequently recoils (i.e. during the propulsion phase of SSC tasks) (Brughelli and Cronin, 2008a). An example of the spring–mass model and how it corresponds to the human body. From the spring–mass model, Kleg can be calculated as the ratio of the peak ground reaction force (GRF) to peak leg compression during the period of ground contact (McMahon and Cheng, 1990). This direct measure of Kleg requires access to a force platform system, which is becoming increasingly affordable and utilised in applied practice (Lake et al., 2018). Other methods can also be used to calculate Kleg, based on body mass and either the natural period of oscillation (McMahon et al., 1987; Cavagna et al., 1988) or temporal characteristics such as ground contact and flight times (Dalleau et al., 2004; Morin et al., 2005). Although the latter methods (i.e. based on body mass and temporal factors) have been less frequently reported in the scientific literature (Brughelli and Cronin, 2008b; Serpell et al., 2012), they are commonly used in applied practice as these measurements of Kleg are easily attainable from simple jump mats, optoelectronic systems (e.g. Optojump) and even smartphone applications (Balsalobre-Fernández et al., 2016). The limitation of using field-based calculations of Kleg is that they do not directly include force and deformation in their calculations and so they provide somewhat of a proxy of ‘true’ Kleg. Indeed, the suggested criterion method of calculating Kleg involves considering movement in multiple planes via three-dimensional motion analyses (Liew et al., 2017), but this is beyond most practitioners’ scope and equipment access. At the very least, practitioners should give consideration to the method that they use to calculate Kleg (Maloney and Fletcher, 2021). Stiffness and performance The implications of MTS being primarily regulated by pre-programmed and reflex muscle activation, and somewhat influenced by tendon stiffness and joint geometry, is that it is acutely sensitive to changes in SSC task type and intensity which, in turn, influence SSC function (Ishikawa and Komi, 2004; Ishikawa et al., 2005; McMahon et al., 2014). For example, when drop jumps (DJs) were performed from increasing drop heights (10 cm lower than ‘optimal’ drop height, with optimal drop height determined by best jump height achieved, and 10 cm higher than ‘optimal’ drop height), vastus lateralis (VL) muscle activation increased, decreased and remained unchanged during the pre-contact, braking and propulsive phases, respectively, but tendon recoil decreased (Ishikawa et al., 2005). Tendon recoil also reduced by virtue of increased drop height for the medial gastrocnemius (MG) and its activation patterns were similar to those reported for the VL in the pre-contact and braking phases; however, the MG showed increased activation during the propulsive phase (Ishikawa et al., 2005). Interestingly, the SLR amplitude decreased for the MG but increased for the VL during DJs performed from the highest drop (Ishikawa et al., 2005). This is perhaps explained by the MG showing a reduction in lengthening during the braking phase, whereas the VL demonstrated a general increase in lengthening during this phase (Ishikawa et al., 2005), since the muscle spindle stretch reflex detects the rate and magnitude of muscle lengthening (Taube et al., 2012). These results illustrate that variations in MTS and thus SSC function for a given task and intensity are muscle specific (as noted by the differential response of the VL and MG MTUs) and that high stiffness (as shown for the highest drop condition) does not always transfer to improved performance (e.g. improved jump height). The differential stiffness strategies of the individual VL and MG muscle–tendon components during various DJ tasks mentioned above (Ishikawa et al., 2005) are echoed in the results of a range of studies where the researchers explored the associations between muscle activation strategies and both Kleg and Kjoint for a range of DJ tasks. For example, there were significant correlations between Kleg and the magnitude of preactivation of the MG, lateral gastrocnemius (LG), VL and hamstrings during the performance of DJs, by decathletes, from a height of 20 cm (Arampatzis et al., 2001b). Interestingly, when DJs were performed from heights of 40 and 60 cm, relationships between Kleg and the magnitude of pre-activation were demonstrated for VL and the hamstrings only for this group of athletes (Arampatzis et al., 2001b). For female athletes, significant correlations between Kleg and the magnitude of pre-activation of the MG, LG and VL were found for bilateral DJs performed from a 20-cm height, whereas the magnitude of pre-activation of MG and VL, only, were correlated to Kleg attained during DJs from 40 cm (Arampatzis et al., 2001a). Nine healthy males also demonstrated a relationship between preactivation of the VL muscle and Kknee during DJs performed from 50 cm (Horita et al., 2002). Recent research by Helm and colleagues, which focused on unanticipated versus anticipated DJs (e.g. drop height was known, unknown or falsely stated [drop height was different to what the subjects were told]), explained that anticipation is key for precise timing of neuromuscular responses during ground contact and jump outcomes, such as jump height (Helm et al., 2019, 2020). The outcomes of these studies may reflect the training status of the subjects (i.e. they were not high-level athletes), but also they may rationalise the inclusion of various jumping exercises to enhance an athlete’s overall MTS abilities and SSC function, perhaps even those that include unanticipated drop heights. However, further research is needed to explore the efficacy of this suggestion. The earlier described results pertaining to the varying muscle activation responses to DJs performed from different drop heights echo the different Kjoint contributions to total Kleg that have been highlighted for a range of other athletic performances. For example, ankle stiffnes (Kankle) has been shown to be the primary determinant of Kleg during hopping in place at high (≥2.0 Hz) hopping frequencies whereby the ability to hop at high frequencies requires high levels of Kleg due to the associated short contact times (Farley et al., 1998; Hobara et al., 2011). Contrastingly, Kknee was the primary modulator of Kleg at low (≤1.5 Hz) hopping frequencies which requires lower levels of Kleg and where greater hop heights are noted by virtue of greater time spent on the ground (Hobara et al., 2009, 2011). Similarly, Kknee was also the primary determinant of Kleg during both low(6.5 m s−1) velocity running (Arampatzis et al., 1999) and maximal sprint running (Kuitunen et al., 2002). These differential Kjoint contributions to total Kleg across different SSC tasks reflect differential muscle–tendon contributions to these tasks, with the contribution of tendon (in terms of comprising greater total lengthening and shortening within the MTU) being higher and muscle length being almost constant (i.e. isometric) when Kleg increases (McMahon et al., 2013b). Based on the results of the research presented above, it is apparent that there is an appropriate amount of Kleg for success in a particular SSC task. This notion is supported by a range of scientific studies related to jumping. For example, when DJs were performed from heights of 20–60 cm, jump height was maximised when participants adopted a range of Kleg strategies (Arampatzis et al., 2001a, 2001b; Laffaye and Choukou, 2010). However, the general trend in these studies was that too much Kleg had a negative impact upon vertical jump height (Arampatzis et al., 2001a, 2001b; Laffaye and Choukou, 2010) and this was especially seen in a study whereby DJs were performed from very high (80 and 100 cm) drop heights (Walshe and Wilson, 1997). The potentially inhibiting effect of excessive Kleg was also demonstrated during a high jumping manoeuvre, as greatest jump heights were achieved when participants adopted a more compliant (i.e. less stiff) leg strategy (Laffaye et al., 2005). The aforementioned results suggest that the degree of Kleg required to successfully complete a jumping-based task depends upon both the aims (e.g. maximal height attainment vs. fast execution [i.e. short contact time]) and type (e.g. hopping vs. DJ) of the specific task being performed. Several studies have also reported that Kleg was associated with increased submaximal running velocity (Farley and Gonzalez, 1996; Stefanyshyn and Nigg, 1998; Arampatzis et al., 1999; Hobara et al., 2010) and increased running economy (McMahon and Cheng, 1990; Heise and Martin, 1998; Dutto and Smith, 2002; Rabita et al., 2011) but not with maximal sprint acceleration (Chelly and Denis, 2001; Lockie et al., 2011; Pruyn et al., 2014). The reason for Kleg being beneficial to DJ from lower heights, as compared to DJ from greater heights and the high jump, can be explained by increased Kleg being linked to shorter ground contact times and increased vertical GRFs (Arampatzis et al., 2001a, 2001b). When increasing jump height is the desired outcome, then vertical net impulse (area underneath the net force–time curve) must be increased (Kirby et al., 2011). Although net impulse can be maintained or increased by increasing vertical GRFs when ground contact times decrease (as seen when employing a stiff jumping strategy), it seems that the latter prevails when high Kleg is demonstrated in DJs performed from greater heights and during the high jump. Similarly, researchers have shown that the achievement of faster top running speeds was more closely related to the production of a greater resultant GRF than to an increase in stride frequency (Weyand et al., 2000). Therefore, if running was to be performed with high Kleg, ground contact times would decrease (Farley et al., 1991; Arampatzis et al., 2001a, 2001b), which would reduce the time available for force production (Weyand et al., 2010). A reduction in resultant GRF during running would likely reduce stride length (McMahon and Cheng, 1990; Kerdok et al., 2002). This is, as for jumping, due to a reduction in net impulse. For example, unless a reduction in ground contact time is accompanied by at least the maintenance of, or an increase in, GRF, there will be a reduction in net impulse. Therefore, top running speeds may plateau with an increase in Kleg, in spite of a potential increase in stride frequency (McMahon et al., 1987; Farley and Gonzalez, 1996; Hobara et al., 2010). Researchers did indeed find that the fastest man on earth (i.e. Usain Bolt) ran with significantly lower Kleg, lower stride frequency and longer ground contact times during competition when compared with his two closest rivals (Taylor and Beneke, 2012). In terms of running economy, it is known that the storage and release of elastic energy will help to reduce the work produced by the muscle itself (Roberts and Marsh, 2003; Lichtwark and Barclay, 2010; Perl et al., 2012) and although previous studies revealed that a high Kleg strategy was associated with improved running economy (McMahon and Cheng, 1990; Heise and Martin, 1998; Dutto and Smith, 2002; Rabita et al., 2011), a stiffer MTU may not always elicit a more economical outcome. For example, previous researchers have examined the relationship between MG muscle fascicle length and Achilles tendon stiffness and maximum efficiency during a range of running and walking tasks (Lichtwark and Wilson, 2007, 2008; Lichtwark et al., 2007) and despite maximum efficiency for both running and walking occurring at similar values of tendon stiffness, it was suggested that moving towards a stiffer tendon would reduce efficiency in the walking task but may be more ideal for running, when coupled with longer muscle fibres to optimise efficiency. However, a modelling study indicated that muscle fibre lengths could vary by approximately one and a half times (45–70 mm) and tendon stiffness by approximately threefold (150–500 N mm−1) to give optimal efficiency in a given walking or running task (Lichtwark and Wilson, 2008), which further highlights both the individual and task-specific nature of ‘optimal’ MTS, which has been echoed in more recent work (Moore et al., 2019). In conclusion, the amount of MTS required during an SSC task depends on desired task outcome (Figure 3.6). If reducing ground contact time and increasing GRF is sought then stiffer is better but if increasing joint angular velocity to increase short sprint acceleration or jump height is sought then too much stiffness will be detrimental. Acutely modulating an athlete’s MTS strategy in the direction of stiffening their legs via verbal coaching cues etc. will increase GRFs and load rates and so this should only be done if they are appropriately conditioned and (in line with the previous point) if the task warrants a stiffer strategy (Figure 3.6). A safer and more sensible approach to increasing MTS is through long-term training rather than via acute modulation (i.e. immediately coaching a change in movement strategy), which will be discussed in the next section. A schematic illustrating how the legs change from being more compliant (opposite of stiff) to more stiff for a range of stretch-shortening cycle tasks. DJ, drop jump. Stiffness and training Only a few studies to date have examined the effects of training interventions on Kleg and Kjoint, as determined during lower-limb SSC actions (Table 3.1). Most of the training interventions included in these studies were very distinct, which makes it somewhat difficult to make any definitive conclusions about the most effective training methods for increasing Kleg and Kjoint, but there are some general trends noted across studies which warrant discussion. Table 3.1 Summary of studies that have determined the effects of training interventions on global lower-limb stiffness measures Study Subjects Training programme overview Training duration Result Toumi et al. (2004) 8 male handball players 6 × 10 reps of leg press at 70% 1RM 6 weeks (4 No change in sessions/week) Kleg (CMJ) Cormie et al. (2010) 8 strengthtrained males 7 × 6 reps of jump squat at 0% 1RM (2 sessions) + 3 × 5 reps of jump squat at 30% 1RM (1 session) 10 weeks (3 Increase in Kleg sessions/week) (CMJ) Cormie et al. (2010) 8 strengthtrained males 3 × 3–6 reps of back squat at 75–90% 1RM 10 weeks (3 Increase in Kleg sessions/week) (CMJ) Hunter and 14 males Marshall (mixed (2002) sports) 1–4 × 3–8 reps of CMJs, 1–2 × 6–10 reps of DJs (30–90 cm) & 2–3 × 6–10 reps of deadlift/squat at 60–100% 1RM 10 weeks (2 Increase in Kleg sessions/week) (CMJ) Decrease in Kleg (DJ 30, 60 and 90 cm) Millet et al. (2002) 7 male triathletes 3–5 × 3–5 reps of hamstring curl, leg press, seated press, parallel squat, leg extension, and heel raise at >90% 1RM 14 weeks (2 No change in sessions/week) Kleg (hopping) Increase in Kleg (running) Arabatzi and Kellis (2012) 9 physically active males 4–6 × 4–6 reps of power clean, snatch, clean and jerk, high pull, half-squat at >85% 1RM 8 weeks (3 Increase in Kleg sessions/week) (DJ 20 and 60 cm) Arabatzi and Kellis (2012) 9 physically active males 4–6 × 4–6 reps of leg press, leg curl, leg extension, bench press, half-squat of at >85% 1RM 8 weeks (3 Increase in Kleg sessions/week) (DJ 20 cm)Decrease in Kleg (DJ 60 cm) Toumi et al. (2004) 8 male handball players 6 × 10 reps of leg press at 70% 1RM and 3 × 5 reps of crossover jump 6 weeks (4 Increase in Kleg sessions/week) (CMJ) 1RM, one repetition maximum; CMJ, countermovement jump; DJ, drop jump; Kleg, leg stiffness; Kankle, ankle stiffness. Study Subjects Training programme overview Kubo et al. (2007) 24 5 × 10 reps of unilateral hopping 12 weeks (4 Increase in and DJs (20 cm) at 40% 1RM sessions/week) Kankle (DJ 20 cm) Kubo et al. (2007) 24 physically active males 5 × 10 reps of unilateral calf physically raise at 80% 1RM active males Training duration Result 12 weeks (4 No change in sessions/week) Kankle (DJ 20 cm) 1RM, one repetition maximum; CMJ, countermovement jump; DJ, drop jump; Kleg, leg stiffness; Kankle, ankle stiffness. Generally, traditional resistance exercises performed individually with ≤80% one repetition maximum (1RM) tended not to increase Kleg and Kjoint (Toumi et al., 2004; Kubo et al., 2007), unless performed concurrently with plyometric exercises (Toumi et al., 2004). Individual traditional compound resistance exercises can increase Kleg, however, if performed with a relative load of up to 90% 1RM (Cormie et al., 2010). Multiple traditional resistance exercises performed with ≥85% 1RM have been shown to increase task-specific Kleg (Millet et al., 2002; Arabatzi and Kellis, 2012). For example, the results presented by Millet et al. (2002) showed increased Kleg measured during running but not during hopping at 2.0 Hz. These taskspecific differences in Kleg seen post-intervention are most likely due to the training programme being knee-dominant (Table 3.1) in light of Kknee being the primary modulator of Kleg during running (Arampatzis et al., 1999; Kuitunen et al., 2002) and Kankle being the primary determinant of Kleg when hopping at 2.0 Hz (Farley et al., 1998; Hobara et al., 2011). Contrastingly, the training programme included in the study by Arabatzi and Kellis (2012) was also knee-focused (weightlifting or traditional compound resistance training), although Kleg increased during DJs performed from 20 but not 60 cm, despite the latter drop height being more synonymous with Kknee regulation (Arampatzis et al., 2001b); this is possibly due to the relatively short training duration of 8 weeks. Similarly, moderate–heavy (60–100% 1RM) traditional compound resistance exercise performed concomitantly with plyometric exercises increased Kleg during countermovement jump performance, but reduced Kleg during DJs performed from ≥30 cm drop heights (Hunter and Marshall, 2002). However, the participants tested by Hunter and Marshall (2002) had never performed any structured plyometric training prior to the commencement of the study nor were they given any verbal instructions either before or during the jump performances, which may have influenced these findings. In contrast to the contradictory Kleg and Kjoint adaptations brought about via traditional compound resistance-training interventions mentioned above, all training programmes that included plyometric, ballistic or weightlifting exercises increased Kleg and Kjoint (Kubo et al., 2007; Cormie et al., 2010; Arabatzi and Kellis, 2012). The differential adaptations to Kleg and Kjoint following different exercise modalities and intensities have been attributed to the different mechanisms that modulate MTS attainment. For example, heavy resistance training (≥80% 1RM) leads to greater strength (i.e. muscle force) capacity and although muscle strength is not a direct measure of muscle stiffness it can be thought of as a proxy for stiffness (Pearson and McMahon, 2012). Additionally, tendon stiffness is related to the forceproducing capacity of the muscle (Muraoka et al., 2005; Arampatzis et al., 2007) and, as has been shown in several studies, tendon stiffness increases in response to traditional resistance training, in addition to isometric and eccentric-focused training (refer to the systematic review and meta-analysis on this topic by Bohm et al., 2015). Alternatively, enhanced muscle recruitment strategies (commonly associated with plyometric training and weightlifting: Chimera et al., 2004; Arabatzi and Kellis, 2012) may explain increased post-training Kleg and Kjoint (Taube et al., 2012), as muscle strength and tendon stiffness generally do not increase following plyometric training (Kubo et al., 2007; Bohm et al., 2015) unless performed with a very high volume (Fouré et al., 2010, 2011). The mixed results of training studies presented in Table 3.1, particularly when interpreted alongside the underpinning mechanisms for MTS adaptation, highlight the efficacy of including both traditional resistance (i.e. strength) and power-focused exercises in a training programme designed to increase MTS. Traditional compound resistance exercises, particularly when utilised by relatively weak athletes, should be performed for at least 8–12 weeks as this is the minimum time likely needed to induce increases in tendon stiffness, despite muscle strength gains occurring from as soon as 4 weeks (Kubo et al., 2010, 2012). If an athlete is relatively strong then it may be prudent to include low-load SSC tasks alongside traditional resistance exercises (particularly as they progress through the training weeks) to facilitate the previously mentioned enhanced muscle activation strategies that can be gained through this (Chimera et al., 2004). Because increases in muscle strength generally outweigh increases in tendon stiffness, due to the differential time-course of adaptation of these structures to resistance training (Kubo et al., 2010, 2012), moderate–highload SSC tasks performed too early may lead to excessive strain of the lower-limb tendons (McMahon et al., 2013a), thus these should be avoided until at least after the 12-week resistance-training period, unless the athlete is deemed to be ‘strong’ (see Chapter 2) and is used to performing such SSC tasks. A recent study suggested that the magnitude of Kleg adaptations to training (plyometric training, in this case) is sports-specific, with taekwondo athletes demonstrating a 31% post-training increase in Kleg, but rhythmic gymnasts showing no significant change (Dallas et al., 2020). 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Aside from short (<30-s) single bursts of maximal effort, a large proportion of the energy generated for skeletal muscle contraction is derived using aerobic metabolic processes. The necessity to possess high levels of aerobic fitness is perhaps obvious in endurance sports, such as distance running, road cycling, and rowing, where continuous efforts can last from several minutes to many hours. In intermittent sports, the ability to display high levels of maximal power and engage in frequent changes in speed is at least as important as the aerobic performance of athletes. In the chaotic and unpredictable environment of an intermittent sport, it is the rapid recovery of anaerobic substrates and transient kinetics of oxygen consumption that more accurately describe the relevance of aerobic fitness. Furthermore, while many intermittent sports may appear similar in terms of the duration of play and the distribution of effort, there are important differences, such as the size of the playing area, unique positional demands, and the rules that govern play. These factors influence the degree to which aerobic fitness is important relative to other physical qualities and therefore the time that a strength and conditioning (S&C) coach devotes to development of aerobic fitness. The aim of this chapter is to explore the components of aerobic fitness and the main factors that limit each component, to enable S&C coaches to design appropriate training practices to enhance these capabilities in their athletes. Moreover, for the S&C coach working with endurance athletes, an appreciation of the physiological determinants limiting performance and the typical training practices athletes engage with is also vital. SECTION 1 Bioenergetics of exercise To produce energy within the muscle cell, adenosine triphosphate (ATP) is broken down by ATPase enzymes to adenosine diphosphate (ADP) and inorganic phosphate (Pi). At the onset of a forceful muscular contraction, the ATP utilisation rate in the involved skeletal muscle can increase 1000fold, compared to at rest. Despite this sudden and rapid increase in the demand for energy during exercise, ATP never gets close to being fully depleted in muscle cells due to the tight coupling between the rate of ATP hydrolysis and ATP synthesis. The three pathways for ATP synthesis in skeletal muscle are: (1) phosphorylation of ADP to ATP using phosphocreatine (PCr); (2) anaerobic glycolysis; and (3) oxidative phosphorylation in the mitochondria. PCr is broken down into creatine and a phosphate that can be transferred to the ADP molecule to resynthesise ATP using the creatine kinase enzyme as the catalyst. In skeletal muscle, the activity of creatine kinase is quite high and energy can be produced rapidly; however, the capacity of the system is very low (<10-s maximal work). At the onset of exercise, glucose (derived from muscle glycogen) is converted to glucose-6-phosphate and subsequently to pyruvic acid, which in the absence of oxygen reduces to lactic acid, a process that also resynthesises two molecules of ATP. This anaerobic glycolytic process generates ATP at a slower rate than the PCr pathway, but has a far greater capacity, so is the predominant pathway for up to around a minute of near-maximal exercise. Lactic acid dissociates to lactate and hydrogen ions, with the latter implicated in the inhibition of key regulatory enzymes associated with glycolysis. Lactate that diffuses into the blood provides a useful indication of the activation of the anaerobic glycolytic system (i.e. exercise intensity) and the remainder is largely oxidised in the muscle and other tissues. However, there is still a widely held belief that lactic acid causes fatigue, which is inaccurate (Brooks, 2001). In the presence of oxygen, pyruvate is converted to acetyl coenzyme-A, which forms the major entry point for metabolic fuels (fat and carbohydrate) into the tricarboxylic acid (or ‘Krebs’) cycle in the mitochondria. The Krebs cycle degrades acetyl coenzyme-A to carbon dioxide and hydrogen, plus resynthesises one molecule of ATP. The hydrogen atoms subsequently enter the electron transport chain that uses oxidative phosphorylation to yield 38 ATP molecules from glucose metabolism, or 130 ATP from a fatty acid. Clearly the only energy pathway with the capacity to support prolonged exercise is the aerobic system. The three energy systems described above are often considered as a hierarchy, which is only appropriate if the relative total capacities for ATP generation are considered; however, the metabolic response to exercise relies on input through all three pathways that occurs simultaneously. Rather, the extent to which each pathway is being utilised is primarily dependent upon the demand for ATP turnover, i.e. the intensity of exercise. The contribution of oxidative phosphorylation to the energy required for a single maximal sprint is negligible; however, when sprints (≤10 s) are repeated with short recovery periods (≤60 s), the aerobic contribution increases with time (Gaitanos et al., 1993). Possessing a higher level of aerobic fitness, therefore, tends to be associated with a lower fatigue index, better repeated sprint ability (Girard, Mendez-Villanueva and Bishop, 2011), and a higher relative contribution of oxidative metabolism to each sprint (Balsom et al., 1994). Crucially, resynthesis of PCr is an oxidative process and therefore PCr recovery kinetics between repeated maximal efforts is highly sensitive to oxygen availability (Haseler, Hogan and Richardson, 1999). Additionally, Pi accumulation is considered to be a major cause of fatigue during repeat sprint work, with aerobic endurance training thought to enhance the rate of Pi removal during recovery periods (Yoshida and Watari, 1993; Hogan, Richardson and Haseler, 1999). Components of aerobic fitness An athlete’s aerobic fitness is dependent upon the following physiological constructs: maximal oxygen uptake (V̇O2max), exercise economy, lactate threshold, fractional utilisation, critical power/speed, and oxygen uptake kinetics. All of these components of aerobic fitness are required to varying degrees depending upon the oxidative nature of the event an athlete is preparing for. For example, performance in long-distance running and road cycling is heavily reliant on exercise economy and the speed that athletes can sustain at lactate threshold. For intermittent sports, V̇O2max represents the ‘gold-standard’ measure of aerobic fitness and coaches would be best served prioritising development of this component. A detailed understanding of each aerobic capability is therefore required for S&C coaches who work with both endurance and intermittent sport athletes; however, it is noteworthy that the aerobic contribution to continuous events lasting 1–3 min is also substantial (Gastin, 2001). Maximal oxygen uptake V̇O2max reflects the combined ability of the pulmonary, cardiovascular, and muscular systems to uptake, transport, and utilise oxygen in the mitochondria of working muscles, respectively (Poole and Jones, 2017). It is well established that V̇O2max is a key determinant of both middle-distance (e.g. Cosgrove et al., 1999; Ingham et al., 2008; Blagrove, Howatson, et al., 2019) and long-distance endurance performance (e.g. Coyle et al., 1991; O’Toole and Douglas, 1995; Bassett and Howley, 2000), therefore the objective for all endurance athletes should be to maximise their aerobic power. Although V̇O2max is undoubtedly important for any endurance athlete, well-trained athletes have a time to exhaustion at 100% of V̇O2max of 5–10 min (Billat et al., 1994). Therefore, the proportional contribution of V̇O2max to events that fall within (or close to) this window of time, such as Olympic rowing and 3-km running, is higher than other aerobic fitness components. In a laboratory setting with individuals who are familiar with aerobic exercise, V̇O2max is assessed using a continuous incremental test that begins at a moderate intensity and progresses to a severe intensity, ideally over 6– 12 min, until volitional exhaustion is reached. Expired air is collected during the test and analysed for concentrations of oxygen and carbon dioxide to determine V̇O2max, defined as a mathematical plateau in oxygen uptake occurring shortly before exhaustion is reached (Poole and Jones, 2017). This should coincide with a heart rate that is within 10% of agepredicted maximum (220 − age in years). The linear relationship that exists between oxygen uptake and intensity at submaximal work rates and the ensuing plateau in oxygen uptake that occurs at exhaustion are shown in Figure 4.1. In a field-based setting, the multi-stage fitness test (Léger et al., 1988) and yoyo level 1 intermittent recovery test (Bangsbo, Iaia and Krustrup, 2008) provide valid and reliable alternatives that enable prediction of V̇O2max in healthy individuals. Relationship between intensity and oxygen uptake response during an incremental test. Oxygen uptake during the early stages of the test represents exercise economy and the plateau in oxygen uptake represents maximal oxygen uptake (V̇O2max). In this hypothetical example, two athletes with the same V̇O2max (dashed line) may differ in terms of their exercise economy and power at V̇O2max (dotted lines). V̇ The Fick equation defines that V̇O2max is the product of maximal cardiac output (stroke volume × heart rate) and the difference in oxygen concentration between arterial and venous blood. This suggests that adaptations underpinning an improvement in V̇O2max could be a consequence of either central (oxygen delivery by cardiovascular system) or peripheral (oxygen extraction at muscular level) mechanisms (Levine, 2008). Central mechanisms relating to increases in blood volume, red blood cell mass, and stroke volume largely explain inter-individual variability in V̇O2max values and correlate well with improvements after training (Montero, Diaz-Cañestro and Lundby, 2016). Although theoretical models (Wagner, 2015) suggest improvements in V̇O2max may be partly explained by peripheral factors such as augmented capillarisation and increases in size and density of mitochondrial content, there is little experimental evidence indicating these mechanisms limit oxygen extraction. Circulatory factors (total oxygen-carrying capacity of blood) therefore appear to be the dominant factor underlying improvements in V̇O2max (Lundby, Montero and Joyner, 2017). As both replenishment of PCr and the removal of intracellular Pi are oxygen-dependent processes, it is unsurprising that many studies have observed a relationship between V̇O2max and performance decrements during repeated sprinting (e.g., McMahon and Wenger, 1998; Bishop and Edge, 2006; Rampinini et al., 2009). However, other studies have noted low associations between V̇O2max and the drop-off in power/speed during repeated sprint tasks (e.g., Bishop, Lawrence and Spencer, 2003; Silva, Guglielmo and Bishop, 2010; Dardouri et al., 2014). The reasons for the discrepancies are likely to relate to the work-to-rest ratios employed in the studies, with higher ratios (or shorter sprint distances) generally showing weak associations compared to lower work-to-rest ratios. Furthermore, as V̇O2max largely reflects the ability of the cardiovascular system to deliver oxygen, recovery from sprints may be more closely governed by respiration at the muscle level (Girard, Mendez-Villanueva and Bishop, 2011). Figure 4.2 provides V̇O2max scores for elite endurance athletes, which represent the upper limits for human aerobic power (Haugen et al., 2017), and reference values for other sports plus the 50th percentiles for healthy adults. Elite male endurance athletes tend to possess V̇O2max values of >75 mL kg−1 min−1 and their female counterparts >65 mL kg−1 min−1, which is virtually double that of age-matched sedentary controls. Exercise modality impacts measurements of V̇O2max due to variations in the total muscle mass involved, hence elite cross-country skiers tend to have higher V̇O2max values than world-class cyclists. Although V̇O2max is highly trainable, it is believed to have a strong genetic component (Bray et al., 2009). In elite endurance athletes, V̇O2max values are likely to be close to the genetic ceiling, and therefore tend to be similar and poor at explaining the interindividual variability in performances (Conley and Krahenbuhl, 1980). Therefore, understanding and improving other components of aerobic fitness are also important. Maximal oxygen uptake values for male and female elite endurance athletes, elite athletes from selected intermittent sports, and healthy individuals (20– 40 years old) from the population (50th-percentile values from several studies shown; Kaminsky, Arena, and Myers, 2016). Population-level descriptors for aerobic training status are also shown (Winter et al., 2006). Shaded boxes for elite intermittent sport athletes represent typical maximum and minimum values reported. Numbers within brackets reflect the mean values reported in a review paper or across several original papers. MMA, mixed martial arts. (Data taken from: Powers and Walker, 1982; Jones, 2006; Montgomery, 2006; Kovacs, 2007; Saltin et al., 2007; Berthelot et al., 2008; Burr et al., 2008; Ziv and Lidor, 2009; Burtscher, Nachbauer and Wilber, 2011; Gilenstam, Thorsen and Henriksson-Larsén, 2011; Lenetsky and Harris, 2012; Manchado et al., 2013; Ransdell, Murray and Gao, 2013; Datson et al., 2014; Phomsoupha and Laffaye, 2015; Chaabène et al., 2015; Tønnessen et al., 2015; Bell et al., 2017; Blagrove, Howatson and Hayes, 2017; Haugen et al., 2017; Solli, Tønnessen and Sandbakk, 2017; Rønnestad et al., 2019; Slimani et al., 2019; Spanias et al., 2019.) Exercise economy and mechanical efficiency Exercise economy refers to the oxygen or energy cost of performing exercise at a submaximal intensity. To obtain a valid measurement of economy in an athlete, a ‘steady state’ of oxygen uptake is required, therefore only moderate intensities of exercise are appropriate for testing. More economical athletes will use less energy to complete a given amount of physical exercise, and thus can rely on a greater relative contribution from aerobic metabolism for longer, thereby delaying fatigue. Exercise economy should not be confused with ‘exercise efficiency’, although in a colloquial sense the terms are often used interchangeably. Whereas economy is usually quantified physiologically using oxygen consumption and substrate utilisation values, efficiency is a mechanical term that refers to the effective external work that is performed as a percentage of the total energy expended to produce that work. Unlike other physiological components of aerobic fitness that are predominantly limited by cardiovascular and metabolic processes, exercise economy is also influenced by biomechanical, anthropometric, neuromuscular, and technological factors (Figure 4.3). Crucially, several of these factors are modifiable with appropriate S&C coaching and training interventions. Specifically, biomechanical factors that relate to how force is modulated during a sports skill can potentially be altered with S&C practices. For example, gait re-training approaches may improve running economy (Moore, 2016), and weightlifting derivatives offer a means of developing appropriate movement sequencing for enhancing rowing efficiency (Soper and Hume, 2004). Neuromuscular factors relating to the rate and magnitude of muscle activation, and contribution of passive structures to elastic energy storage and return (i.e., tendon stiffness), are also known to influence the behaviour of force–length–velocity properties of muscles, thereby affecting energy turnover (Fletcher and MacIntosh, 2017). Indeed, eccentric strength, maximal strength and rate of force development have been shown to relate to better running economy (Barnes, McGuigan and Kilding, 2014; Li et al., 2021) and cycling efficiency (Sunde et al., 2010; Louis et al., 2012). Although a high V̇O2max is considered a prerequisite for elite endurance performance, in a group of highly trained athletes with similar V̇O2max scores, exercise economy or efficiency is a far better predictor of performance (Conley and Krahenbuhl, 1980; Lucía et al., 1998; Ainegren et al., 2013). Inter-individual variation in exercise economy can be as high as 30% in groups of endurance athletes with comparable V̇O2max values, and improvements in economy appear to be closely related to performance improvements (Beneke and Hütler, 2005; Saunders et al., 2010; Hoogkamer et al., 2016). Furthermore, case studies of the former world-record holder for the women’s marathon (Jones, 2006) and a former elite cyclist (Coyle, 2005) show that V̇O2max remained relatively stable over long periods of time (7–11 years), yet economy/efficiency continued to improve and could explain performance progression. Factors that influence an athlete’s exercise economy with examples. The lactate threshold and fractional utilisation At low–moderate relative exercise intensities, the contribution of anaerobic processes to energy provision is negligible, therefore blood lactate remains similar to resting values. Figure 4.4 shows that as exercise intensity continues to rise and the demand for energy increases, blood lactate rises exponentially, reflecting greater reliance on the anaerobic glycolytic pathway. An athlete’s power (or speed) at fixed blood lactate concentrations, or blood lactate for a given power output, is an important predictor of aerobic endurance (Steinacker, 1993; Yoshida et al., 1993; Bentley et al., 2001) and repeated sprint performance (Silva, Guglielmo and Bishop, 2010). The lactate threshold is represented by the first rise (>0.2 mmol L−1) in blood lactate (1–2 mmol L−1) from baseline (Jones, Carter and Doust, 1999; Figure 4.4, panel i), which in well-trained endurance athletes represents an intensity that can be sustained for hours. The proportion of V̇O2max that an athlete can access and maintain for long periods is referred to as ‘fractional utilisation’, and is also an important factor in endurance performance (Maughan and Leiper, 1983). For example, elite marathon runners can sustain ~85% of their V̇O2max for the duration of the event, whereas recreational-level runners are closer to 60% (Sjodin and Svedenhag, 1985; Jones, 2006). An athlete’s lactate threshold corresponds closely with the fractional utilisation of V̇O2max that can be sustained for a given duration (Bassett and Howley, 2000), therefore an increase in power or speed at lactate threshold also allows a greater proportion of maximal aerobic power to be accessed. A shift to the right of the lactate curve (Figure 4.4, panel i) represents an improvement in performance, which is primarily underpinned by metabolic adaptations relating to an ability to buffer and clear metabolites from the blood (Jones and Carter, 2000). Power at maximal oxygen uptake Although V̇O2max and exercise economy are highly useful physiological parameters, they are of limited practical use to athletes because they fail to provide a meaningful expression of power that can be used to prescribe training and predict performance. Power (or speed) at V̇O2max (also known as ‘maximal aerobic speed’: MAS) provides a composite measure of V̇O2max and exercise economy based upon the economy–intensity relationship extrapolated to the V̇O2max value. As shown in Figure 4.1, an athlete with superior (lower) economy at a range of submaximal intensities who possesses a similar V̇O2max to another athlete is likely to have a superior speed at V̇O2max. As V̇O2max represents a ceiling of an individual’s aerobic metabolic power, a poor value will also generate a weak power at V̇O2max score. The amalgamation of two important physiological qualities into this single determinant appears to more accurately differentiate performance in well-trained runners (Stratton et al., 2009; McLaughlin et al., 2010) and elite rowers (Ingham et al., 2002) compared to other components of aerobic fitness. Power at V̇O2max is usually defined as the minimal power output that elicits V̇O2max (Billat and Koralsztein, 1996). It can be determined directly based upon the results of an incremental test to exhaustion, as shown for the two athletes in Figure 4.1. If V̇O2max is determined using an alternative method (e.g., increasing treadmill gradient), the oxygen uptake–intensity relationship from a submaximal incremental test can be extrapolated, and power/speed at V̇O2max calculated by rearranging the linear regression equation. MAS can also be estimated in a field-based setting using a 5-min running test (Berthon et al., 1997), or by applying the following equation to the result of the multi-stage fitness test (for adults): MAS = 1.81 × final shuttle stage – 7.86 (Berthoin et al., 1992). Physiological profile and training zones for an elite male endurance runner. Panel (i) displays results of a submaximal incremental treadmill running test, which can be used to identify lactate threshold (dotted line) and the corresponding heart rate zone for moderate-intensity continuous training for this athlete (<162 beats min−1). Speed at maximal oxygen uptake (V̇O2max), determined from a maximal test, is also shown (23.1 km h−1) along with maximal (‘max’) heart rate. Speeds above V̇O2max are considered in the ‘extreme’ exercise domain. The typical running speeds where exercise economy would be quantified are also displayed. Panel (ii) displays the speed–duration relationship based upon the athlete’s best race performances (800 m to 5 km) at the time of testing. The hyperbolic relationship is plotted, with critical speed represented by the horizontal asymptote (dashed line; 20.8 km h−1). This critical speed is identified in panel (i) to demarcate the boundary between the heavy-intensity and severe training zones (181 beats min−1). Work performable at any speed above critical speed is represented by W′. Panel (iii) shows the hyperbolic relationship between running speed and time linearised by plotting running speed against 1/time, where the y-axis intercept represents critical speed and the gradient of the slope represents W′. Critical power and W′ Between the lactate threshold and power/speed that elicits V̇O2max lies a physiological threshold that generates the maximal sustainable oxidative metabolic rate, which is an important prerequisite for predicting performance and guiding training decisions (Jones and Carter, 2000). The literature is awash with a plethora of terms and definitions to identify the maximal metabolic steady state, such as ‘maximal lactate steady state’, various ventilatory thresholds, ‘lactate turn-point’, ‘anaerobic threshold’, ‘D-max’ threshold, and ‘onset of blood lactate accumulation’ (Jones et al., 2019). Crucially, these terms represent different physiological events and processes and therefore do not provide a valid reflection of the maximal metabolic steady state that is attainable by an athlete (Jamnick et al., 2018; Jones et al., 2019). The critical power (or speed) model represents exercise tolerance at the boundary between the heavy- and severe-intensity domains (Figure 4.4). Two main parameters can be assessed using the critical power model, which is defined as the curvilinear relationship between power output and time to exhaustion in the severe-intensity domain. Firstly, critical power itself is widely recognised as the most important fatigue threshold in exercise physiology, and represents the critical metabolic rate separating two distinct physiological domains that promote different adaptations (Poole et al., 2016). When critical power is maintained in well-trained endurance athletes, it leads to attainment of V̇O2max and ultimately exhaustion, usually in ~30–45 min (Burnley and Jones, 2007). The second parameter that can be quantified from the model is the curvature constant of the power–time hyperbola above critical power, known as W ′ (pronounced ‘W prime’), which is represented by the total distance that can be covered prior to exhaustion at a constant power output (Jones et al., 2010). Above critical power, anaerobic processes quickly begin to predominate, and provided exercise can be sustained long enough (>2 min), V̇O2max will still be attained (Vanhatalo et al., 2016). As shown in Figure 4.4 panel ii, the magnitude of the difference between critical power/speed and actual power/speed will dictate the size of W′ and therefore the rate at which the finite work capacity will be utilised. Critical power is a strong determinant of endurance cycling performance (e.g., Black et al., 2014; Morgan et al., 2019) and middle-distance running performance is strongly related to critical speed models in trained runners (Bosquet et al., 2006). Recently, the critical power concept has been broadened to intermittent exercise, which may have important implications for the real-time monitoring of fatigue and residual performance capacity in game sports (Jones and Vanhatalo, 2017). Knowledge of an athlete’s critical power and W′ enables a coach or exercise physiologist to calculate sustainable speeds or accurately predict tolerance limits in the severe-intensity domain, thereby informing tactics, positioning, and pacing strategies to optimise performance. Critical power and W′ are traditionally generated by recording the average power and time to exhaustion for four or five separate high-intensity constant work-rate exercise bouts in the severe exercise domain that each last between 2 and 15 min (Figure 4.4, panel ii). Alternatively, if recent race performances are available for three or more events that take between 2 and 15 min to complete, these can also be used. This enables the power–time hyperbolic relationship to be plotted and the asymptote (levelling off) of the curve to be calculated, which represents critical power. A less complicated and more user-friendly strategy to identify the critical power value is shown in Figure 4.4, panel iii. The curvilinear power–time relationship can be expressed linearly by plotting power/speed against 1/time. The relationship is described using the regression equation y = mx + c, where the slope is m and represents W′, and c is the intercept with the y-axis and identifies critical power. The method described above requires exhaustive exercise bouts to be completed over multiple days with sufficient recovery, which can be time consuming. An alternative 3-min all-out single-bout test has fortunately been validated using cycle ergometry (Burnley, Doust and Vanhatalo, 2006; Vanhatalo, Doust and Burnley, 2008) and running (Broxterman et al., 2013). A further popular index of aerobic fitness that S&C coaches working with cyclists may encounter is the ‘functional threshold power’ (FTP), which is calculated as 95% of the mean power sustained during a 20-min time trial, and estimates the power sustainable for ~1 hour (Gavin et al., 2012). Although the FTP is often used interchangeably with critical power in the coaching community, the validity of this is questionable (Morgan et al., 2019). Oxygen uptake kinetics The aforementioned aerobic fitness components represent key determinants of endurance performance; however, they do not describe the dynamic and instantaneous nature of energy transfer that occurs during intermittent sports, nor in endurance events where the pace and terrain vary (Burnley and Jones, 2007). The oxygen uptake kinetic response refers to the rate at which oxygen consumption rises during exercise to meet the required energy demand via oxidative phosphorylation (Figure 4.5). At the onset of exercise (or a repeat sprint), there is a short delay in the oxygen uptake response followed by a sharp exponential rise (‘fast component’) until the demand for energy is met (defined by a plateau in oxygen uptake). Above moderate intensities of exercise approaching critical power, a ‘slow component’ in oxygen uptake will also be observable; this is characterised by an upward drift in oxygen consumption over a prolonged period. Exercise at the upper end of the extreme zone, which is highly anaerobic and leads to exhaustion before V̇O2max is attained, is characterised by a single-exponential profile that describes the fast component only. Oxygen uptake kinetics during moderate- (dotted line), heavy- (dashed line), and severe-intensity (hatched-line) exercise. The time constant that defines the exponential rise in oxygen uptake at the onset of exercise (‘fast exponent’) dictates the oxygen deficit during moderate-intensity exercise. Heavy-intensity exercise is characterised by oxygen uptake continuing to rise beyond ~2 min, albeit at a reduced rate (‘slow component’). Quantification of exercise economy is only valid when there is an absence of a slow component (‘steady state’). Oxygen uptake continues to rise rapidly during severe-intensity exercise until maximal oxygen uptake is reached. During high-intensity exercise at the upper end of the severe-intensity zone (e.g. <1min sprints), only a fast component in oxygen uptake kinetics would be observable. A more rapid oxygen uptake kinetic response enhances muscle metabolic stability, accompanied by a lower oxygen deficit, thereby offsetting fatigue. Oxygen uptake kinetics is an important determinant of endurance performance (Burnley and Jones, 2007; Jones and Burnley, 2009), and longer-distance endurance athletes seem to possess faster oxygen uptake responses compared to middle-distance athletes matched for competitive status (Kilding, Winter and Fysh, 2006). As alluded to previously, the ability to recover sprint ability during intermittent sports performance is largely dependent upon the recovery of PCr and metabolites associated with fatigue, which are governed by oxidative processes. Faster oxygen uptake kinetics to exercise of severe intensity is associated with smaller decrements in repeated sprint performance (Dupont et al., 2005, 2010; Rampinini et al., 2009), although it has been suggested that this correlation is spurious, and it is aerobic fitness (V̇O2max) rather than metabolic control that governs the relationship (Buchheit, Hader and Mendez-Villanueva, 2012). Certainly, endurance training, which increases oxygen transportation and delivery, capillarisation, mitochondrial density, oxidative enzyme activity, and muscle perfusion, has also been shown to improve V̇O2max and oxygen uptake kinetics (Phillips et al., 1995; Koppo, Bouckaert and Jones, 2004). A large body of work has illustrated the importance of the warm-up for acutely enhancing oxygen uptake kinetics (Jones et al., 2011). In particular, a warm-up that includes a short period of high-intensity activity (60–85% of peak power output) lasting 3–6 min is sufficient to positively influence subsequent endurance performance via an improvement in oxygen uptake kinetics at the onset of exercise (e.g., Gurd et al., 2006; Bailey et al., 2009; Mattioni Maturana et al., 2018). Several studies have also investigated the effects of high-intensity intermittent and single-sprint approaches to enhancing the oxygen uptake response at the start of exercise (Burnley, Doust and Jones, 2002; Bishop, Bonetti and Spencer, 2003; McIntyre and Kilding, 2015). For example, when compared to a continuous warm-up of lower intensity, a priming protocol involving 5 × 10-s near-maximal sprints (50 s recovery) has been shown to enhance kayak 2-min time trial performance by a small but significant margin (Bishop, Bonetti and Spencer, 2003). SECTION 2 Strategies to develop aerobic fitness Based upon an understanding of the physiological factors that limit endurance performance, several key thresholds emerge that can clearly demarcate aerobic training zones for athletes (Figure 4.4, panel i): Moderate zone: intensities below the lactate threshold Heavy zone: intensities above the lactate threshold and below critical power/speed Severe zone: intensities above critical power/speed and below power/speed at V̇O2max Extreme zone: intensities above power/speed at V̇O2max. A schematic displaying the main strategies to develop the components of aerobic fitness for various sports, including recommendations for exercise prescription, is shown in Figure 4.6. Discussion of repeat sprint training and peri-maximal sprint interval training is beyond the scope of this chapter as the physiological demands are largely associated with anaerobic metabolism and neuromuscular factors (see Chapter 5). Repeat sprint training is characterised by bouts of maximal effort (≤10 s) interspersed by incomplete recoveries (≤60 s) to mimic sports-specific scenarios (Girard, Mendez-Villanueva and Bishop, 2011). Sprint training requires full interrepetition recovery to ensure that close to absolute maximal power/speed can be achieved in each repetition. For competitive long-distance athletes, the sprint at the end of an event often determines the winner. It is a misconception that high volumes of endurance training cause athletes to lose their explosive power/speed; rather, it is the lack of stimulus directed towards maintaining (or indeed improving) this capability that causes the deterioration (Mujika and Padilla, 2000). It is therefore important that endurance athletes include a small amount of maximal power/speed training in their programme year-round (Sandford et al., 2019), and this can form part of S&C sessions (Blagrove, Howe et al., 2020). Training strategies and recommended exercise prescription to develop aerobic fitness components for various categories of sports. %HRmax, percentage of maximum heart rate; V̇O2max, maximal oxygen uptake. Continuous moderate-intensity training Continuous exercise performed at a moderate intensity (below lactate threshold; <75% maximum heart rate; <70% power/speed at V̇O2max) is usually prolonged (30 min to several hours) in nature and represents an important mode of training for endurance athletes (Midgley, McNaughton and Jones, 2007). Exercise in this domain enhances stroke and plasma volume, and increases capillary and mitochondrial density that improves the efficiency of metabolic processes and V̇O2max (Holloszy and Coyle, 1984; Hellsten and Nyberg, 2015). This training zone is used extensively by endurance athletes for ‘easy’ active recovery training, which punctuates more intensive interval training workouts (Seiler, 2010), but has less functional relevance for intermittent sport performers. It has been recognised that endurance training history is an important factor determining superior exercise economy (Morgan et al., 1995) and several case reports have demonstrated continued improvement in exercise economy or efficiency over long periods of time with increased volume of aerobic training, despite little alteration in V̇O2max (Conley et al., 1984; Coyle, 2005; Jones, 2006). A recent meta-analysis has also shown that continuous training is more effective than interval training for improving exercise economy in recreational endurance runners (González-Mohíno et al., 2020). Furthermore, recreational runners possess higher stride-to-stride movement variability, more inconsistent muscle recruitment patterns, and longer durations of muscle activity compared to moderately trained runners (Chapman et al., 2008). These factors suggest an inferior level of motor control in lesser-trained endurance athletes, which is in line with findings from across the motor learning literature showing that long-term practice of a skill decreases movement variability, and results in reduced amplitude and duration of muscle activity, thus improving exercise economy (Thoroughman and Shadmehr, 1999; Osu et al., 2002). Tempo training An intensity of exercise that falls above the lactate threshold but below critical power (Figure 4.4) is often colloquially referred to as ‘steady’: too fast to be used for active recovery sessions, and too slow to stimulate meaningful cardiovascular adaptations. Exercise in the upper end of this zone, where blood lactate is increasing >1 mmol L−1 for every 1 km h−1 increase in speed (~2–4 mmol L−1), is often referred to by endurance athletes as ‘tempo’ training. Tempo sessions are usually performed continuously (20–60 min), but when the intensity approaches critical power, exercise can be performed as long intervals of 8–20 min with a short recovery, e.g., 4 × 8 min (2-min recovery). These sessions are popular with long-distance endurance athletes (e.g., marathon runners and road cyclists) as regular exposure to these intensities is slightly higher than competition power/speed and can increase lactate threshold and fractional utilisation (Midgley, McNaughton and Jones, 2007). Interval training Both continuous training and interval training (above critical power) elicit improvements in V̇O2max following a 3–24-week training intervention (Milanovic, Sporis and Weston, 2015). However, there is a large body of evidence that demonstrates interval training provides a more potent stimulus to maximise aerobic adaptations (Bacon et al., 2013; Gist et al., 2014), including in highly trained endurance athletes (Kubukeli, Noakes and Dennis, 2002; Laursen and Jenkins, 2002). A multitude of different interval training methods have been shown to enhance the components of aerobic fitness. For endurance athletes, the optimal intensity to develop aerobic fitness (specifically, V̇O2max and critical power) appears to be around power/speed at V̇O2max, which corresponds to an intensity of 90– 100% maximum heart rate (Billat and Koralsztein, 1996; Stöggl and Sperlich, 2014). Repeated sprint training (i.e., near-maximal sprints ≤ 10 s, ≤ 60 s recovery), and even maximal speed training, has been shown to improve V̇O2max in moderately trained games players (Ross and Leveritt, 2001; Bishop, Girard and Mendez-Villanueva, 2011), demonstrating that in less aerobically trained athletes, most types of interval training are likely to enhance aerobic fitness capabilities. Rather, in well-trained endurance athletes, there is a greater requirement for careful deliberation around how interval training is prescribed and progressed. Taken together, research findings suggest that the use of a 1:1 or 2:1 work-to-rest ratio optimises interval training for aerobic development, including enhancement of intermittent sports performance. For example, 8 × 2-min repetitions (1 min recovery) performed at 80–90% of V̇O2max have previously been recommended as a suitable session for improving aerobic fitness in athletes who require repeated sprint ability in their sport (Bishop, Girard and Mendez-Villanueva, 2011). A session of 4 × 4 min (3 min active recovery) at 90–95% maximum heart rate has also been advocated for soccer players (Helgerud et al., 2001). ‘Tabata’ sessions have been popularised over the last 20 years due to their time efficiency (4 min of high-intensity exercise), and involve 20-s bouts of exercise with 10 s recovery, repeated eight times, and performed at 115–130% of the power/speed associated with V̇O2max (Tabata et al., 1996; Viana et al., 2018, 2019). Other session examples from peer-reviewed publications that have reported the training of gold medallists from major international championships include 4 × 6 min (1 min recovery) in a 1500-m runner (Tjelta, 2013), 5 × 4–5 min (2–3 min recovery) in a cross-country skier (Solli, Tønnessen and Sandbakk, 2017), and 10 × 1 min (~45 s active recovery) in a long-distance runner (Pugliese et al., 2014). Although these types of session are likely to be more beneficial than moderate-intensity continuous training for improving V̇O2max in athletes who are moderately aerobically trained, it is unclear which specific strategy offers the best outcome. It is likely that adaptations to longer work interval bouts (3–6 min per repetition) are more centrally (cardiovascular) derived, whereas shorter high-intensity sessions (e.g. Tabata sessions) provide greater peripheral-level adaptations. Additionally, the work-to-rest ratios suggested (Figure 4.6) by no means represent ‘the rule’, as middle-distance athletes (e.g., 400-m swimmers, rowers, 1500-m runners) will often undertake extended sprint efforts (20–40 s duration) with long recoveries (work-to-rest ratio of 1:10) within competitive phases of training to enhance event-specific speed. Manipulation of technical sport practices It has been suggested that the technical training completed by intermittent sport athletes on a regular basis is sufficient to enhance aerobic fitness (Hill-Haas et al., 2011). This has appeal because the simultaneous development of technical skills, tactical aptitude, and physiological factors is time-efficient, and could maximise motivation in sub-elite and younger athletes. Indeed, in male youth soccer players, small-sided games are an effective method for developing aerobic capabilities compared to conventional endurance training (Moran et al., 2019). Certainly, in recreational-level games players, and adolescent athletes at the specialisation stage of their development, small-sided games should be prioritised to provide concurrent improvements of aerobic fitness and technical skills (Harrison et al., 2015; Moran et al., 2019). However, in games players of higher qualification status and young athletes pursuing proficiency in their chosen sport, a combination of small-sided games and interval training is likely to offer greater benefits, particularly during offseason preparatory periods (Harrison et al., 2015). Equally, in short-burst intermittent sports where aerobic fitness is far less important than other physical attributes (e.g., rugby, baseball, cricket), technical practices are likely to provide enough stimulus to stress the metabolic systems appropriately. S&C coaches utilising small-sided games with the aim of improving aerobic fitness should consider how task constraints alter the physiological response of training. Specifically, a smaller number of involved players, a larger playing area, an absence of goalkeepers, and a rule that reduces the number of touches permitted all increase the physiological intensity in soccer games (Clemente, Martins and Mendes, 2014). Training intensity distribution in endurance athletes As discussed, interval training (in the severe- and extreme-intensity zones) has been shown to provide greater enhancements in endurance sport performance compared to moderate-intensity continuous training. Instinctively, S&C coaches will often take these findings at face value and may be tempted to level criticism at endurance athletes and their coaches for following a high-volume paradigm of training. There are several issues and caveats associated with the literature that has compared moderateversus high-intensity focused approaches in endurance athletes, and which S&C coaches should be aware of: Studies are often short in duration. High-intensity interval training has a high physiological burden, therefore frequent and excessive use of this style of exercise in the long term may lead to overtraining (Kellmann, 2010). Consequently, the findings of studies can only be applied to the duration over which the training intervention was carried out. Indeed, adding additional high-intensity interval training sessions in the 4–8 weeks prior to a major competition as part of a long-term periodised plan seems highly appropriate, and is typically the approach employed by well-trained and elite endurance athletes (Stöggl and Sperlich, 2015). Studies may be observing a ‘peaking effect’ that can be attributed to the reduction in training volume rather than the increase in intensity. In studies that have used well-trained endurance athletes, who are likely to be habitual high-volume exercisers, manipulating training towards an intensity bias approach may also act as a novel stimulus to reduce feelings of staleness (Gustafsson, Kenttä and Hassmén, 2011). Lastly, the primary dependent variables examined in studies are usually V̇O2max and time trial performance; therefore, based upon the principle of training specificity, it is likely that the training regimen that most closely matches the intensities associated with V̇O2max elicitation and time trial performance will improve the most. Often, other important aerobic fitness components are not measured as part of studies, therefore it is unknown whether a high-intensity dominant approach to training would promote these capabilities to the similar extent. Based upon this brief critique and previous discussion, it is likely that a combination of moderate-intensity continuous and high-intensity interval training sessions yield the greatest benefit to endurance performance in the long term (Seiler, 2010). Several models have emerged from the training literature in elite endurance athletes; the three main approaches are shown in Figure 4.7: Endurance training intensity distribution for three common approaches adopted by endurance sport athletes. An approach where a high proportion (75–90%) of training time is dedicated to moderate-intensity exercise, with decreasingly smaller amounts to heavy zone training (10–20%) and severe-intensity training (5–10%) has been termed a ‘pyramidal design’. A ‘threshold approach’ involves athletes spending a large portion of their total training time (35–55%) in the ‘heavy’ domain with the remainder (45–55%) largely spent in the moderate-intensity zone (Seiler and Kjerland, 2006). Lastly, a method termed the ‘polarised training’ approach consists of a high volume of moderate-intensity training (~80%), a low amount of training in the heavy domain (~5%) and 15–20% of training time in the severe and extreme domains (Stöggl and Sperlich, 2015). In the majority of observational studies, elite athletes from rowing (Fiskerstrand and Seiler, 2004), cross-country skiing (Solli, Tønnessen and Sandbakk, 2017; Rasdal, Moen and Sandbakk, 2018), cycling (Schumacher and Mueller, 2002), distance running (Jones, 2006), and paratriathlon (Mujika, Orbañanos and Salazar, 2015) tend to adopt a pyramidal approach to training, with a high volume of moderate-intensity exercise, particularly during general preparatory phases, and small amounts of high-intensity interval training. Interestingly, the majority of experimental studies (6 weeks to 5 months) in endurance performers of all levels demonstrate superior responses to a polarised training approach, especially compared to a threshold intensity distribution (see reviews: Stöggl and Sperlich, 2015; Rosenblat, Perrotta and Vicenzino, 2019). Spending high volumes of training time (>10%) in the heavy-intensity domain has been associated with diminished training gains (Munoz et al., 2014), therefore current recommendations are to avoid this ‘middle ground’ for easy recovery training volume and interval training sessions. Longitudinal retrospective reports of elite athletes and international training squads also provide evidence that a shift towards a polarised training approach characterises higher levels of performance (Fiskerstrand and Seiler, 2004; Ingham, Fudge and Pringle, 2012; Orie et al., 2014). The role of strength-training exercise with endurance athletes Strength training and aerobic endurance training are diverse exercise modalities offering vastly different functional outcomes. Endurance training (low load–high repetition) elicits largely cardiovascular and metabolic changes such as mitochondrial biogenesis and changes to substrate metabolism, whereas strength training (high load–low repetition) is associated with an increase in contractile protein content and maximal contractile force output (Coffey and Hawley, 2007). It may therefore seem counterintuitive that strength training may positively affect components of aerobic fitness and enhance endurance performance. As previously highlighted, exercise economy is partly dependent upon the intrinsic contractile energetic cost of the muscle fibres recruited during exercise, as well as the peak fibre force, shortening velocity, magnitude of fibre length change, and rate of contractions. These neuromuscular factors can potentially be positively influenced by strength-training activities. Moreover, muscular performance characteristics can be acutely enhanced as a result of their recent contractile history (Tillin and Bishop, 2009), which offers a potential for short-term improvement in endurance performance. Strength training may also play a role in offsetting the risk of overuse injury (Lauersen, Andersen and Andersen, 2018), which is common in endurance athletes, and has been cited as the most frequent reason for the inclusion of S&C in training programmes (Blagrove et al., 2020). Post-activation performance enhancement High-intensity conditioning contractions using strength-training exercises have become a popular means of acutely enhancing muscle contractile properties that benefits subsequent explosive athletic performance (Seitz and Haff, 2016). Following a low-intensity aerobic warm-up, performing a maximal or near-maximal strength exercise 5–10 min prior to a bout of aerobic endurance exercise may also be effective for enhancing performance (Blagrove, Howatson and Hayes, 2019). Indeed, a single set (5–6 repetitions) of depth jumps appears to acutely enhance running economy in high-performing adolescent middle-distance runners compared to a traditional low-intensity warm-up (Blagrove, Holding, et al., 2019). Similarly, band-resisted squat jumps (4 × 5 repetitions) have also been shown to improve performance in a session of 5 × 1-km runs (Low et al., 2019). Moreover, a series of pre-session ‘strides’ (6 × 10 s at 1500-m pace) wearing a weighted vest (20% of body mass) has also provoked an acute benefit to running economy and time to exhaustion in well-trained distance runners (Barnes et al., 2015). The early stages of both a 1-km rowing ergometer time trial and a 20-km static cycle were also significantly improved following maximal isometric contractions (5 × 5 s) and a highload leg press protocol (4 × 5 repetition maximum), respectively (Feros et al., 2012; Silva et al., 2014). In each of the aforementioned studies, welltrained or elite endurance athletes were used, and most participants possessed a background in strength training (Feros et al., 2012; Silva et al., 2014; Barnes et al., 2015; Low et al., 2019). The extent to which a postactivation performance enhancement is elicited in endurance athletes also appears closely related to the training status of the limb exposed to the conditioning stimulus (Hamada, Sale and Macdougall, 2000). Therefore, S&C coaches should consider the type of endurance athlete who may benefit from a post-activation performance enhancement warm-up protocol. Chronic strength training A large body of literature has investigated whether strength training (i.e., heavy resistance training, explosive power training, plyometrics or mixedmodality training) can improve performance and/or the physiological factors that underpin endurance events, compared to a group who only carries out aerobic endurance training (see reviews: Berryman et al., 2018; Blagrove et al., 2018; Thiele et al., 2020). In general, findings support the implementation of regular strength training as an addition to sport-specific endurance training to enhance exercise economy and performance. Typically, studies show a small–moderate benefit (2–8%) to exercise economy and performance from incorporating 2–3 sessions per week of strength training for a period of 6–14 weeks, compared to a control group (Denadai et al., 2017; Berryman et al., 2018). Most investigations that utilise resistance training as part of their strength-training intervention observe large improvements in strengthrelated metrics with little change in measures of body composition following the training period. This is important because resistance training is associated with a hypertrophy response that increases total body mass and decreases capillary density, oxidative enzymes, and mitochondrial density (Tesch, Komi and Hakkinen, 1987; Dudley, 1988), which is likely to adversely impact upon aerobic performance. Strength training-induced effects to exercise economy and performance do not appear to be moderated by strength-training type, athlete age or training status. Indeed, beneficial changes to running economy have been observed in both post-pubertal adolescent distance runners (Mikkola et al., 2007; Blagrove et al., 2018) and masters runners (Piacentini et al., 2013). Summary Possessing an understanding of aerobic fitness is important for S&C practitioners because: (1) it may be within their remit to assess and develop components of aerobic fitness when working with intermittent sports performers; and (2) when supporting endurance sport athletes, developing effective S&C practices is predicated on a familiarity with the factors that limit performance and how athletes prepare for their event. The power elicited at lactate threshold and critical power are valid physiological constructs that demarcate the boundaries between moderate–heavy and heavy–severe exercise intensity zones, respectively. These parameters, along with V̇O2max and exercise economy, provide an invaluable framework to understand and develop aerobic fitness in athletes. In intermittent sports, aerobic metabolism plays a major role in the restoration of homeostasis during the recovery periods between high-intensity efforts. Endurance training increases mitochondrial density, which enhances PCr and oxygen uptake kinetics and therefore improves intermittent sprint performance. Interval training, at a work-to-rest ratio of 1:1 or 2:1, appears to be the most potent stimulus to enhance several important aerobic fitness capabilities. However, S&C coaches should expect well-trained endurance athletes to be undertaking high volumes of aerobic training, with a large proportion of the total volume (~80%) performed at a moderate intensity. Supplementing the training of an endurance athlete with twice-weekly strength-training sessions is likely to enhance exercise economy and improve performance over a period of several months. Highly trained endurance athletes may also benefit from the inclusion of high-intensity sprints or a high-load strength exercise in the latter stages of a warm-up. References Ainegren, M. et al. 2013 Skiing economy and efficiency in recreational and elite cross-country skiers. 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European Journal of Sport Science, 9(6), 375–386. 5 Repeat sprint ability: physiological basis and implications for training Anthony N. Turner and David Bishop DOI: 10.4324/9781003044734-7 Introduction Many sports involve frequent bursts of high-intensity movements, interspersed with brief recovery intervals (consisting of complete rest or low- to moderate-intensity activity), over an extended period of time (1–4 hours) (Glaister, 2005; Spencer et al., 2005). Therefore, the ability to recover and to reproduce performance during subsequent high-intensity efforts is an important fitness requirement of athletes engaged in these disciplines and has been termed repeated-sprint ability (RSA). While many different types of training have been proposed to improve RSA, highintensity interval training (HIIT) and sprint interval training (SIT) have been suggested as a means of developing many of the factors contributing to RSA. Given the apparent importance of HIIT and SIT for developing RSA, it is important that strength and conditioning coaches have a thorough understanding of how to manipulate the programming of these to best achieve improvements in RSA. Therefore, the aims of this chapter are to: (1) provide a brief overview of the underlying physiology of repeated sprints; (2) discuss the interaction between sprint intervals (duration and frequency) and metabolic energy supply; (3) identify various approaches to HIIT and SIT programming and their physiological basis for adaptation; and, finally, (4) discuss RSA testing that can then be used to judge the efficacy of training. The metabolic demands of repeated sprints RSA requires both a high maximal sprint power and the ability to maintain high power during each subsequent sprint. A high maximal sprint power is related to the ability to deplete large amounts of high-energy phosphates at a fast rate. The human muscle stores ~25 mmol/kg dry muscle (dm) of adenosine triphosphate (ATP). With a peak ATP turnover rate of ~15 mmol/kg dm/s, that is enough to fuel 1–2 s of maximal work (Gaitanos, Williams, Boobis, & Brooks, 1993). Therefore, from a metabolic perspective, power is dictated by the amount and rate at which ATP is resynthesised and then hydrolysed. ATP is never actually fully depleted (as it is also used for basic cellular functioning), depleting by 45% in a 30-s sprint (Boobis, Williams, & Wooton, 1982) and between 15% and 30% in a 10-s sprint (Jones et al., 1985). As ATP stores are broken down, various metabolic pathways (energy systems) collaborate to resynthesise ATP in an attempt to maintain peak rates of ATP turnover. As the brief recovery times between repeated sprints will lead to only a partial restoration of energy stores, the amount of ATP resynthesised is likely to be an important determinant of the ability to maintain high power during each subsequent sprint. With respect to the energy systems used to resynthesise ATP, there is a trade-off between power and capacity. The contribution of each energy system is determined by exercise intensity, bout frequency and the duration of the rest period. The energy systems are phosphocreatine (PCr), anaerobic glycolysis and the aerobic/oxidative system; these are briefly discussed in the next sections. Phosphocreatine There are ~80 mmol/kg dm of PCr stored in the muscle (Gaitanos, Williams, Boobis, & Brooks, 1993) – around three times the amount of ATP. With a turnover rate of ~9 mmol ATP/kg dm/s (Hultman & Sjöholm, 1983), PCr stores are largely depleted within 10 s of sprinting (Glaister, 2005). The PCr system has the fastest ATP turnover rate of all energy systems, as there is only one enzymatic reaction (compared to the nine that occur with glycolysis, for example). As with ATP, and because of the contribution made by the other pathways, PCr is not normally completely depleted. For example, during all-out efforts, PCr is only depleted by 60– 80% over 30 s (Boobis, Williams, & Wooton, 1982), 40–70% over 10 s (Jones et al., 1985), 30–55% over 6 s (Boobis, Williams, & Wooton, 1982) and 25% over 2.5 s (of electrical muscle stimulation) (Hultman & Sjöholm, 1983); these results suggest that the ATP for a short sprint is also heavily subsidised by anaerobic glycolysis. Because the recovery of power output maps the time course of PCr resynthesis (Sahlin & Ren, 1989; Bogdanis, Nevill, Boobis, Lakomy, & Nevill, 1995; Mendez-Villanueva, Edge, Suriano, Hamer, & Bishop, 2012) and is attenuated by creatine supplementation (Mujika et al., 2000), PCr availability is likely to be a major factor governing the ability to repeat a maximal sprint effort (Glaister, 2005). PCr is resynthesised by the aerobic system within the mitochondria, via the creatine shuttle, and requires one molecule of ATP to resynthesise ATP. Given this cost, restoration happens when energy requirements are low, such as during recovery periods. As such, the contribution of PCr to subsequent sprints is governed by the length of the rest period; PCr resynthesis occurs at around 1.3 mmol/kg dm/s (Gaitanos, Williams, Boobis, & Brooks, 1993). Approximately 85% of PCr stores are restored in 2 min, 90% in 4 min and 100% in 8 min (Harris et al., 1976; Hultman, Bergstrom, & Anderson, 1967). Furthermore, recovery only happens when the blood supply to the working muscle is not occluded, which in turn is suggestive of why an active recovery between bouts is important (and may expedite PCr resynthesis). For example, an active recovery (vs. passive) consisting of cycling at submaximal intensities significantly increased peak power using 8 × 6-s cycle sprints with 30 s of rest (Signorile, Tremblay, & Ingalls, 1993). In addition to aiding PCr resynthesis, the active recovery may reduce muscle acidosis by speeding up the removal of hydrogen ions (H+) and lactate (LT) from the working muscles; this would also increase the use of LT as a fuel source (Signorile, Tremblay, & Ingalls, 1993). Adaptations that aid the resynthesis of ATP by the PCr system likely result from increases in the enzymes creatine kinase and myokinase (the latter catalyses the phosphorylation of two adenosine diphosphate (ADP) molecules to ATP and adenosine monophosphate (AMP)), and adaptations to the aerobic system such as increased blood flow and mitochondrial biogenesis. For example, Bishop et al. (2008) reported improvements in PCr resynthesis following a HIIT protocol of 6–12 × 2-min repetitions at approximate maximal oxygen uptake (~V̇O2max), with 1-min rest periods. Adaptations here were attributed to improvements in aerobic fitness. This was in contrast to 8 × 30-s repetitions at ~130% V̇O2max, with 90-s rest periods, where no change was found. There is, however, limited research investigating the effects of different types of training on PCr resynthesis. Anaerobic glycolysis During brief maximal sprints, the rapid drop in PCr stores is offset by increased activation of glycolysis and glycogenolysis; the former relates to the breakdown of glucose from the blood stream and the latter to the breakdown of glycogen in the cytoplasm. The maximal turnover rate of ATP production via these pathways is around ~8 mmol/kg dm/s (Hultman & Sjöholm, 1983; Jones et al., 1985; Gaitanos, Williams, Boobis, & Brooks, 1993; Parolin et al., 1999). This system involves multiple enzymatic reactions, so is not as fast as the PCr system, but collectively they maintain an ATP turnover rate of ~12 mmol/kg dm/s (Boobis, Williams, & Wooton, 1982; Gaitanos, Williams, Boobis, & Brooks, 1993). Glycolysis actually uses one ATP, as glucose must first be converted into glucose 6-phosphate via the hexokinase reaction once it enters the cytosol; this point should emphasise the importance of starting competitions in a fully glycogen-loaded state. The rapid onset of anaerobic glycolysis with maximal work can be noted by studies that report high values of LT (>4 mmol/L) within 10 s (Boobis, Williams, & Wooton, 1982; Jones et al., 1985). Surprisingly, values as high as 40 mmol/kg dm have been recorded after just 6 s of sprint cycling (Dawson et al., 1997). Following different types of training, adaptations to this system include increases in the enzymes phosphorylase, phosphofructokinase (PFK) and pyruvate dehydrogenase (PDH). PFK is considered the regulatory enzyme here, responding to increased cellular levels of AMP and inorganic phosphate (Pi), as would be expected at the start of a sprint. Increases in PDH activity ensure that pyruvate production is more closely matched to oxidation, thus increasing acetyl coenzyme A provision for the tricarboxylic acid (TCA) cycle. This is an important adaptation to RSA, as it means less production of lactate acid or, rather, the accompanying increases in H+. Training-induced changes in phosphorylase and PFK are likely greater using intervals that stimulate maximal accumulated oxygen deficit (Bishop, Girard, & Mendez-Villanueva, 2011); for example, training that involves repeated 30-s bouts (Bogdanis, Nevill, Boobis, Lakomy, & Nevill, 1995). Furthermore, greater rest durations between repetitions appear needed (>4 min) to ensure a maximally high intensity of work, and thus maximal stimulation of glycolytic enzymatic activity. With intramuscular stores of around 400 mmol/kg dm (Gaitanos, Williams, Boobis, & Brooks, 1993), glycogen availability is not likely to majorly compromise ATP provision during the repeated sprints typically used during research studies (Glaister, Stone, Stewart, Hughes, & Moir, 2005). Instead, it may be the progressive changes in metabolic environment (as noted by the aforementioned high LT values) that ultimately cause a reduction in ATP provision via this system. For example, Gaitanos et al. (1993), using 10 × 6-s sprints with 30-s rest periods, found that the first sprint produced ATP using 50% PCr and 44% glycolysis, while the tenth sprint used 80% PCr and 16% glycolysis; this was accompanied by a 27% loss in power output, an 11 mmol/L increase in muscle LT and a significant drop in ATP production rate. In such scenarios, noting the relatively forgiving work-to-rest (W:R) ratio of Gaitanos et al. (1993), the shortfall in energy is thus provided by the aerobic system (McGawley & Bishop, 2015). Hydrogen ion flux and buffer capacity The anaerobic conversion of pyruvate yields LT and H+. LT, however, is not the cause of fatigue and can be used as an energy substrate. For this, LT is transported in the blood to the liver, referred to as the Cori cycle, and converted into glucose. Instead, the H+ accumulation decreases intracellular pH, which in turn has been reported to inhibit oxidative phosphorylation and the activity of glycolytic enzymes (such as PFK), as well as the binding of calcium to troponin and thus muscle excitation–contraction coupling (Nakamaru & Schwartz, 1972). Therefore, the removal of H+ from skeletal muscle is likely to be of importance for the ability to sustain repeated sprints (Pilegaard, Domino, Noland, & Bangsbo, 1999). For example, while the trained and untrained may have similar release rates of LT and H+ during intense exercise, the intracellular-to-interstitial gradients of these are lower in the trained population (Sahlin & Henriksson, 1984). Combined, these results suggest a trainable muscle buffer capacity that may be important to repeated-sprint performance. The transient nature of the physiological pH (i.e. 7.4), which is affected by changes in H+, is governed by a series of buffering mechanisms. These attenuate the effects of H+ on metabolism by removing H+ when the pH declines (creating an acidic environment) and by releasing H+ when the pH increases. There are both intracellular (i.e. protein and phosphate groups) and extracellular (i.e. proteins, haemoglobin and the bicarbonate pool) buffers. As the H+ diffuses out of the muscle into the blood, it is buffered by bicarbonate (via the bicarbonate buffering system), thus attenuating changes in plasma pH by shifting the chemical equilibrium according to Le Chatelier’s principle. For example, any excess H+ will associate with bicarbonate (forming carbonic acid), thus resulting in a smaller net increase in acidity. The reaction is illustrated in equation 5.1, below. This buffering system is further facilitated by an increase in respiration rate to remove excess CO2 and thus acidity. Interestingly, one of the reasons you vomit during high-intensity training is that this provides the quickest means to remove large amounts of acid – the stomach is full of hydrochloric acid. In a similar way to bicarbonate, phosphate ions (see equation 5.2, below) and carnosine act as intracellular buffers. Carnosine is a dipeptide formed of two amino acids, beta-alanine and histidine, with the former often regarded as an ergogenic aid to HIIT-type activities (Artioli, Gualano, Smith, Stout, & Lancha, 2010). Similarly, supplementation with sodium bicarbonate can be beneficial (Bishop, Davis, Edge, & Goodman, 2004), as is a combination of both (Tobias et al., 2013). Bishop et al. (2004) have shown that muscle buffer capacity (calculated in vivo from the ratio of blood LT to changes in pH and as per equation 5.3) and RSA (5 × 6-s cycle sprints, departing every 30 s) are significantly correlated (r = 0.72, n = 23); this relationship with RSA was actually higher than that for V̇O2max and LT (r = 0.60 and 0.55, respectively). Further, Edge et al. (2006) have shown that increases in buffer capacity are intensitydependent. In two groups matched for volume and showing similar improvements in V̇O2max and LT post-training, only the high-intensity group (working at 120–140% LT) significantly improved buffer capacity. Improvements in buffer capacity are also attributable to improvements in the sarcolemmal LT/H+ transport capacity as well as an enhanced content of monocarboxylate transport proteins (MCT1 and MCT4) (Pilegaard, Domino, Noland, & Bangsbo, 1999). where CO2 = carbon dioxide, H2O = water, H2CO3 = carbonic acid, H+ = hydrogen ion and HCO3− = bicarbonate ion where HPO42− = hydrogen phosphate, H+ = hydrogen ion and PO43− = phosphate ion. for calculating buffer capacity (β), where Δ = change and La− = lactate (Sahlin & Henriksson, 1984). Aerobic metabolism Unlike the anaerobic resynthesis of ATP that occurs in the cytoplasm of the cell, oxidative resynthesis occurs in the mitochondria. Here, pyruvate (via PDH) is converted to acetyl coenzyme A (rather than lactic acid), where it then enters the TCA cycle and then the electron transport chain, before yielding 28 moles of ATP (vs. 1 from the PCr system, 2 from glycolysis and 3 from glycogenolysis). This system contributes to ATP provision sooner than commonly believed. For example, during the first 6 s of a 30-s maximal sprint (Parolin et al., 1999), or the first 5 s of a 3-min intense bout (> 120% V̇O2max) (Bangsbo, Krustrup, González-Alonso, & Saltin, 2001), an ATP turnover rate of ~1 mmol ATP/kg dm/s was hypothesised; this contributed ~10% of total energy produced. Also, as sprints are repeated, the V̇O2 of successive sprints will increase (Gaitanos, Williams, Boobis, & Brooks, 1993; Spencer, Bishop, Dawson, & Goodman, 2005) if recovery periods are not sufficient to resynthesise PCr, oxidise LT and remove accumulated intracellular Pi (through ADP phosphorylation via myokinase). For example, McGawley and Bishop (2015) investigated the V̇O2 during the first and last sprints during two 5 × 6-s repeated-sprint bouts, separated by passive rest, such that work done between each bout was the same. These investigators sought to assess the influence made by oxidative metabolism on RSA, hypothesising that reductions in fatigue and improved sprint times would be related to markers of aerobic fitness. Across both bouts, the V̇O2 during the first sprint was significantly less than the last sprint (p < 0.001), the estimated aerobic contribution to the final sprint (measured in kJ) was V̇ significantly related to V̇O2max (r = 0.81, p = 0.015 and r = 0.93; p = 0.001, respectively) and finally, the V̇O2 attained in the final sprint was not significantly different from V̇O2max (p = 0.284 and p = 0.448, respectively). The authors concluded that given the continuous increases in V̇O2 across sprints, V̇O2max might be a limiting factor to performance in later sprints. However, while V̇O2 may increase with successive sprints, the supply of ATP made by the aerobic system is significantly less than required for repeated sprints (Gaitanos, Williams, Boobis, & Brooks, 1993) and uses a lower ATP turnover rate. As such, while this could guard against a build-up of fatiguing by-products (and sprint frequency/duration can be increased), it would not be able to sustain power output (i.e. sprint performance). RSA is greater when tested in conditions of hyperoxia (Charles et al., 1996; Hogan, Kohin, Stary, & Hepple, 1999) or enhanced oxygen availability (via erythropoietin injection) (Balsom, Ekblom, & Sjodin, 1994); the opposite is true when RSA is tested in hypoxic conditions (Balsom, Gaitanos, Ekblom, & Sjodin, 1994). The consensus is that a greater quantity of PCr at the start of each sprint would reduce the demand on anaerobic glycolysis (and concomitant fatiguing by-products, e.g. H+ and Pi) and enhance ATP turnover (Glaister, Stone, Stewart, Hughes, & Moir, 2005). Glaister (2005) concludes that the key role of the aerobic system during repeated sprints is the return to homeostasis during rest. The natural assumption is that increasing V̇O2max will increase recovery rates and thus improve RSA. While there is little contention to this, it is worth noting that there is probably an optimal value above which further increases in RSA may not be noted (Bishop, Girard, & Mendez-Villanueva, 2011). Section summary and non-chemical sources of fatigue Sprint power is dictated by the amount and rate at which ATP is resynthesised and then hydrolysed, and three mechanisms principally contribute to ensuring that ATP is resynthesised as fast as it is hydrolysed. These are: (1) the donation of a phosphate group from PCr; (2) substratelevel phosphorylation involving the breakdown of glycogen or glucose to pyruvate; and (3) oxidative phosphorylation. The rate of hydrolysis is based on the number of reactions required, while the ability to sustain ATP turnover at fast rates is based on PCr availability and avoiding metabolic by-product accumulation (e.g. Pi, H+). As sprint frequency increases, and rest periods do not allow for sufficient recovery, ATP synthesis becomes progressively supported by oxidative phosphorylation. While oxidative phosphorylation allows for sustained work periods and repeated efforts, it does so with reduced metabolic power and thus RSA declines. It should be noted that declines in RSA are also related to additional muscular and neurochemical factors not outlined above. These include muscle excitability, whereby during intense contractions, the Na+–K+ pump cannot effectively reaccumulate the K+ into muscle cells, with the subsequent K+ efflux causing muscle membrane depolarisation, and thus reduction of muscle excitability (Clausen, Nielsen, Harrison, Flatman, & Overgaard, 1998). There may also be reductions to neural drive (i.e. a decrease in recruitment, firing rate, or both) and a reduced cerebral function owing to disturbances in neurotransmitter concentrations (e.g. serotonin, dopamine, acetylcholine) (Ross, Leveritt, & Riek, 2001). Also, altered muscle recruitment strategies, such as timing delays between agonist and antagonist muscle activation – highlight a possible decrease in muscle coactivation with fatigue (Hautier et al., 2000) – and a preferential recruitment of slow-twitch motor units (Matsuura, Ogata, Yunoki, Arimitsu, & Yano, 2006). There may also be changes in stiffness regulation, with the negative effects of a more compliant system outlined in Chapter 3. Finally, fatigue is likely to result from several homeostatic perturbations including hyperthermia, dehydration and muscle damage. Determinants of RSA performance Most RSA studies cite V̇O2max as the major determinant of RSA performance – no surprise given its role in PCr resysnthesis and the contribution it makes as intervals extend. However, there are conflicting findings regarding this relationship that appear largely attributable to the RSA test used. For example, a moderate correlation (r = −0.35) between V̇O2max and RSA was found when using 8 × 40-m sprints with 30 s of active recovery between sprints (Aziz, Chia, & Teh, 2000), but not 6 × 20m sprints with 20 s of recovery between sprints (Aziz, Mukherjee, Chia, & Teh, 2007). Bishop et al. (2004) utilised an RSA involving 5 × 6-s cycle sprints, departing every 30 s, and found a relationship between RSA and V̇O2max of r = 0.60. The discrepancies between these and others are probably attributable to the length and frequency of the sprints used, as this is likely to alter the contribution of the aerobic system (Balsom, Seger, Sjodin, & Ekblom, 1992). In essence, V̇O2max has not been reported to relate to RSA when only a few sprints of less than 40 m (or 6 s) have been used (Da Silva, Guglielmo, & Bishop, 2010). Also, in protocols using a W:R ≥ 1:5, sufficient recovery may be provided for the aerobic system to resynthesise ATP and PCr despite inadequate fitness levels. Unsurprisingly, RSA has also been found to strongly correlate with peripheral factors (Spencer, Bishop, Dawson, & Goodman, 2005). For example, Da Silva et al. (2010) showed that an RSA test consisting of 7 × 35-m sprints (involving a change of direction) and a between-sprint recovery period of 25 s produced high values of LT (15.4 ± 2.2 mmol/L). Logically, then, Da Silva et al. (2010) found that the velocity at the onset of blood LT accumulation (vOBLA) better correlated with RSA performance (r = −0.49); vOBLA reflects peripheral training adaptations, such as increased capillary density, the ability to resynthesise PCr and the capacity to transport LT and H+ (Billat, Sirvent, Py, Koralsztein, & Mercier, 2003; Thomas, Sirvent, Perrey, Raynaud, & Mercier, 2004). Therefore, to improve RSA, it appears prudent not to only target the development of vOBLA, but also the muscles’ buffer capacity. Several intervals of 30–60 s, with 1:1 W:R, may therefore be beneficial. Also, to enable the accumulation of H+, passive recovery between intervals may be best. Finally, Da Silva et al. (2010) (protocol aforementioned) and Pyne et al. (2008) (using 6 × 30-m sprints with 20 s of rest) found that the strongest predictor of RSA was actually anaerobic power, i.e. the fastest individual sprint time; this explained 78% of the variance and had a relationship (r) of 0.66 respectively. These results suggest that in addition to training targeting the improvement of V̇O2max, vOBLA and muscle buffer capacity, some training should also focus on improving strength, power and sprint speed (including acceleration). As well as traditional gym and track-based sessions (outlined in Chapters 15 through 19), this may also need to include single-repetition, all-out 30-s intervals, to maximally activate glycolytic flux and thus adaptations in PFK and phosphorylase. The former adaptations may be on account of increases in rate of force development, stretch-shortening cycle mechanics, movement efficiency and also increases in type II muscle fibre content. These fibres, which contain higher amounts of PCr than type I (Sant’Ana Pereira, Sargeant, Rademaker, de Haan, & van Mechelen, 1996), may be able to replenish ATP faster. However, this advantage may diminish after several sprints as type I fibres have better mitochondrial density and thus are better able to resynthesise PCr. Furthermore, and as an additional caveat, enhanced initial sprint performance via improved glycolytic flux may actually lead to increased fatigue in subsequent sprints given the likely build-up of additional fatiguing by-products. So this training intervention may need to be supported by others aimed at increasing V̇O2max and buffer capacity, to truly see it as a positive adaptation. Training to improve RSA As discussed above, RSA can be improved by increasing V̇O2max, vOBLA and muscle buffer capacity, as well as strength, power and sprint speed. Here we will focus on V̇O2max, vOBLA and muscle buffer capacity via HIIT and SIT, as training for strength, power and sprint speed are discussed in Chapters 15 through 19. Interestingly, with regard to aerobic capacity, a series of meta-analyses show that HIIT and SIT are as effective, if not more so, at increasing aerobic capacity when compared to moderate-intensity continuous training (MICT) (Sloth, Sloth, Overgaard, & Dalgas, 2013; Gist, Fedewa, Dishman, & Cureton, 2014; Weston, Taylor, Batterham, & Hopkins, 2014; Milanović, Sporiš, & Weston, 2015; Taylor, Macpherson, Spears, & Weston, 2015). These modes also better stimulate improvements in muscle buffer capacity and thus vOBLA, as will be explored shortly. According to Weston et al. (2014) and MacInnis and Gibala (2017), HIIT, also referred to as aerobic interval training, is defined as ‘near-maximal’ efforts, generally performed at an intensity that elicits ≥80% (but often 85– 95%) of maximal heart rate, with bouts typically lasting up to ~5 min. SIT, also referred to as anaerobic interval training or speed endurance training, is characterised by efforts performed at intensities equal to or greater than the pace that would elicit V̇O2max, including ‘all-out’ or ‘supramaximal’ efforts, with bouts typically lasting ≤45 s. MICT describes exercise that is performed in a continuous manner and at lower intensities than HIIT (Figure 5.1). Below we will provide examples of some SIT and HIIT protocols and associated findings, before exploring the physiological basis of their underpinning mechanisms. How modes of training differ between moderate-intensity continuous training (MICT), high-intensity interval training (HIIT) and sprint interval training (SIT). HR max, maximum heart rate; V̇O2max, maximal oxygen uptake. As illustrated in Table 5.1, Gibala et al. (2006) compared SIT consisting of 4–6 repetitions of 30-s work at ‘all-out’ supramaximal intensity (~700 W), with 4-min recovery, with MICT consisting of 90–120 min at ~175 W. Both groups completed six training sessions over 14 days, accumulating a total exercise duration of 135 min and 630 min respectively. Post-training, both groups revealed significant improvements in 750-kJ time trial performance, muscle buffer capacity and concentrations of various aerobic enzymes (such as COX, which is an enzyme acting within the electron transport chain), along with a concomitant decrease in muscle glycogen utilisation – no significant differences were noted between groups. This study was later repeated by Burgomaster et al. (2008), who compared SIT consisting of 4–6 repetitions of 30-s work at ‘all-out’ supramaximal intensity (~500 W), with 4-min recovery, with MICT consisting of 40–60 min at ~150 W. Both groups undertook training for 6 weeks, with the SIT group training 3 times per week and the MICT 5 times per week. This resulted in a total exercise duration of 90 min and 270 min respectively. Post-training, both groups revealed significant improvements in aerobic enzyme concentration, including citrate synthase (CS), which is an enzyme that acts in the first step of the citric acid cycle, and β-HAD, which is an enzyme involved in fatty acid metabolism. Furthermore, increases in PDH concentrations and fat oxidation were noted, with concomitant decrease in carbohydrate oxidation and muscle PCr utilisation. Of note, CS is considered a proxy of mitochondrial content given its relationship with total mitochondrial content assessed via electron microscopy. Finally, there was again no significant difference between groups (Table 5.1). Table 5.1 Group Comparison of sprint interval training (SIT) vs. high-intensity interval training (HIIT) vs. moderate-intensity continuous training (MICT) protocols on peripheral muscle adaptations and central adaptations. Results reveal that adaptations across protocols are similar, despite the large differences in total exercise time MICT SIT HIIT Adaptations ‘All-out sprint’ (~700 W) Not tested Both groups significantly improved: Gibala et al. (2006) Intensity 65% V̇O2max (~175 W) PCr, phosphocreatine; PGC-1α, proliferator-activated receptor y coactivator-1α. Group MICT SIT Protocol 90–120 min continuous exercise 30 s × 4–6 repeats, 4 min recovery Total 630 min over duration 6 sessions (across 2 weeks) HIIT Adaptations Time trial performance Muscle 15 min (intervals) + 120 min (recovery) over 6 sessions (across 2 weeks) buffer capacity Aerobic enzyme concentration Fat oxidation Glycogen sparing Burgomaster et al. (2008) Intensity 65% V̇O2max (~150 W) ‘All-out sprint’ (~500 W) Not tested Both groups significantly improved: Aerobic Protocol 40–60 min continuous exercise 30 s × 4–6 repeats, 4 min recovery enzyme concentration Fat oxidation Glycogen Total 270 min over duration 30 sessions (across 6 weeks) sparing 10 min (intervals) + 80 min (recovery) over 18 sessions (across 6 weeks) PCr concentration PGC-1α protein content Matsuo et al. (2014) Intensity 65% V̇O2max 120% V̇O2max 90% V̇O2max PCr, phosphocreatine; PGC-1α, proliferator-activated receptor y coactivator-1α. All groups significantly improved: Group MICT SIT HIIT Adaptations Protocol 40 min continuous exercise 30 s with 15 s rest, repeated 7 times 3 min work, with 2 min rest at 50% V̇O2max, repeated 3 times 40 sessions (across 5 weeks) 40 sessions (across 5 weeks) V̇O2max SIT and HIIT groups significantly improved: Total 40 sessions duration (across 5 weeks) Left ventricular mass Stroke volume Resting heart rate PCr, phosphocreatine; PGC-1α, proliferator-activated receptor y coactivator-1α. Professor Ulrik Wisloff and colleagues developed a four-by-four HIIT method that has proven popular and effective with soccer players and Nordic skiers. While the physiological adaptations noted between SIT and HIIT training are comparable, it appears that SIT predominantly drives improvements in V̇O2max via increased oxidative capacity in the peripheral muscles, while HIIT predominantly drives improvements in V̇O2max via increases in stroke volume and blood flow (i.e. central factors) (Helgerud et al., 2007; Matsuo et al., 2014). A comparison of the four-by-four HIIT method with other work-matched methodologies is summarised in Table 5.2 (Helgerud et al., 2007). Also, and as described by Baker (2011), aerobic fitness can be improved using a HIIT protocol consisting of 15-s intervals at 100–120% maximal aerobic speed (MAS), with a 1:1 W:R and continuing for 5–10 min. Table 5.3 shows how to calculate interval distances from a 3km run, and how to organise these sessions within team sports. When estimating MAS, any distance (or time) can be used but the athlete should be working for >5 min (Baker, 2011). When training for a sport like boxing, for example, it may be prudent to use these types of methods early on in the periodised plan (to ensure an appropriate aerobic base), before progressing the athletes towards shorter yet higher-intensity intervals that are more specific to the sport. In sports such as football, and particularly for midfielders where a high V̇O2max may be just as important as RSA, it may be prudent to include these throughout the periodised plan. Table 5.2 Effective training systems to enhance aerobic fitness Training Protocol group Training intensity Pretraining V˙O2max (mL/kg/min) Posttraining V˙O2max (mL/kg/min) Long slow distance (LSD) running Low– moderate 55.8 ± 6.6 56.8 ± 6.3 Lactate Continuous run at lactate threshold threshold (85% HRmax) for (LT) 24 min running Moderate– high 59.6 ± 7.6 60.8 ± 7.1 15/15 interval running 47 repetitions of 15-s intervals at 90–95% HRmax with 15 s of active resting periods at warm-up velocity, corresponding to 70% HRmax between High 60.5 ± 5.4 64.4 ± 4.4* 4 × 4-min interval running 4 × 4-min interval training at 90–95% HRmax with 3 min of active resting periods at 70% HRmax between each interval High 55.5 ± 7.4 60.4 ± 7.3* Continuous run at 70% HRmax for 45 min * Significantly (p < 0.001) different from pre- to post-training. HRmax, maximum heart rate. Table 5.3 Training protocol Interval distances for high-intensity interval training using maximal aerobic speed (MAS), and calculated using a 1.5-mile run time of 10 min (Baker, 2011) 15-s intervals at 100–120% MAS Work-to-rest ratio of 1:1 Repeat over 5 min using multiple sets as appropriate Calculating 100% MAS v = d/t where v = velocity (m/s), d = distance (m) and t = time (s) 3 km = 3000 m; 12 min 30 s = 750 s v = 3000/750 = 4 m/s Calculating interval distance If an athlete runs 4 m every second, then he/she will run 60 m in 15 s (4 × 15) Calculating 120% MAS 1.2 × 100% MAS value, i.e., 4 m/s × 1.2 = 4.8 m/s Notes on shuttles and variations using agility drills A 30-m shuttle for example, i.e., out and back and covering 60 m, probably represents 120% MAS as you must factor in the change of direction Don’t We do not recommend calculating lane distance for everyone in the group. individualise Instead, simply group runners based on 30-s intervals too much What does it look like? For example, group 1: 16 min (960 s) for 3 km run (MAS = 3.125 m/s), therefore they run out and back 23 m (≈ 120% MAS given the turn), up to group 6: 10 min (600 s) for 3 km (MAS = 5 m/s) = 37.5 m out and back What if you do not have the space? Assuming only a 20-m shuttle is available: prior to the run (but within the 15 s), athletes perform an exercise, the intensity of which is dependent on how short the lane is. The exercise may be a series of tuck jumps or as simple as starting from a prone position The physiological basis for the peripheral muscle adaptations noted through HIIT and SIT has been explained by MacInnis and Gibala (2017) and Gibala (2020). These authors describe how exercise intensity mediates mitochondrial biogenesis, with a greater metabolic signal for adaptation occurring at higher intensities on account of the increased cellular stress. At higher intensities, ATP turnover is greater, and this is supplemented by an increase in the utilisation of glucose and glycogen, culminating in the accumulation of intracellular LT, creatine, AMP and ADP. These metabolic changes, and in particular low glycogen and the AMP:ATP ratio, increase the activity of AMP activated protein kinase (AMPK; along with CaMKII, which responds to elevated levels of cytosolic Ca2+ during muscle contraction), which act as a ‘cellular energy gauge’. AMPK controls the overall balance between energy production and energy utilisation in all eukaryotic cells, with its activation tilting the balance towards energy production. The greater the activation of these kinases, the greater the expression of mRNA for proliferator-activated receptor y coactivator-1α (PGC-1α). To further demonstrate the intensity-dependent nature of these metabolic signals (which are independent of volume) and subsequent adaptions, Di Donato et al. (2014) also found that mitochondrial protein synthesis was greater in response to continuous exercise performed at a higher intensity relative to work-matched exercise performed at a lower intensity. Understanding this cascade of cellular signals and reactions goes some way to explaining the otherwise counterintuitive finding that high-intensity exercise can be just as beneficial, if not more so, as the more traditional mode of training aerobic capacity via moderate- to low-intensity, continuous training. Furthermore, appreciating that low cellular energy stimulates the activity of AMPK, which in turn drives mitochondrial biogenesis via PGC-1α, provides some rationale behind the beneficial results noted within several fasted or, rather, train-low paradigms (Bartlett, Hawley, & Morton, 2015; Marquet et al., 2016). In these, athletes will typically consume a low-carbohydrate meal prior to bedtime and then train in the morning before breakfast. Training in such a glycogen-depleted state will quickly activate AMPK. However, it should be noted that while this may drive increases in mitochondrial protein synthesis, the enzyme PDH will be down-regulated given the decreased metabolism of glycogen and subsequently reduced accumulation of LT. As such, adaptations in this enzyme – and by extension, vOBLA and muscle buffer capacity – would be compromised. Therefore, in line with other modes of training, a variety of HIIT and SIT protocols should be used; these can be further manipulated via nutrition, and supported by strength and power training. With regard to the central adaptations noted by SIT and HIIT, these have been nicely detailed within the study of Matsuo et al. (2014). Through cardiac magnetic resonance imaging (MRI) they revealed that an 8-week (5 times per week) SIT (30 s at 120% V̇O2max, with 15-s rest, repeated 7 times) and HIIT (3 min at 85–90% V̇O2max, with 2-min rest at 50% V̇O2max, repeated 3 times) intervention increased left ventricular mass, systolic performance (ejection fraction) and thus stroke volume and resting heart rate. (The results are illustrated in Table 5.1.) Furthermore, improvements in the contractile performance of the cardiomyocyte through improved Ca2+ cycling were hypothesised. At the cellular level, Ca2+ has an important role in the contraction–relaxation rates of the cardiomyocyte and it may be that submaximal rather than maximal exercise intensity better stimulates increasing Ca2+ sensitivity in the cardiomyocyte. These results may explain that while there is generally no statistically significant difference between SIT and HIIT protocols with regard to central adaptations (and noting the large variation in protocols across the literature), HIIT tends to experience slightly improved results when assessed via effect size analysis. In closing, training approaches associated with HIIT, SIT and each energy system discussed above are identified in Table 5.4. Table 5.4 High-intensity interval training (HIIT) based on each energy system Training focus Training plan Rationale Phosphocreatine system Gym-based strength and power Track-based max. speed and acceleration (SIT) Repeated bouts (6–12) of 6–30 s, with ~60-s rest (SIT) ≥ 2-min intervals, separated by relatively shorter rest periods, e.g. 1 min, and ≥ 4 reps (HIIT) Increase initial sprint speed May increase PCr stores by virtue of increased type II fibre concentration Reduced effort through increases in strength, power (including RFD and SSC mechanics) and technical proficiency Increases in aerobic capacity and thus creatine shuttle efficiency Anaerobic glycolysis Maximal-intensity 30-s intervals, separated Maximally activate and thus by 4–10 min to ensure subsequent adapt key enzymes, e.g. PFK intervals are again maximally utilising and phosphorylase anaerobic glycolytic enzymes (SIT) Muscle buffer capacity Repeated bouts (~6) of 30–60-s intervals, with work-to-rest ratio of 1:1. Utilise a passive recovery (HIIT) Increase and accumulation of H+ and thus buffer capacity Aerobic system Longer-duration (≥ 2-min) intervals (at ~ V̇O2max), separated by relatively shorter rest periods, and ≥ 4 reps (HIIT) Improve PCr resynthesis via the creatine shuttle, mitochondrial biogenesis and enhanced blood flow SIT, sprint interval training; PCr, phosphocreatine; RFD, rate of force development; SSC, stretchshortening cycle; PFK, phosphofructokinase; H+, hydrogen ion. Reporting results from RSA tests It is important to judge the efficacy of any training intervention, and this can be done by monitoring an athlete’s RSA over time. Once a drill has been designed that replicates the sport and, importantly, requires athletes to work at an intensity that represents (and even surpasses) a worst-case scenario bout of play, there are considerations with regard to data analysis. The method of data analysis for RSA testing should principally centre on the following: (1) fastest sprint; (2) total or mean RSA time; or (3) the rate of fatigue (or performance drop-off). The last factor can be reported by one of two methods: (1) sprint decrement (Sdec) or (2) fatigue index (FI). The formula for each, according to Spencer et al. (2005) is listed below in equations 5.4 and 5.5, respectively. Unlike the FI, the Sdec takes into account all sprints and is less influenced by a good or bad start or finish. To improve reliability, Spencer et al. (2005) advise that, 5 min prior to testing, athletes complete a single criterion sprint. During the subsequent first sprint of the RSA test, athletes must achieve at least 95% of this score. Should they fail, the test is terminated and restarted following another 5min break. While total (or mean) sprint time demonstrates good reliability (CV < 3%), indices of fatigue give unacceptable levels of reliablility (CVs 11–50%); therefore we advise that the former should predominantly be used (Spencer, Fitzsimons, & Dawson, 2006; Oliver, 2009). Conclusion It is the manipulation of exercise duration, frequency and rest period that brings about specific adaptations to metabolic pathways. The results of Balsom et al. (1994) provide a useful summary of this point. They found that 40 × 15-m sprints (~2.5 s) with 30-s rest could be completed without any reduction in performance. However, using the same rest period, 40 × 30-m (~4.5 s) and 15 × 40-m (~6 s) sprint times increased significantly, and after only the third 40-m sprint, times were already significantly longer. Blood LT was also only elevated in the longer sprints. 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Sports Medicine, 44(7), 1005–1017. 6 Concurrent training Rodrigo Aspe, Richard Clarke, Gareth Harris and Jonathan Hughes DOI: 10.4324/9781003044734-8 Introduction Successful sports performance is multifaceted and includes optimal preparation of skill, tactics, and physical qualities. Activities such as marathon running and weightlifting have clear physical qualities at opposite ends of a continuum. For example, a marathon runner requires excellent aerobic capacity, with elite athletes typically demonstrating maximum oxygen consumption (V̇O2max) values of 70–85 ml kg−1 min−1 (Joyner & Coyle, 2008), while, in contrast, weightlifting necessitates high levels of muscular force, and as a result, a greater cross-sectional area (CSA) of type II muscle fibers (Aagaard et al., 2011; Fry et al., 2006). Therefore, the amount of time dedicated to enhancing strength and power qualities by the endurance athlete is markedly lower than that dedicated by the weightlifter, just as the time dedicated to aerobic qualities is lower for the weightlifter compared to the marathon runner. Many sports require a range of physical qualities, including both strength/power and aerobic capacity for optimal performance. For instance, in a single rugby union match, it may be necessary for a player to accelerate past their opponent in a line break (acceleration and power), ruck and maul in offensive and defensive plays (muscular mass and strength), and cover large distances tackling opponents throughout (aerobic capacity). Therefore, training for rugby and many other team sports requires multiple physical qualities, which often need to be developed concurrently (Chiwaridzo, Ferguson, & Smits-Engelsman, 2016). Typically these qualities are classified into two simple training paradigms, endurance and strength training. Endurance training is commonly denoted by low–moderateintensity (∼70% V̇O2max) and high-volume training, which places greatest demand on oxidative metabolism and promotes adaptations specific to enhanced oxygen uptake and delivery, such as increased mitochondrial and capillary density (Baar, 2014). In contrast, strength training is characterized as high-intensity (≥80% one repetition maximum (1RM)) and low-volume, and places greater demand on anaerobic metabolism and promotes adaptations enhancing muscle CSA and neuromuscular efficiency to enhance force production (Farup et al., 2012). Herein lies the concern, as concurrent strength and endurance training promotes diverse physiological adaptations (Nader, 2006). It is important that strength and conditioning coaches and sport scientists have appropriate physiology knowledge to optimize programming, and thus training adaptations. The aim of this chapter is to discuss the adaptive response to concurrent exercise and identify how periodization can minimize the interference effect of diverse adaptations. The interference effect An interference effect has been reported when strength and endurance exercises are performed concurrently (Hickson, 1980). The cause appears to be linked to the differing physiological responses and adaptations to strength and endurance training, possibly due to the high volume and long duration that are often associated with endurance-based training (Wilson et al., 2012). It is presumed that endurance exercise interferes with resistance exercise sessions (via residual fatigue and/or substrate depletion) and therefore blunts any muscular developments, e.g., muscle fiber-type alterations and architectural adaptations (Leveritt & Abernethy, 1999; Murlasits, Kneffel, & Thalib, 2018). Neural development It has been well documented that increases in maximal strength during the initial weeks of strength training can be largely attributed to the increased motor unit activation of the trained agonist muscles (Häkkinen et al., 1998; Häkkinen, Kraemer, Newton, & Alen, 2001a; Häkkinen et al., 2001b). It has also been demonstrated that strength training, performed concurrently with endurance training, may have no detriment to neuromuscular characteristics in elite endurance populations with no resistance-training experience (Mikkola, Rusko, Nummela, Paavolainen, & Häkkinen, 2007; Paavolainen, Häkkinen, Hamalainen, Nummela, & Rusko, 1999; Støren, Helgerud, Stoa, & Hoff, 2008; Taipale et al., 2010) and recreationally resistance-trained men (Jones, Howatson, Russell, & French, 2013). Häkkinen et al. (2003) demonstrated that alongside large increases in maximal force, there was an increase in the maximum integrated electromyography (EMG) signal in the leg extensor muscles during a concurrent training program lasting 21 weeks. Increases in EMG amplitudes via strength training would result from an increased number of active motor units and/or an increase in their rate coding (Sale, 1992). However, there are conflicts in the literature, where an interference effect has been demonstrated. It is purported to manifest as: (1) alterations in the neural recruitment patterns of skeletal muscle (Chromiak & Mulvaney, 1990; Gergley, 2009); (2) limitations in force generation (Rhea et al., 2008; Rønnestad, Hansen & Raastad, 2012); and (3) increased neuromuscular fatigue from increased training demands of high-volume endurance training (Davis, Wood, Andrews, Elkind, & Davis, 2008; Pattison, Drinkwater, Bishop, Stepto & Fyfe, 2020). Interestingly, any impairments were less evident in the early stages of training (first 4 weeks), which may indicate that there is a progressive interference to neuromuscular function with prolonged concurrent training periods (Pattison et al., 2020). These findings have been supported via a meta-analysis that indicated that, whilst muscular power increased, the magnitude of change was lower in concurrent-trained groups (effect size (ES) = 0.55) than in strength-only trained groups (ES = 0.91) (Wilson et al., 2012). It is speculated that forces at high contraction velocities, i.e., movements that need ‘explosive’ strength with high levels of rate of force development (RFD), are affected more by endurance training than force at low contraction velocities (Dudley & Djamil, 1985; Wilson et al., 2012). Therefore, in sports that require explosive strength development and/or maintenance, coupled with endurance capabilities, decrements in muscular power may be likely and a result of impaired contraction velocity or RFD (Häkkinen et al., 2003). Muscular development Following periods of concurrent training, skeletal muscle CSA has been found to be depressed (Bell, Petersen, Wessel, Bagnall, & Quinney, 1991) and, within the total CSA, it has been evidenced that individual muscle fibers have hypertrophied to a lesser degree (Bell, Syrotuik, Martin, Burnham, & Quinney, 2000; Kraemer et al., 1995). Mikkola et al. (2012) postulate that, during bouts of concurrent training, optimal adaptation of trained muscles to both strength- and endurance-training stimulus may not be morphologically or metabolically possible. It has been theorized that an increased catabolic state of skeletal muscle could lead to a reduced change in the CSA (Bell et al., 2000; Kraemer et al., 1995). In support of this, it has been discussed that there is a likely impact of testosterone and cortisol interference due to mixed endocrine responses to training, where strength training stimulates an increase in testosterone and prolonged endurance training increases basal levels of circulating cortisol (Taipale & Häkkinen, 2013; Taipale et al., 2010). In addition, endurance training may decrease muscle fiber size in order to accommodate increases in capillary and mitochondrial density (Sale, MacDougall, Jacobs & Garner, 1990). This may be due to the oxidative stress imposed on the muscle and the requirement to optimize the kinetics of oxygen transfer because of the additional endurance training (Häkkinen et al., 2003). Furthermore, a lack of development in muscle CSA during concurrent training could be attributed to overtraining induced by chronic muscle glycogen depletion (down-regulating the signaling cascade required for protein accretion, as well as reducing training performance) and an increase in catabolic hormones (Mikkola et al., 2012). Further analysis demonstrates that potential interferences to muscle hypertrophy during concurrent training are more prominent when strength training is performed concurrently with running compared to cycling (Wilson et al., 2012). This is likely explained by greater levels of muscle damage in running (eccentric muscle action) and thereby reducing the development of muscle tissue via competing demands for tissue regeneration via the inflammatory process (Clarkson & Hubal, 2002; Wilson et al., 2012). Molecular signaling Excessive bouts of endurance exercise are known to reduce rates of protein synthesis for several hours following the cessation of training (Rennie & Tipton, 2000). Molecular signaling research has evidenced that during (and following) endurance training the metabolic signaling pathways that are linked to substrate depletion and calcium release and uptake into the sarcoplasmic reticulum are activated (Coffey & Hawley, 2007). The secondary messenger adenosine monophosphate-activated kinase (AMPK) is activated, as its role is to increase mitochondrial function to enhance aerobic capacity via the breakdown of glycogen and fatty acids to fuel activity (Rose & Hargreaves, 2003). However, this activation inhibits the mammalian target of rapamycin (mTOR), whose role is to mediate skeletal muscle hypertrophy through up-regulation of protein synthesis via activation of ribosome proteins (Bodine, 2006). Knowledge of this signaling system informs us that conditions of low glycogen and high concentrations of calcium and adenosine monophosphate (AMP) (as would occur during aerobic training) would activate the AMPK pathway, thus protein accretion (via the mTOR pathway) is significantly reduced (Figure 6.1). Therefore, strength training in a fatigued state may not be best practice. Putative adaptive pathways in response to the concurrent programming of endurance and resistance exercises in a training program. Cardiorespiratory development There is empirical evidence that in elite endurance athletes, strength training can lead to enhanced long-term (>30-minutes) and short-term (<15minutes) endurance capacity (Aagaard & Andersen, 2010). Investigations into adaptations of cardiorespiratory function have indicated that there are no differences in the magnitude of adaptation when endurance training is completed in isolation or concurrently with strength training (Bell et al., 2000; McCarthy, Pozniak, & Agre, 2002). The greatest impact on cardiorespiratory adaptations arises when peripheral adaptations (e.g., capillary and mitochondrial density) are blunted. As the volume and intensity of resistance training increase, competition for contractile protein synthesis (promoting an increase in fiber size and muscle CSA) and an increase in glycolytic enzymes exist (Docherty & Sporer, 2000). The more recent focus on cardiorespiratory adaptations has investigated the acute effects of concurrent training on oxidative metabolism (Alves et al., 2012; Kang et al., 2009). Alves et al. (2012) did not observe differences in mean values of V̇O2 or heart rate (HR) during endurance exercise performed prior to or following a strength-training session. However, Kang et al. (2009) demonstrated greater mean values for participants’ V̇O2 when endurance exercise was performed following strength training compared with endurance exercise only. There are a number of methodological differences that can explain these results, i.e., intensity of endurance exercise, strength exercises chosen, and populations used. The positive effects of strength training for endurance athletes may occur independently of changes in cardiorespiratory development (Paavolainen et al., 1999) and could be due to improvements in RFD that aid improvements in exercise economy. An improved force profile may augment RFD and the time required to produce the desired force for each movement, reducing ground contact time (GCT) (Hoff, Gran, & Helgerud, 2002; Paavolainen et al., 1999; Sedano, Marín, Cuadrado, & Redondo, 2013). Moreover, an enhanced force profile can augment the utilization of elastic energy in the muscle–tendon system, decrease GCT, and reduce the demand on ATP production, thus improving exercise economy (Wilson and Lichtwark, 2011). Underlying all these proposed mechanisms, it may be that there is an individual response that is coupled to an athlete’s training experience (Fyfe & Loenneke, 2017). When comparing moderately trained athletes with well-trained athletes, it has been evidenced that higher activation of molecular mechanisms leading to both myofibrillar and mitochondrial protein synthesis occurs in less-trained populations regardless of the concurrent nature of the training (Nader, von Walden, Liu, Lindvall, Gutmann, Pistilli & Gordon, 2014; Perry, Lally, Holloway, Heigenhauser, Bonen & Spriet, 2010). This is attributed to the philosophy that, in lessdeveloped athletes, any stimuli may induce significant alterations to a cell’s homeostasis and, therefore, lead to greater training-induced adaptations, and that endurance-based athletes could be considered less developed in strength parameters and therefore the interference effect is a reduced factor in their training development. Training strategies to minimize interference Training periodization Periodizing a training program (which should include the planning of all tactical and technical training) for a sport that includes a range of physical qualities and planning of multiple training units within a training day, microcycle, and mesocycle, needs to be cautiously managed to minimize the interference effect, as one training unit may inhibit adaptations to a previous or subsequent training unit. In addition, the inclusion of training units such as technical and tactical skills within the sport may provide enough stimuli to maintain or enhance physical qualities and such training stressors should be considered in the periodized plan to optimize fitness and minimize fatigue (Issurin, 2010; Suarez-Arrones et al., 2014). Wong et al. (2010) investigated a concurrent training program using professional football players during an 8-week pre-season. Programming prioritized 1RM half back squat and yo-yo intermittent recovery test (YYIRT) performance, alongside sport-specific tactical and technical training units. The experimental group completed twice-weekly strengthtraining units and 8 minutes of high-intensity running sessions (low volume) on the same day, in addition to their normal 6–8-weekly soccertraining units. The control group completed their normal 6–8-weekly soccer-training units. Results demonstrated significant improvements for the experimental group in 1RM half back squat (+25 kg) and YYIRT (+298 m) but only the YYIRT (+137 m) for the control group. Similarly, Enright et al. (2015) demonstrated half back squat 1RM improvements during a 5-week in-season concurrent training program that included strength training, soccer-specific endurance training, technical, and tactical sessions. In this study design, all groups completed a concurrent training protocol and sequencing was manipulated. Training groups either completed strength–endurance or endurance–strength, separated by ~1 hour. Regardless of sequence, both groups significantly improved half back squat 1RM by 10.3% and 19.1%, respectively. However, the more pronounced changes and larger increase observed in the endurance–strength training situation may suggest that the concurrent training sequence, in association with adequate recovery duration between training bouts and nutrient availability, may be able to modulate significant changes in physical performance measures. These applied research examples demonstrate minimal interference effect and suggest that, within professional sport, both strength and aerobic measures can be augmented with concurrent training programs over prolonged periods. With regard to maximizing strength-training adaptations for strengthand power-based athletes (contact sport), Appleby et al. (2012) assessed strength over a 2-year period in professional rugby union players. Findings indicate increases in strength are highly related to increases in lean body mass and the magnitude of improvement is related to initial strength level. However, the degree of strength improvement diminishes with increased strength, training experience (4–7 years), and if athletes do not have the capacity to increase lean body mass (Baker, 2013). Consequently, it is important to recognize methodological differences in concurrent training research. Comparing athletes with a low resistance-training age to welltrained strength athletes is unwise as the stimulus for adaptation is different. Longitudinal research where strength-based athletes have participated in concurrent training (Appleby et al., 2012; Baker, 2013; Stodden & Galitski, 2010) has typically dedicated specific training periods such as pre-season (Appleby et al., 2012) or off-season (Stodden & Galitski, 2010) to hypertrophy development and included a minimum of three resistancetraining sessions per week for this mesocycle. This form of block/emphasisbased periodization enables a large training stimulus to be applied to welltrained athletes. During in-season, training frequency is reduced to a minimum of one session per week to maintain physiological adaptations made in the pre- and off-season. In the Appleby et al. (2012) and Stoden and Galitski (2010) studies, 1RM strength improved within year 1 and year 2, alongside the inclusion of speed, agility, aerobic capacity, technical, and tactical training units. This in-season reduction in strength-training frequency demonstrates wellthought-out programming with regard to concurrent training volume and periodization. As such, there is no decrease in strength, which is a positive outcome in this scenario (Baker, 2013). A review on the development, retention, and decay of strength in trained athletes further confirms these programming variables, suggesting that, to maintain strength, 1–2 training units per week are required (McMaster, Gill, Cronin & McGuigan, 2013); this low-frequency stimulus could be sufficient due to athletes undertaking substantial doses of high/rapid force-generating activities during technical and tactical training sessions. Interestingly, it also speculated that a detraining period of 3 weeks has minimal effect on muscular strength (McMaster et al., 2013). This provides valuable programming information with regard to the duration of strength-training residuals and the potential for programming adjustments, such as an opportunity to reduce resistancetraining volume and implement a tapering strategy, or increase training volume to target another physical quality. For successful periodization within sports where concurrent training is required, it would be prudent to determine off-season and in-season periods to establish specific training goals. Furthermore, determining pre-season and in-season mesocycle goals would help focus programming and lessen the interference effect of physiological adaptations of diverse physical qualities. For example, Garcia-Pallares et al. (2009) demonstrated in elite kayakers that strength and endurance qualities can be trained concurrently with positive performance outcomes. The distinctive aspect of this research was coupling hypertrophy training with aerobic training at 90% of V̇O2max in the first mesocyle and strength training and maximal aerobic power training (high-intensity aerobic training, between 90% and 100% of V̇O2max) in the second mesocycle. The rationale for this was the physiological adaptations expected, as hypertrophy (increase in contractile proteins synthesis) and aerobic power training (increase in oxidative capacity modulated by changes to oxidative enzymatic reactions) promote opposing adaptations at a peripheral level (Garcia-Pallares et al., 2009). Emphasizing fitness qualities in this manner has the potential to limit the interference effect based on specific physiological adaptations. The use of transition or detraining periods from strength-training units within programming may also be beneficial as: (1) this period may enable restoration and supercompensation; and (2) another training unit may be prioritized without detrimental effects to strength (McMaster et al., 2013; Sedano et al., 2013). Special attention should be considered in regard to the type of sport; for example, contact sports may necessitate hypertrophy and an increased frequency of resistance-training units whilst minimizing the amount of aerobic training units completed. Training session sequencing One opportunity to manipulate training variables and reduce interference may be through the sequencing of training units within a microcycle. In programs that include both strength- and endurance-based training stimuli in the same session, the training response may be different depending on whether endurance or strength training is performed first. In a metaanalysis, Eddens et al. (2018) included ten studies directly comparing intrasession exercise sequence and the interference effect. Results identified that performing resistance training first enhanced the improvement in lowerbody dynamic strength within prolonged concurrent training programs (weighted mean difference, 6.91% change; 95% confidence interval (CI) 1.96–11.87 change; p = 0.006). Similar findings were also reported by Murlasits et al. (2018), whose meta-analysis directly compared strength and endurance-training sequence on performance measures and identified a significantly different effect size of 3.96 kg (95% CI 0.81–.10 kg), indicating the superiority of the strength-prior-to-endurance order. Interestingly, Ratamess et al. (2016) demonstrated endurance training performed 10 minutes before strength training resulted in 9.1–18.6% fewer repetitions performed compared to strength training only. Therefore, it is plausible that the order effect is explained by residual fatigue, with the stress of the preceding endurance training acting to inhibit the quality of the strength-training session. Training recovery Insufficient recovery between training sessions may limit the desired adaptations from previous training. Residual fatigue from aerobic training may reduce the quality of strength-training sessions by alterations in neural recruitment patterns (Chromiak & Mulvaney, 1990; Gergley, 2009), inhibiting force generation capacity (Rhea et al., 2008; Rønnestad et al., 2012) or neuromuscular fatigue (Davis et al., 2008; Leveritt & Abernethy, 1999). For example, Robineau et al. (2016) concluded that strength and power adaptations were inhibited unless at least 6 hours’ recovery was allowed between training sessions (strength followed by high-intensity endurance exercise); however, a 24-hour recovery period was superior to further reduce interference. Furthermore, Sale et al. (1990) reported that strength and endurance training performed on the same day (alternating order) had no effect on muscle hypertrophy, but did cause a significant reduction in strength development in untrained men compared to separateday training (approximately 24 hours’ rest). It is likely that increasing recovery between sessions reduces the magnitude of the interference effect as there is less disruption in post-training signaling pathways (Lundberg et al., 2012) and an increased period for protein synthesis, restoration, and opportunity to replenish fuel stores (Chtourou et al., 2014). Further, the interference effect may also be increased when the same muscle groups are utilized for strength- and endurance-based training (Craig et al., 1991; Sporer & Wenger 2003). Sporer and Wenger (2003) report that lower-body strength was significantly decreased for at least 8 hours after completion of a cycling submaximal aerobic training session (36 minutes’ cycling at 70% maximal power at V̇O2) and a cycling highintensity interval training session (3 minutes’ work and 3 minutes’ rest at 95–100% of maximal power at V̇O2), with no difference between groups at any recovery time point. However, a meta-analysis, examining the interference of aerobic and resistance training, suggests interference effects are primarily body part-specific as performance decrements were found in lower-, but not upper-, body exercise (Wilson et al., 2012). Therefore, athletes who engage in multiple strength training units per week may benefit from utilizing a split training routine where upper-body strength training is completed on days that contain aerobic training sessions (given these predominantly tax the legs). Training intensity It may also be important to consider endurance training intensity, as Chtara et al. (2008) and Davis et al. (2008) reported that interference is more likely to occur at aerobic training intensities close to maximal oxygen uptake. Ratamess et al. (2016) investigated the acute response of strength performance initiated 10 minutes after four different endurance (running) protocols. These included: (1) continuous moderate intensity for 45 minutes; (2) continuous moderately high intensity for 20 minutes; (3) highintensity intervals for 15 minutes (with 15 minutes of low intensity in between); and (4) continuous moderately high-intensity uphill for 20 minutes. Results demonstrated all endurance protocols observed a significant strength-training performance deficit (repetitions) compared to strength training only. Interestingly, protocol 3 (most intensive) led to the greatest performance decrement followed by protocol 1 (most extensive). With regard to longer-term research, Varela-Sanz et al. (2017) investigated two matched-volume concurrent training protocols of different training intensities for a duration of 8 weeks. Subjects were randomly allocated to either: (1) a traditional training group who completed continuous running at 65–75% of maximal aerobic speed (MAS) and 10–12RM three times per week, or (2) a polarized group that combined brisk walking of 35–40% MAS and 15RM twice weekly; and brisk walking at 35–40% MAS, 15second intervals at 120% MAS and 5RM in the third session. Results demonstrated similar strength and endurance improvements for both groups; however, only the polarized group were able to maintain lowerbody explosive power by means of a jump test. In this regard, the results suggest that the polarized distribution of training attenuates the interference effect in respect to neuromuscular performance, which may be due to a combination of factors such as a low weekly training frequency (4 rest days per week) or superior programming related to employing low-intensity brisk walking and reduced frequency of high-intensity training, thus limiting fatigue. Interestingly, it has also been reported that high-intensity aerobic training may minimize the interference effect due to the recruitment of high-threshold motor units and a potential reduction in training volume. For example, Wong et al. (2010) reported significant improvements in strength, sprint speed, and aerobic performance after strength sessions were utilized concurrently with high-intensity aerobic training (15:15 s at 120% MAS and passive recovery). Notably, this training allowed for approximately 5 hours between the morning strength session and the afternoon high-intensity aerobic session, which may have also contributed to the significant adaptations found; high-intensity interval training is discussed further in Chapter 4. Training frequency, volume, and mode Optimal training frequency is also important as a number of studies investigating concurrent training have reported varied conclusions on whether endurance training attenuates strength and power adaptations (Abernethy & Quigley, 1993; Craig et al., 1991; Hennessy & Watson, 1994; Kraemer et al., 1995; McCarthy, Agre, Graf, Pozniak, & Vailas, 1995; Sale et al., 1990). Jones et al. (2013) speculated that these differences may be linked to endurance training frequency, as attenuated responses are more often reported in studies utilizing a high (Craig et al., 1991; Hennessy & Watson, 1994; Kraemer et al., 1995) vs. a low training frequency (Abernethy & Quigley, 1993; McCarthy et al., 1995; Sale et al., 1990). Jones et al. (2016) examined the effects of endurance training frequency in a 6-week training intervention in which participants were randomly assigned to one of four experimental conditions: (1) strength training only; (2) concurrent strength and endurance training at a ratio of 3:1; (3) concurrent strength and endurance training at a ratio of 1:1; or (4) a control. Results demonstrated that an increase in the frequency of endurance training and total training volume within the concurrent training paradigm resulted in the attenuated development of lower-body strength when compared with strength training alone. Moreover, earlier work from the same research group demonstrated that recreationally trained men completing high-frequency strength and muscular endurance training (both 3 × per week) resulted in lower strength and hypertrophy adaptations compared to groups performing strength only (3 × per week) or lowfrequency strength and muscular endurance training (3 × strength and 1 × endurance per week) (Jones et al., 2013). Subsequently, it may be important to evaluate the desired physiological outcome and manipulate strength to endurance training ratio dependent on the training goals. It seems prudent that if muscular strength or hypertrophy is a priority, the frequency and ratio of endurance training should be low, as endurance-training frequencies of greater than three times a week have been shown to attenuate strength performance (Häkkinen et al., 2003; Izquierdo- Gabarren et al., 2005; Jones et al., 2013, 2016; Kraemer et al., 1995). It should be noted that methodological differences make comparing and contrasting frequency research problematic due to manipulation of the acute program variables and the amount of permutations available which mainly affect training volume. Wilson et al. (2012) produced a meta-analysis of concurrent training studies that demonstrated negative significant and meaningful relationships between endurance-training frequency, duration, and lower-body adaptations in hypertrophy (r = −0.26; r = −0.75, respectively), strength (r = −0.31; r = −0.34, respectively) and power (r = −0.35; r = −0.29, respectively) indictaing an interfrenece effect. Whilst there were significant negative relationships, the majority are weak and suggest minimal interference effect for strength and power adaptations. Therefore, prescription of training loads should be monitored, as when concurrent training is necessary, the overall training load is likely to be higher, in both frequency and duration, due to needing to meet this minimum-dose response of two different fitness qualities (Figure 6.2). The recommended decision-making process during periods of concurrent training. SIT, sprint interval training. Summary In summary, the concurrent training research provides equivocal findings on rate and magnitudes of adaptations (positive and negative in their manifestation) across a number of physiological variables, including strength, power, and cardiorespiratory functions. This wide range of findings may be due to the wide range of acute program variables contributing to the potential interference effect. Although it is not fully understood, the research seems to support the concept that the interference effect has its greatest effect on strength development (via hypertrophic adaptations) and that the most likely mechanism of this interference is linked to the molecular signaling activated from the type of training undertaken. Athletes who require high levels of muscular strength and hypertrophy, therefore, should endeavor to limit any long periods of concurrent training. During the planning of training, overall periodization, including microcycles and mesocycles, needs to be cautiously managed to control fatigue and minimize the interference effect (see Figure 6.1 for recommendations). It would be prudent to determine off-season and inseason periods to establish specific training goals where as much focus can be placed on a single training outcome as possible. It may also be optimum to reduce the frequency of endurance training (and strongly consider total accumulated fatigue) when hypertrophy adaptations are required. During training cycles when concurrent training is unavoidable, it would be sensible to consider the level of stimulus required of different modes of training and determine a minimal dose–response. For example, detraining or transition periods of up to 3 weeks from strength-training units may be beneficial to allow supercompensation of other physical qualities, such as speed and agility, to be prioritized. Practical guidelines for concurrent training include: 24 hours of rest between strength- and endurance-training units, though where this is not possible, 6–8 hours would be sufficient. In addition, muscle recruitment and mode of exercise should be considered, for example, where training necessitates two training units in one day, upper-body strength could be coupled with on-feet aerobic training. Alternatively, off-feet aerobic training (cycling, rowing, and ski-erg) could be matched with lower-body strength training to minimize extensive eccentric stress. In scenarios where training sessions must be combined, and strength development is key, a strength–endurance order should be used. Finally, to maximize strength adaptations, two rest days should be provided and endurance training frequency of less than three sessions per week is advised. Applied training case study Given the necessity for numerous elite sporting populations to develop strength and aerobic capacity simultaneously, a significant demand has been placed upon the practice of effective concurrent training methods. Working within amateur or semi-professional sport this demand is even more apparent due to varying external life commitments, e.g., employment, especially those involving manual labor. Scheduling for appropriate adaptations with little time available to train becomes a challenge; therefore, there is a requirement to complete both strength and aerobic capacity training within a single training session. In this applied training case study, the population comes from an elite women’s rugby team in the UK and their typical weekly in-season schedule can be seen in Table 6.1. Table 6.1 Typical training week Day Combined sessions (semi-professional) Monday 18:00–19:00 Upper-body strength 19:00–20:00 Off-feet conditioning 17:00–18:00 Lower-body strength 19:00–20:30 Combined conditioning + rugby Tuesday Wednesday Active recovery Thursday 17:00–18:00 Total body strength 19:00–20:30 Combined conditioning + rugby Friday Active recovery Saturday Game day Sunday Day off Due to logistical constraints in the training environment (squad size, floor space) this group of players were split into two training groups in one continuous 120-minute session. One group performed resistance training (RT) prior to aerobic capacity training (ACT), and the other group performed ACT prior to RT. Session content for all players was the same and training took place in-season three times per week. Table 6.2 provides the programming variables used during an 8-week training block to provide sufficient stimulus for the physiological adaptations required for performance in their sport. Table 6.2 Programming for concurrent training over an 8-week block Training period Weeks 1–3 4–6 7–8 Warm-up sets 2 3 3 Duration 3 min 3 min 3 min Recovery 30 s 30 s 30 s Sets upper body 3 3 3 Sets lower body 3 3 3 Repetitions 10 6 3 Intensity (% 1RM) 70% 80% 90% Recovery 2 min 3 min 3 min Repetitions plyometrics 6 6 6 Repetitions hamstrings 6 6 6 Short intervals 2 × 8 min of 30/30 s 2 × 10 min of 30/30 s 2 × 12 min of 30/30 s Sprint intervals 4 × 30 s all-out 6 × 30 s all-out 8 × 30 s all-out RT workload Main exercise Complementary exercise Act workload RT, resistance training; 1RM, one repetition maximum. Resistance-training design Every session began with a warm-up focused on movement skills. Strength training included exercises of the lower body (squat, deadlift, and lunges) and upper body (bench press, chin up, and bent-over row) (Table 6.2). Training was divided into three periods, during which the intensity progressively increased. The first period (weeks 1–3) aimed to prepare participants for maximal-strength training. The second period (weeks 4–6) and the third period (weeks 7–8) were designed to increase maximal strength (Table 6.2). Each set of squats was immediately followed by plyometric jumps. Exercises were alternated during each training session, alternating lower- and upper-body exercises. Players were free to change weight during the training period in order to achieve the programmed repetitions. Aerobic capacity training design Two different ACT sessions were performed outside on an artificial pitch. A specific 15-minute warm-up, consisting of moderate, cruising, and sprinting runs, preceded each aerobic training session. The first consisted of short intervals and included two sets of interval running. Players would alternate 30-s runs at 100% of their individual MAS with 30 s of active recovery at 50% MAS, where MAS was obtained from a 1200-m test. The second sprint interval included repetition of 30-s running all-out efforts with 4 min of passive recovery. Table 6.3 Mean (± SD) values for performance measures conducted in elite women’s rugby players pre- and post-8 weeks of concurrent training interventions Performance test Squat 1RM (kg) Bench press 1RM (kg) Maximal aerobic speed (m/s) Pre Post % Change RT-ACT group 93.1 (15.3) 98.5 (14.2)* 5.5% ACT-RT group 97.5 (21.2) 101.5 (18.6)* 4.1% RT-ACT group 61.0 (12.9) 65.0 (12.8)* 6.5% ACT-RT group 60.7 (21.7) 63.1 (22.0)* 4.0% RT-ACT group 3.5 (0.4) 3.7 (0.4)* 5.7% ACT-RT group 3.5 (0.4) 3.7 (0.5)* 5.7% * Denotes a significant difference compared to baseline (p < 0.05). 1RM, one repetition maximum; RT-ACT, resistance training–aerobic capacity training; ACT-RT, aerobic capacity training–resistance training. 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Effect of preseason concurrent muscular strength and high-intensity interval training in professional soccer players. The Journal of Strength & Conditioning Research, 24(3), 653–660. Part II Programming and monitoring for your athlete 7 Periodisation Shyam Chavda, Anthony N. Turner and Paul Comfort DOI: 10.4324/9781003044734-10 Introduction Periodisation (also referred to as phase potentiation) is regarded as a superior method for developing an athlete’s performance (Haff, 2004a, 2004b; Stone et al., 1999a, 1999b, 2000). However, because peak performance can only be maintained for 2–3 weeks (Stone, Stone, & Sands, 2007), the ability to phase training appropriately to ensure that the athlete’s peak level of performance coincides with a competition date long into the future (e.g. the Olympics, or key matches in team sports) is a skill fundamental to all strength and conditioning (S&C) coaches. Such levels of performance may only be attained following the appropriate application of periodisation, whereby a calculated manipulation of training parameters (e.g. frequency, intensity, duration, volume, exercise selection) ensures optimal adaptations and minimal fatigue at the point of competition. Despite an apparent lack of scientific rigour to govern its application (Kiely, 2018), periodisation is widely practised (Durell, Puyol, & Barnes, 2003; Ebben & Blackard, 2001; Ebben, Carroll, & Simenz, 2004; Simenz, Dugan, & Ebben, 2005) and recommended (Haff, 2004a, 2004b; Plisk & Stone, 2003). As training is multifaceted in nature, it is important to understand that athletes are committed to a process which prepares them not just physically, but technically, tactically and psychologically, to enable them to achieve high levels of performance in their sport (Stone, Stone, & Sands 2007). Although the primary focus of this chapter is the physical preparation of the athlete, when designing a periodised programme, a holistic approach must ensue to account for the compounding effect of fatigue and overall stress experienced by the athlete. This will require a multidisciplinary approach of technical and tactical coaches working alongside sport scientists and athletes, to help appropriately structure training cycles to align and therefore optimise the primary focus of training for that period. Once this overarching approach is taken, the distribution of training (i.e. gym-based training, on-pitch training, etc.) (Figure 7.1) can be programmed appropriately so as to ensure the distribution of mode and training is appropriate to elicit the desired effects. (a) Distribution of training load; (b) distribution of training modes in Olympic fencers. (Adapted from Turner et al., 2015.) We should also note that the science and practice of periodisation are largely based on hypothesis-generating studies, anecdotal evidence and related research, with most studies only being short-term experimental periods (e.g. 5–16 weeks) using subjects with limited training experience (Kiely, 2018). However, despite these challenges to an evidence-based ideology, there is enough anecdotal evidence, case study reports and empirically similar research to advocate its use across all population groups. Therefore, the aim of this chapter is to provide the S&C coach with a detailed overview of periodisation so that they may be cognisant of its theory and methodology. It is hoped that this will further facilitate its implementation and successful application. Defining periodisation It is often perceived that periodisation and programming are one and the same. This misconception can lead to potential confusion and inconsistency in communication between S&C coaches and therefore the differences between the two need to be addressed. Periodisation may be defined as a macromanagement of strategically aligned phases of training, whereby peak performance is brought about through the potentiation of biomotors and the management of fatigue and accommodation. This is governed by the prescription of training frequency, exercise selection and order, intensity, sets and repetitions (Cunanan et al., 2018a; DeWeese et al., 2015). These constituent parts make up a programme, which, when appropriately organised, should present an identifiable pattern based on the intended objectives of the training phase (Cunanan et al., 2018a). The logical manipulation of these variables will often display as an inverse relationship between volume and intensity (volume load) (Figure 7.2), with the only notable exceptions being during periods of planned overreaching (discussed later). More recently, researchers have identified that manipulating training load via cluster sets (Tufano et al., 2016, 2017a, 2017b) and higher-volume (sets) powerlifting protocols (Schoenfeld et al., 2014) may also permit higher volumes of training at higher intensities. (For a detailed review of the use of cluster sets, see Chapter 13.) However, careful implementation of such strategies should be considered, preferably away from competition, to ensure that the higher training volumes do not negatively impact performance due to the associated increase in fatigue. Relationship between volume, intensity and training specificity over the three main phases of training. GPT, general physical training; SSPT, sportspecific physical training; Comp, competition. Plisk and Stone (2003) suggest that periodisation should be applied on a cyclic or periodic basis, structured into macro-, meso- and microcycles, that progress from extensive to intensive workloads. These cycles are often defined by their allotted period of time, with a macrocycle typically referring to a year, a mesocycle (each period/phase of focused training) 2–8 weeks, dependent on the competition schedule and a microcycle 1 day to 1 week (Figure 7.3). There is, however, large variability in the time course of each, with, for example, macrocycles running 4 years in the case of Olympic training programmes (quadrennial plan). Also, mesocycles are often divided into 4 ± 2-week blocks as this appears to provide the optimal time frame for adaptation in well-trained athletes (Matveyev, 1977; Plisk & Stone, 2003; Stone, Stone, & Sands, 2007; Zatsiorsky & Kraemer, 2006). Basic components of a periodised plan. GPT, general physical training; SSPT, sport-specific physical training. (Adapted from Naclerio, Moody, and Chapman, 2013.) Periodisation is also often defined by its progression from general to special tasks (Figure 7.2), whereby there is a conscious incorporation of technique/sport-specific biomotors as the programme progresses and competition nears. It is important to note that, in terms of sport specificity, this refers to training, which results in adaptations that achieve specific, preestablished goals, and not mimicking the movements of sporting tasks. Bompa and Haff (2009) also report three major phases of periodisation: the preparatory phase, the competitive phase and the transition phase. In addition, the preparatory phase has two sub-phases: general physical training (GPT) and sport-specific physical training (SSPT) (Table 7.1). The objective of the GPT is to improve the athlete’s work capacity and maximise adaptations in preparation for future workloads (Graham, 2002). This may typically be used in the off- or pre-season, where there are limited skill-based sessions, therefore allowing for higher workloads and optimal recovery. The importance of this phase is highlighted by Zatsiorsky and Kraemer (2006), who use the analogy “soon ripe, soon rotten”. Along with data from Fry, Webber, et al. (2000) and Stone et al. (2007), this suggests that the average training intensity is inversely correlated with: (1) the time a performance peak can be maintained; (2) the height of that performance peak; and (3) the rate of detraining (Figure 7.4). Table 7.1 The main phases and sub-phases of periodisation Training phase Preparatory phase GPT SSPT Phase objective • ↑ Work (aerobic and anaerobic) capacity • ↑ Neuromuscular functioning • Refine technique • Develop sport-specific biomotor ability • Develop sport-specific energy metabolism GPT, general physical training; SSPT, sport-specific physical training. Competitive phase Maintain biomotor conditioning Soon ripe, soon rotten. Training intensity is inversely correlated with: (1) the time a performance peak can be maintained; (2) the height of that performance peak; and (3) the rate of detraining. (Adapted from Stone et al., 2007.) The SSPT serves as a transition into the competitive phase, whereby physical capacity is developed specific to the physiological profile of the sport and where sport-specific biomotors are perfected. During the competitive phase, the work capacity developed during the SSPT should be maintained as a minimum objective. However, in team sports with regular competition and extended competition phases, mesocycles may be attributed to maintenance of some attributes and development of others. This phased approach is also essential to ensure that the desired muscular adaptations occur, as strength and power training result in different architectural adaptations (discussed in detail in Chapter 2). Following the SSPT, Bompa and Haff (2009) also presented the transition phase (TP), which provides a period of restitution between macrocycles or intense mesocycles. This phase serves as an opportunity for athletes to actively rest and partake in recreational activity, complementary to the movement patterns and motor skills experienced in their primary sport (Haff, 2004a). The length of this phase and the number of times it is used within a macrocycle will be dependent on the structure of the periodised plan and the number of competitive phases the athlete will partake in. For example, an athlete competing in weightlifting may only have three major competitions in a year (i.e. regional qualifier, nationals and an international). Therefore, following each competition phase, the athlete will undergo a transition to allow for recovery, with each phase lasting between 2 and 6 weeks, with longer transitions following the most intense period of preparation and competition (i.e. following the international competition). This momentary withdrawal from specific training stressors coincides with Selye’s general adaptation syndrome (GAS) model, in which he states that stress reactions are well tolerated for short periods, although persistent long periods of stress are likely to cause complications and therefore it is beneficial to withdraw stress (Cunanan et al., 2018a). Given that stress is multifaceted, this phase provides opportunity for both physiological and psychological restitution for the athlete. Recovery and adaptation The foundation of periodisation is governed by the management of stress. Stress is multifaceted in nature and therefore factors other than physical stress brought about by training must also be considered when designing a periodised plan (Kiely, 2018). If stress is compounded by external pyschoemotional factors experienced by the athlete, a significant reduction in recovery and adaptation may present itself. For example, dual-career athletes such as students will have added academic stress (i.e. examinations and coursework), which may affect their readiness to train and increase injury potential (Mann et al., 2016) during periods of demanding physical training or high competition loads. Furthermore, their perception of the training task may also be altered during periods of high pyscho-emotional stress and therefore influence fitness adaptations based on the imposed training stressor (Kiely, 2018). As S&C coaches, it is important to factor in periods of external stress and accommodate this within the loading paradigms used within a meso- and microcycle. Mesocycle blocks are usually arranged in a 3:1 loading paradigm (Figure 7.5), whereby the load (volume or intensity depending on the goals of the phase) gradually increases for the first three microcycles (weeks) before an unloading phase in the fourth (creating the typical undulating appearance of periodised programmes). The unloading phase reduces accumulated fatigue, thereby allowing adaptations to manifest (Haff, 2004a, 2004b; Plisk & Stone, 2003). The importance of appropriately planned work-to-rest ratios (with respect to training sessions) should be noted, with Plisk and Stone (2003) suggesting that the greater the number of progressive loading steps, the greater the number of unloading steps required, e.g. a 6:2 paradigm. Since the majority of training adaptations take place during recovery periods (Haff, 2004a), the need to reduce accumulated fatigue to facilitate the adaptation processes cannot be understated. The 3:1 loading paradigm, illustrating the increase and then dissipation of excessive fatigue. The importance of recovery phases for the purposes of adaptation is well established (Haff, 2004a, 2004b). The S&C coach must therefore ensure that work-to-rest ratios are appropriately planned (e.g. utilising the 3:1 step loading paradigm) to avoid excessive fatigue and a reduced stimulus for adaptation. According to Stone et al. (2007), this trade-off is described by three principal theories: (1) Seyle’s GAS; (2) stimulus–fatigue–recovery– adaptation (SFRA) theory; and (3) the fitness–fatigue (fit–fat) theory. General adaptation syndrome The GAS paradigm describes the body’s physiological response to stress, which, according to Selye (1956), is the same despite the stressor. The GAS model assumes three distinct phases during stress, which, for the following example, will be an exercise-training session. The alarm phase (phase 1) represents the recognition and initial response to the session. This may be in the form of fatigue, stiffness or delayed-onset muscle soreness, for example. The resistance phase (phase 2) is then initiated, in which the body is returned to either its pre-exercise session homeostasis or its new adapted higher state (i.e. supercompensation occurs). Finally, and assuming the accumulation of stress is too great (e.g. the absence of an unloading week), the exhaustion phase (phase 3) occurs and may be considered synonymous with overtraining if it continues over a prolonged period (Stone, Stone, & Sands, 2007). The GAS model is depicted in Figure 7.6. The general adaptation syndrome (GAS) model. While GAS is the main underlying foundation on which periodisation and the pursuit for adaptation are founded, some resistance towards its application within sport has been raised (Buckner et al., 2017, 2018; Kiely 2018). The main argument exists that the original work by Hans Selye focused on a pathological stress response induced by pharmaceutical implementation and exercise in rodents, therefore raising the issue of whether Selye’s experimental data can be related to resistance exercise in humans (Buckner et al., 2018). It has been refuted as to whether the training stressors experienced by athletes are indeed sufficient enough to cause an alarm phase in which adaptation becomes a response (Buckner et al., 2018), and therefore questions whether a periodised approach to programming is more beneficial than a non-periodised approach (Buckner et al., 2017). In addition, the lack of empirical evidence supporting the application of the GAS model during training has been raised (Buckner et al., 2018). While these are plausible arguments, Cunanan and colleagues (2018a, 2018b) uphold a strong rationale as to why the application of GAS can help S&C coaches develop highly efficient periodised programmes. Much of the support behind the broad application of the GAS model and its use within periodisation comes from the culmination of both experimental data (albeit somewhat limited in elite athletes) and supporting literature, in addition to anecdotal practice from coaches (Cunanan et al., 2018a, 2018b). Cunanan and colleagues coherently discuss the applicability of GAS, highlighting that: (1) GAS provides a mechanistic and conceptual model to help understand the relationship between stress, adaptation and fatigue, as experienced by athletes; and (2) Selye’s original work highlighted the need for periodicity due to the cyclic stress–recovery response, implying that training (i.e. resistance training) would also require planned variation and recovery. Stimulus–fatigue–recovery–adaptation theory The SFRA concept (Verkhoshansky, 1979, 1981, 1988) suggests that fatigue accumulates in proportion to the magnitude and duration of a stimulus. Then, following the stimulus (e.g. an exercise session), the body is rested, enabling fatigue to dissipate and adaptations (often referred to as supercompensation) to occur. This concept also suggests that if the stress is not applied with sufficient frequency (also known as density), detraining (also known as involution) will occur. It is also important to note that if competition frequency is high, then training frequency will have to reduce to permit appropriate recovery. Moreover, involution time is influenced by the length of the preparation period (Stone, Stone, & Sands, 2007), with greater training programme duration increasing the duration of the residual effects (Figure 7.4) (Zatsiorsky & Kraemer, 2006). In addition, and by virtue of this, the duration of subsequent preparation phases can progressively decrease. The importance of preparation has been previously discussed within this chapter. The SFRA concept is illustrated in Figure 7.7. The stimulus–fatigue–recovery–adaptation (SFRA) concept. The SFRA concept is also used to describe the supercompensation observed following periods of planned overreaching (Verkhoshansky, 1981, 1988). For example, the accumulation of fatigue from the sequential execution of similar training sessions (i.e. a concentrated, primarily unidirectional loading of, for example, strength/power training), usually with a progressive increase in volume, is superimposed on one another. This leads to excessive fatigue and acutely (~4 weeks) diminished strength and power capabilities. However, following the return to normal training, or a “deload” period (and by virtue of a delayed training effect phenomenon), they then rebound beyond their initial values (Fry, Webber, Weiss, Fry, & Li, 2000; Stone & Fry, 1998). This strategy, however, is reserved for elite-level athletes whose window for adaptation is small and therefore requires more intense interventions to bring about a supercompensation response (Bompa & Haff, 2009). Planned overreaching strategies are briefly discussed later in this chapter. Fitness–fatigue paradigm Currently, this is the most prevailing theory of training and adaptation (Chiu & Barnes, 2003; Plisk & Stone, 2003; Zatsiorsky & Kraemer, 2006) and is considered the basic tenet of a taper (discussed later in this chapter) (Mujika & Padilla, 2003). According to this paradigm, athlete preparedness may be evaluated based on the main after-effects of training: fitness and fatigue (Zatsiorsky & Kraemer, 2006). Unlike the GAS and SFRA concept, which assumes fitness and fatigue share a cause-and-effect relationship, the fit–fat model suggests they demonstrate an inverse relationship. This implies that strategies that maximise fitness and minimise fatigue will have the greatest potential to optimise athlete preparedness (Stone, Stone, & Sands, 2007). The fit–fat concept is illustrated in Figure 7.8. The fitness–fatigue paradigm. An additional key difference between the fit–fat concept and the aforementioned models is that it differentiates between the actions of various stressors, such as neuromuscular and metabolic stress (Chiu & Barnes, 2003), implying that the after-effects of fitness and fatigue are exercise-specific (Stone, Stone, & Sands, 2007; Zatsiorsky & Kraemer, 2006). This suggests that if the athlete is too tired to repeat the same exercise with acceptable quality, they may still be able to perform an alternative exercise to satisfaction (Figure 7.9), which also aids in reducing monotony for athletes. This, for example, provides the basic tenet to hypertrophy programmes incorporating 3–5-day splits and concurrent training involving both aerobic and resistance workouts. Athlete preparedness based on the specific form of fatigue. (Adapted from Zatsiorsky and Kraemer, 2006.) Training monotony The lack of “change” associated with monotonous training volume, intensity or mode can predispose an athlete to stagnation (Stone et al., 1991; Zatsiorsky & Kraemer, 2006). Also, as described by the principle of diminishing returns (Zatsiorsky & Kraemer, 2006), as an athlete improves, in whichever attribute they are developing, the room for adaptation decreases and therefore so does the rate of adaptation (Figure 7.10). It is therefore of utmost importance to incorporate variability within the design of periodised S&C plans, and this serves as the rationale for the regular application of novel and semi-novel tasks (exercise deletion and representation) (Stone, Stone, & Sands, 2007); Table 7.2 illustrates how this may be incorporated within a periodised plan. As a word of caution, however: too much variability can reduce the opportunity for the body to adapt to a given stimulus and reduce the development of skill acquisition (Bompa & Haff, 2009). The principle of diminishing returns. Table 7.2 Exercise deletion and representation Mesocycle 1 2 3 Example 1 Exercise Countermovement jump (CMJ) Delete CMJ from programme; replace with drop jump Reintroduce CMJ into programme Example 2 Exercise Depth jump (clear flexion/extension of joints, prolonged ground contact time [GCT]) Delete depth jump and replace with drop jump (reduced flexion/extension of joints, short GCT [<250 ms]) Reintroduce depth jump into programme Application of periodisation Basic model of periodisation The type of periodised model used should reflect the S&C training age of the athlete and not their competition age or rank. It is considered prudent therefore to initiate S&C programmes with basic periodised models. These generally entail little variation and relatively flat workloads (Stone, Stone, & Sands, 2007), with the main emphasis being on the logical and thus potentiated progression of biomotors (e.g. strength-endurance → strength → power). Figure 7.11 illustrates a basic model. Basic model of periodisation entailing little variation and relatively flat workloads. As an example of this basic strategy, the athlete completes a hypertrophy/strength-endurance phase for 6 microcycles (i.e. 6 weeks or one mesocycle), a strength phase for 4 microcycles and then a power phase for 4 microcycles (Table 7.3). Note that the strength-endurance phase is longest in duration; this is because volume is considered a key stimulus for hypertrophy, which will also help to increase work capacity, ready for the subsequent phases. It also provides the athlete with more time to master the various movements required of the following phases. Each phase (dependent on the prescribed volume loads) may be further separated by an unloading week, as may happen following the power phase and before the competition. In addition, higher- and lower-volume days may also be prescribed where there is a notable change in intensity, therefore altering the stimulus for strength adaptation. This strategy, considered appropriate for athletes with a low S&C training age, introduces them to S&C (i.e. its merits and the discipline required) and periodisation (i.e. the need to systematically alter the emphasised biomotors and a quality-over-quantity approach) and enables them to get a “feel” for gym-based training interventions as well as developing their associated technique. As a final note on this basic model (which is actually applicable to all models), to ensure athletes get the most out of each phase, the S&C coach should ensure they are technically sound to perform the exercise of each phase before progressing on to it. For example, power cleans and snatches may be part of the power phase; however, the athlete may have to start practising and developing them, along with their derivatives, in the strength-endurance phase and maintain them in the strength phase. In the strength-endurance phase, cluster sets might be used, for example, to ensure maintenance of technique and velocity. (See Chapter 13 for a detailed discussion of the implementation of cluster sets.) In the strength phase, weightlifting pulling derivatives using loads ≥ 100% one repetition maximum (1RM) power clean might be used, as force production is key to their effective use during the power phase (see Chapter 16) (Suchomel, Comfort, and Lake, 2017; Suchomel, Comfort, and Stone, 2015). Table 7.3 Example sessions used as part of a basic periodised model Example Example Example power session hypertrophy session strength session 3 × 8–15 @ 60–75% 1RM, working toward MMF, < 3 min between sets and exercises 4 × 4 @ 4–6RM (~85–90% 1RM), > 3 min between sets and exercises Exercises: Squats, Romanian deadlift, bench press, pull-ups. Weightlifting and plyometric techniques may be developed as part of the warm-up Intensity: 5 × 3 @ variable loads (see below), > 3 min between sets and exercises Exercises: clean (70–90% RM), jump squats (0–50% 1RM), plyometrics (body mass) and medicine ball throws. Strength may be maintained with 3 × 3 squats @ 85–90% 1RM. Volume load presented as sets × repetitions × load. 1RM, one repetition maximum; MMF, momentary muscle failure. Intermediate model of periodisation As the athlete’s S&C age advances and adaptations begin to plateau, greater variability becomes paramount. In addition, due to the enhanced work capacity of the athlete, greater volume loads are undertaken, thus the need for planned recovery sessions. The periodised programme begins to evolve into wave-like increases in volume loads (Matveyev, 1972, 1977) that typically fluctuate at the microcyclic level (Stone et al., 1999a, 1999b). This is referred to as summated microcycles and is usually represented as the 3:1 paradigm previously discussed. In addition, and due to the need to incorporate variability, each microcycle can incorporate multiple biomotors (e.g. strength, power and speed work), some for the purpose of maintenance and potentiation, and others for the purpose of development and adaptation. Additional methods of incorporating variability and thus adaptation include inter-session variability (e.g. heavy/high-volume and light/lower-volume days and exercise deletion and re-presentation methods) and intra-session variability (e.g. cluster sets and post-activation performance enhancement protocols). Figure 7.12 illustrates this traditional approach to designing periodised programmes, which is attributed to Matveyev (1972, 1977). An example intermediate periodised programme is illustrated in Table 7.4. The traditional, undulating approach to the design of periodised training, which is attributed to the work of Matveyev (1977). Note the 3:1 loading method within each mesocycle. Table 7.4 Two example strength sessions and two example power sessions, which can be implemented as part of an intermediate periodised programme Strength session 1 Strength session 2 Power session 1 Power session 2 Volume load presented as sets × repetitions × load. * Used to develop/maintain technique and strength/power; 1RM, one repetition maximum; CMJ, countermovement jump; NHC = Nordic hamstring curls. Strength session 1 Strength session 2 Power session 1 Power session 2 Back squats (5 × 3 ~90% 1RM) Clean pulls (3 × 3 ~90% 1RM)* Power snatch from hang (5 × 3 ~80% 1RM) Power clean from hang and split jerk (5 × 3 ~75% 1RM) Jump shrugs (3 × 5 ~35% 1RM)* Split squat (3 × 3 ~85% 1RM) Split jerk (3 × 4 ~80% 1RM) Front squats (3 × 3 ~85% 1RM)* Bent-over row (3 × 5 ~85% 1RM) Romanian dead lift (3 × 3 ~85%) 1RM Deadlifts (3 × 3 ~85% 1RM)* Drop jumps (5 × 5) Bench press (3 × 5 ~85% 1RM) Pull-ups (3 × 3 ~85% 1RM) CMJ (5 × 5 (body mass)) Bench press (3 × 3 ~85% 1RM)* NHC (3 × 3 bodyweight) Military press (3 × 3 Pull-ups (3 × 3 ~85% ~85% 1RM) 1RM)* NHC (3 × 3 body weight) Volume load presented as sets × repetitions × load. * Used to develop/maintain technique and strength/power; 1RM, one repetition maximum; CMJ, countermovement jump; NHC = Nordic hamstring curls. Advanced model of periodisation As the athlete’s S&C age advances and the windows of adaptation begin to diminish further, more advanced strategies are required, which incorporate yet more variability and greater volume loads. The majority of the emphasis is now placed on the prescription of volume loads through advanced strategies such as the conjugate system (Figure 7.13; also known as the coupled successive system) (Verkhoshansky, 1986). Because this places the athlete dangerously close to the overtraining syndrome, athletes undertaking this system must be able to tolerate very high volume loads (Plisk & Stone, 2003) and the S&C coaches applying these interventions must be highly skilled. Furthermore, it may be advisable to ensure athletes have at least 2 years’ formal S&C experience, with associated strength adaptations, as this is usually associated with increases in the anabolic environment of the body (by virtue of increased testosterone relative to cortisol) and thus greater tolerance to demanding training. The conjugate sequence system pioneered by Yuri Verkhoshansky (1986). The conjugate system involves periods of planned overreaching, followed by periods of restitution (Plisk & Stone, 2003). Plisk and Stone (2003) suggest that this is best implemented in blocks of four microcycles with only one primary emphasis (e.g. strength), and maintenance loads allocated to other abilities (e.g. speed/power). This system aims to saturate the emphasised training stress, causing cumulative fatigue and concurrent decreases in performance; this of course can be difficult within team sport environments where fixture congestion is common (e.g. soccer, basketball). Then, during the following restitution blocks, the emphasis is reversed (Figure 7.13). For example, the volume load for strength training markedly drops whilst that for speed work is moderately increased. By virtue of a delayed training effect phenomenon, the athlete’s strength capabilities undergo supercompensation. A practical example of the conjugate system, adapted from the work of Plisk and Stone (2003) and Stone et al. (2007), is illustrated in Table 7.5. Table 7.5 A practical example for applying and adapting the conjugate system Training emphasis Accumulation Restitution block 1 block 1 Accumulation Restitution block 2 block 2 Duration 4 weeks 2–3 weeks 4 weeks 2–3 weeks Strength and power training 16 sessions @ 4 days/week 4–6 sessions @ 2 days/week 16 sessions @ 4 days/week 4–6 sessions @ 2 days/week 9 sessions @ 3 days/week 8 sessions @ 2 days/week 9 sessions @ 3 days/week Speed and agility 8 sessions @ 2 training days/week Support for the conjugate system may be gleaned from studies investigating the response of the endocrine system to prolonged (≥3 weeks) and severe increases in volume load (Fry, Webber, Weiss, Fry, & Li, 2000; Hakkinen, 1989; Hakkinen, Pakarinen, Kauhanen, & Komi, 1988; Pendalay & Kilgore, 2001; Ratamess et al., 2003). In general, these researchers report significant decreases in resting/pre-exercise testosterone concentration and the testosterone:cortisol ratio, followed by supernormal levels and corresponding performance improvements upon returning to normal volume loads with a subsequent taper. These findings are considered significant as testosterone concentration and the testosterone:cortisol ratio are indices of the anabolic/catabolic state of the body (Fry, Kraemer, et al., 2000; Plisk & Stone, 2003). As a word of warning, however, practitioners should limit the duration of these concentrated blocks so that an overtraining syndrome does not develop (Plisk & Stone, 2003). Also, S&C coaches should be attentive to the potential signs and symptoms of overtraining with each passing week (Foster, 1998; Jones, 1991; Stone et al., 1991). A scoping review by Bell et al. (2020) outlines the literature looking at ways to identify the threshold between functional overreaching and the necessary avoidance of overtraining. By definition, functional overreaching represents an acute decrease in performance (days) followed by a subsequent supercompensation. Non-functional overreaching similarly starts with a reduction in performance, but usually over a longer period (weeks) and with no increase of performance following full recovery. As previously mentioned, if exposure to high-volume load remains consistent, overtraining syndrome can see the athlete face long-term reductions in performance over several months (Bell et al., 2020). This opportunity to increase performance in well-trained individuals is highly sought after, but consideration as to the threshold that exists between functional overreaching and non-functional overreaching can be a challenging task. Much of the literature on overreaching has explored biochemical markers, such as testosterone and cortisol and their ratio; however, these are likely to be altered independently of performance, but may provide the acute training state of the athlete (Bell et al., 2020). Another method to identify training state that may help distinguish between functional and non-functional overreaching is the use of surrogate performance tests such as maximal jump tasks and isometric or dynamic mid-thigh pulls and their associated variables (Haff et al., 2008; Suarez et al., 2019). Sensitivity of associated variables attained from these tests has shown reductions in response to high-volume resistance training and may therefore help differentiate between fatigue and overreaching (Bell et al., 2020). While “high-volume” is often associated with overreaching, the reader should note that the interpretation of what is deemed high or low will be governed largely by inter-individual variances. That is to say, what is highvolume for one athlete may only be moderate for another. Therefore, when planning functional overreaching in well-trained athletes, a surrogate measure and/or biochemical markers may serve as a guide to monitor the training state of the athlete and better identify the individual’s threshold between functional and non-functional overreaching and therefore elicit greater improvements in performance. Where equipment to monitor surrogate measures are not afforded, the use of historic volume loads via a training diary may also help the S&C coach to identify the athlete’s reaction to specific loading protocols and potentially help to determine a volume load threshold to optimise performance increases. Maintenance programmes Maintaining peak performance for 35 weeks The traditional periodisation strategies identified above are concerned with athletes who need to peak for a single or acute (<2 weeks) phase of competitions, e.g. track athletes and martial artists. Some athletes, however, especially team sport athletes, must reach their peak as part of pre-season training, and then maintain it for periods of up to 35 weeks, ideally peaking for the final. For example, Kraemer et al. (2004) showed that both starting and nonstarting soccer players experienced reductions in sport performance over an 11-week period of the competitive season. Although more pronounced in the starters, the fact that performance reductions were observed in all players indicates that performance adaptations may be independent of total match play and that the volume load of practices/S&C sessions should be carefully evaluated. Of significance was the fact that a catabolic environment (increased cortisol and decreased testosterone) was initiated in the pre-season and not obviated throughout the competition phase. This may have determined the metabolic status of the players as they entered the competitive period. While this may be exclusive to the training approach of collegiate soccer, or those that require athletes to get into shape quickly, the need for athlete restoration, particularly as they enter the competitive phase, can be noted. In a professional sporting environment, where fixture congestion can be a real concern over a prolonged duration, it is worth noting that both an excessive total training volume and an obsession over “recovery sessions”, while excluding an appropriate high-load, low-volume strength stimulus, will result in a reduction in performance. Further challenges associated with maintenance programmes may be gleaned from studies undertaken by Kraemer et al. (1989) and Aldercrentz et al. (1986). These investigators reported that sprint running increases circulating concentrations of cortisol and decreases concentrations of plasma testosterone. Therefore for sports such as rugby and soccer, which may be categorised as high-intensity intermittent exercise, with a prevalence of repeated bouts of maximal effort sprints, it is likely that an adverse metabolic environment will present itself if training programmes are not appropriately periodised. Non-traditional approach to periodisation It has been suggested that while the traditional form of periodisation (discussed above) is appropriate during the off- and pre-season, a nontraditional form of periodisation is more viable for team sports during the in-season (Gamble, 2006; Hoffman, Kraemer, Fry, Deschenes, & Kemp, 1990; Kraemer et al., 2000, 2003, 2004). At times, this may be out of necessity because of its ability to adapt to a sport’s competition calendar and its ease of administration within long seasons (Hoffman, Kraemer, Fry, Deschenes, & Kemp, 1990; Kraemer et al., 2000, 2003). This form of periodisation involves changes in volume loads and biomotor emphasis on a session-to-session basis. An example of a non-traditional periodised programme is illustrated in Table 7.6. One of the merits of this system is suggested to be the ease with which sessions can be quickly tailored to the competition schedule of the athlete (Haff, 2004a). If, for example, a competition is suddenly cancelled or arranged, the athlete can switch to the heavy or light training day, respectively. In addition, a microcycle and a mesocycle can be defined by the number of completed sessions or rotations, respectively, of the prescribed programme. Table 7.6 Day Example microcycle completed as part of a non-traditional periodisation strategy* Monday Wednesday Friday Day Monday Wednesday Friday Emphasis and volume load Pushing strength: 4 × 4 @ 4–6RM (~85–90% 1RM) Pulling strength: 4 × 4 @ 4–6 RM (~85– 90% 1RM) Power: 5 × 3 @ variable loads (dependent on the exercise) Example exercises Squats, bench press and overhead press Romanian deadlift, pull-ups and barbell row Weightlifting and derivatives, and plyometrics * Note that a mesocycle may be considered complete following a set number of rotations and athletes can rearrange the order based on competition scheduling. Finally, hypertrophy sessions are avoided due to the higher associated training volumes. 1RM, one repetition maximum. Finally, for the purposes of maintenance, a training frequency of 2 days per week is often recommended for training during the competitive phase (Ebben & Blackard, 2001; Ebben, Hintz, & Simenz, 2005; Haff, 2004b; Gamble, 2006; Simenz, Dugan, & Ebben, 2005). However, including even two S&C sessions a week for team sport players involved in regular competition may prove difficult. Gamble (2006) suggests that the issue of limited training time may be addressed by combining S&C training with sport practice. For example, speed, agility and plyometrics training can be included in team practices, and metabolic conditioning can be maintained through game-related conditioning methods. In addition, the skill element specific to each, particularly the latter example, encourages its use by sports coaches (Gamble, 2004). This tactical metabolic training approach can be structured according to work:rest ratios of the specific sport (Gamble, 2007; Plisk & Gambetta, 1997) and dominant energy systems. The taper The progressive increases in the volume load of periodised S&C programmes are likely to accumulate excessive fatigue and overstress the neuroendocrine system. This will reduce the stimulus for adaptation (as previously discussed) and lead to adverse circulating hormonal concentrations (Fry & Kraemer, 1997). However, a reduction in training with a concomitant optimal anabolic environment (or reduced catabolic processes) induced by a taper could potentially enhance performance (Izquierdo et al., 2007). The taper requires a reduction in the volume (i.e. exercises, sets or repetitions) of training in the final days before important competition, with the aim of optimising performance (Bosquet, Montpetit, Arvisais, & Mujika, 2007). It should be stressed that the objective of the taper is to dissipate the accumulated fatigue (enabling performanceenhancing adaptations to become apparent) rather than advance the athlete’s level of fitness (Mujika & Padilla, 2003). Significant improvements after tapering have been reported in numerous sports and Table 7.7 gives details of the associated performance gains, as summarised by Wilson and Wilson (2008). Table 7.7 Summary of performance gains following a taper 5–6% improvements in criterion competition performance gains Up to 20% increases in neuromuscular function (i.e. strength and power) 10–25% increases in cross-sectional area of muscle tissue 1–9% improvements in V̇O2max (this is likely a consequence of hypervolaemia, up to a 15% increase in RBC production and increased oxidative enzyme activity) Up to an 8% increase in running economy Serum testosterone may increase by 5%, with a corresponding 5% decrease in cortisol Catecholamines may be reduced by up to 20% Reduced creatine kinase concentrations (suggestive of decreased muscle damage following a workout) A 10% increase in anti-inflammatory immune cells, with a concomitant decrease in inflammatory cytokines Increased muscle glycogen stores (17–34%; often proportional to the reduction in volume load) especially following CHO loading. However, care should be taken to match energy intake with the reduced energy expenditure that characterises the taper Reduced RPE, depression, anger, and anxiety and increased vigour Decreased sleep disturbances V̇O2max, maximal oxygen uptake; RBC, red blood cell; CHO, carbohydrate; RPE, rate of perceived exertion. Adapted from Wilson and Wilson (2008). Taper strategies Generally, three types of taper are used: a step taper, a linear taper and an exponential taper (Figure 7.14). A step taper involves an immediate and abrupt decrease in training volume, e.g. decreasing the volume load by 50% on the first day of the taper and maintaining this throughout. A linear taper involves gradually decreasing the volume load in a linear fashion, e.g. by 5% of initial values every workout. The exponential taper decreases volume at a rate proportional to its current value (half-life), e.g. by 5% of the previous session’s values every workout. In addition, exponential tapers can have fast or slow decay rates. Also, Bosquet et al. (2007) suggested an additional taper, referred to as a “two-phase taper”, which involves a classical reduction in the training load, followed by a moderate increase during the last days of the taper (Figure 7.15). The objective of this strategy is to reduce the athlete’s fatigue before the reintroduction of more prolonged or intense efforts. The efficacy of the two-phase taper may be gleaned from anecdotal observations of the progressive improvement in performance often observed in an athlete from the first round of a competition to the final (Thomas, Mujika, & Busso, 2009). This form of taper requires further investigation. Schematic representation of the three principal tapering strategies. (Adapted from Mujika and Padilla, 2003.) Schematic representation of the two-phase taper. (Adapted from Thomas et al., 2009.) The optimal taper strategy As previously mentioned, a taper involves a reduction in the volume load of either of, or a combination of, the moderators or training, i.e. intensity, volume and frequency. The optimal manipulation of these variables may be best evidenced from the meta-analysis conducted by Bosquet et al. (2007); Table 7.8 summarises their findings, measured as effect sizes, for which the scale proposed by Cohen (1988) was used in their interpretation. Accordingly, the magnitude of the difference was considered trivial (<0.20), small (0.20–0.49), moderate (0.50–0.79) or large (≥0.80). Table 7.8 Effect of training variables on the effect size of taper-induced performance adaptations Variable Effect size p d 95% CI ≤20% −0.02 −0.32–0.27 0.88 21–40% 0.27 0.04–0.49 0.02 41–60% 0.72 0.04–1.09 0.0001 ≥60% 0.27 −0.03–0.06 0.07 Yes −0.02 −0.04–0.33 0.91 No 0.33 0.19–0.47 0.0001 Yes 0.24 −0.03–0.52 0.08 No 0.35 0.18–0.51 0.0001 ≤ 7 days 0.17 −0.05–0.38 0.14 8–14 days 0.59 0.26–0.92 0.0005 15–21 days 0.28 −0.02–0.59 0.07 ≥ 22 days 0.31 0.14–0.75 0.18 Step 0.42 −0.11–0.95 0.12 Progressive 0.30 0.16–0.45 0.0001 ↓ in volume ↓ in intensity ↓ in frequency Duration of taper Pattern of taper CI, confidence intervals; d, Cohen’s d effect size; p, significance value; ↓ magnitude of the difference was considered trivial (<0.20), small (0.20–0.49), moderate (0.50–0.79) or large (≥0.80). Data from Bosquet et al. (2007). The results from Bosquet et al. (2007) revealed that the optimal taper is 2 weeks in duration and consists of exponentially reducing the volume of training by 41–61%, whilst maintaining both the intensity and frequency of sessions. It should be noted that the large variability between studies, as suggested by 95% confidence intervals, suggests that not all athletes will respond favourably to this taper prescription, which may be attributable to the differences in training status and accumulated fatigue prior to the taper, i.e. greater volume reductions are necessary when previous training durations are longer and more intense. Summary and conclusion Periodisation represents an optimal strategy for organising S&C programmes. The selected strategy (i.e. basic, intermediate, advanced, nontraditional) should be based on the level of the athlete and the constraints of the competitive season. 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Maladaptation in response to accumulated psychophysiological stress can exacerbate performance decrements and increase the risks of injury (Kentta & Hassmen, 1998; Soligard et al., 2016). The density of contemporary training and competitive schedules can reduce recovery periods and thus potentially compromise an athlete’s readiness for further training and/or competition (Skorski et al., 2019). Various recovery modalities are used in sport to counter exercise-induced homeostatic perturbations that could diminish performance (Barnett, 2006). However, the interaction among workload and fatigue, muscle damage, soreness (and concomitant perception), and recovery and adaptation is complicated (Sands et al., 2016) and may be positively (Capps & Mayberry, 2009; Halson et al., 2014; Ihsan et al., 2015; MarquesJimenez et al., 2016) or negatively (Broatch et al., 2018; Higgins et al., 2011; Roberts et al., 2015) affected or unaffected (Cheung et al., 2003; Costello et al., 2012; French et al., 2008) by the intervention. The purpose of this chapter is to provide insight regarding the physiological mechanisms that underpin prevalent recovery strategies to guide efficacious practice. Recovery strategies Strategies that have been shown to support recovery (Barnett, 2006) after exercise include water immersion therapy (cold [Halson et al., 2014], hot [Vaile et al., 2008a], contrast [Gill et al., 2006], thermoneutral [Versey et al., 2013]), compressive techniques (compressive garments [Marques-Jimenez et al., 2016], intermittent pneumatic compression [Cochrane et al., 2013], massage [Poppendieck et al., 2016]), whole-body cryotherapy (WBC) (Lombardi et al., 2017), and sleep (Halson, 2008). Although modalities have been classified as short-term or long-term or peripheral (direct application to a body part) or central (less direct systemic effect) (Minett & Duffield, 2014; Sands et al., 2016), it is generally difficult to separate the effectiveness of individual strategies given that many are used concurrently by athletes (Amann, 2011). Whether directly or indirectly, most of these strategies enhance circulation (blood and lymphatic flow) (Barnett, 2006; Bishop et al., 2008; Sands, 2016) to attenuate intramuscular fluid pressure (swelling), which is linked to delayed-onset muscle soreness (DOMS) via the inflammatory cascade after exerciseinduced muscle damage (EIMD) (Appell et al., 1992), and aid the removal of metabolites and cellular debris to restore acute (i.e., 0–72 hours post-exercise) function (Bishop et al., 2008). Less well described are the adaptive effects of recovery over longer time periods. A summary of practical recommendations for recovery strategies is provided in Table 8.1. Table 8.1 Practical recommendations for recovery strategies Recovery strategy Practical recommendations Water immersion therapy CWI 1–3 sets of 5–15 min at 11–15°C (whole-body [head-out] immersion) immediately following high-intensity exercise (Halson, 2011; Versey et al., 2013) HWI HWI may not enhance acute performance recovery; future investigation regarding protocol characteristics (e.g., duration, temperature, depth) is needed (McGorm et al., 2018) CWT 3–6 (cold and hot) sets of 60 s at 8–15°C followed by 1–3 min at 38–42°C for 9–15 min following high-intensity exercise (Versey et al., 2013) CG Apply immediately and for 72 hours after high-intensity muscle-damaging exercise; custom-fitted CG exert greater pressure than standard-size CG, which may enhance performance recovery effects (if blood flow is not restricted) (Kraemer et al., 2004) IPC Apply immediately for 72 hours after high-intensity muscle-damaging exercise; pulse pressure of cells 1 (distal), 2–4, and 5 (proximal) are 70, 80, and 60 mmHg, respectively; pulse time and rest time are typically preset (by the manufacturer) at 30 s for 15 min (Cochrane et al., 2013; Hoffman et al., 2016; Sands et al., 2015) Compressive techniques Massage 5–12 min after mixed-type exercise to enhance acute performance recovery (Poppendieck et al., 2016) WBC 30 s at −60°C followed by 2 min at −135°C with a 2-min break between bouts (Selfe et al., 2014) immediate and recurrently following high-intensity muscle-damaging exercise (Hausswirth et al., 2011; Pournot et al., 2011a). CWI, cold-water immersion; HWI, hot-water immersion; CWT, contrast water therapy; CG, compression garments; IPC, intermittent pneumatic compression; WBC, whole-body cryotherapy. Water immersion therapy Water immersion therapy, which consists of four modes based on water temperature (cold [< 15°C], hot [> 36°C], contrast [alternation of immersion in cold and hot water], thermoneutral-water immersion [15–36°C] [Versey et al., 2013]), is a popular recovery strategy that has been the focus of several reviews (Bleakley & Davison, 2010; Broatch et al., 2018; Tipton et al., 2017; Wilcock et al., 2006). In addition to analgesic effects (Coffey et al., 2004), hydrostatic pressure elicits a cephalad redistribution of blood flow (Arborelius et al., 1972) that elicits physiological alterations, including intracellular and intravascular fluid shifts, reduction of muscle edema, and elevated cardiac output (Wilcock et al., 2006) that supports the removal of metabolic end products and substrate transportation post-exercise to restore acute function and assist tissue repair (Coffey et al., 2004). Cold-water immersion (CWI) CWI complements the effects of hydrostatic pressure given that cold-induced vasoconstriction may lessen muscle perfusion and interstitial fluid diffusion (Gregson et al., 2011) and reduce cellular, lymphatic, and capillary vessel permeability to dissipate edema (Cote et al., 1988). This decreases pain and mitigates the loss of force production (Smith, 1991). Reducing edema can also reduce cellular oxygen demand as a consequence of capillary constriction to lessen hypoxic cell damage and reduce immune cell infiltrates that may augment cellular injury to moderate subsequent tissue damage and necrosis (Capps & Mayberry, 2009; Wilcock et al., 2006). Additionally, metabolism can be slowed by >50%, which may facilitate oxygen diffusion to damaged tissues (Capps & Mayberry, 2009). Whilst this response reduces peripheral blood flow to maintain core temperatures, increases in central metabolism to offset the physiological responses to CWI may activate the sympathetic nervous system, induce oxidative stress, proliferate cellular and systemic free radicals, increase the production of waste products, and dissipate energy stores that can further exacerbate muscle stress and hinder the recovery process (Bleakley & Davison, 2010; Wilcock et al., 2006). However, a decrease in body temperature slows nerve transmission to stimulate an analgesic effect and reduce muscle spasm, which can lessen the perception of pain after damaging exercise (Wilcock et al., 2006). Thus, largely dependent on the protocol, CWI may hinder or hasten the recovery of exercise-induced decrements in function and performance (Bleakley & Davison, 2010; Broatch et al., 2018). While this is covered later, it is worth noting that this may be advantageous during periods of intensive competition/fixture congestion, but not desirable if aiming to facilitate positive adaptations. For example, athletic preparation staff may choose to limit the use of water immersion therapy during the general physical preparation phase of an annual training plan to enhance physical adaptations (Table 8.2) and increase its use during a competition week to enhance recovery (Table 8.3). Table 8.2 Example of a 12-week periodized training plan for college soccer and recommendations for use of water immersion therapy Fitness phase GPP SPP Phase duration 9 weeks 3 weeks Phase objectives Increase muscle mass, strength, and general work capacity Weekly training density 6–8 Increase sport-specific technical/tactical proficiency and work capacity and strength and rapid force production 10–12 Day of week D1 D2 D3 Training mode ST RT Off COD RT TT Betweensession break 6–8 h 0h Training load H L D4 RT M-H D5 D6 D7 D1 D2 D3 D4 ST Off TTS TTS RT TT RT TTS TTS TTS 6–8 h 6–8 h 6–8 h 6–8 h H H M H-M L Water immersion therapy D5 D6 D7 TTS RT Off TTS TTS L *CWT **CWT *CWT **CWI **CWI TTS 6–8 h 6–8 h M-H H **CWI **CWI *after the first training session; **after the second training session. COD, change of direction; CWI, cold-water immersion; CWT, contrast water therapy; D, day; GPP, general physical preparation; H, high; L, low; M, moderate; RT, resistance training; SPP, special physical preparation; ST, speed training; TT, tempo training; TTS, technical/tactical session. Table 8.3 Starter Example of an in-season week for American football and recommendations for use of water immersion therapy Training load D1 D2 D3 D4 D5 Game day M H Off M L H Training mode RT RT TTS TTS Between-session break 6–8 h 6–8 h Water immersion therapy *CWT **CWI *CWT CWI CWI M-H M Off TTS Redshirt/ reserve Training load M H Off Off TTS M-H *after the first training session; **after the second training session. CWI, cold-water immersion; CWT, contrast water therapy; D, day; H, high; L, low; M, moderate; RT, resistance training; ST, speed training; TTS, technical/tactical session. Training mode TTS Between-session break RT RT RT ST TTS TTS TTS RT 6–8 h 6–8 h 6–8 h Water immersion therapy *after the first training session; **after the second training session. CWI, cold-water immersion; CWT, contrast water therapy; D, day; H, high; L, low; M, moderate; RT, resistance training; ST, speed training; TTS, technical/tactical session. Owing to methodological inconsistencies (e.g., immersion and exercise protocol, participants’ training background, timing, performance outcome, length of the study) and participant bias (Broatch et al., 2014), studies investigating the benefits of CWI have produced mixed results (Broatch et al., 2018). Briefly, muscle strength and power (Higgins et al., 2017; Vaile et al., 2008b), endurance performance (Ingram et al., 2009), intermittent exercise (Roswell et al., 2009, 2010), markers of EIMD (Eston & Peters, 1999; Leeder et al., 2012a), inflammation (Montgomery et al., 2008; Peake et al., 2008), DOMS (Higgins et al., 2013; Vaile et al., 2008b), and perceptions of fatigue (Higgins et al., 2017; Leeder et al., 2012a) have been shown to benefit from CWI. However, CWI has been shown to have no benefit (Coffey et al., 2004; Higgins et al., 2017; Howatson et al., 2009; Jakeman et al., 2009; King & Duffield, 2009; Kinugasa & Kilding, 2009) or a negative effect (Broatch et al., 2018; Crowe et al., 2007; Schniepp et al., 2002; White et al., 2014) on these same outcomes by others. Although immersion protocols that involve whole-body immersion (head out) at a temperature of 11–15°C for 5–15 min (Halson, 2011; Versey et al., 2013) have been generally shown to enhance post-exercise function (Mujika et al., 2018), the effects of regular CWI on muscle adaptation are less clear (Tipton et al., 2017). Accepting the proposition that recovery strategies can blunt the pro-inflammatory phase of inflammation that is critical for muscle remodeling (Chazaud, 2016), regular postexercise CWI may diminish training adaptations. However, the outcome may depend on the nature of exercise. For example, CWI has been shown to alter the adaptive response to resistance training (Fuchs et al., 2020; Fyfe et al., 2019; Roberts et al., 2015) via decreases in muscle blood flow (Gregson et al., 2011) that can subdue the acute inflammatory response (Chazaud et al., 2003). In turn, this is believed to impair muscle protein turnover (Fujita et al., 2006; Timmerman et al., 2010). The activation of adenosine monophosphatedependent protein kinase (AMPK) in response to cold-water temperatures (Oliveira et al., 2004) may also suppress mammalian target of rapamycin (mTOR) (Roberts et al., 2015) and inhibit ribosomal biogenesis to hinder muscle hypertrophy and strength gains. Roberts et al. (2015) showed that CWI decreased acute satellite cell activity and the activation of kinases that regulate muscle hypertrophy. Negligible improvements in isokinetic work and type II muscle fiber cross-sectional area were also demonstrated. Over 12 weeks, these effects may have been compounded to lessen the anticipated gains in muscle mass and strength. Indeed, 7 weeks of regular CWI has been shown to attenuate increases in type II muscle fiber cross-sectional area compared to passive recovery in resistance-trained males (Fyfe et al., 2019). Basal protein degradation markers were increased, whereas mTOR1 signaling was blunted 1 and 48 hours post-training after CWI. In agreement with the findings of Roberts et al. (2015), post-workout CWI attenuated muscle fiber growth. However, lower-body muscle strength was improved to similar levels in each group, which contrasts with the findings of Roberts et al. (2015). Collectively, the available data suggest that CWI after resistance training may not be advised if muscle hypertrophy is desired (Fyfe et al., 2019; Roberts et al., 2015). Apart from Yamane et al. (2006), who reported attenuated improvements in maximal oxygen uptake (V̇O2max) and endurance performance following 4–6 weeks of routine CWI compared to passive recovery, the available evidence, on balance, does not indicate deleterious effects of CWI on endurance performance or markers of adaptation resulting from endurance training (Aguiar et al., 2016; Broatch et al., 2017; Halson et al., 2014). Halson et al. (2014) showed that CWI completed four times per week over a 3-week overreaching period followed by an 11-day taper significantly improved performance in a high-intensity interval cycling test. Allan et al. (2017) and Ihsan et al. (2014) found that 15 min of lower-extremity CWI after near-maximal intermittent cycling and 30 min of submaximal running followed by intermittent running to exhaustion, respectively, enhanced the expression of peroxisome proliferator-activated receptor y coactivator-1α (PGC-1α) compared to the control groups. Markers of mitochondrial biogenesis were not confined to a single bout of exercise (Ihsan et al., 2015). Performance indices (V̇O2max, running velocity), signaling kinase content (PGC-1α, AMPK, p38 mitogen-activated protein kinase [p38 MAPK]), and enzyme activities indicative of mitochondrial biogenesis were significantly greater in participants who employed CWI versus passive recovery over 4 weeks of endurance training. In contrast, however, endurance performance and similar markers of mitochondrial biogenesis (PGC-1α, p53, heat shock 70 kDa protein 1, AMPK, p38 MAPK) and function did not significantly differ between CWI (10°C for 15 min) and passive recovery groups who completed 4 and 6 weeks of cycling sprint and high-intensity training, respectively (Aguiar et al., 2016; Broatch et al., 2017). Ihsan et al. (2015) caution that, whilst mitochondrial biogenesis may be enhanced, regular CWI can concomitantly decrease mitochondrial efficiency. Although the results of studies do not indicate any negative effects, the use of CWI to improve endurance performance and increase the content of signaling proteins related to mitochondria biogenesis has been questioned (Bleakley & Davison, 2010; Broatch et al., 2018; Tipton et al., 2017; White et al., 2014). Hot-water immersion (HWI) The influence of HWI on recovery has been less well researched, although it may be acutely harmful (e.g., burns, rapid decrease in blood pressure, hypotension, faintness, loss of vasomotor control, tachycardia: Nagasawa et al., 2001; Turner et al., 1980). However, researchers have shown that HWI can provide acute restorative benefits (Kuligowski et al., 1998; Peake et al., 2017a; Pournot et al., 2011a; Vaile et al., 2008a, 2008b; Viitasalo et al., 1995) and may enhance training adaptations (Peake et al., 2015). Muscle strength and power (Vaile et al., 2008b, Viitasalo et al., 1995), markers of EIMD (Vaile et al., 2008b; Viitasalo et al., 1995), and inflammation (Kuligowski et al., 1998) have been shown to be lower following HWI, although contradictory findings have been demonstrated in studies that have used similar experimental protocols (Kuligowski et al., 1998; Pournot et al., 2011a; Vaile et al., 2008b). HWI may benefit muscle adaptation as heat shock factor-1 and its effectors (heat shock proteins) have been shown to protect against oxidative damage, apoptosis, and adenosine triphosphate depletion (Hatade et al., 2014; Maglara et al., 2003) and downregulate enzymes and transcription factors that cause protein degradation (Dodd et al., 2009; Gehrig et al., 2012) and activate anabolic signaling pathways (Gwag et al., 2013) that stimulate muscle remodeling (McGorm et al., 2018; Peake et al., 2015). However, post-exercise HWI has been shown not to enhance acute recovery via heat shock protein, cytokine, or macrophage response (Peake et al., 2017a). Following 10 weeks of lower-extremity resistance training, relative gains in muscle mass were significantly lower among participants who routinely employed HWI compared to passive recovery (Peake et al., 2017a). Although strength significantly improved in each group, increases were substantially less in the experimental condition (Peake et al., 2017a). Based on limited data, HWI may not have a significant effect on post-exercise recovery and could mitigate adaptations to training (Versey et al., 2013). Contrasting water temperature (CWT) Whereas cold and hot water temperatures cause vasoconstriction and vasodilation respectively, it has been suggested that CWT alternates cold and heat to evoke a “pumping action” that can increase blood flow and therefore lessen the extent and duration of inflammation (Bieuzen, 2013; Hing et al., 2008). However, this notion has been challenged, as CWT may not produce the intramuscular temperature changes needed to elicit this effect (Higgins & Kaminski, 1998; Hing et al., 2008). Although beneficial effects, including vasodilation and vasoconstriction, increased blood flow, reduction of markers of muscle damage (creatine kinase [CK]) and inflammation, and decreased swelling, pain, and muscle stiffness (Cochrane, 2004) have been demonstrated with CWT, the physiological mechanisms that potentially underpin CWT have not been well described (Hing et al., 2008). In their review, Versey et al. (2013) stated that less than half of the studies that investigated the effects of post-exercise CWT on recovery and performance found beneficial effects. Whereas CWT elicited acute improvements in performance, muscle strength and power (Vaile et al., 2007, 2008a, 2008b; Versey et al., 2011), endurance (Higgins et al., 2011; Versey et al., 2012), intermittent exercise (King & Duffield, 2009), markers of EIMD (Eston & Peters, 1999; French et al., 2008), inflammation (Eston & Peters, 1999; Vaile et al., 2007, 2008b), DOMS (Dawson et al., 2005; French et al., 2008; Gill et al., 2006; Ingram et al., 2009; Kuligowski et al., 1998; Vaile et al., 2008b), perceived exertion (Higgins et al., 2017; Versey et al., 2011), and perceptions of fatigue (Kinugasa & Kilding, 2009; Versey et al., 2011), the effects have been found to be negligible (Dawson et al., 2005; Dupuy et al., 2018; Hamlin, 2007; Higgins et al., 2017; King & Duffield, 2009; Kinugasa & Kilding, 2009; Pournot et al., 2011a) and detrimental by others (Higgins et al., 2011, 2017; Pournot et al., 2011a; Versey et al., 2011, 2012). Research that showed beneficial effects of CWT employed similar protocols that differed substantially from studies that showed negligible or detrimental effects (Versey et al., 2013). More recent meta-analyses have confirmed these overall findings (Dupuy et al. 2018; Higgins et al., 2017). Moreover, in contrast to other immersion modes, less is known regarding the long-term adaptive effects of regular CWT. Despite largely positive acute effects on anaerobic performance (Bieuzen, 2013), particularly in response to temporary increases in workload, a disrupted adaptive response has been found with regular use (Chazaud, 2016; Peake et al., 2017b). Evidence suggests that CWI and CWT elicit similar acute positive recovery effects compared to HWI or thermoneutral-water immersion (Vaile et al., 2008a, 2008b; Versey et al., 2013). However, it is not clear which immersion protocol is most effective (Versey et al., 2013). Like CWI, no ideal prescription for CWT exists; whether treatment ought to culminate with CWI or HWI is not clear. Nevertheless, 60 s at 8–15°C followed 1–3 min at 38–42°C for 9–15 min has been recommended (Bieuzen, 2013; Versey et al., 2013). In summary, CWT and CWI are generally effective in maintaining or limiting decreases in performance during condensed sport schedules (Bieuzen, 2013). However, ongoing exposure may blunt adaptive responses to certain modes of exercise and may be contraindicated during particular training periods (Chazaud, 2016; Peake et al., 2017b; Skorski et al., 2019). Compressive techniques Compressive techniques, including compression garments (CG), intermittent pneumatic compression (IPC), and massage to facilitate recovery following exercise, are now commonly accessible by athletes. However, disparate findings regarding the restorative effects of these modalities can in part be attributed to differences in study design and interand intra-individual variations in participant training status, stress response to exercise, post-treatment perception of recovery, preferential bias, and other confounding factors (sleep, nutrition, mood, etc.). Compressive garments (Hill et al., 2014a; Marques-Jimenez et al., 2016) and IPC (Couturier & Duffield, 2013) have been shown to elicit positive psychophysiological effects in individuals of different physical activity levels in the days after various modes of strenuous exercise. In contrast, massage, which is difficult to standardize (Sands, 2016), has demonstrated equivocal findings, as indicated by several meta-analyses (Dupuy et al., 2018; Moraska, 2005; Poppendieck et al., 2016; Weerapong et al., 2005). Given the high heterogeneity between studies, recommendations relating to IPC need to be made with caution. Compression garments Traditionally used to treat clinical pathologies, CG are now widely used for restorative purposes; the induced external pressure gradient is believed to reduce swelling and pain, and enhance lymphatic flow to remove myocellular debris following muscle-damaging exercise (Hill et al., 2014b; Kraemer et al., 2001a). Studies have shown progressive decreases in swelling at 24, 48, and 72 hours (Bovenschen et al., 2013; Brown et al., 2020; Carling et al., 1995; Davies et al., 2009; Kraemer et al., 2001a,b) and positive moderate effects on markers of EIMD (i.e., CK, lactate dehydrogenase [LDH]) at 24, 48, and 96 hours after compression treatment (Brown et al., 2020; Davies et al., 2009; Duffield et al., 2008, 2010; French et al., 2008; Jakeman et al., 2010a, 2010b; Kraemer et al., 2001a, 2001b), although the effects appear to be dependent on time (reduced LDH only after 24 hours post-treatment) (Davies et al., 2009; Kraemer et al., 2001a), the primary site of muscle damage (Kraemer et al., 2001a), participants’ training status (Maughan & Gleeson, 2010), and the mode and relative novelty of exercise (thus the degree of EIMD) (MarquesJimenez et al., 2016). However, given the high inter- and intra-individual variability of these markers and their poor temporal relationship with muscle function (Friden & Lieber, 2001), it is difficult to reliably determine the progressive magnitude of post-treatment effectiveness on EIMD. CG have shown beneficial effects on muscle swelling at 48 and 72 hours after a range of exercise protocols (Marques-Jimenez et al., 2016). According to Kraemer et al. (2004), these effects are related to the time period in which intramuscular and subcutaneous swelling is generally evident. As such, a reduction in swelling could attenuate the proinflammatory response that can elicit further muscle damage (Kraemer et al., 2001a) and cause soreness (Jakeman et al., 2010a, 2010b). Thus, post-intervention reductions in muscle swelling may align with demonstrated reductions in perceived soreness between 24 and 72 hours (Carling et al., 1995; Davies et al., 2009; Duffield et al., 2008, 2010; French et al., 2008; Jakeman et al., 2010a, 2010b; Kraemer et al., 2001a, 2001b; Sands et al., 2015) and attenuated performance decrements (as indicated by countermovement jump and squat jump height, muscle strength and power, and sprint and change of direction) at 24, 48, 72, and 96 hours post-exercise (Brown et al., 2020; Duffield et al., 2008; Jakeman et al., 2010a, 2010b; Kraemer et al., 2001a, 2001b). Despite these positive results, researchers have demonstrated equivocal findings within and between studies (Marques-Jimenez et al., 2016) owing to the mode of exercise, application of the garment, outcome measures, subjective bias, and, notably, the exerted pressure (Couturier & Duffield, 2013; Davies et al., 2009). Although results have shown improvements in perceived muscle soreness post-exercise, inter-individual variations in response to, and the complex nature of, EIMD (Clarkson & Hubal, 2002) may be responsible for inconsistencies – inconsistencies that limited practical recommendations relating to the practice (Couturier & Duffield, 2013; Marques-Jimenez et al., 2016). Additionally, a range of pressures (15–35 mmHg) have been used in studies examining the potential benefits of post-exercise muscle compression (Hill et al., 2015). Whereas lower pressures (<25 mmHg) may not elicit physiological responses (e.g., increased blood flow and osmotic pressure), greater pressures can restrict blood flow, which may hinder recovery (Hill et al., 2015). As such, there may be an optimal level of pressure required to elicit the greatest increase in venous blood flow (Driller & Halson, 2013). Determining this is challenging given differences in limb and tissue size and individual variability in the sensitivity to blood flow changes (Bishop et al., 2008; Couturier & Duffield, 2013). Interestingly, Brown et al. (2020) showed that custom-fitted CG, which exerted substantially greater pressures than standard-size CG, were associated with significantly greater improvements in recovery (e.g., lower plasma CK activity and reduced muscle swelling) in rugby players. Additional questions regarding the length of time CG should be applied, the influence of posture relative to the exerted pressure, and how treatment may affect longer-term recovery ought to be addressed so that more definitive recommendations can be provided (Marques-Jimenez et al., 2016). Nevertheless, the available evidence suggests that athletes can benefit from CG, particularly to facilitate acute recovery, if applied immediately post-exercise and up to 72 hours following muscledamaging exercise (Kraemer et al., 2004). Intermittent pneumatic compression Pneumatic compression dynamically inflates and deflates sleeves secured around limbs to elicit intermittent pulse compression (Cochrane et al., 2013). Similar to static compression, IPC can increase arterial blood flow and venous and lymphatic return and reduce swelling (Couturier & Duffield, 2013; Sands, 2016). However, compared to static compression, IPC has been shown to exert greater pressures to enhance lymphatic drainage, which may increase the velocity of blood flow and hasten the dissipation of swelling and removal of cellular debris to improve soft-tissue healing (Capps & Mayberry, 2009; Havas et al., 1997; Khanna et al., 2008). Recently, Zuj et al. (2017, 2019) showed that IPC enhanced limb blood flow and tissue oxygenation during recovery, although it did not attenuate muscle force loss in a range of muscle actions at low (30° per second) and high (180° per second) angular velocities after muscle- damaging exercise (Cochrane et al., 2013) or improve recovery following long-distance running (Draper et al., 2020; Heapy et al., 2018; Hoffman et al., 2016; Overmayer & Driller, 2017). Collectively, the available data show no significant effects of IPC on markers of EIMD (e.g., C-reactive protein [CRP]) (Draper et al., 2020; Overmayer & Driller, 2017) or subsequent performance (Heapy et al., 2018) and mixed results regarding subjective measures of recovery (Draper et al., 2020; Heapy et al., 2018; Hoffman et al., 2016; Overmayer & Driller, 2017). IPC showed no effects on performance, markers of inflammation, and non-significant improvements in self-reported soreness in a group of American football players at 3 and 24 hours post-training (Chase, 2017). In addition to the inconsistent findings and the potential lack of accessibility of IPC in most sport settings, specific recommendations to guide IPC pulse pressure, pulse time, duration, and length of treatment are not clear. Massage Massage, which involves a range of different techniques, including vibration, is perceived to improve blood flow and reduce muscle swelling, pain, and stiffness, and reduce functional decrements post-exercise. However, excluding an ameliorated psychophysiological response (Delextrat et al., 2013; Hemmings, 2001; Mancinelli et al., 2006), and therefore a heightened sense of relaxation (Olausson et al., 2010), only limited evidence supports these claims (Davis et al., 2020; Weerapong et al., 2005). Reviews have shown that whilst massage is a popular recovery modality among athletes, its effects are trivial and equivocal (Davis et al., 2020; Moraska, 2005; Nedelec et al., 2013; Poppendieck et al., 2016). A meta-analysis that included 22 randomized control studies showed that massage elicited a ~3% improvement in performance; more than half of the included studies showed negligible effects, whereas five and four studies showed mixed and negative results, respectively; larger effects were found for shorter massage durations (5–12 min) and recovery periods (5–10 min) after and between high-intensity exercise bouts in untrained athletes (although the average performance improvements were considered relevant for elite athletes) (Poppendieck et al., 2016). A more recent metaanalysis concluded that massage did not enhance measures of performance or perceived fatigue; however, it did have the potential to reduce DOMS (Davis et al., 2020). Understanding that the sensitization of pain receptors (nociceptors) via inflammatory cell infiltrates can to some degree underlie muscle soreness (Hyldahl & Hubal, 2014), massage may provide an analgesic effect through a reduction in muscle swelling (Crane et al., 2012; Smith et al., 1994). Immediately after and 2.5 hours following 10 min of massage, muscle biopsies showed reduced inflammatory markers (nuclear factor kappa B, prostaglandin E2 [PGE2], interleukin [IL]-6, tumor necrosis factor-α [TNF-α]) and increased mitochondriogenesis which, taken together, may have reduced pain and hastened muscle repair in participants who performed a 30-min exhaustive bout of upright cycling (Crane et al., 2012). In a similar study, a 30-min massage (administered 2 hours after eccentric exercise) showed reduced neutrophil accumulation and lower CK levels and perceived soreness at 30-min intervals over 8 hours and at 8, 24, 48, 48, 73, 96, and 120 hours, respectively, compared to a control group (Smith et al., 1994). Thus, limited massage durations may enhance acute recovery by suppressing inflammation. According to Weeks and Horan (2009), the benefits of massage may be psychological rather than physiological. Positive psychological effects on perceived recovery have been repeatedly demonstrated (Davis et al., 2020; Dawson et al., 2004; Delextrat et al., 2013; Farr et al., 2002; Hemmings, 2001; Hilbert et al., 2003; Mancinelli et al., 2006). However, these findings should be interpreted with caution, as many studies investigating the effects of massage have had methodological flaws relating to an assortment of massage techniques, lack of a control group, and often a rapport between masseuse and athlete that has the potential to influence subjective findings (Sands, 2016). Nevertheless, athletes’ partiality for massage should not be disregarded despite negligible and ambiguous findings. Whole-body cryotherapy WBC was initially employed nearly 40 years ago to treat rheumatoid arthritis (Lombardi et al., 2017). More recently, WBC has been equivocally shown to reduce muscle inflammation and damage (Pournot et al., 2011b; Ziemann et al., 2014) and enhance subjective recovery (Bleakley et al., 2014) and psychological parameters (Schaal et al., 2015) following, and during periods of, rigorous training. Briefly, WBC has been shown to induce peripheral vasoconstriction to enhance muscle oxygenation, lower heart rate, and increase stroke volume, and stimulate parasympathetic nervous system activity, which can favor post-exercise recovery (Kruger et al., 2015; Lombardi et al., 2017; Zalewski et al., 2014). Additionally, WBC has been shown to evoke anti-inflammatory effects, indicated by a reduction and increase in pro- (IL-2, IL-8, IL-1β) and anti- (IL-10, IL-1 receptor agonist) inflammatory cytokines, respectively, and discordant effects on IL-6, and lessen muscle damage, indicated by the inhibited release of intracellular enzymes (CK, LDH) and PGE2 and CRP (Ferreira-Junior et al., 2014; Pournot et al., 2011b), which may underlie subjective markers (Gregorowitcz & Zagrobelny, 1998; Pournot et al., 2011b; Schaal et al., 2015) and function (Fonda & Sarabon, 2013; Hausswirth et al., 2011). However, mechanistic underpinnings are widely debated (Ferreira-Junior et al., 2014; Lombardi et al., 2017). Based on conflicting findings (Costello et al., 2012; Fonda & Sarabon, 2013; Guilhem et al., 2013; Hausswirth et al., 2011; Kruger et al., 2015; Vieira et al., 2015) and the limited number of randomized studies, WBC may not improve functional recovery (Bleakley et al. 2014; Costello et al., 2015), although methodological heterogeneity, notably, the timing and frequency of treatment, has confounded results (Lombardi et al., 2017). Given that the pro-inflammatory process is evoked immediately following EIMD, delayed exposure to WBC may be too late to elicit a favorable response (Ferreira-Junior et al., 2014). Muscle damage, soreness, and function were not affected after WBC was applied 24 hours postexercise (Costello et al., 2012), whereas a single treatment immediately following plyometric training reduced muscle swelling and improved the rate of strength recovery compared to controls (Ferreira-Junior et al., 2014). In contrast, immediate post-training exposure showed no effects on performance, soreness, or recovery (Guilhem et al., 2013; Russell et al., 2017; Vieira et al., 2015). Thus, the timing of treatment (relative to exercise) may or may not be impactful. Results that favor WBC are generally observed among studies that repeat exposure over consecutive days. Successive treatments elicited positive effects on muscle strength and soreness following long-distance running and eccentric resistance training (Fonda & Sarabon, 2013; Hausswirth et al., 2011; Pournot et al., 2011b) compared to a single exposure and three short sessions interspersed by a week in soccer and rugby players, respectively (Russell et al., 2017; Selfe et al., 2014). Accordingly, a single session prescribed immediately after eccentric exercise induced similar effects as passive recovery (Ziemann et al., 2014). However, when exposure was repeated twice daily over 5 days, enhanced physiological alterations (IL-6 and IL-1β were not changed and IL-10 was substantially elevated) were shown compared to the control group (Ziemann et al., 2014). It should be noted that the results may have been impacted by the repeated bout effect (Ferreira-Junior et al., 2014). Nevertheless, a single session may not be adequate to induce a beneficial effect (Lombardi et al., 2017). Despite widespread differences in protocols (e.g., temperature, acute timing and duration of exposure, participants’ training status, body composition, preceding exercise mode) (Lombardi et al., 2017), WBC may be optimized via 30 s at −60°C followed by 2 min at −135°C with a 2min break between bouts (Selfe et al., 2014). Immediate and recurrent post-exercise WBC exposure may elicit superior effects compared to a single delayed treatment (Fonda & Sarabon, 2013; Hausswirth et al., 2011; Pournot et al., 2011b; Ziemann et al., 2014). The results of a number of studies have shown that WBC has a positive effect on subjective parameters (Gregorowitcz & Zagrobelny, 1998; Hausswirth et al., 2011; Hausswirth, 2013; Lombardi et al., 2017; Pournot et al., 2011b; Schaal et al., 2015). Improved psychological recovery, indicated by an enhanced perception of muscle fatigue, pain, and well-being, has been shown in competitive endurance athletes and elite synchronized swimmers (Hausswirth et al., 2011; Pournot et al., 2011b; Schaal et al., 2015). Compared to passive recovery, WBC also significantly improved sleep duration and latency during a week of intensified training (Schaal et al., 2015). Post-exercise parasympathetic reactivation, induced biochemical release (e.g., dopamine, serotonin, beta-endorphin), and decreased and increased pro- and anti-inflammatory cytokines, respectively, speculatively contributed to improved mood and sleep patterns and therefore the possible deterrence of non-functional overreaching (Schaal et al., 2015; Tipton et al., 2017). In related findings, WBC has been shown to improve sleep, sense of relaxation, mood, and symptoms of depression in patients undergoing treatment (Gregorowitcz & Zagrobelny, 1998; Rymaszewska et al., 2003, 2008). Additionally, recurrent exposure could strengthen the immune system and reduce the susceptibility to infection (Hausswirth & Mujika, 2013). Given that overtrained athletes can present similar symptom profiles as clinically depressed patients (Dishman, 1983) and demonstrate a weakened immune function (Fry et al., 1994), WBC may potentially be useful during periods of extreme physiological stress that result in psychological perturbation (Clow & Hucklebridge, 2001; Slavich & Irwin, 2014). In summary, methodological inconsistencies make it difficult to establish the efficacy of WBC and its application, particularly due to the financial costs involved. However, the positive psychological effects (i.e., subjective indices) of WBC exposure should not be overlooked. Sleep Surveys on recovery strategies in elite sport revealed that 95% and 100% of practitioners and team sport athletes, respectively, considered sleep to be an effective recovery strategy (Nedelec et al., 2013; Venter, 2014). Sleep regulates numerous physiological and psychological functions that influence recovery (Nedelec et al., 2015b). Examination regarding the impact of sleep deprivation has informed much about the function of sleep (Nedelec et al., 2015a) and its relevance to recovery (Halson, 2008). The degree to which sleep patterns are disturbed is related to physiological alterations that can affect performance and adaptation (Halson, 2008). Several theories have been proposed regarding the function of sleep (Frank, 2006), including the neurometabolic theory, which posits that sleep assists in the restitution of the nervous and metabolic cost imposed by the waking state (LeMeur et al., 2013). Sleep deprivation has been shown to delay glycogen repletion (Skein et al., 2011) speculatively due to prolonged wakefulness and therefore further energy expenditure (Skein et al., 2011; VanHelder & Radomski, 1989). The hindered resynthesis of depleted muscle glycogen following high-intensity exercise resulted in lower glycogen concentrations the next day compared to controls, which may have negatively impacted subsequent intermittent sprint performance (Skein et al., 2011). Additionally, sleep is theorized to elicit a restorative effect on the immune and endocrine systems (Halson, 2008; VanHelder & Radomski, 1989). Fragmented sleep was associated with an elevated pro-inflammatory cytokine response (IL-6, IL-1β, TNF-α) during an intensive training period in competitive rowers (Main et al., 2010) and heightened CK and CRP concentrations during the course of recovery in rugby league players (Skein et al., 2013). Irwin et al. (2006), who demonstrated similar results in the morning following a sleepless night, suggested that the intensified inflammatory response was mediated by the nuclear factor κB inflammatory signaling system and through growth factor hormone response pathways. Dattilo et al. (2011) suggested that sleep deprivation could elicit reductions in insulin-like growth factor-1 and testosterone concentrations and increase cortisol levels, thereby eliciting a catabolic state in which muscle damage and soreness are manifested (Haack & Mullington, 2005) and muscle remodeling is impaired (Akerstedt & Nilsson, 2003). In related findings, sleep restriction over several days has been shown to lower muscle protein synthesis rates in recreationally trained males (Saner et al., 2020). Collectively, disrupted sleep patterns can exacerbate EIMD and hinder adaptive remodeling (Halson, 2008; Nedelec et al., 2015a, 2015b; Saner et al., 2020), which can lower exercise tolerance (i.e., increased perceived exertion) (Fullagar et al., 2015), decrease emotional well-being (Dinges et al., 1997), and increase injury risk (Milewski et al., 2014). Despite equivocal findings regarding its efficacy, recovery strategies may positively affect sleep, which can have pronounced effects on psychophysiological functions believed essential to the recovery process (Nedelec et al., 2015b). Although it is important to isolate recovery strategies to evaluate their effects on recovery processes, investigation regarding the interaction between recovery strategies and sleep is ecologically valid (Lovell et al., 2013; Nedelec et al., 2013). According to Halson (2008), several different recovery strategies may initiate sleep onset and decrease inflammation and DOMS – increasing the quality of sleep. Accordingly, the use of CWI (15 min) and CG (3 hours post-training) in conjunction with enhanced sleep hygiene was shown to improve sleep time (total time in bed and minutes asleep) and increase time in play, stroke rate, and lower-body power and reduce perceived exertion and fatigue following a twice daily, on-court training and matchplay sessions in highly trained tennis players (Duffield et al., 2014). Sleep duration was largely affected by recommendations to improve sleep hygiene that included the facilitation of a cool environment (~20°C) and the avoidance of light and electronic stimulants (e.g., television, cellular phones, computers) 30 min prior to bed (Duffield et al., 2014). Given that many athletes are vulnerable to regular disturbances in sleep (Leeder et al., 2012b), there is value in educating them regarding the benefits of sleep and providing them with individualized recommendations to enhance sleep hygiene so as to enhance post-exercise recovery (Duffield et al., 2014; Nedelec et al., 2013). A summary of the activities that will help enable good sleep is provided in Table 8.4. Table 8.4 Practical recommendations to improve sleep Schedule training appropriately Set intense training before 6 p.m. Avoid early-morning training Adapted from Le Meur et al. (2013) and Nedelec et al. (2015a, 2015b). Maintain a consistent sleep schedule Set a regular bed and wake-up time, including on off-days Participate in daytime activities and exposure to bright morning light on off-days Nap briefly (i.e., 5–30 min) in the early afternoon and not during the morning or evening Eat and drink appropriately Avoid large meals close to bedtime Avoid caffeine after noon Avoid alcohol Avoid excessive water intake prior to bedtime Maintain a bedtime routine that promotes relaxation Avoid exposure to bright light Avoid electronic devices and television 30 min prior to bedtime Take a warm shower or bath prior to bedtime Avoid activities other than sleeping while in bed Reduce noise Ensure a cool room temperature (~20°C) Have a comfortable bed Manage psychophysiological stress Employ recovery strategies to reduce soreness and enhance sleep quantity and quality (e.g., cold-water immersion, contrast water therapy, whole-body cryotherapy) Employ techniques to fall and return to sleep Assume a relaxed position while in bed Focus on relaxation versus sleep Remove the bedroom clock Adapted from Le Meur et al. (2013) and Nedelec et al. (2015a, 2015b). Conclusion Although recovery strategies have been shown to lessen exercise-induced homeostatic perturbations that can diminish acute function (Barnett, 2006), methodological inconsistencies and inter- and intra-individual variations in response to, and the complex nature of, EIMD (Clarkson & Hubal, 2002) may be responsible for differences in research findings. These inconsistencies limit the practical recommendations that can be made relating to a number of recovery techniques. In addition to accessibility and practicality, recovery strategies are commonly preferred based on perception and past experience (Crowther et al., 2017; Simjanovic et al., 2009), thus inherent bias may obscure the actual effects (Sands, 2016). Nevertheless, the partiality for particular modalities should not be disregarded despite equivocal findings and the potential for detrimental adaptive effects. Stress-induced arousal, if persistent, can initiate a catabolic shift that athletes’ mood may reflect (Anshel & Sutarso, 2007; Mujika et al., 2018). Essential to the resolution of arousal is the reduction of stress via relaxation (Sands, 2016). As such, the inclusion or withholding of preferential modalities may influence the stress response and therefore the sensation of fatigue to preceding and subsequent exercise (Ament & Verkerke, 2009). As psychological drives can underpin physiological mechanisms to initiate responses to perceived homeostatic perturbations (St. Clair-Gibson et al., 2017), modalities may enhance function because they positively influence subjective parameters (Sands et al., 2016; Skorski et al., 2019). In summary, the astute and timely application of recovery strategies may attenuate acute functional decrements via psychophysiological mechanisms. Practical applications When considering which recovery intervention to implement, practitioners should consider the rocks, pebbles, and sand analogy to determine which intervention is most appropriate. Once practitioners have decided on their “big rocks” of recovery they can use Figure 8.1 to help determine when in the training cycle it is most appropriate to implement specific recovery methods for their athletes. Flow chart detailing factors to consider when determining the implementation of recovery methods. Whilst interventions to hasten recovery following exercise may disrupt some adaptive processes (Chazaud, 2016; Peake et al., 2017b), inadequate recovery may affect the quantity and quality of subsequent training sessions, hinder competitive performance, and increase the chance for injury (Kentta & Hassmen, 1998; Soligard et al., 2016). Barnett (2006) suggested that whilst sport-specific fitness is important, reducing fatigue and improving post-exercise recovery will influence competitive success. Halson et al. (2014) have provided two rationales that may inform practice. First, restorative strategies may enable short-term intensive loading that could enhance training effects. Second, modalities may be withheld and cycled during distinct training phases (Sands, 2016) to maximize adaptive effects and lessen desensitization to certain techniques. Similar to exercise programming, the prescription of recovery strategies is likely a trade-off in conflicting demands (Zatsiorsky & Kraemer, 2006). Accepting this proposition, several factors should be considered: The prior training load (nature and extent of the exercise stimulus) should be assessed in accordance with contextual factors (e.g., age, gender, training status, level of performance, psychological profile) given its influence on acute and amassed fatigue and therefore function (Mujika et al., 2018; Skorski et al., 2019). The recovery intervention should consider the nature and extent of fatigue and the time between training bouts or competition (and available resources) (Bieuzen, 2013). Intervention may be contraindicated if there is adequate time for natural recovery between exercise bouts (Skorski et al., 2019). Consideration of the short- and long-term goals of the training session relative to the individualized training plan is important. Withholding modalities during certain times of year (e.g., general physical preparation period) or for certain athletes (e.g., reserves) may improve the adaptive response to particular modes of training (e.g., strength and hypertrophy) and enhance hormetic effects (Peake et al., 2015; Skorski et al., 2019). As psychological factors are important to performance, recovery strategies should consider the athlete’s preference. Recommendations for acute recovery Several strategies, including water immersion therapy, compression techniques, and WBC, have been shown to reduce perceived fatigue and hasten acute recovery via enhanced circulation (directly or indirectly) to decrease inflammation, which is linked to DOMS after EIMD (Appell et al., 1992; Barnett, 2006; Bishop et al., 2008; Sands, 2016). Among compression techniques, massage can evoke a beneficial acute psychophysiological response (Hemmings, 2000). However, CWI elicited comparable and greater improvements in perceived fatigue and performance, respectively, 24 hours postcompetition (Delextrat et al., 2013). Additionally, CWI showed a larger average effect size across studies for performance compared to massage (Poppendieck et al., 2013, 2016). Custom-fitted CG, if worn immediately, and over successive days, following highintensity exercise can also enhance acute recovery (Brown et al., 2020), although CWT more effectively attenuated soreness post-EIMD (French et al., 2008). Recurrent and immediate post-exercise WBC may be useful to deter non-functional overreaching and psychological perturbation as a consequence of concentrated loading (Schaal et al., 2015). However, CWI more effectively reduced soreness, improved lower-body power, and enhanced the perception of recovery at 48, 72, and 24 hours, respectively, compared to WBC (Abaidia et al., 2016). Compared to CWI, CWT generally shows superior immediate effects on fatigue after time trial, match, and damaging exercise (Bieuzen, 2013), whereas CWI showed superior effects on performance and subjective measures at 24–72 hours (Ingram et al., 2009). Accordingly, CWI elicited a significantly lower rating of perceived fatigue over 4 days post-exercise (Bleakley et al., 2012). Additionally, cold exposure (e.g., CWI, WBC), along with recommendations to improve sleep hygiene, may initiate sleep onset and improve sleep duration and quality (Halson, 2008), which has been shown to support numerous physiological and psychological functions that may be essential to the recovery process (Nedelec et al., 2015b). Given its accessibility and practicality in most settings, CWI and CWT may be viable options to enhance acute recovery. References Abaidia, A.E., Lamblin, J., Delecroix, B., Leduc, C., McCall, A., & Nedelec, M. 2016. 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Kilduff DOI: 10.4324/9781003044734-12 SECTION 1 Literature review Depending on the sport and level of competition, team sport players may commence competitive encounters anywhere between 09:00 and 11:00 (e.g., rugby 7s and academy football games) and 20:00–21:00 (e.g., elite evening matches) local time. While start times are likely determined by extraneous factors, including the demands of television (Drust et al., 2005), athletes may experience changes in physical performance throughout the waking day (Chtourou and Souissi, 2012; Teo et al., 2011a, 2011b). In addition to the importance of appropriate non-match-day preparatory strategies (e.g., tapered training, prior nutritional interventions such as carbohydrate loading, etc.), a role exists for interventions performed on match-day itself to acutely enhance subsequent performance (Kilduff et al., 2013a; Russell et al., 2015b) and/or to offset any residual fatigue from the training week or previous competition. This chapter provides practical suggestions for modified practices regarding the match-day activities of team sports players. Although not mutually exclusive, such strategies can broadly be categorised as those which are implemented: (1) more than 3 hours before a match commences (e.g., prior priming exercises); (2) less than 3 hours before a player’s pitch-entry (e.g., modified warm-up/rewarmup practices, ischaemic pre-conditioning [IPC], and hormonal priming); and (3) during scheduled within-match breaks (e.g., half-time heat maintenance strategies). Strategies implemented more than three hours before a match commences Prior priming exercise Testosterone (T) concentrations are positively related to indices of physical performance deemed crucial to team sports performance, with positive correlations existing between baseline T concentrations and indices of muscular power production (Crewther et al., 2009, 2012a, 2012b; Cook and Crewther, 2012a). Endogenous T may also be positively associated with aspects of athletic behaviour related to motivation and confidence to compete (Cook and Crewther, 2012b), and game-ranked performance scores in rugby union players (Gaviglio et al., 2014). As T shows circadian rhythmicity, with an early-morning peak followed by a transient decline through the day (Kraemer et al., 2001; Teo et al., 2011a), offsetting this circadian decline could benefit performance during sporting activities performed in the afternoon or evening. Resistance exercise can acutely raise T concentrations (Kraemer and Ratamess, 2005), and may thus benefit subsequent competitive performance if an event is commenced with elevated T. Ekstrand et al. (2013) demonstrated that morning resistance exercise that included back squats performed to failure and power clean exercises improved throwing distance in well-trained shot-putters 6 hours later. Similarly, improved afternoon performance was observed when rugby union players had completed sprints (5 × 40 m) and whole-body resistance exercises (bench press and back squat routines up to 100% of three repetition maximum values) 6 hours beforehand (Cook et al., 2013b). Notably, the morning exercise attenuated a circadian decline in T concentrations compared with a rested control condition (Cook et al., 2013b). Such findings highlight a potential role for specific modes of morning priming exercise to improve afternoon or evening performance, and that such findings may be modulated by changes in hormone status (Harrison et al., 2019). Although the greatest benefits may be realised between 6 and 33 hours after the priming stimulus, delayed effects could exist for 1–48 hours following resistance exercise priming (Harrison et al., 2019). The literature to date suggests that when progressively loading over multiple sets with limited total volume, performing high-load (≥ 85% one repetition maximum [1RM]) traditional resistance exercises or low-load (30–40% 1RM) ballistic exercises may be the most beneficial for improving markers of strength, power, and/or sprinting performance thereafter (Harrison et al., 2019). However, acknowledging the practical considerations associated with the pre-competition practices of professional team sport players, the methods of morning exercise typically examined may preclude their use on competition day. Whole-body resistance exercises, particularly if performed to nearmaximal load and/or momentary muscle failure, are unlikely to be tolerated and routinely adopted in the pre-competition setting irrespective of potential efficacy (Harrison et al., 2020). Such considerations may at least partly explain the discrepant observations from high-performance sport practitioners who indicated that they no longer used (30%) or had never implemented (19%) prior priming exercise despite overwhelming support from survey respondents (84%) who believed it was beneficial (Harrison et al., 2020). Moreover, many practitioners also reported prescribing priming strategies such as unloaded jumps, which although they are likely to be better tolerated on match-day, have limited evidence supporting their efficacy. Russell et al. (2016) compared the effect of different, potentially more feasible, methods of morning exercise on afternoon performance. Six 40-m sprints (incorporating 180° changes of direction) performed ~5 hours before subsequent exercise improved sprinting and jumping performance while eliciting positive effects on salivary T compared with a passive control. Additionally, upper-body resistance exercise augmented sprint performance and elicited favourable T concentrations, whereas cycle sprints increased countermovement jump performance. Such findings highlight a possible role of priming methods that may be better accepted by players and coaches on the day of competition and transfer to match-specific performance indicators such as sprinting. Notably, 78% of practitioners surveyed by Harrison et al. (2020) reported implementing some form of exercise on the day of competition, a practice that could provide the opportunity to target a priming response (e.g., by modifying existing field-based sessions) even if heavy-resistance exercise is not possible or desirable. The efficacy of priming for enhancing subsequent performance may vary considerably between individuals, even when characteristics such as age, mass, and strength are matched (Fry et al., 1995). Although Fry et al. (1995) reported no overall performance improvements following resistance exercises incorporating weightlifting derivatives, a group of ‘responders’ was identified for whom ~4.5–6.0% increases in jumping and weightlifting performance were observed 5–6 hours after the priming session. Such findings emphasise the importance of individualising match-day strategies to optimise the preparations of any given player. Additionally, future research opportunities also exist to explore the impact of prior priming exercise on match-related key performance indicators. Strategies implemented less than three hours before pitch-entry Ischaemic pre-conditioning Multiple bouts of skeletal muscle ischaemia (induced using a cuff or tourniquet) interspersed with periods of reperfusion are known as IPC, a practice that could acutely enhance muscle function when administered ~1– 2 hours before competition (Bailey et al., 2012; Jean-St-Michel et al., 2011; Lisboa et al., 2016). These benefits may arise via mechanisms such as increases in muscle blood flow resulting from changes in adenosine concentrations and the function of intra-muscular adenosine triphosphate (ATP)-sensitive potassium channels, improved oxygen delivery and metabolite clearance, and/or potential increases in excitation–contraction efficiency (de Groot et al., 2010; Pang et al., 1995). With regard to athletic performance, IPC has produced improvements in time to exhaustion (Crisafulli et al., 2011), anaerobic performance (Bailey et al., 2012; Jean-St-Michel et al., 2011; Lisboa et al., 2016), and muscle activation (Wilson et al., 2013b). Whilst not all studies implementing IPC with regard to intermittent sports players have yielded positive results (Gibson et al., 2013), inter-individual variability seems to exist and the benefits of IPC may also be time-dependent. In support, Lisboa et al. (2016) reported that the ergogenic effects of IPC (4 × 5-min bouts of occlusion at 220 and 180 mmHg for thighs and arms, respectively) manifested after a 2or 8-hour post-IPC recovery period, having been absent when IPC was performed within 1 hour of subsequent exercise. Given such findings, it could be notable that Cook et al. (2014) identified an occlusion-dependent elevation in salivary T immediately following a resistance exercise session that also utilised IPC. Although further research is required in this area, the available evidence suggests that IPC could be used as a passive strategy on the day of competition to improve subsequent physical performance, or potentially in combination with prior resistance exercise to augment the benefits of morning priming for attenuating circadian declines in T. Hormonal priming It is typical for key coaching messages to be delivered in pre-match talks that outline tactical practices (<3 hours prior to competition) and aim to motivate and instil confidence in players through the use of verbal persuasion (<1 hour prior to competition), before being reinforced during the team warm-up and the final 20 min before the start of competition. Substitute players may also receive specific tactical information once the match is under way whilst awaiting and preparing for pitch-entry. However, the extent to which such practices influence a player’s performance remains somewhat unclear. When performed 75 min before a match, positive coach feedback accompanying footage of a player’s successful skill execution has been reported to benefit pre-game T concentrations and overall match performance ratings (Cook and Crewther, 2012b). Conversely, cautionary coach feedback and observing videos of an opponent’s success produced larger cortisol (C) responses and inferior match-play performance. When considered alongside observations that presenting highly trained males with aggressive or intense training videos acutely raised T and improved 3RM back squat performance 15 min later (Cook and Crewther, 2012a), these findings suggest watching videos and receiving associated feedback could influence hormonal and performance responses and provide a suitable strategy for the preparation of team sports players before competition. In the context of applied practice, it may be worthwhile including such strategies during team briefings that often include the use of video footage and performance analysis. Moreover, the foregoing data may suggest that the environment to which substitute players are exposed (e.g., the state of the game) prior to pitch-entry could influence their hormonal and/or performance responses. Modifying the warm-up Increased intensity The principal aim of a pre-match or pre-pitch-entry warm-up is to transition players from a state of rest to a state of exercise readiness while minimising accumulation of residual fatigue. Typical match-day warm-ups occurring before kick-off often last between ~20 and 45 min, and begin with lowintensity activities including stretching and activation drills, before progressing in intensity with the inclusion of sport-specific movement patterns and technical/tactical drills (Towlson et al., 2013). However, observations from beyond team sports suggest that warm-up intensity could be modified in order to better enhance subsequent physical performance (Cook et al., 2013a; Ingham et al., 2013). Changing warm-up exercise from 300 m of striding (6 × 50 m) to an equidistant bout of combined striding (100 m) and race-pace running (200 m) enhanced subsequent 800-m running performance by ~1% (Ingham et al., 2013), whilst a ~30% increase in typical warm-up intensity improved mean 20-m resisted sprint performance in elite bob-skeleton athletes (Cook et al., 2013a). Beneficial effects on repeated sprint ability have also been observed in team sports players following a warm-up that incorporated actions conducted above, versus below, the anaerobic threshold (Anderson et al., 2014). So long as tolerable limits are not exceeded (Bishop et al., 2001), it is likely that increasing warm-up intensity may contribute to improved exercise performance thereafter by inducing desirable physiological responses (e.g., increases in body temperature) that are of a greater magnitude than would be elicited from a lower-intensity warm-up. Whilst the efficacy of such practices is yet to be confirmed with regard to more prolonged competition durations (e.g., ≥45 min), and in a variety of environmental conditions that may be faced on match-day (e.g., hot and humid versus cold and dry), results of a systematic review highlight a benefit to performing warm-up activities that reach ~90% of an individual’s maximum heart rate for improving outcomes in isolated performance tests of explosive team sports-specific tasks such as sprints and jumps (Silva et al., 2018). Protection of gains A player’s own preferences (e.g., final kit and tactical preparations), prematch ceremonies (e.g., meeting with dignitaries, national anthems), and specific rules and regulations (e.g., pitch protection policies or the use of ‘call rooms’) may result in a 10–20-min period that separates the end of the warm-up and the start of competition. Notably, similar durations in temperate conditions can elicit losses in body temperature with concomitant declines in physical performance that largely negate the benefits of the initial warm-up (Kilduff et al., 2013b; Russell et al., 2015a; West et al., 2013b). These findings highlight the potential role for interventions that attenuate such declines between warm-up cessation and onset of matchplay, both in the context of starting and substitute players entering a game. Passive heat maintenance is a strategy that aims to minimise heat losses, thus maintaining body temperature by applying specialised garments or heating methods, and has shown efficacy in terms of body temperature preservation and physical performance maintenance following active warmups (Kilduff et al., 2013b; West et al., 2016). For example, wearing a survival garment during a ~15-min post-warm-up recovery period attenuated core temperature losses by ~50% when compared with normal training attire, while also benefitting lower-body power output and repeated sprint ability in professional rugby league players (Kilduff et al., 2013b). Additionally, combining passive heat maintenance with 3 × 5 countermovement jumps (20% body mass load) in the post-warm-up period has provided further performance-protecting effects over either strategy alone (West et al., 2016). These data highlight that the post-warm-up transition period is an opportunity for practitioners to improve subsequent performance by offsetting body temperature declines prior to kick-off. In hot or humid conditions, combining lower-limb passive heat maintenance with pre-cooling strategies such as ice slurry ingestion may preserve muscle temperature while allowing core temperature to remain below a level that could negatively affect performance (Beaven et al., 2018). Although the precise timeframes for introduction may differ between sports (e.g., depending on regulations and strategies), substitute players typically face substantial delays between the end of the pre-match warm-up and their entry on to the pitch. This extended period between the initial prematch warm-up and pitch-entry could allow further temperature and performance decrements for substitutes compared with the ~10–20-min transition experienced by members of the starting team (Hills et al., 2018, 2021; West et al., 2013b). For example, replicating the typical pre-pitchentry practices of soccer substitutes resulted in both core temperature and indices of physical performance declining to pre-warm-up levels well in advance of simulated second-half pitch-entry (Hills et al., 2021). Notably, observations from professional soccer substitutes highlighted that increasing the amount of rewarm-up activity performed prior to pitch-entry appeared to benefit post-pitch-entry physical outputs and potentially contributed to improved match scorelines compared with the implementation of minimal rewarm-up activities that were akin to normal practice (Hills et al., 2019, 2020). Practitioners should therefore consider the unique demands of substitutes, as well as starting players, when seeking to optimise match-day preparations relating to the warm-up. Post-activation potentiation (PAP) A muscle’s force production capabilities can be influenced by its recent contractile history (Kilduff et al., 2008). As long as the mechanisms of potentiation outweigh the residual effects of co-existing fatigue, performing certain high-intensity contractions has the potential to acutely enhance subsequent exercise performance via mechanisms including increased actinmyosin myofilament sensitivity to Ca2+, enhanced motor neuron recruitment, and/or a more favourable central input to the motor neuron (Tillin and Bishop, 2009; Wilson et al., 2013a) – a phenomenon referred to as PAP and, more recently, post-activation performance enhancement (PAPE). Acknowledging that PAP/PAPE may be modulated by the timing of the intervention relative to subsequent exercise, alongside other factors such as a player’s strength, training experience, or muscle fibre composition (Hamada et al., 2003; Kilduff et al., 2008; Wilson et al., 2013a), this chapter focuses on modifiable factors relating to the volume and type of preload stimulus applied on match-day. Most studies demonstrating PAP have employed moderate to heavy (i.e., 60–95% 1RM) resistance exercise as the stimulus, with multiple sets augmenting subsequent muscular power output to a greater extent than a single set in trained individuals (Wilson et al., 2013a). However, similar to the use of prior priming activities, practical considerations associated with the pre-competition routines of team sports players mean that heavyresistance exercise is unlikely to be feasible immediately before a game. Identifying alternative methods of inducing PAP that require less equipment and/or might be better tolerated by players and coaches on the day of competition is therefore appealing. Ballistic activities such as weighted jumps are associated with the preferential recruitment of type II motor units (Desmedt and Godaux, 1977), and may therefore be utilised as a PAP stimulus. Depth jumps are able to increase subsequent strength (Masamoto et al., 2003) and explosive performance (Hilfiker et al., 2007), while the use of isometric maximal voluntary contractions can also induce PAP (Hamada et al., 2003). Moreover, 3 × 3 ballistic bench throws at 30% 1RM improved upper-body power output after an 8-min recovery period – improvements that were similar in magnitude to those induced by a more traditional heavyresistance exercise bout (i.e., 3 × 3 bench press at 87% 1RM; West et al., 2013a). A practical means of eliciting PAP within the constraints often existing in team sports was examined by Turner et al. (2015), who observed that 3 sets of 10 repetitions of alternate-leg bounding on an indoor surface whilst wearing a weighted vest (incorporating 10% of body mass) improved 10- and 20-m sprint performance by 2–3% at 4 and 8 min post-bounding, when compared with a walking control condition. Whether such responses occur on surfaces more relevant to outdoor match-play (e.g., grass) remains to be confirmed. Regardless of whether ballistic or heavy-resistance exercise is used as a preload, the optimal recovery time between stimulus and subsequent performance appears typically to be ~7–10 min (Kilduff et al., 2008; West et al., 2013a; Wilson et al., 2013a). Given the timeframe separating the end of the warm-up and the match kick-off (i.e., typically >10 min), the benefits of PAP could therefore be somewhat limited to the initial stages of a player’s competition involvement. However, it has not yet been determined whether the introduction of substitutes who have induced a PAP response prior to pitch-entry (e.g., having performed targeted ballistic or isometric exercises pitch-side) could subsequently influence markers of team sport performance at varying stages of a game and/or whether PAP has promise as a potential strategy for use at half-time or during other scheduled breaks in play. Strategies implemented during scheduled within-match breaks (e.g., half-time) Half-time typically includes players returning to the dressing room, engaging in tactical discussion, receiving medical treatment, and consuming nutritional ergogenic aids (Russell et al., 2015b; Towlson et al., 2013). However, 20% of soccer players have their least intense 15-min period of a match within the initial stages of the second half (Mohr et al., 2005) and reductions in physical performance capacity are frequently observed immediately after half-time compared with first-half values (Lovell et al., 2013; Russell et al., 2015a, 2018). Half-time has therefore been proposed as an opportunity to enhance subsequent performance (Russell et al., 2015b). To avoid replication of information previously discussed, an overview of studies reporting the specific use of half-time interventions now follows. However, where practicalities allow, the aforementioned strategies (e.g., PAP, hormonal priming, etc.) may also wish to be considered at half-time as well as during other scheduled breaks in play (e.g., quarter-time, drinks breaks, before extra-time etc.). Heat maintenance strategies Muscle and core temperature may decline by >1°C during a 15-min passive half-time (Lovell et al., 2013; Mohr et al., 2004), responses that were related to decreases in physical performance capacity. As was the case postwarm-up, strategies to offset body temperature losses may represent beneficial half-time interventions during matches played in temperate conditions. For example, wearing a survival jacket throughout a 15-min simulated half-time attenuated core temperature declines and better maintained physical performance amongst professional rugby union players compared with passive control conditions (Russell et al., 2015a, 2018). Observed ergogenic effects notwithstanding, the logistics of passive heat maintenance strategies must be considered in the context of applied practice as some players (e.g., those receiving injury treatments) may be averse to wearing additional clothing during half-time. Alternative methods of heat preservation include short bouts of rewarmup activity. Seven minutes of moderate-intensity running commencing midway through half-time attenuated a 1.5°C reduction in muscle temperature and offset the 2.4% decrements in mean sprint performance observed during a passive control trial (Mohr et al., 2004). Beneficial body temperature and/or physical performance responses (i.e., compared with a passive half-time) have also been observed when rewarm-up activities consisted of field-based agility exercise, resistance exercise, low-tomoderate-intensity jogging and calisthenics, or whole-body vibration training (Edholm et al., 2014; Lovell et al., 2013; Zois et al., 2013). Similarly, rewarm-ups that included sport-specific technical actions have also been proposed to benefit subsequent skilled performances when conducted during a ~15-min half-time period (Zois et al., 2013). Additive effects of combining active rewarm-ups and passive heat maintenance have also been demonstrated as ~8 min of wearing a survival jacket followed by ~7 min of jogging and ball skills produced more favourable temperature and performance responses compared with either strategy alone (Russell et al., 2018). That said, practitioners must consider the duration of half-time activities performed with reference to players’ other half-time commitments (e.g., tactical, medical, nutritional, etc.). SECTION 2 Practical applications Match-day itself provides opportunities to enhance competition performance for team sports players (Kilduff et al., 2013a; Russell et al., 2015b). Acute performance enhancements have been observed following appropriate warm-ups, half-time and post-warm-up heat maintenance strategies, IPC, hormonal priming, and prior priming exercise. As most team sports competitions commence at times between 09:00 and 21:00, the potential may exist for practitioners to combine several of these interventions in pursuit of additive performance-enhancing effects. Moreover, specific player populations may present their own unique opportunities, such as the use of frequent rewarm-ups and/or PAP for substitutes about to enter the field of play. To understand the ‘windows of opportunity’ that may exist on matchday, it is important to contextualise current practice. A theoretical model of the typical activities that may be performed by team sports players in the 12 hours before an away match (with overnight hotel stay), with a 20:00 kickoff (0 h), is presented in Figure 9.1. However, as the match-day practices of professional sports teams are very often structured and rigid in nature, any proposed modifications must complement existing protocols. Figure 9.1 presents a theoretical model of implementing the performance-enhancing strategies outlined in this chapter to supplement existing practices. Model of implementing the performance-enhancing strategies. Summary As the use of prior priming activities, a well-structured warm-up, and appropriate post-warm-up, half-time, and pre-pitch-entry interventions have each demonstrated performance benefits, a method which combines several of these strategies whilst ensuring compatibility with existing match-day routines might interest strength and conditioning coaches working with team sports players. Acknowledging the constraints that often exist when implementing modifications on match-day, a practical model that allows combination of several interventions could theoretically elicit additive effects over the use of any strategy in isolation. References Anderson, P., Landers, G. & Wallman, K. 2014. Effect of warm-up on intermittent sprint performance. 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Highintensity re-warm-ups enhance soccer performance. International Journal of Sports Medicine, 34, 800–805. 10 Fitness testing and data analysis John J. McMahon, Paul Comfort and Anthony N. Turner DOI: 10.4324/9781003044734-13 Why fitness test? Fitness-testing data should inform the strength and conditioning coach’s decision-making process when developing and refining the athlete’s training programme (Thornton et al., 2019). Conducting fitness-testing batteries with an individual athlete or a squad of athletes provides practitioners with an objective method of comparing, or monitoring changes in, specific fitness qualities (e.g. strength, power, speed, etc.) that are key performance indicators of the athlete’s sport. The specific fitness qualities that are assessed as part of fitness-testing batteries should be determined following a detailed needs analysis of the athlete’s sport, with, where appropriate, consideration also given to different positional demands of the sport. The results gleaned from fitness-testing batteries should be used to inform the athlete’s upcoming training priorities and, if applicable, provide insight into the success of the athlete’s previous training cycle(s). Fitnesstesting results should, therefore, be used by practitioners to facilitate the construction of effective training programmes by identifying a given athlete’s area(s) for improvement and highlighting what may or may not have worked well for the athlete in the previous training cycle(s). When to test Fitness testing could initially take place at the beginning of the pre-season training cycle, as the results of testing conducted at this time point would provide a baseline of fitness data which will inform this initial training block (based on identified strengths and weaknesses), and serve as a reference point for data collected as part of further fitness-testing sessions conducted throughout the remainder of the season. The fitness-testing results obtained at the beginning of the pre-season training cycle would also inform how much the athlete’s fitness has been compromised during the preceding off-season period. However, it may be prudent to exclude certain maximal-intensity fitness tests from the very beginning of the pre-season training cycle to avoid unnecessary exposure to risk of injury after a period of inactivity (i.e. the off-season). Instead, identifying an appropriate window of opportunity for certain maximal-intensity fitness tests further into the athlete’s training cycle may be preferable but the precise timing would, of course, be team- and context-dependent (Buchheit and Brown, 2020). The latter approach could also be a solution for all fitness tests when working with athletes who compete in a sport that does not incorporate a specific pre-season period (e.g. combat athletes). Where possible, the same fitness-testing battery would initially be conducted twice (typically interspersed by a 5–7-day gap) at the beginning of pre-season, or an alternative appropriate window of opportunity, in order for the standard error of measurement (SEM) of each test to be established. This would ensure that the within-subject variability of each fitness test parameter is known for each athlete tested. The SEM can be used to inform the practitioner of what a meaningful change in each fitness parameter would be for a given athlete or squad of athletes and thus will help the practitioner to identify ‘meaningful’ changes in a particular test score in subsequent fitness-testing sessions. If it is not appropriate or feasible to test the athlete(s) twice in fairly quick succession (i.e. after 5–7 days), and thus for athlete/squad-specific test measurement error to be established, then practitioners should use published (preferably sport-specific) test SEM values to help them identify meaningful changes in subsequent performance. The readers are referred to a relatively recent review article and the associated supplementary digital materials for an excellent overview of determining SEM and applying it to determining meaningful performance changes (Swinton et al., 2018). After testing at least once at the beginning of the pre-season training cycle, or an alternative appropriate window of opportunity, the scheduling of subsequent fitness-testing sessions will vary from sport to sport, depending upon several factors such as the duration and scheduling of the season. Generally, however, practitioners should at least aim to fitness test athletes again at the end of the pre-season training cycle, or an alternative appropriate period, so that athletes’ level of preparedness for competition can be benchmarked against published/squad normative data (see Chapter 11 for information on how to go about this) and compared to the fitness test results gathered during the previous fitness-testing session (i.e. to inform the magnitude of improvement/decline in each assessed fitness quality). Preferably, fitness testing will take place at some point within the competitive season (particularly for sports whose season includes a break from competition) to assess the physical demands of competition on athletes’ fitness characteristics. If this is not possible then an alternative solution could be to select one or two key fitness tests (e.g. the vertical jump) to conduct on a frequent basis as part of continual athlete-monitoring procedures. Although fitness-testing scheduling throughout the season may vary between sports, it should be conducted when athletes are ‘rested’, i.e. sufficient time [~48 hours] must have lapsed after the last competition/intense training session. Additionally, when periodic fitness testing does take place, athletes should be tested at approximately the same time of day to account for circadian rhythms and body temperature, which impact several physical and morphological qualities such as muscle strength (Gauthier et al., 2001; Teo et al., 2011), power output (Teo et al., 2011; West et al., 2014) and tendon stiffness (Onambele-Pearson and Pearson, 2007; Pearson and Onambele, 2006). Test selection Once a rationale for conducting fitness testing has been determined and the appropriate timing of fitness testing has been identified, it is important to decide upon which test(s) to conduct. Strength and conditioning coaches now have an overwhelming number of choices when it comes to deciding which tests to conduct with their athletes (Gabbett et al., 2017). Fundamentally, they must ask themselves what they hope to gain from conducting the testing (Gabbett et al., 2017). With respect to recoverymonitoring test selection, practitioners working in soccer suggested that practically employable and cost-effective (time and finance) monitoring tools, which provide meaningful data, are most useful for guiding player preparedness decisions (Harper et al., 2019). Ultimately, fitness test selection will depend upon the previously identified demands of the sport (as achieved through conducting an evidence-based needs analysis) and, if applicable, will consider position-specific physical requirements. Other factors, such as the athlete’s age and training status, should also be considered when determining appropriate test selection. For example, a commonly used and widely accepted measure of ascertaining an athlete’s maximal dynamic strength capacity is the one repetition maximum (1RM) test. This type of test requires athletes to perform up to five single-repetition sets (after an appropriate warm-up) of a given exercise with a gradually increasing load until an incomplete attempt occurs (Baechle et al., 2008). The penultimate repetition (i.e. the last successful lift achieved) is then considered to be the athlete’s 1RM load for that exercise. It may, however, be deemed inappropriate to conduct a 1RM test with weaker or beginner athletes. In this case, a 3RM or 5RM test of dynamic strength might be more appropriate, assuming the athlete can perform the selected exercise with correct technique, as it has been shown that the load lifted in these multiple repetition tests of dynamic strength can be used to predict the 1RM load (Reynolds et al., 2006). It should be noted, however, that the ability to accurately predict 1RM loads from multiple-repetition tests of strength depends upon the exercise used (Hoeger et al., 1990; Shimano et al., 2006) and so this should be considered in advance of testing. It is worth noting, however, that the 1RM power clean test, which requires a higher degree of technical competency than commonly tested compound exercises such as the back squat, has been shown to be reliable even in youth (Faigenbaum et al., 2012) and inexperienced collegiate (Comfort and McMahon, 2015) athletes, following a sufficient period of familiarisation, with a smallest detectable difference of ~5%. When an athlete does not demonstrate correct exercise technique at high loads but determining maximal strength for the athlete is deemed to be a requirement, then performing a multi-joint isometric ‘strength’ assessment, such as the isometric squat or mid-thigh pull, could be a suitable option. Isometric strength tests require minimal familiarity (providing that the athlete is familiar with the dynamic performance of the associated task and puts in maximal effort during each repetition), skill and time when compared to dynamic strength tests, which arguably makes them better suited to testing both beginner/weaker individuals and groups of athletes. These factors also enable multi-joint isometric tests to yield high reliability and low variability values (Blazevich et al., 2002; Comfort et al., 2015; Dos’Santos et al., 2016; Haff et al., 2015; Thomas et al., 2015), thus increasing the sensitivity of these tests for detecting ‘meaningful’ performance changes. Additionally, strong associations have been reported between isometric and dynamic strength tests (Comfort et al., 2019), which means that the values derived from isometric strength tests can be used to inform dynamic load prescription for a given training cycle by applying the relevant prediction equation (De Witt et al., 2018). A limitation of isometric strength tests, however, is that they require a force platform, which, although cheaper validated force platforms are now available (Lake et al., 2018), could restrict accessibility for some athletes, and the capacity of fixing a barbell at the required position (i.e. a custom rig or power rack). However, strain gauge alternatives have been shown to be valid and reliable, albeit that only peak force can be assessed in most cases (James et al., 2017). In addition to isometric tests offering a suitable alternative to dynamic 1RM testing, recent studies have shown that 1RM values attained in a range of bench press (Bosquet et al., 2010; García-Ramos et al., 2016a; Jidovtseff et al., 2011) and squatting derivatives (Bazuelo-Ruiz et al., 2015; Conceição et al., 2016) can, in most cases, be almost perfectly predicted from the barbell velocity measured using a linear position transducer during these exercises performed with submaximal loads (and applying the relevant prediction equations). This approach, like some of the other approaches discussed earlier, may help to overcome the potential for safety/injury risk issues associated with 1RM testing of beginner/weaker athletes. Similar to isometric strength tests and equipment, linear position transducers have been shown to yield valid and highly reliable measurements of system and barbell velocity, which enables this method to be compared to gold-standard methods of assessing velocity (e.g. force platforms if measuring system velocity) and used to detect performance changes (García-Ramos et al., 2016b; Garnacho-Castaño et al., 2015; Giroux et al., 2015). It is worth noting, however, that these predictions tend to be less reliable than direct measures, meaning a greater magnitude of change is required to identify a meaningful change. Maximal sprint performance is highly regarded as an important determinant of performance in many sports, but the distances over which maximal sprint performance should be assessed will depend on the typical sprint distances covered during competitive sport play and preferably, position-specific sprint distances should be considered. Similarly, if jump testing is deemed to be important to include within a testing battery for a given sport, then attention should be given to the type(s) of jumps performed in competition. For example, are the jumps performed in the sport usually performed unilaterally or bilaterally, with or without a countermovement, with or without arm swing, vertically or horizontally? Each of these factors should be considered when deciding upon the type(s) of jump test(s) to conduct. There are also other reasons why specific jump tests may be selected as part of the fitness-testing battery, even if they are not commonly performed as part of the athlete’s sport. For example, the squat jump (SJ) might be tested along with the countermovement jump (CMJ), even if the former is not typically performed as part of the sport, simply in order to provide an indication of how well an athlete can utilise the stretch-shortening cycle (SSC). As such, an eccentric utilisation ratio (EUR) can be calculated (EUR = CMJ height ÷ SJ height), with a ratio of >1.0 demonstrating that the use of the SSC results in a greater jump height; however, if the ratio is ≤1.0 the SSC needs to be developed (McGuigan et al., 2006). It should be noted that the EUR can be influenced by differences in the distance through which the athlete’s centre of mass moves from the bottom of the squat (or countermovement) to take-off. Thus it would be prudent to report propulsion displacement, as it is commonly referred to, alongside EUR results to aid interpretation (McMahon et al., 2021). In summary, fitness test selection will be informed by both the typical demands of the sport and the general athletic qualities that underpin these demands. Equipment selection Once it has been decided which test(s) will be conducted, the next step is to decide which equipment to use for the selected test(s). Ideally, the goldstandard equipment for testing each fitness quality should be used where possible; however, this may be unrealistic from both an accessibility and time perspective for many practitioners. An example of the latter is that although some practitioners working with a team sport may have access to expensive direct gas analysers for measuring maximal aerobic capacity, it would take a very long time to assess a full squad on this parameter. Instead, practitioners should consider using alternative equipment that has been validated against the currently considered gold-standard equipment when access to the latter is either impossible or unrealistic. In referring back to the aforementioned example of measuring maximal aerobic capacity, basic equipment such as cones, a measuring tape and an audio device could be used to conduct the yo-yo intermittent recovery test (YIRT) or multistage fitness test (MSFT), which have both been shown to provide a valid, field-based alternative to direct gas analysis (Krustrup et al., 2003; Ramsbottom et al., 1988). In terms of quantifying jump performance, a force platform is considered to be the gold-standard equipment (García-López et al., 2013), particularly when using the take-off velocity method of calculating jump height (Moir, 2008), but similar to direct gas analysers, force platforms may be inaccessible for some practitioners due to their general cost, despite cheaper commercial force platforms now being available. In recent years, however, many cheaper alternatives (that calculate jump height using the flight time method) have been validated. For example, optoelectronic systems have been shown to yield similar jump height values to those attained using a force platform (García-López et al., 2013; Glatthorn et al., 2011). Jump mats have generally been shown to yield inaccurate but reliable measurements of jump height (García-López et al., 2013; McMahon et al., 2016a; Nuzzo et al., 2011), meaning that their values can be easily and correctly converted through published equations (GarcíaLópez et al., 2013; McMahon et al., 2016a). It is worth taking into consideration that the accuracy of jump height values attained from jump mats depends on the type of jump being performed and the level of performer, with lower accuracy seen for short-contact jumps such as the drop jump (Kenny et al., 2012) and for athletes who can jump very high (Whitmer et al., 2015). An even cheaper alternative method of measuring jump height from flight time is through smartphone applications, with jump height attained using the My Jump app, for example, showing almost perfect agreement with values attained from a force platform (BalsalobreFernández et al., 2015). It must be noted here that the flight time method of calculating jump height is prone to errors when compared to the take-off velocity method (Moir, 2008; Yamashita et al., 2020) due to, for example, tucking of the legs during the flight phase and so standardising the instructions given to athletes regarding the flight phase of the jump is especially important when assessing jump height in this manner (see the ‘Standardising protocols’ section, below, for more information). Fully automatic timing systems, such as those used at international athletics events, are considered to be the gold-standard equipment for measuring linear sprint speed (Haugen and Buchheit, 2016; Haugen et al., 2012b). These systems are, however, very expensive and impractical for most practitioners to utilise (Haugen and Buchheit, 2016). Due to this, several alternatives of varying practicality have been suggested in the literature, such as electronic timing gates, laser guns and high-speed videography (Haugen and Buchheit, 2016). Of these suggestions, electronic timing gates are perhaps the most practical in terms of accessibility and speed of data processing and thus are frequently used in both research and applied settings (Haugen and Buchheit, 2016). The accuracy of sprint times recorded by electronic timing gates does, however, depend on several factors, including the type of photocells used (e.g. single- versus dualbeam). Unlike single-beam electronic timing gates (Earp and Newton, 2012; Haugen et al., 2014), dual-beam electronic timing gates have been shown to reduce the likelihood of an athlete’s arms or legs breaking the beams, rather than their hips, as is preferred (Yeadon et al., 1999). Nevertheless, single-beam electronic timing gates are still commonly used in both research and applied settings (Carr et al., 2015; Dos’Santos et al., 2017), possibly due to them being cheaper to purchase (Earp and Newton, 2012), and they have been validated against fully automatic timing systems (Haugen et al., 2012b). Split-beamed and post-processing timing gates are also available for use, although the errors in sprint times attained by splitbeamed timing gates are similar to those measured via single-beamed systems (Haugen et al., 2012a, 2013) and the test–retest reliability of postprocessing timing gates is currently unknown (Haugen and Buchheit, 2016). Although gold-standard equipment can provide more detail about each fitness characteristic, in reality, the type of equipment selected by practitioners to test specific fitness qualities depends upon accessibility, feasibility and affordability. Whether using gold-standard equipment or validated alternatives, it is vitally important to understand the associated SEM to allow accurate decisions to be made regarding training adaptations (this is discussed in more detail in Chapter 11). As some validated equipment alternatives of a similar cost have larger measurement error than others, it would be prudent to choose the alternative equipment that has the highest degree of accuracy. Another important consideration when selecting equipment for testing certain fitness characteristics is sampling frequency capability. For example, if assessing vertical jump height using a force platform, it has been suggested that a minimum sampling frequency of 1000 Hz should be used (Owen et al., 2014; Street et al., 2001). On the other hand, a sampling frequency range of 500–2000 Hz had no effect on force–time variables assessed during the isometric mid-thigh pull (Dos’Santos et al., 2019). Alternatively, it has been recently suggested that the minimum sample frequency of linear position transducers for yielding quality movement velocity data is 25 Hz and that sampling above this frequency does not improve recording precision and may, if an excessively high sample frequency is selected, have adverse effects on data quality (Bardella et al., 2017). Each of these factors should be considered in order to inform the best equipment choice for a given purpose and budget. Standardising protocols Another very important factor to consider as part of the fitness-testing process is the standardisation of protocols for the test(s) to be conducted, as this will affect the reliability, variability and comparability of the data collected. For dynamic strength tests, the standardisation required might be as simple as ensuring correct barbell placement (e.g. high or low barbell position in the back squat; Wretenberg et al., 1996), the range of motion (e.g. squat depth) is consistent (Bryanton et al., 2012) and athletes put in a maximal effort. The latter point is, indeed, a requirement of all maximalintensity fitness tests. Additionally, the rest period prescribed between trials may affect the results gathered. For example, during 1RM back squat testing, there were no significant differences in the ability to lift a maximal load when subjects were given 1, 3 or 5 minutes’ rests between lifts (Matuszak et al., 2003), although a greater percentage of the subjects lifted successfully after the 3- versus the 1-minute rest period (76 versus 94%), suggesting that a minimum of 3 minutes’ rest should be prescribed between 1RM attempts. Therefore, adequate test-specific rest periods should be prescribed between recorded trials to improve test accuracy. For jump tests, many factors need to be standardised to glean consistent data. For example, when jump testing it is important to consider whether or not athletes are permitted to swing their arms, as this has been shown to augment jump height (Hara et al., 2006, 2008; Walsh et al., 2007) but slightly reduce measurement reliability (Markovic et al., 2004). Also, the range of motion (e.g. countermovement or starting depth) (Gheller et al., 2015; Kirby et al., 2011; McBride et al., 2010) and movement/contact time (Arampatzis et al., 2001; Walsh et al., 2004) will influence the resultant jump height and associated force–time variables, if using a force platform. This highlights the importance of being clear and consistent with the coaching cues used (e.g. ‘jump as fast and as high as possible’) when jump testing athletes (Louder et al., 2015; McMahon et al., 2016b). Sprint testing typically has even more methodological factors than strength and jump testing that need to be standardised. For example, the accuracy of sprint times recorded by electronic timing gates will depend upon the height at which they are set up (Cronin and Templeton, 2008; Yeadon et al., 1999), the starting distance from the first beam (Haugen et al., 2015; Altmann et al., 2015) and the starting stance (Frost and Cronin, 2011; Frost et al., 2008; Johnson et al., 2010). Thus, the standardisation of protocols can relate both to the equipment setup and the instructions given to the athlete. Both should be ‘optimised’ to increase the quality of the collected data. Testing order The order of testing is largely dictated by the amount of recovery required following a given test and so usually baseline measurements of height, mass, body composition and range of motion would be performed first, followed by skill- and/or speed-based tests (jumps, change of direction/agility and sprints), then maximal-strength tests (dynamic or isometric) and finally, muscular endurance and/or aerobic capacity tests. In reality, the order of fitness testing will depend upon time/equipment availability and the number of athletes being tested and so a ‘round-robin’ approach might be adopted by practitioners when larger groups of athletes are being tested in a single session. If this is the case, then the testing order for a given athlete should remain the same in subsequent testing sessions and, ideally, the aerobic capacity tests should be performed last by all athletes. The latter is much more feasible when the YIRT or MSFT is conducted in a large space, allowing several athletes to be tested at the same time. Of course, these recommendations for order of testing assume that all fitness tests will be conducted within a single testing session or day but, as mentioned earlier, there may be differing windows of opportunity for conducting certain maximal-intensity fitness tests which will be determined on an individual sport and context basis. Data analysis After all testing has been completed, at least some (if not most) of the data will need to be processed, as most equipment/software does not provide instantaneous results. Like the testing protocols, the way in which data are analysed post-testing will also greatly influence the accuracy, reliability and variability of the results. The analysis of force–time data is probably the main type of commonly collected data that varies most between published studies and, most likely, in practice. Thus, the standardisation of force–time data analysis is of paramount importance to allow for accurate interpretation of these data. For example, when analysing vertical jump force–time data, the method of determining bodyweight and the thresholds used to identify the onset of movement and the instants of take-off and touchdown will greatly influence factors such as jump height and reactive strength index modified, in addition to variables calculated through forward dynamics procedures such as velocity and power (Eagles et al., 2015; Owen et al., 2014; Street et al., 2001). Additionally, correctly identifying the beginning and end of the braking (if a countermovement is included) and propulsive phases of the vertical jump (Figure 10.1) is important for ensuring correct calculations of several variables in each of these phases (McMahon et al., 2018), including mean and peak force, time to peak force, rate of force development and impulse. Analysing rate of force development attained in the isometric mid-thigh pull at predetermined time bands rather than as an average between the onset of force production and peak force has been shown to be superior from a reliability perspective (Haff et al., 2015), which further justifies standardisation of the analysis of force–time data for specific tests. Example of correctly identifying the unweighting, braking and propulsive phases of a countermovement jump force–time curve (solid grey line) by overlaying the velocity–time curve (dotted black line). The dotted grey line represents zero centre of mass velocity. Another consideration when analysing force–time data is how much detail is wanted from the data. For example, only gross measures of a given performance (e.g. mean and peak values of force and related data) are typically reported and compared between fitness-testing sessions, whereas comparing performance data sampled throughout the entire movement (which is typically referred to as a temporal phase analysis or statistical parametric mapping) can yield far more detailed information about how performances/changes in performances are achieved. Indeed, the latter approach has been shown to provide detailed information about neuromuscular fatigue in the countermovement jump (Gathercole et al., 2015), the effect of external load on jump squat performance (Cormie et al., 2008), the effect of weightlifting derivatives on expressions of force (Suchomel and Sole, 2017) and differences in neuromuscular function between senior and academy rugby league players (McMahon et al., 2017). Even if a full temporal-phase analysis is considered to be too complex, there is an often underutilised abundance of additional variables that can be calculated from force–time data, with just a basic understanding of forward dynamics procedures, that can further inform practitioners of their athletes’ capacity. To conclude, the standardisation of data analysis is very important and must be applied consistently within and between testing sessions. Where possible, the criterion method (e.g. Owen et al., 2014) for analysing a particular dataset should applied. If a criterion method has not yet been established for analysing a given dataset or if certain equipment is used that provides instantaneous results via undisclosed data analysis methods, then practitioners should at least be consistent and transparent with their data analysis procedures. When comparing data collected through fitness-testing batteries to the normative data from published studies, practitioners should pay particular attention to the methods of data analysis employed in those studies before forming their conclusions. Another point to consider is the normalisation of strength and kinetic data for body mass (or employing other appropriate scaling techniques such as those that consider body height and fat-free mass) before comparing these results between sessions and athletes, and to published studies, as these data in particular are largely influenced by an athlete’s size (Folland et al., 2008). References Altmann, S., Hoffmann, M., Kurz, G., Neumann, R., Woll, A. & Haertel, S. 2015. Different starting distances affect 5-m sprint times. The Journal of Strength & Conditioning Research, 29, 2361–2366. Arampatzis, A., Schade, F., Walsh, M. & Bruggemann, G.P. 2001. Influence of leg stiffness and its effect on myodynamic jumping performance. 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For example, it is important to remember that sports coaches are unlikely to be statistically trained (Robertson et al., 2017) or have the time available to synthesise text-dense written reports, which will make them less impactful (Buchheit, 2017). Therefore, it is of paramount importance to present fitness test results to sports coaches in an intuitive (i.e. by avoiding complicated numbers or scientific terms) and visual format (McGuigan et al., 2013; Buchheit, 2017; Lockie et al., 2018). The exact method of analysing and then visually presenting fitness test data may vary slightly depending upon the individual preferences of the audience to which the fitness test results will be presented (Buchheit, 2017; Robertson et al., 2017). The number of fitness test results to be included in the report will also be considered. Ultimately, it is likely that different modes of visually impactful presentation of performance test results will be employed by strength and conditioning coaches, depending upon the target audience and relative priority (i.e. urgency) of results. With the above in mind, this chapter will explore some of the different fitness test result analysis methods and visual formats in which key data may be presented to athletes and the key members of their training/performance team. The chapter begins with data analysis options, followed by data presentation options in which applied case-study examples are provided. Data analysis Including several fitness tests as part of athlete fitness-testing batteries results in the accumulation of many different types of data. Most of these data, once analysed, will be reported with different units of measurement. Some of these data and their units of measurement are relatively easy to understand, such as change-of-direction time reported in seconds (s) and jump height reported in metres (m) or centimetres (cm). However, other fitness test data, such as isometric peak force reported in Newtons (N) and sprint momentum reported in kilograms-metre per second (kg·m/s), are less intuitive. Similarly, several variables with different units of measurement can be reported from a single test, such as when the countermovement jump test is performed using a force platform. To overcome the difficulty of presenting several fitness test results, with many different units of measurement, to athletes and coaches, one may benefit from reporting standardised data presented on an intuitive scale. In this section, different options on how to convert fitness test result data to a standardised form and how to compare athletes’ performances to the squad mean score are introduced. z-scores A z-score (sometimes referred to as a standard or standardised score) represents how many standard deviations an individual athlete’s test score is from the mean test score (usually the squad mean when applied in teamsport settings). It is calculated using the following formula (McGuigan et al., 2013; Lockie et al., 2018): z-score = (the individual athlete’s test score – the squad mean [average] test score) ÷ the squad standard deviation for the test score Applying the above equation, if a rugby athlete acehived a vertical jump height of 42 cm and their squad attained a mean ± standard deviation vertical jump height of 36 ± 4 cm, the z-score would be 1.5. In other words, the athlete achieved a vertical jump height score that was 1.5 standard deviations higher (i.e. better, in this example) than the squad mean score. The first assumption of the z-score calculation is that the squad mean and squad standard deviation values for the fitness test score are normally distributed. This can be assessed via a test of normal data distribution such as the Shapiro–Wilk test. The second assumption of the z-score calculation is that the sample size (i.e. number of individual athlete’s data) from which the squad mean and standard deviation are derived is ≥30 (Turner et al., 2019). Additionally, it is important to select an equivalent time-period from which the squad mean and standard deviation for each fitness test score were calculated (Thornton et al., 2019). For example, one should compare an athlete’s pre-season test score to the squads’ current or pooled-historic pre-season test score, as one may expect fitness test scores to vary across different phases of the sport season. When calculating z-scores, it is worth remembering at this point that ~68%, ~95% and ~99.7% of normally distributed values attained for a given fitness test will fall within 1, 2 and 3 standard deviations of the mean, respectively (Figure 11.1). Therefore, most z-scores range between −3 and 3, accounting for ~99.7% of normally distributed values (Turner et al., 2019). A z-score of −3 may be assumed to be undesirable as it represents a result that is 3 standard deviations below the mean score, but for some fitness test results, such as the time taken to complete a linear sprint or change-of-direction task, a negative z-score is preferable (because this would represent a faster performance in those tests). To avoid possible confusion caused by this, it has been suggested that absolute z-scores (i.e. positive z-scores for positive outcomes) should be presented for all performance test results (Pettitt, 2010; Lockie et al., 2018). Therefore, from this point forward, the reader is to assume that a positive z-score reflects a better performance with the opposite being true for negative z-scores, unless otherwise stated. A typical normal data distribution curve with z-scores and the corresponding percentage of data that they comprise. The z-score can be calaculated for all fitness test results, which overcomes the aforementioned difficulties associated with reporting several fitness test results that contain many different units of measurement. Furthermore, it has been suggested that a total score of athleticism (TSA) can be calculated for athletes by calculating the average of the z-scores attained for a range of fitness tests (Turner et al., 2019). The TSA is said to provide insight into how ‘well rounded’ athletes are with respect to the key fitness tests associated with their sport. The TSA can be used as an alternative or an accompaniment to presenting individual test scores for every single test performed, with the individual test data used to identify key training priorities. As an example, the earlier example of the rugby athlete’s z-score of 1.5 for vertical jump height has been added to Table 11.1, along with z-scores for other performance test results and the TSA. The athlete, whose data are shown in Table 11.1, demonstrated superior vertical jump and relative strength ability (as denoted by positive z-scores) but inferior short sprint and absolute strength ability (as denoted by negative z-scores) compared to the squad mean. However, on balance, the athlete compared averagely overall within the squad, as denoted by the TSA of zero (Table 11.1). This highlights the importance of inspecting the individual z-scores that comprised the TSA calculation, as it can be achieved in several ways (i.e. consistent z-scores for each test that are close to the TSA value, or several high and low z-scores that are not aligned with the TSA value). Table 11.1 Example performance test results, corresponding z-scores and total score of athleticism Sprint test 5-m time (s) 10-m time (s) Athlete’s result 1.18 1.88 Squad mean 1.07 1.81 Squad standard deviation 0.07 0.08 z-score −1.5 −1.0 Vertical jump test CMJ height (cm) CMJ, countermovement jump; SJ, squat jump. SJ height (cm) Sprint test 5-m time (s) 10-m time (s) Athlete’s result 42 38 Squad mean 36 35 Squad standard deviation 4 6 z-score 1.5 0.6 Isometric mid-thigh pull test Peak force (N) Rel. peak force (N/kg) Athlete’s result 3630 42 Squad mean 3667 38 647 6 Squad standard deviation z-score Total score of athleticism −0.1 0.7 0.0 CMJ, countermovement jump; SJ, squat jump. Modified z-scores The term modified z-score yields similar information to the traditional zscore presented above, but can have different meanings. For instance, the term modified z-score can be used to indicate the replacement of the mean with the median in its calculation. This modified z-score may, therefore, be considered more robust than the standard z-score because it is less influenced by outliers (extreme scores, as detected via a test of normal data distribution) within a squad data set. This type of modified z-score can be calculated using the following equation: In addition to the above purpose, McGuigan et al. (2013) also used the term modified z-score to describe the comparison of an individual athlete’s fitness test result to a predetermined ‘benchmark’ mean and standard deviation result for the same test using the following formula: The predertermined benchmark mean and standard deviation may be derived from peformance test results that have been publishsed in the scientific literature (e.g. normative data). It is important to ensure, where possible, that the benchmark data are derived from the same methods employed to collect and analyse the athlete’s data, or to at least understand the margin of error expected when comparing fitness test results obtained via different methods before interpreting the results. For example, the just jump system, which is used to quantify jump performance, has been shown to overestimate jump height values but they can be converted to accurate values (McMahon et al., 2016), which would need to be done before being used for benchmarking purposes. There are benefits to comparing the athlete’s data to benchmark data, not least the fact that comparing the athlete’s data to the squad mean alone may under- or over-represent athletes’ performances depending on the ability of the squad as a whole. For example, an athlete may achieve a large z-score with respect to the squad mean but their performance could be substandard when compared to benchmark data if the squad mean score is below average or poor. Alternatively, the mean squad performances in each test can be compared to published normative data, rather than each individual athlete’s scores, and the data interpreted with any differences to published norms in mind. It is also worth being mindful that no athlete wants to be average and therefore just because they achieve a performance in line with the mean of the squad, or a specific benchmark, this does not mean that the performance is sufficient. More recently, the term modified z-score was used to describe the comparison of within-athlete data between different testing occasions (McGuigan, 2017). This alternative modified z-score can be calculated using the following formula: The above method helps to quantify the magnitude of improvement the athlete demonstrated for each performance test between testing occasions. It has been suggested that magnitudes of <0.20, 0.20–0.49, 0.50–0.79, ≥0.80 for standardized differences in means (e.g. z-scores) between testing occasions can be interpreted as trivial, small, moderate and large, respectively, much like when interpreting effect sizes (Cohen, 1988). Using this scale can help to guide consistent use of language when communicating such results to the athlete’s performance team or writing fitness test reports. Given that the term modified z-score has been used to describe several modifications to the traditional z-score equation, one should be transparent with how modified z-scores have been calculated to enable them to be accurately interpreted by others involved with the performance testing of athletes. It could be argued, however, that z-scores do not produce the most intuitive numbers or scale for athletes and coaches; thus we will now discuss alternative options which may be superior to z-scores from an intuition standpoint. We have also provided a conversion table to illustrate how z-scores correspond to the alternative approaches discussed (Table 11.2). Table 11.2 Corresponding percentile, standard ten (STEN) and t-score values for a given z-score z-score Percentile STEN t-score 5.0 100.0 10.0 100 4.5 100.0 10.0 95 4.0 100.0 10.0 90 3.5 100.0 10.0 85 3.0 99.9 10.0 80 2.5 99.4 10.0 75 2.0 97.7 9.5 70 1.5 93.3 8.5 65 1.0 84.1 7.5 60 z-score Percentile STEN t-score 0.5 69.1 6.5 55 0.0 50.0 5.5 50 −0.5 30.9 4.5 45 −1.0 15.9 3.5 40 −1.5 6.7 2.5 35 −2.0 2.3 1.5 30 −2.5 0.6 0.5 25 −3.0 0.1 0.0 20 −3.5 0.0 0.0 15 −4.0 0.0 0.0 10 −4.5 0.0 0.0 5 −5.0 0.0 0.0 0 Standard ten scores To make z-scores easier for coaches and athletes to understand, they can be converted to a standard ten (STEN) score which allows them to be presented on a scale of 1–10 (Thornton et al., 2019). As with z-scores, the STEN score is derived from the typical bell-shaped curve of normally distributed data (Figure 11.1), thus is it is important to check that the fitness test data obtained from the squad or published source conform to this assumption. The average STEN score is 5.5, thus the formula for converting a z-score to a STEN score is shown below: STEN scores are always rounded up, so a score of 9.5 would be rounded up to 10. The conversion of typical z-scores to the corresponding STEN score is presented in Table 11.2, where each STEN unit corresponds to 0.5 standard deviation. A potential benefit of converting a z-score to a STEN score is that it removes the inclusion of negative numbers and it involves a scale of values that is likely to be more intuitive to most coaches and athletes (i.e. a performance scale of 0–10). A potential limitation of STEN scores is that several upper- and lowerbound z-scores will share the same STEN score and so they distinguish a relatively narrow range of performances. For example, a z-score of ≤ −3.0 and ≥ 2.5 will share a STEN score of 0 and 10, respectively (Table 11.2). Therefore, while STEN scores may be more intuitive for coaches and practitioners to understand than z-scores, some of the other alternatives described below may be preferable. t-scores In a similar manner to STEN scores, t-scores avoid the use of small and sometimes negative numbers and can be easily calculated from the z-score using the following formula: The conversion of typical z-scores to the corresponding t-score is presented in Table 11.2, where each t-score increment of 10 corresponds to 1 standard deviation. It has been suggested that t-scores, like STEN scores, are more conventionally appreciated by coaches and athletes because they ‘rank’ fitness test data on a scale of 1–100 rather than, for example, a z-score range of −5.0 to 5.0 (Turner et al., 2019). Turner et al. (2019) also highlight that t-scores, if preferred to z-scores, can be calculated directly from the fitness test score by using the following formula: A different t-score calculation to the one presented above can also be made if the sample size from which the squad mean and standard deviation are derived is <30 and when the population standard deviation is unknown. It is thought to be inaccurate to estimate the population standard deviation from the sample itself (i.e. the standard deviation of the fitness test data collected with a squad of athletes) when the sample size is small (i.e. <30). Fitness test data obtained from fewer than 30 athletes are likely to adhere to a t-distribution rather than a normal distribution (Turner et al., 2019). A tdistribution of data points is shorter and wider than data that are normally distributed and, because this t-score calculation depends on the sample size, reference tables must be used to interpret the magnitude of the athlete’s score relative to the squad mean. Fortunately, however, in software such as Microsoft Excel we can simply use the t.dist function where we state the sample size and Excel will assess our value against the appropriate table, illustrating the data as a percentage. We can then assess that percentage in terms of where our athlete places, as per z-scores, and as illustrated in Figure 11.2. Before using the t.dist function, the value must first be converted to a t-score using the formula presented below: A typical normal data distribution curve with z-scores, corresponding standard ten (STEN), t-score and percentile values and integrated traffic-light system example. One way of overcoming a squad sample size <30 is to create a larger database of squad fitness test scores over time. For example, this could be achieved by adding fitness test scores that have been obtained from equivalent athletes (e.g. same age and performance level) using identical methods (e.g. equipment and coaching cues) and time periods of testing (e.g. pre-season) to a digital repository or database. If increasing sample size over time is logistically difficult, using the aforementioned t.dist function in Microsoft Excel is a suitable alternative approach. Percentiles Percentiles are another option for making fitness test results more intuitive for athletes and coaches to understand. Like STEN scores and t-scores, they avoid the use of small and sometimes negative numbers. Percentiles can be easily calculated from z-scores in applications such as Microsoft Excel via the following formula: A percentile represents the value below which a percentage of data falls. For example, the 20th percentile is the value below which 20% of observations may be found. Percentiles have been routinely calculated for fitness test results obtained from a range of populations, particularly for children to track as they grow over time. More recent applications of percentiles include those that have been applied to key countermovement jump variables obtained from force platforms (Sole et al., 2018; McMahon et al., publish ahead of print) and fitness-testing results for law enforcement officers (Lockie et al., 2018, 2020). Like with z-scores and STEN scores, percentiles can be calculated for normally distributed data, so again, it is important to check for normal data distribution before proceeding with percentile calculations. As with STEN scores, several upper- and lower-bound z-scores will share the same percentile. For example, a z-score of ≤ −3.5 and ≥ 3.5 will share a percentile of 0 and 100, respectively (Table 11.3). This is unlikely, however, to alter decision making based on typical thresholds used to distinguish performance ‘bands’ when benchmarking an athlete’s results to their peers/normative data (e.g. poor, average, good, excellent, etc.). Table 11.3 Example performance test results and corresponding individual and average percentiles Sprint test 5-m time (s) 10-m time (s) Athlete’s result 1.18 1.88 Squad mean 1.07 1.81 Squad standard deviation 0.07 0.08 Percentile 6.7 15.9 Vertical jump test CMJ height (cm) SJ height (cm) Athlete’s result 42 38 Squad mean 36 35 4 6 93.3 72.6 Squad standard deviation Percentile Isometric mid-thigh pull test Peak force (N) Rel. peak force (N/kg) Athlete’s result 3630 42 Squad mean 3667 38 647 6 Squad standard deviation Percentile Total score of athleticism 46.0 50.0 (percentile) CMJ, countermovement jump; SJ, squat jump. Data presentation 75.8 Once athletes’ fitness test results have been converted to a standardised format to facilitate intuitive reporting of the test scores, using any of the options discussed in the previous section, there are several options for presenting them in a visually appealing manner. It is beyond the scope of this chapter to discuss all data presentation options available to the practitioner, but we do provide some common, yet impactful, examples based on both the limited published research available and our applied experience. Traffic-light system A traffic-light system (TLS) refers to a method of colour coding fitness test results in red, amber or green (sometimes including various shades of each colour) corresponding to a negative, neutral or positive change in a test result (or low-, average- or high-achieving test results if used to ‘benchmark’ the athlete’s performance to others). It has been suggested that TLSs are an appealing option for strength and conditioning coaches who tend to work in a time- and resource-constrained environment (McMahon and Mundy, 2018). This is because a TLS is quick to produce (e.g. use of conditional formatting in Microsoft Excel), visually appealing and intuitive for coaches and athletes to interpret (Robertson et al., 2017). Although easy to construct and interpret, determining the TLS’s red, amber and green performance ‘bands’ for a given fitness test result usually requires comparison with extensive historical data obtained from the team you are working with or published normative data sets that were collected and analysed using equivalent methods (Robertson et al., 2017). However, once the fitness test data have been converted to a standardised form, based on any of the methods described in the data analysis section, it is somewhat easier to determine the TLS’s red, amber and green performance bands or thresholds. While there is no criterion method of identifying performance bands that denote a negative (amber–red, depending on magnitude), neutral (no colour or amber, depending on application [discussed further below]) or positive (green) fitness test score, in this section we propose one approach that may be benefical to practitioners. The first thing to point out is that our method of constructing performance bands based on standardised units (rather than absolute benchmarks) that may then feed into a TLS requires the athlete’s individual performances in the fitness tests to be compared to an appropriate mean and standard deviation (e.g. from the squad or normative data), in line with the recommendations provided in the data analysis section. Assuming, therefore, that the selected mean and standard deviation are appropriate, our proposed method is based on the typical scale used to interpret standardised scores. Specifically, we consider what magnitude of difference (when comparing an individual athlete’s fitness test scores to the squad mean or normative data) or change (when comparing an individual athlete’s fitness test scores post-intervention to their pre-intervention scores) is likely to be required for it to be greater than the associated tests’ measurement error. The standard error of measurement (SEM), which is commonly referred to as the typical error within the profession of strength and conditioning, of each fitness test score is likely to exceed the smallest worthwhile change (0.2 × the squad or normative data standard deviation, which is equivalent to a z-score of 0.2) associated with each test. Thus, constructing benchmarks and the associated TLS based on a small z-score of ≤0.2 (or equivalent number for the other standardised scores presented in the previous section) is probably nonsensical. However, most of the typical fitness tests conducted within strength and conditioning (based on published research and our own data analyses) yield an SEM that falls below the moderate worthwhile change (0.5 × the squad or normative data standard deviation, which is equivalent to a z-score of 0.5). Therefore, our suggested approach is to use 0.5 z-score (or equivalent) increments when constructing the performance bands that feed into a TLS, as this should account for the worst-case-scenario SEM values for most (but ideally all) fitness tests. In other words, most fitness test scores should have an associated SEM that is low enough to enable moderate differences (between athletes) or changes (within athletes) to be determined with confidence. With this in mind, an illustration of our suggested approach for constructing TLS performance bands, which includes the associated z-scores, STEN scores, percentiles and t-scores, is presented as Figure 11.2. Of course, practitioners could quantify the SEM associated with each of the fitness tests that they conduct with their athletes to determine the precise z-score (or equivalent) that denotes a ‘meaningful’ difference or change and instead use those values to construct a TLS. However, the SEM when expressed as a standardised score is going to be different for each fitness test result and so it would be very difficult to produce a quick (preferably automated) fitness test report with an integrated TLS if one was to adpot this approach. A TLS can be used to colour-code fitness test results according to performance band attainment irrespective of the format in which the key fitness test results will be reported to the athlete and coaches. For example, a TLS can be included with tabulated fitness test results. If presenting fitness test results as in Table 11.3 with an integrated TLS, we advocate the presentation of important data only and removing unnessary decimal points from reported values, along with the other excellent suggestions provided by Buchheit (2017). Even if the recommendations of Buchheit (2017) have been followed, data tables are generally considered to be less visually appealing and intuitive than graphical data representations. Thus, some options for reporting fitness test results in graphical formats are discussed in the following sections. Radar charts Radar charts (sometimes referred to as spider charts) allow three or more fitness test results for an individual athlete to be presented on axes with an equal origin. Therefore, radar charts can be constructed using z-scores, percentiles, STEN scores and t-scores. Radar charts are particularly useful when reporting baseline fitness test scores by comparing each athlete’s score to the squad or normative data mean and standard deviation, or changes in an individual athlete’s fitness scores between two occasions (e.g. pre- and post-training intervention). We will discuss both applications of radar charts in this section. We have used t-scores in the examples provided to facilitate ease of interpretation (i.e. an intuitive 0–100 scale), but the principles discussed may be applied to any other standardised score that has been discussed in this chapter. Example results of a pre-season fitness-testing battery that was conducted within rugby league are presented as a radar chart using a standardised t-score scale with integrated TLS in Figure 11.3. As can be seen, the benefit of converting multiple individual fitness test results to standardised scores and then presenting them within a single radar chart is that the athlete’s relative strengths and weaknesses can be easily visually identified, even when a lot of fitness test scores are presented at once. In this example, a white band for t-scores ranging from 45 to 55 has been applied to represent the squad mean score, plus and minus half a standard deviation to account for the (hopefully) upper limit of each test’s measurement error. For example, the athlete’s result for left-side change-ofdirection time (actual t-score of 48) and eccentric utilisation ratio (actual tscore of 46) is interpreted as being equivalent to the squad mean. Conversely, all other fitness test scores may be confidently interpreted as being better (various shades of green) or worse (amber or various shades of red) than the squad mean, with their obvious best peformances seen for the maximal strength (isometric mid-thigh pull) and sprint momentum (owing to their larger than average body mass, given that their sprint times are below average) tests and their obvious worst peformance seen for the countermovement jump height test. The TSA indicates that the athlete’s allround performance in the fitness-testing battery was comparable to the squad mean, albeit comprised of several better and worse performances in the individual fitness tests. Such intuitively presented fitness test results should enable audiences (e.g. coaches and athletes) to quickly identify areas for the athlete’s future improvement which can then be addressed in their upcoming training programme (such as ballistic training in the present example). Example results of a pre-season fitness-testing battery conducted within rugby league and presented as a radar chart using a standardised t-score scale and integrated traffic-light system. As well as presenting three or more fitness test results for an individual athlete within a single radar chart, it is possible to present several results from the same or a few fitness tests. This approach may be particularly useful when conducting force platform assessments with athletes, as practitioners may identify several force platform variables of interest from a single force platform assessment (e.g. when conducting the countermovement jump test) or wish to combine results from two force platform assessments (e.g. when calculating dynamic strength index). To that end, example results from force platform assessments that were conducted as part of a pre-season fitness-testing battery within rugby league are presented as a radar chart using a standardised t-score scale with integrated TLS in Figure 11.4. As can be seen, the athlete included in this example performed very well compared to his peers, as noted by him being ranked first in the squad for the TSA. Upon visual inspection of the force platform assessment results, eccentric utilisation ratio (calculated as countermovement jump height divided by squat jump height) is the only score that falls below the squad average and in the amber performance band. That is not to say that the athlete would not benefit from further improving the physical qualities that he has excelled at in comparison to his peers, but that eccentric utilisation ratio is the only test score that is evidently below the standard set by the squad mean. Example results from force platform assessments that were conducted as part of a pre-season fitness-testing battery within rugby league presented as a radar chart using a standardised t-score scale and an integrated traffic-light system. Upon further insepection of the force platform assessment results, it can be seen that the joint highest t-score of 69 was obtained for reactive strength index modified and squat jump height. As reactive strength index modified is calculated from the countermovement jump data as jump height divided by time to take-off, the larger t-score for reactive strength index modified than for countermovement jump height (t-score of 66) suggests that this athlete performed the countermovement jump with a shorter time to take-off than the squad mean. Reducing time to take-off in the countermovement jump can reduce jump height, thus the reason why the athlete jumped higher in the squat jump than in the countermovement jump (hence generating an eccentric utilisation ratio of less than 1) could have been due to them restricting their propulsion displacement in the countermovement jump to facilitate a shorter time to take-off (McMahon et al., 2021). Therefore, the eccentric utilisation ratio of less than 1 may merely be a reflection of the athlete’s preferred countermovement jump strategy rather than an indication of a poor utilisation of the stretch-shortening cycle (which is what the eccentric utilisation ratio supposedly reveals). Thus, the informed practitioner may not wish to place too much emphasis on the athlete’s below-average eccentric utilisation ratio alone, but rather focus on a combined maximal strength and ballistic training programme given the overall balance of the athlete’s mostly positive results and his dynamic strength index score of 0.7 (Figure 11.4). As mentioned in the data analysis section, modified z-scores (and thereafter any of the other standardised scores discussed) can be calculated to illustrate changes in an athlete’s fitness-testing scores from baseline testing, such as after a training intervention, for example. To that end, example results from a countermovement jump assessment that was conducted using a force platform as part of a pre-season fitness-testing battery within rugby league are presented as a radar chart using a standardised t-score scale with integrated TLS in Figure 11.5. In this example, the white band for t-scores ranging from 45 to 55 has been applied to represent the athlete’s baseline mean score, plus and minus half a standard deviation to account for the upper limit of each score’s measurement error. Also, a reduction in countermovement time, countermovement displacement and propulsion time was considered a positive outcome but, to avoid possible confusion, arrows have been added next to the variable labels to denote whether the absolute score for these tests increased or decreased between testing occasions (e.g. countermovement time in seconds decreased, hence the downward arrow, but this is shown as an increased t-score due to it being considered a positive outcome). Again, the radar chart with integrated TLS makes it easy for the audience to quickly interpret within-athlete changes in key fitness test results. In this example, the athlete improved in all aspects of countermovement jump performance (Figure 11.5). Even though the upward arrow denotes an increase in countermovement displacement, the tscore of 47 falls within the white performance band comprised of the baseline mean ± SEM, thus it should be interpreted as no change. If subsequent countermovement jump tests were to be performed with this athlete, the latest test results could be compared to the baseline results alone (as in Figure 11.4), to the previous results alone or overlaid with the previous test results so that an additional data series showing the latest results is presented alongside the previous test results, depending upon the practitioner’s preference. Example results from a countermovement jump assessment that was conducted using a force platform as part of a pre-season fitness-testing battery within rugby league presented as a radar chart using a standardised tscore scale and an integrated traffic-light system. Conclusion This chapter has discussed some of the data analysis options available to practitioners to facilitate the sometimes difficult task of presenting multiple fitness test results, often containing unfamiliar units of measurement, in the form of standardised scores. Standardised scores enable several fitness test results with different units of measurement to be presented on the same intuitive scale, such as 0–100 (i.e. t-score). Some methods of visually presenting standardised scores were then discussed in the form of developing a TLS, including suggestions on how to construct colour-coded performance bands, and then plotting key results in a simple radar chart with integrated TLS. Examples of radar charts with integrated TLS to present baseline fitness test results attained across multiple fitness tests, several baseline force platform assessment results and within-athlete changes in key countermovement jump assessment results were then provided and discussed. 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Turner, A.N., Jones, B., Stewart, P., Bishop, C., Parmar, N., Chavda, S. & Read, P. 2019. Total score of athleticism: holistic athlete profiling to enhance decision-making. Strength & Conditioning Journal, 41, 91–101. 12 Eccentric training: scientific background and practical applications Mellissa Harden, Paul Comfort and G. Gregory Haff DOI: 10.4324/9781003044734-15 A central theme of this chapter is focusing on eccentric muscle actions and the use of eccentric exercise as a tool for enhancing strength and athletic performance. Several eccentric resistance-training modalities are available to the strength and conditioning coach, each of which has unique biomechanical characteristics that can stimulate unique physiological and performance adaptation. It is well documented that habitual use of eccentric exercise, usually with isolated singlejoint tasks, can result in a larger and stronger muscle that has the potential to generate higher-power outputs when compared to traditional isotonic training. Unfortunately, many of the methods incorporated in these eccentric training studies lack ecological validity and are therefore not easily applied to normal multi-joint resistance-training exercises. In contrast, accentuated eccentric loading (AEL) may be a viable method of providing eccentric overload during traditional multi-joint exercises. To assist coaches with their understanding of eccentric muscle actions and training, section 1 will provide a summary of the theoretical basis for employing eccentric training. This part of the chapter is designed to help strength and conditioning coaches better understand the unique characteristics of eccentric muscle actions and how integrating this type of muscle action into training may translate to an enhanced physical performance capacity. The second part of this chapter explores various eccentric training modalities and specific eccentric resistance-training methods to assist practitioners with the application of eccentric training within an athlete’s training programme. Introduction Strength and conditioning coaches prescribe numerous resistance-training methods with the aim of enhancing athletic performance and reducing injury risk. Training usually draws upon a variety of exercises that emphasise different muscle actions (i.e., eccentric, isometric, concentric, and coupled eccentric–concentric [isotonic]). Training that incorporates different types of muscle action will not only improve sporting movements that draw upon these specific muscle actions, but will also take advantage of the beneficial effects of the physiological adaptations that are unique to each muscle action (e.g., increased fascicle length associated with maximal eccentric actions: [Franchi et al., 2014, 2015; Geremia et al., 2019]), potentially leading to higher maximal shortening velocity and therefore power (Narici, 1999; Lieber and Fridén, 2000). Muscle actions vary in their neural, mechanical, metabolic, and cardiovascular characteristics, and therefore tend to result in distinctive physiological adaptations following routine training. It is important that strength and conditioning coaches are aware of the unique characteristics and adaptations resulting from different modes of training and understand the potential role these adaptations play in the physical and performance development of athletes, as well as their potential for reducing injury risk. A greater understanding of the unique characteristics associated with eccentric training will ensure that the strength and conditioning coach can develop relevant and effective training programmes and more effectively interpret research in this area. While the benefits of traditional isotonic strength-training methods are generally well accepted (Cormie et al., 2011a, 2011b; Suchomel et al., 2016, 2018), it is important to consider the limitations of such strategies when the aim is to increase eccentric muscle strength. (Traditional training principles for the development of strength and power are discussed in detail in Chapter 2.) During traditional modes of strength training the maximal load lifted is determined by the maximal concentric strength, thereby limiting the ability to take advantage of the increased force generation capacity that is possible during eccentric muscle actions. While both concentric and eccentric strength increase in response to traditional strengthtraining methods, eccentric training can permit loads up to 150% of the load used during the concentric phase (Hortobágyi and Katch, 1990; Dufour et al., 2004; Harden et al., 2019), which provides unique opportunities to apply greater load during the eccentric muscle action. However, it is important to note that this higher level of eccentric force production varies between individuals, likely due to familiarity with the task and the athlete’s relative strength levels (Harden et al., 2018; Hody et al., 2019). SECTION 1 Unique characteristics associated with eccentric muscle actions Eccentric muscle actions occur when the force generated by the muscle is less than the force imposed by an external stimulus, causing the muscle to lengthen whilst active. In this instance, work is done on the lengthening muscle and the associated connective tissues store mechanical energy (Lindstedt et al., 2001). During tasks such as running, sprinting, and reactive jumping (i.e., stretch-shortening cycle [SSC] actions), elastic potential energy is stored within the connective tissues of the muscle–tendon unit during the eccentric phase, then released and utilised during the propulsive phase, supplementing the force produced from concentric muscle action (LaStayo et al., 2003). In this instance, the muscle–tendon unit acts as a spring and the release of stored energy acutely enhances force production characteristics during the concentric phase, when compared to a concentric-only muscle action. Additionally, when a muscle is lengthened during SSC tasks, the muscle spindle is stimulated via both the rate and magnitude of muscle lengthening and results in an increased force and rate of force production via the stretch reflex. However, during tasks such as landing and braking (i.e., decelerative actions), stored elastic energy is dissipated as heat, via hysteresis. In such instances muscles and tendons act as ‘shock absorbers’ to dampen impact forces upon ground contact (LaStayo et al., 2003). Enhancing the function of muscle via eccentric training can therefore facilitate performance during tasks that utilise the SSC or enhance the capability to decelerate the body (Liu et al., 2020). It is worth noting that in individuals who do not have well-developed strength, traditional strength-training methods are an effective means of enhancing SSC function, to a greater extent than jump training alone (Cormie et al., 2007, 2010a, 2010b, 2010c; Earp et al., 2011). So, for these individuals the application of traditional strength-training methods should be the priority. Eccentric muscle actions are characterised by a combination of distinct mechanical, neural, metabolic, and circulatory qualities. In terms of mechanical qualities, there are increased cross-bridge forces and passive forces from the contribution of structural elements within the sarcomere. During eccentric muscle actions, active lengthening of the muscle results in a different interaction of actin and myosin filaments (Linari et al., 2004; Herzog, 2014). The forcible detachment of cross-bridges does not rely on adenosine triphosphate (ATP) splitting, as per the normal cross-bridge cycling processes, and leaves the myosin filaments in an active state such that they are able to rapidly reattach back to actin (Lombardi and Piazzesi, 1990). Along with the activation of the second head of myosin, and possible increased number of stronger attachments to the actin filaments, this can result in a greater number of cross-bridge attachments at a given time, thus increasing cross-bridge force (Linari et al., 2000). Furthermore, contribution of passive tension from the inherent stiffness of structural elements within the sarcomere can further contribute to force enhancement during eccentric muscle actions (Nishikawa, 2016). It is accepted that muscles are stronger during eccentric versus isometric (i.e., constant muscle length) or concentric (i.e., shortening) muscle actions. Researchers have documented that individuals are up to 50% stronger during maximal eccentric exercise versus maximal concentric exercise (Hortobágyi and Katch, 1990; Dufour et al., 2004; Harden et al., 2019). Coaches should be mindful, however, that there is clear variability in the magnitude of additional force that can be produced during eccentric actions compared to concentric and isometric actions (Harden et al., 2019), which may be attributable to both the athlete’s relative strength levels (Hody et al., 2019) and their familiarity with the eccentric task. When considered simplistically, an individual is generally able to lower a weight that is much heavier than what they can lift. Therefore, during traditional exercise whereby loading is limited by concentric strength, eccentric strength is challenged to a much lesser extent given that maximum eccentric strength is much greater than maximum concentric strength. This distinct characteristic of eccentric muscle actions enables the application of greater loads during the eccentric phase, well beyond what can be applied during concentric muscle actions. Interestingly, Refsnes (1999) reported that strong athletes tolerate lower eccentric loads relative to their one repetition maximum (1RM), providing an example of eccentric loads of 105–110% 1RM in world-class power lifters, while lower-level athletes may tolerate loads of 120– 130% 1RM. Similar results highlighting a greater discrepancy in eccentric and concentric loads between weaker and stronger individuals have also been reported by researchers (Hollander et al., 2007; Harden et al., 2019). In a practical context, when looking to develop eccentric strength, information regarding the enhanced force production capability of eccentric muscle actions has led to the application of loads that exceed conventional coupled eccentric– concentric 1RM during multi-joint exercise. During multi-joint eccentric exercises loads of up to 150% 1RM have been used for trained individuals (Harden et al., 2018), when using AEL (e.g., additional load from hydraulics in research, or in applied settings the use of weight releasers, so that the additional load is removed at the end of the eccentric phase, resulting in a load that is <1RM during the concentric phase of the lift). However it is important to note that not all trained individuals are able to tolerate such high relative loads (Harden et al., 2018, 2019), with weaker individuals demonstrating a greater discrepancy between concentric and eccentric load (Hollander et al., 2007; Harden et al., 2019), meaning that a conservative approach to eccentric loading should initially be adopted. Interestingly, for a given force output, muscles require less energy and activation (per unit of force) during eccentric versus concentric or isometric actions (Abbott et al., 1952). For the same level of submaximal force output, muscle activation is notably lower during eccentric versus concentric muscle actions (Franchi and Maffiuletti, 2019). Researchers have also shown that for the same work output, energy expenditure is approximately four-fold less during eccentric versus concentric exercise; eccentric actions are associated with markedly lower oxygen uptake for a given submaximal mechanical power output (Bigland-Ritchie and Woods, 1976; Overend et al., 2000; Meyer et al., 2003). Dufour et al. (2004) provide additional insight into the distinct metabolic and circulatory response associated with eccentric exercise. When comparing eccentric and concentric cycling at a similar mechanical power output, the authors reported that eccentric muscle work induces lower metabolic and cardiovascular responses (lactate accumulation, oxygen consumption, cardiac output, and heart rate) than concentric muscle work. However, eccentric and concentric cycling performed at a similar submaximal metabolic power output (i.e., oxygen uptake), resulted in greater cardiovascular stress (cardiac output and heart rate) during eccentric cycling as the mechanical power required to achieve the target metabolic power output was five times greater than that required during concentric cycling. Subsequently, the authors attributed the increased cardiovascular stress to thermoregulatory or muscle tension-induced responses. In terms of unique neural qualities, it has been suggested that the preparation, planning, and performance of eccentric muscle actions appear to differ from concentric muscle actions due to differences in the onset of brain activity and associated brain area that are involved immediately before and during movement (Fang et al., 2001). This is a unique strategy for control of motor unit activation and discharge rate. At a given force output or when under similar loading conditions, eccentric muscle actions are associated with reduced muscle activation and discharge rate of the activated motor units when compared to concentric muscle actions (Bigland-Ritchie and Woods, 1976; Pasquet et al., 2006; Aagaard, 2018). Unlike concentric muscle actions, there is evidence of incomplete muscle activation during maximal eccentric muscle actions (Aagaard, 2018; Aagaard et al., 2000; Spurway et al., 2000). The activation shortfall has been attributed to inhibitory mechanisms (Aagaard, 2018), potentially due to stimulation of the Golgi tendon organ, attributed to the magnitude and rate of strain to which the tendon is subjected (Chalmers, 2002). The inhibitory response and subsequent voluntary activation deficit are modifiable by targeted strength training, which can reduce or diminish the degree of inhibition (Amiridis et al., 1996; Aagaard et al., 2000; Aagaard, 2018). Additionally, it is common for eccentric muscle actions to be associated with the preferential recruitment of higher-threshold motor units (Nardone and Schieppati, 1988; Nardone et al., 1989); however, this is not widely accepted and remains a topic of debate within the scientific literature (Chalmers, 2008; Duchateau and Enoka, 2016). In summary, when using eccentric muscle actions there is potential to perform a given submaximal force (and even when performed with supramaximal loads) with metabolic, neural, and circulatory efficiency compared to isometric and concentric muscle actions. Furthermore, individuals can produce greater muscle force and tension during eccentric versus concentric muscle actions. The practical implications of these features are: individuals can perform greater work at a given submaximal exercise intensity individuals can tolerate greater external load during eccentric exercise versus conventional isotonic training methods, i.e., individuals can lower more than they can lift so movements can be loaded to a greater extent when using certain eccentric or eccentrically biased training approaches, such as AEL. During eccentric exercise, muscles can experience unique muscle strain which could stimulate cascade of distinct physiological events resulting in increased fascicle length associated with maximal eccentric actions (Franchi et al., 2014, 2015; Geremia et al., 2019), leading to higher maximal shortening velocity and therefore increased potential for power development (Narici, 1999; Lieber and Fridén, 2000). Eccentric training has also been reported to result in fibre shifts to faster myosin heavy-chain isoforms (Friedmann et al., 2004; Friedmann-Bette et al., 2010), associated with increased force and power production (Aagaard and Andersen, 1998; Friedmann-Bette et al., 2010). Exploiting these unique characteristics of eccentric muscle actions has the potential to stimulate distinct and potent, neuromuscular, and physiological adaptations. The nature of these adaptations, which will be discussed next, could prove beneficial for rehabilitation, physical development of athletes, and performance during sport. SECTION 2 Classification of eccentric exercise modalities In 1972, Arthur Jones wrote the article ‘Accentuate the negative’ which was featured in IronMan magazine (Jones, 1973). Jones (1973) suggested that readers think about how much they can lower, rather than how much they can lift. Jones (1973) appeared to have coined the term ‘negative training’, for what is now more commonly referred to as ‘eccentric training’. Although he popularised the training method for developing strength and stimulating hypertrophy (predominantly in bodybuilding), the idea is likely to be based upon scientific findings that were published in the preceding years (Abbott et al., 1952; Petersen, 1960; Doss and Karpovich, 1965; Huxley, 1969; Mannheimer, 1969). Since this first notation of eccentric training in the applied literature, the scientific basis explaining the use of eccentric training methods has continued to evolve. There are potential benefits related to emphasising the eccentric phase during training: increased time under tension ([TUT]: e.g., tempo training, where the duration of the eccentric phase of isotonic exercises is prolonged, albeit that this method does not take advantage of the higher force production capability of eccentric actions) potentially benefitting hypertrophic adaptations increased load during the eccentric phase (e.g., AEL, where additional load is provided by weight releasers during the eccentric phase), which may enhance strength-related adaptations due to unique architectural adaptations, which may also reduce injury risk. Technologies used to apply eccentric training are becoming more advanced, and equipment that facilitates the ability to perform eccentric training is becoming increasingly more accessible. For example, flywheel devices are readily available (Petré et al., 2018), in addition to weight releasers (Merrigan et al., 2020a, 2020b; Doan et al., 2002), with some more advanced techniques including motorised devices to increase eccentric loads used in research (Frohm et al., 2005; Harden et al., 2018, 2019). The availability of such devices to accentuate the eccentric load has prompted a large influx of information regarding the efficacy of eccentric training for the purpose of advancing physical performance. It is worth noting that flywheel devices appear to result in forces during the eccentric phase that are comparable to those during the concentric phase, but generally not greater than the concentric phase (Suchomel et al., 2019). Eccentric training is an umbrella term used for several different eccentric training modalities. Eccentric training modalities include modifying the eccentric phase of an exercise, such that it differs from the conventional application of load. This provides an option for introducing training variety by offering a novel training stimulus. Recently, Franchi and Maffiuletti (2019) made a distinction of eccentric training modalities and recognised the unique underpinning biomechanical demands and neuromuscular profiles of the different modalities. The following eccentric training modalities were identified: isoweight, isokinetic, and isoinertial, whereby each modality comprises a different constant: weight, velocity, and inertia, respectively, and therefore differ in their variability and demand for self-adjustment during movement. The piece stimulated a number of comments and viewpoints from several other researchers regarding the distinction and classification of other forms of eccentric activity, for example, isopower (i.e., constant power output) (Coratella et al., 2019). A summary of this information is presented in Table 12.1. Table 12.1 Four eccentric training modalities and specificities underpinning each modality Classification/modality Isoweight Isoinertial Isokinetic Isopower Constant External load/bodyweight Inertia Velocity Power output Examples Free weights, landings Flywheel and (vertical entry), conic pulley deceleration (horizontal entry using augmented, accentuated, or eccentric only/negatives approaches) Dynamometry Cycle and step ergometry * Supramaximal intensity results from using non-specific measures of ECC strength to prescribe intensity. ** Potentially possible with technique modification. *** Supramaximal intensity does not apply as the intensity is specific to ECC strength. More + signs indicate more evidence in this area. ROM, range of motion; CON, concentric; ECC, eccentric; MVC, maximal voluntary contractions. Adapted from Franchi, M.V. and Maffiuletti, N.A. 2019. Distinct modalities of eccentric exercise: Different recipes, not the same dish. Journal of Applied Physiology (1985), 127, 881–883. Classification/modality Isoweight Isoinertial Isokinetic Isopower Factors affecting output Tempo/cadence, ROM, drop height (landings), running/entrance velocity (decelerations) Tempo/cadence, ROM, target intensity/effort during CON phase, technique (timing/position of onset of deceleration during ECC) Intensity of effort, ROM Cadence Possible movement Coupled ECC-CON, ECC only Coupled ECCCON Coupled ECC-CON, ECC only ECC-only movement Eccentric intensity Submaximal Maximal Supramaximal* Submaximal Maximal Supramaximal** Submaximal Maximal*** Submaximal Maximal*** Eccentric loading During coupled ECC- Determined by CON, ECC load CON capacity can be dissociated and inertial of from CON load flywheel/conic using specialised pulley equipment or techniques. For ECC only, ECC load can be applied using specialised equipment or safety racks and spotters Dependent on preset target force output relative to ECC MVC Dependent on preset target power output Eccentric load prescription Commonly based on non-ECC-specific measures of strength Based on CON output Considers ECCspecific strength Considers ECCspecific strength Prevalence of use Research + Practice +++ Research +++ Practice +++ Research ++++ Practice + Research +++ Practice ++ * Supramaximal intensity results from using non-specific measures of ECC strength to prescribe intensity. ** Potentially possible with technique modification. *** Supramaximal intensity does not apply as the intensity is specific to ECC strength. More + signs indicate more evidence in this area. ROM, range of motion; CON, concentric; ECC, eccentric; MVC, maximal voluntary contractions. Adapted from Franchi, M.V. and Maffiuletti, N.A. 2019. Distinct modalities of eccentric exercise: Different recipes, not the same dish. Journal of Applied Physiology (1985), 127, 881–883. During isokinetic exercise, an individual is simply required to produce force, ideally with maximal intent, without having to control the speed of the movement, as the velocity of the movement is controlled by the isokinetic dynamometer. In contrast, a greater degree of self-adjustment is required during isopower exercise, where movement velocity is not regulated via equipment. Instead, an individual must produce a force whilst attempting to voluntarily control the movement by matching a predetermined cadence. An isopower ergometer adjusts in response to an individual’s cadence to maintain a constant power output. A given power output can be achieved by applying a greater force output using a lower cadence or vice versa. Similarly, a high degree of self-adjustment is required during isoweight exercises whereby controlled movement is an interplay of acceleration and deceleration. During isoweight exercise, an individual must act to produce sufficient force and under voluntary control to match a predetermined performance constraint, for example, over a set range of motion (ROM) (e.g., during a squat) or fall height (e.g., during a drop jump) in order to produce a sufficient force at an appropriate rate to accept, equal, or overcome an anticipated mechanical force that is imposed on the musculoskeletal system. For example, during AEL one research group has recommended high loads, with a large relative difference (≥40% 1RM on weight releasers), creating a 80–120% ratio of concentric (80% 1RM) to eccentric loading (120% 1RM) (Merrigan et al., 2020a), which is in line with suggestions from over 30 years ago (Poliquin, 1988). These distinctions are particularly important because the different characteristics associated with the range of eccentric exercise modalities are likely to alter the neuromuscular control strategy (Duchateau and Enoka, 2016), and thus lead to distinct adaptive responses, and neurological and architectural adaptations (Guilhem et al., 2010; Coratella et al., 2015; Doguet et al., 2016). It is important for practitioners to understand the distinct qualities of the different approaches to eccentric training so that more accurate decisions can be made about the most appropriate form of eccentric training to use within a training programme based on the target adaptations. SECTION 3 Physiological basis for eccentric training Eccentric muscle actions, which occur during eccentric training, occur when the force generated by the muscle is less than the force imposed by an external load. This is in contrast to concentric muscle actions, which are prevalent during concentric training, occurring when the force generated by the muscle is more than the force imposed by an external load. Eccentric muscle actions are associated with unique neural control strategies (Enoka, 1996) and distinct mechanical processes (Lieber, 2018) compared to concentric and isometric muscle actions. Therefore, training using eccentric muscle actions may offer a novel stimulus which can result in distinct neuromuscular and morphological adaptations. Acute responses Acute physiological and performance responses are manifested immediately following or in the days after performing an exercise or series of exercises. The acute physiological responses associated with eccentric exercise can impede or enhance performance, depending on the application (i.e., load and volume), and can be indicative of potential longitudinal adaptation. For example, numerous researchers have demonstrated immediate myofibrillar disruption associated with unaccustomed eccentric exercises, which can last for 2–3 days (depending on the volume) and which manifests as delayed-onset muscle soreness (DOMS) (Hody et al., 2019). During this time performance is impaired; however, this initial bout of eccentric exercises can have a protective effect for subsequent eccentric training, known as the repeated-bout effect (RBE) (McHugh et al., 1999; Nosaka and Aoki, 2011). In contrast, if the athlete is familiar with eccentric exercises and acute soreness is not evident, enhanced neurological stimulation and changes in muscle architecture can result in enhanced force production capabilities (Blazevich and Babault, 2019). Repeated eccentric action of muscles whilst undergoing high tension can cause disruption to the contractile and non-contractile elements of the muscle, resulting in temporary muscle soreness and reduction in force output (Morgan and Allen, 1999). Whilst this could be interpreted as a negative effect, it is important to highlight that an element of microdamage is essential to stimulate tissue repair and growth, providing protection against future damage (Nosaka and Aoki, 2011). Importantly, this disruption stimulates muscle protein synthesis, increases intracellular anabolic signalling, and upregulates gene expression (Krzysztofik et al., 2019), whilst creating the RBE (McHugh et al., 1999; Nosaka and Aoki, 2011). These responses are indicative of the potential for muscle hypertrophic response if the exercise is performed habitually, and importantly, are heightened following eccentric exercise compared to traditional loading approaches or concentric muscle actions (Moore and Schilling, 2005; Friedmann-Bette et al., 2010; Franchi et al., 2015; Suchomel et al., 2019). The myofibrillar disruption associated with unaccustomed eccentric exercises (Lauritzen et al., 2009; Hody et al., 2019) has notable implications for the prescription of such tasks, which should be conservative and progressive in nature, to avoid excessive muscle soreness. Such discomfort can discourage individuals from performing specific activities (Hody et al., 2019) and therefore needs to be carefully considered when introducing focused eccentric exercise. Fortunately, a clear RBE is evident with eccentric training, whereby reduced myofibrillar disruption, swelling, and muscle soreness occur in subsequent bouts of the same activity, even after an initial single bout of eccentric exercise (McHugh et al., 1999; Nosaka and Aoki, 2011). Alternatively, accentuating the external load during the descending phase of an exercise can result in an acute enhancement of concentric performance (commonly referred to as post-activation performance enhancement [PAPE]; [Blazevich and Babault, 2019; Merrigan et al., 2020a]). This effect has been attributed to physiological responses such as increased neural stimulation (i.e., more potent myotatic reflex and/or increased motor unit recruitment); storage and subsequent release of energy in elastic structures (i.e., from stretch and recoil of parallel and series elastic components); and increased muscle active state at the onset of concentric action (i.e., greater number of attached cross-bridges) during the propulsive phase (Doan et al., 2002; Moore and Schilling, 2005; Ojasto and Häkkinen, 2009a; Ojasto and Häkkinen, 2009b). These features facilitate forceproducing characteristics particularly during the onset and early phase of the ascending portion of the movement, which is likely to manifest as an improvement in performance outcomes, for example, load lifted, propulsive velocity, or jump height. Performance enhancement can also occur shortly after exposure to a highintensity eccentric conditioning stimulus. The high-intensity nature of the conditioning stimulus can result in continued excitation of the nervous system and enhanced contractile function at a physiological level which, from a performance perspective, can lead to an increase in muscle force output and rate of force development for a given level of stimulation (Blazevich and Babault, 2019). Despite much evidence supporting PAPE in a general training context (Blazevich and Babault, 2019), research investigating the PAPE effects associated with eccentrically biased loading is less prominent. The research that is available is indeterminate; however, recently published research findings indicate that PAPE outcomes are very sensitive to the combination of eccentric and concentric load applications (Merrigan et al., 2020a). The authors suggest that PAPE occurs when there is a large relative difference (≥40% 1RM on weight releasers) between concentric to eccentric load, which provides useful insight for prospective investigations. Moreover, they reported concentric power increased when total load was 120% 1RM, with only 65% 1RM during the concentric phase (55% 1RM on weight releasers), while there was no change when total load was 120% 1RM and 80% 1RM during the concentric phase (40% 1RM on weight releasers). In contrast, other researchers have reported increased eccentric work (unsurprisingly), concentric work, and eccentric and concentric rate of force development (RFD) during AEL loaded squats (105% 1RM eccentric phase, 80% 1RM concentric phase: 25% 1RM on weight releasers), especially when performed as cluster sets, compared to traditional loaded (80% 1RM) sets (Wagle et al., 2018a, 2018b). However, it is not currently known how the acute performance-enhancing effects may translate into chronic neuromuscular adaptations, or whether the increased loads during the eccentric phase result in chronic adaptations as reported with increased eccentric loads during other eccentric training modalities. This section has provided a brief overview of the acute physiological responses to eccentric training. For a more comprehensive review the authors recommend reading the review article by Douglas et al. (2017). Longitudinal responses There is a wealth of evidence indicating that habitual use of eccentric exercise reduces neural inhibition (Aagaard, 2018); increases muscle activation (Higbie et al., 1996; Hortobágyi et al., 1996); increases agonist neural drive; and decreases coactivation of antagonist muscles (Seger and Thorstensson, 2005), and also appears to facilitate the recruitment of type II motor units and shifts the muscle towards a faster phenotype (Hortobágyi et al., 1996; Friedmann-Bette et al., 2010), with Friedman-Bette et al. (2010) using AEL. Habitual use of eccentric exercise has shown to increase eccentric, isometric, and concentric force-producing capacity (Higbie et al., 1996; Hortobágyi et al., 1996; Cadore et al., 2014), resulting in enlargement of muscle cross-sectional area (Vikne et al., 2006; Bogdanis et al., 2018), with some researchers observing a bias towards the development of fasttwitch muscle fibres (Friedmann-Bette et al., 2010). It is worth noting that, when matched for load or work, the hypertrophic adaptations appear comparable between concentric and eccentric muscle actions (Franchi et al., 2014; Schoenfeld et al., 2017); however, the advantage of eccentric training is that loads greater than those used during traditional concentric or isotonic training are possible, resulting in higher forces, which likely result in greater stimuli for adaptation (Walker et al., 2016, 2017). Researchers have reported that eccentric exercise stimulates a distinct myogenic response for architectural remodelling (Franchi et al., 2014), which has been associated with an increase in fascicle length (Baroni et al., 2013; Franchi et al., 2014; Timmins et al., 2016), resulting in an increased potential for fascicle shortening and lengthening velocities and therefore increased power. Furthermore, the use of heavier loads made possible by eccentric training results in greater force production, tendon load, and therefore tendon adaptations, such as cross-sectional area and stiffness (Malliaras et al., 2013). An increase in tendon stiffness could reduce the delay time between muscle activation and movement onset to facilitate the rapid transmission of muscle force to the skeletal system (Lindstedt et al., 2001; Brumitt and Cuddeford, 2015), thereby enhancing RFD and SSC function. A summary of the physiological responses to eccentric training is given in Table 12.2. Although there is not a clear consensus within the scientific literature, these adaptive responses appear to lend towards a stronger, larger, faster contracting muscle. These features enhance the muscles’ potential to rapidly produce force and therefore generate greater power. Given this, there is a great deal of interest from athletes, coaches, and practitioners in the different methods and applications of eccentric training. However, much of the research lacks ecological validity due to the use of varying protocols that are rarely, if ever, applied in practice, e.g., singlejoint isokinetic training, high training volumes, exclusion of other modes of training rather than used as a supplemental mode of training. Table 12.2 Summary of the physiological responses to eccentric training regimes and the role of these responses in developing muscle hypertrophy, strength, and power output Hypertrophy Strength Power output Hypertrophy Strength Power output ↑ Anabolic signalling ↑ Motor unit recruitment ↑ Motor unit recruitment ↑ Satellite cell activation ↑ Activation of motor cortex ↑ Activation of motor cortex ↑ Motor unit recruitment ↑ Force production capacity ↑ Force production capacity ↑ Activation of motor cortex ↑ Motor unit discharge rate ↑ Motor unit discharge rate ↑ Force production capacity ↑ Muscle–tendon unit stiffness ↑ Muscle–tendon unit stiffness ↑ Fast-twitch motor unit preferential recruitment* ↓ Inhibitory response ↑ Type IIx fibre composition (phenotype shift) ↑ Tendon cross-sectional area ↑ Preferential fast-twitch motor unit recruitment* ↓ Inhibitory response ↑ Muscle fascicle length ↑ Type IIx fibre composition (phenotype shift) ↑ Excitation–contraction coupling rates ↑ Muscle fibre shortening velocity ↑ Preferential fast-twitch motor unit recruitment* *Questionable. Adapted from Suchomel, T., Wagle, J.P., Douglas, J.H., Taber, C.B., Harden, M., Haff, G.G. & Stone, M. (2019). Implementing eccentric resistance training. Part 1: A brief review of existing methods. Journal of Functional Morphology and Kinesiology, 4, 38. There are a few exceptions to the longitudinal laboratory-based approaches to eccentric training, with two interesting AEL studies, conducted by Walker and colleagues (2016, 2017). Walker et al. (2016) conducted a 10-week intervention comparing traditional training performed twice per week (including 6RM loads on day one and 10 RM loads on day two) with AEL training with an additional 40% load during the eccentric phase of each exercise, in trained men. After completion of the 10-week training period there were comparable increases in muscle mass and eccentric torque between groups, but the AEL group demonstrated greater increases in isometric torque and repetitions to failure. In another study, using a comparable training protocol, Walker et al. (2017) reported greater increases in maximum voluntary isometric contraction and lower-limb muscle mass in response to training with AEL when compared to training with traditional resistance-training methods. Harden et al. (2020) recently presented an interesting 4-week training study comparing traditional training and AEL using a customised leg press, with an additional group of sprint track cyclists also performing AEL. All groups demonstrated significant and meaningful improvements in concentric and eccentric strength and 1RM squat, but the AEL training resulted in the greatest improvements. In contrast to most other studies, eccentric loads were based on an eccentric 1RM performed on the leg press. Patterson and Raschner (2020) also present an interesting case study demonstrating the longitudinal benefits of supramaximal eccentric training in an alpine ski racer, albeit using a specialised device (intelligent motion lifter) which permits eccentric and isokinetic training during traditional free weight exercises. This section has provided a brief overview of the longitudinal physiological responses to eccentric training (Table 12.2). Several resources are available that discuss the adaptive response in greater detail. The authors recommend comprehensive review articles by Douglas et al. (2017), Wagle et al. (2017) and Suchomel et al. (2019) for more detailed information. SECTION 4 Practical application of isoweight eccentric training methods Due to the extent of the discussion that is possible for each of the classifications mentioned in the previous section, the focus will be on isoweight modalities (e.g., tempo training, augmented eccentric training, AEL, eccentric-only training) that are likely most accessible in applied settings (Table 12.3). With this approach, the constant is the applied load/system mass (body mass + external load), although this will change between the eccentric and concentric phases when weight releasers are used. Performance of specific methods requires constant self-adjustment of force application and movement velocity throughout the range of movement. The degree of self-adjustment is determined by the type of method used and the constraints set out in the programme. The intensity of the task is dictated by the interaction of several variables, for example, tempo/movement velocity, ROM, system load, all of which affect the force imposed on the musculoskeletal system, with increased ROM and decreased velocity increasing TUT. It is very important to note that for multijoint isoweight exercises, if velocity of the eccentric phase is increased, the result is a decrease in force production during the initial unweighting, with a force equal to system mass during any period of constant velocity, resulting in a higher braking force to effectively decelerate at the end of the repetition, which may negatively affect the stimuli if a prolonged period of high eccentric forces is required. Table 12.3 Examples of different isoweight eccentric training methods and application examples for differentlevel athletes Method Tempo Augmented Accentuated Eccentriconly/negative Movement type Coupled ECC-CON Coupled ECC-CON Coupled ECC-CON ECC only Main feature Submaximal ECC load Equal ECC and CON load Submaximal ECC load ECC load > CON load Maximal or supramaximal ECC load ECC load > CON load Maximal or supramaximal ECC load No or minimal CON load ECC, eccentric; CON, concentric; TUT, time under tension; ROM, range of motion; RFD, rate of force development; CMJ, countermovement jump. Method Tempo Augmented Accentuated ECC velocity Slow ECC Fast Aim Increase ECC TUT CON velocity Fast Key Load is not considerations maximal (e.g., <100% 1RM) and does not exploit the capacity for ↑ ECC loading/force production Slow Eccentriconly/negative Fast Slow Enhance CON Emphasise output ECC neuromuscular control and ECC TUT, whilst maintaining an element of natural movement mechanics Minimal time delay between transition maintaining natural movement mechanics Emphasising ECC force ECC output and neuromuscular ECC RFD control throughout full ROM and ↑ ECC TUT Fast Fast Fast / / If ECC or CON load is too high, or if ECC and CON load are not too dissimilar this will negatively affect enhancement of CON output Total load should be >100% CON 1RM Total load should be >100% CON 1RM Total load should be >100% CON 1RM Generally achieved via plyometric style tasks ECC, eccentric; CON, concentric; TUT, time under tension; ROM, range of motion; RFD, rate of force development; CMJ, countermovement jump. Fast Method Tempo Augmented Accentuated Example for advanced athlete As preparation for augmented or accentuated ECC training. Sets of 3 repetitions at 85–90% 1RM. ECC phase ~3 seconds, CON phase maximal intent Weight releasers (e.g., total 80% 1RM – ECC 40%, CON 40%) ECC and CON phases fast Weight releasers (100–150% 1RM, e.g., total 120% 1RM – ECC 40%, CON 80%) Weight releasers (100–120% 1RM, e.g., total 120% 1RM – ECC 60%, CON 60%) In power rack with safety bars Depth landing: ↑ drop height > max. jump height. Add weight vest. Bilateral to unilateral Example for intermediate athlete Hypertrophic stimulus. Sets of 8 repetitions at ~65% 1RM. ECC phase ~5 seconds, CON phase maximal intent CMJ with handheld load release (i.e., resistance bands or dumbbells [jump to box if using dumbbells, to avoid landing on them]) Weight releasers (~100% 1RM, e.g., ECC 50%, CON 50%) Weight releasers (~100% 1RM, e.g., ECC 60%, CON 40%) In power rack with safety bars Depth landing: moderate drop height ~ max. jump height Prerequisites for novice Controlled Bodyweight ECC phase CMJ of movement through full ROM with clear pause prior to CON phase Repeated CMJs Submaximal load and tempo Depth landing: CMJ and stick landing Deceleration following submaximal effort short sprint ECC, eccentric; CON, concentric; TUT, time under tension; ROM, range of motion; RFD, rate of force development; CMJ, countermovement jump. Eccentriconly/negative Tempo Tempo training is characterised by purposefully reducing the ‘natural’ velocity of the exercise during the eccentric (lowering) phase, while using the same external load throughout both phases (eccentric and concentric). In the context of eccentric training, the duration of the lowering phase is prolonged, and the duration of the lifting phase can be performed, in a controlled manner, at a low velocity, or explosively (this should depend on the desired adaptive response, e.g., low velocity to increase TUT for hypertrophy, with maximal intent for strength and power development). However, practitioners must consider that extending the duration of the lowering (eccentric) phase can result in a reduction in key outputs (e.g., velocity and power) during the lifting (concentric) phase. For example, Wilk et al. (2019) reported that an imposed 6-second lowering duration had an adverse effect on movement velocity and therefore power output during the concentric phase of bench press exercise, versus a 2-second lowering duration. Therefore, if maintenance of velocity and power throughout the concentric phase is required, then the time spent performing eccentric muscle actions should not be excessive. In contrast, if the eccentric phase of resistance training is performed at a high velocity, this results in a decrease in force production, until braking occurs in the later stages of the lowering phase, which may be counterproductive in terms of an eccentric stimulus. This may explain why slow eccentric training demonstrated greater improvements in performance than fast eccentric training in a cohort of rugby players (Douglas et al., 2018). However, this method does not make use of the higher force-producing capacity of eccentric muscle actions and therefore is unlikely to result in many of the previously discussed adaptations. Instead, tempo training results in overload via TUT, which can be effective for developing neuromuscular control around key joints and reinforcing exercise technique by promoting maintenance of muscle tension and correct body segment positioning throughout a target ROM. This is a particularly useful approach with novice athletes and can also be an effective way to familiarise a more experienced athlete to eccentric training prior to implementing the exercise with heavier or ‘supramaximal’ load (e.g., >100% 1RM). Given that tempo training does not make use of the greater force-producing capacity of eccentric muscle actions, this method is not the most effective at increasing eccentric strength versus other methods. However, as TUT is positively related to muscle hypertrophy and the premise that training biased towards eccentric muscle actions may stimulate greater muscle hypertrophy than training biased towards concentric muscle actions (Burd et al., 2012; Marzilger et al., 2019, 2020), tempo training could prove beneficial for muscle growth. Improved tendon adaptations may also be achieved as a further benefit of increased TUT (Arampatzis et al., 2010). An example of an approach to tempo training is provided in Table 12.3 and Figure 12.1. The loads used should be <100% 1RM, with corresponding repetitions based on the relative load, keeping in mind that the lower the velocity used during the eccentric phase, the greater the duration and associated fatigue. As such, either the number of repetitions or the relative load may need to be reduced if the duration of the eccentric phase is increased between microcycles. Numerous options are available for progression, including decreasing the movement velocity of the lowering (eccentric) phase, thereby increasing the TUT, increasing the relative load or increasing the number of repetitions; however, only one of these should be used as a progression at any one time, dependent on the primary focus of the period of training. For example, it would make sense to increase load if strength is the primary aim, whereas an increase in duration through a decrease in velocity would make sense if hypertrophy is the primary goal. Schematic diagram illustrating an approach to tempo training. Augmented The primary purpose of augmented eccentric training is to acutely enhance the output during the concentric phase, via stimulation of the neuromuscular system and potentially the SSC. During the eccentric phase a higher load is used (e.g., via weight releasers during squats, or holding and releasing dumbbells during jumping tasks) compared to the concentric/propulsion phase, resulting in enhanced neurological stimulation, in an attempt to enhance the force production characteristics during the concentric phase. To permit an appropriate velocity during the eccentric phase the load used would normally be ≤90% 1RM, with the weight releasers (usually loaded with 30–50% 1RM) set to make contact with the floor and release 5–10 cm prior to the bottom of the movement, to permit sufficient time for deceleration prior to the start of the concentric phase (performed with a load of 40–60% 1RM). When using weight releasers, the additional eccentric load can be applied throughout all repetitions if a cluster set approach is utilised (see Chapter 13 for a detailed discussion of cluster sets), which permits time for two ‘loaders’ to lift the weight releasers and simultaneously load them back on to the barbell (Figure 12.2). In contrast, the weight releasers can be used for additional eccentric overload during the initial repetition and then all subsequent repetitions within the set performed with the reduced load. Figure 12.3 provides such an example, with the final four repetitions within the set performed as speed squats (if the back squat is the exercise used). This approach is beneficial if time is limited or there are insufficient coaches or athletes to reload the weight releasers on to the barbell during each set. It is also worth noting that this may induce a PAPE effect and will be less fatiguing than performing all repetitions using AEL. Schematic diagram illustrating augmented eccentric training using weight releasers, with a total of 80% 1RM as an example. # = time for loaders to place the weight releasers back on the ends of the barbell Schematic diagram illustrating augmented eccentric training during back squats using weight releasers, with a total of 80% 1RM as an example. Accentuated The primary purpose of AEL is to permit loads >100% 1RM to be used during the eccentric phase (Walker et al., 2016, 2017), to take advantage of the higher forces associated with eccentric muscle actions and therefore provide the unique stimuli discussed earlier, to elicit the unique adaptations to eccentric training. (Note: due to the loads involved, it is essential that athletes demonstrate excellent technique on any exercise where such loading is implemented.) When strength-speed development is the primary focus of training, the eccentric phase should be prolonged using a low movement velocity during the eccentric phase and the concentric phase performed with maximal intent, albeit with a sufficient load (e.g., ≥80% 1RM) to result in a relatively low velocity (Figures 12.4 and 12.5). In contrast, if the primary goal is the development of speed-strength, the high total load should still result in a low velocity during the eccentric phase, but the load on the weight releasers should be a higher percentage of the total load, to result in a lower total load during the concentric phase enabling higher velocities during the concentric phase (Figures 12.6 and 12.7). Like the format described for augmented eccentric training, two approaches can be employed. Additional eccentric load can be used during the eccentric phase of each repetition, in a cluster set format (Figures 12.4 and 12.6), or the additional eccentric load can be applied during the first repetition of each set, with the subsequent repetitions performed in the normal format, with no inter-repetition rest (Figures 12.5 and 12.7). Schematic diagram illustrating accentuated eccentric training using weight releasers. # = time for loaders to place the weight releasers back on the ends of the barbell Schematic diagram illustrating accentuated eccentric training using weight releasers. Schematic diagram illustrating accentuated eccentric training using weight releasers. # = time for loaders to place the weight releasers back on the ends of the barbell Schematic diagram illustrating accentuated eccentric training using weight releasers. Progressions within a mesocycle would usually emphasise an increase in total load via an increased load on the weight releasers, resulting in a progressive increase in eccentric loading. Small increases in load during the concentric phase may also be appropriate during the concentric phase if the training focus is strength-speed. As previously mentioned, it is possible to progress up to loads of ~140% 1RM during the eccentric phase; however, such loads should be achieved progressively, ideally across numerous sessions. In addition, a more conservative approach may be advantageous in stronger individuals due to the lower discrepancy between concentric and eccentric strength compared to weaker individuals (Hollander et al., 2007; Harden et al., 2019). As previously mentioned, an effective eccentric load, in trained individuals, implemented by Walker et al. (2016, 2017), was 40% greater than the concentric load (using concentric loads that corresponded to 6RM [~85% 1RM] and 10RM [~70% 1RM] loads). If weight releasers are not available, but a power rack is, it is possible to lower the higher eccentric load to pins and then have training partners/teammates remove some additional load prior to commencing the concentric phase with an appropriately reduced load. It should be noted that while this method permits appropriate eccentric overload, it likely nullifies any SSC benefits due to the pause with the barbell of the pins of the power rack. This may also result in the concentric phase feeling more difficult than when weight releasers are used. To address this, coaches can consider loading the concentric phase relative to concentric 1RM, which is performed from a dead stop from the pins of the power rack, to ensure an appropriate intensity is applied to the concentric phase, given the absence of the contribution of the SSC to concentric force output. Eccentric only Eccentric-only approaches can also be adopted to emphasise the musculotendinous adaptations to supramaximal eccentric loads, although these approaches exclude any potential acute benefits during a subsequent concentric phase, which may manifest from neurological stimulation (e.g., acute PAPE) or utilisation of the SSC. These approaches can more easily be applied to focus on specific muscle groups during single-joint tasks (e.g., knee flexion and extension), especially if a specific deficit in muscle mass or strength has been identified, most commonly in previously injured athletes. It is also possible to adopt this approach with numerous multi-joint exercises (e.g., front squat, split squat, bench press), when power racks are available, or in some cases with no additional equipment (e.g., pull-up variations). For single-joint eccentric training, isokinetic dynamometers are commonly used by researchers; however, even if these devices are available it takes a notable period for individual athletes to conduct some of their training in this manner and would not be feasible for an entire team of athletes. A simple approach for single-joint eccentric training is to perform these exercises on standard resistance machines, using a load >100% 1RM for a single limb, performing the concentric phase with two limbs and then the eccentric phase with one limb. For example, if the concentric 1RM for a single-leg knee extension is 50 kg, perform the concentric phase with 55 kg (110% 1RM) and then lower in a controlled fashion with a single leg. While there is a concentric component to this, it would equate to only a bilateral 55%1RM. For multi-joint tasks, the safe option is to perform exercises (e.g., squat variations, Romanian deadlift, bench press) in a power rack, taking the barbell (>100% 1RM) out of the rack and then performing a controlled eccentric phase, throughout the desired ROM until the barbell rests on the safety pins. The height of the safety pins should be carefully set during the warm-up sets prior to the start of the eccentric repetitions. Ideally, spotters should be used throughout, and the spotters can then lift the bar back to the starting position, prior to the start of the next repetition. This approach generally results in a cluster set approach, due to the period of rest between the end of a repetition and the bar being placed back in the start position. Important considerations for exercise prescription It is important to highlight that the unique qualities mean that when training using eccentric muscle actions, performance capacity is unlikely to conform to recommendations that are commonly used to guide traditional, concentrically biased exercise prescription. Therefore, different approaches to training applications may be required to optimise eccentric training regimes, especially in terms of the volume (sets and repetitions) due to the higher loads and increased potential for muscle damage, especially in weaker athletes and those unfamiliar with supramaximal eccentric exercise, or eccentric exercise in general. The unique features of eccentric muscle actions allow for much greater force to be produced during muscle lengthening versus shortening. However, traditional applications of exercise utilise the same absolute load for the descending (eccentric) and ascending (concentric) phase of an exercise, whereby load prescribed is limited to concentric performance. This approach to loading does not appropriately stimulate the eccentric force-producing capacity of muscle, as the descending portion of the lift is not loaded in relation to the individual’s eccentric maximal force capacity. Instead, practitioners must apply alternative methods to prompt greater force output during the eccentric phase of exercise. This usually involves heavy external loads and demands a very high exercise intensity. There are a multitude of ways to apply and categorise eccentric exercise in research and practice. Usually, isotonic eccentric exercise intensity is prescribed as a percentage of 1RM during coupled eccentric–concentric or concentric-only action, whereby the load will exceed, equal, or be within the force-producing capacity of the traditional 1RM. This is typically categorised as supramaximal (>100% 1RM), maximal (~100% 1RM), or submaximal load (<100% 1RM), respectively. Eccentric training volumes should be employed conservatively, due to the associated muscle damage and DOMS, but can be easily progressed to take account of the RBE. A conservative approach with appropriate progressions is important to ensure compliance and to mitigate any potential negative impact on subsequent training activities. It is common practice for strength and conditioning practitioners, rehabilitation professionals, and sports science researchers to prescribe eccentric training loads grounded on traditional 1RM strength tests (Brandenburg and Docherty, 2002; Barstow et al., 2003; Friedmann-Bette et al., 2010; English et al., 2014; Walker et al., 2016; Douglas et al., 2018). This approach to load prescription, however, overlooks task-specificity and the possibility that some individuals have a different tolerance for eccentric exercise. For this reason, a number of researchers have adopted an eccentric-specific RM assessment (Spurway et al., 2000; Gillies et al., 2006; Vikne et al., 2006; Franchi et al., 2014), in the endeavour to increase the efficacy of eccentric training regimes or enable the comparison of eccentric-only or concentric-only isotonic exercise. 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The effects of eccentric cadence on power and velocity of the bar during the concentric phase of the bench press movement. Journal of Sports Science & Medicine, 18(2), 191. 13 Cluster sets: scientific background and practical applications G. Gregory Haff and Mellissa Harden DOI: 10.4324/9781003044734-16 Introduction When constructing resistance-training programmes there are numerous factors that must be considered in order to optimise the training stimulus. These include exercise choice, training load, number of repetitions and sets, exercise order, training frequency, movement velocity, and duration of rest between sets. Largely guided by the periodised training plan, programming of the aforementioned factors is used to deliver novel training stimuli in order to stimulate improvements in a performance or physiological outcome (Haff et al., 2008b). When a novel training stimulus is incorporated into the training programme there is a greater rate of performance gain, whereas the more familiar the athlete is with the imposed training demands, the slower the overall gain in performance (Hodges et al., 2005). As such, the ability of the strength and conditioning coach to construct programmes that include appropriate training variation (to introduce novelty) is essential for guiding the training process and maximising training outcomes. This is especially true for the advanced or elite athlete (Haff et al., 2008b). One potential part of the training programme where variation can be introduced, that is often overlooked, is the structure of the set (Haff et al., 2008a, 2008b; Tufano et al., 2017a). Traditionally, resistance-training sets are performed in a continuous manner where no rest is taken between the repetitions contained within the set (Haff et al., 2003, 2008b) and rest is prescribed between each individual set (i.e., inter-set rest) (Figure 13.1a). Example set structures used in resistance training. While the traditional set is the most commonly used programming structure, an alternative approach to organising the set is to provide interrepetition (i.e., rest between individual repetitions) (Figure 13.1b) or intraset (i.e., rest between groups of repetitions within a single set) rest intervals that last between 15 and 45 seconds (Figure 13.1c). Globally the inclusion of periodic rest intervals, whilst maintaining the inter-set rest interval, has been termed the cluster set within the scientific (Haff et al., 2003, 2008a, 2008b; Latella et al., 2019) and applied literature (Rader, 1958; Roll and Omer, 1987; Siff and Verkhoshansky, 1999; Polliquin, 2001; Thibaudeau, 2006; Miller, 2011a). While the use of the cluster set has become a popular research topic and has increasingly become a part of the programming practices of strength and conditioning coaches, the roots of this training structure can be traced back to the late 1950s when Perry Rader discussed this topic in IronMan magazine (Rader, 1958). Furthermore, even though the cluster set has a rich history in the training literature, many modern researchers have classified any modification to the set structure or inclusion of periodic rest into a series of repetitions as a cluster set (Marshall, 2011; Marshall et al., 2012; Oliver et al., 2013; Tufano et al., 2017a). As a result, there is debate amongst sport scientists and coaches about what a cluster set entails, the scientific rationale for the use of a cluster set, and how to actually employ this programming strategy into the training practices of athletes. Therefore, the primary goals of this chapter are to elucidate these topics and provide the strength and conditioning coach with useful information that can inform how they utilise various set structures within their resistance-training programmes. SECTION 1 Defining the set In order to understand the various set configurations that can be employed as part of a resistance-training programme, it is essential that the strength and conditioning coach understand the various terminology that can be used to describe the set’s structure (Tufano et al., 2017a). There are four basic categories of sets: (1) traditional; (2) cluster; (3) rest–pause; and (4) rest– redistribution sets. Traditional sets The set is typically defined as a traditional set when the individual repetitions contained within it are completed in a continuous manner without any inter-repetition or intra-set rest intervals (Tufano et al., 2017a) and there is a predetermined inter-set rest interval. The traditional set configuration can be employed with a wide range of repetitions and interset rest intervals in order to modulate the training stimulus that the athlete is exposed to and align with specific training targets. For example, <6 repetitions are traditionally used to target maximal strength, whilst >12 repetitions are typically aligned with strength endurance (Haff and Haff, 2012). Depending on the athlete’s level of development, different repetition ranges can be aligned with different training targets (Table 13.1). For example, repetition ranges of 8–12 are aligned with hypertrophy training for novice athletes, whilst 6–12 repetitions are used to target this adaptation with intermediate and advanced athletes (Haff and Haff, 2012). Ultimately the traditional set is a time-tested and versatile way of programming resistance training. Table 13.1 Traditional training emphasis alignments with repetition ranges Training emphasis Traditional set repetition schemes Training emphasis Traditional set repetition schemesAdvanced Novices Intermediate Muscular endurance 12–20 12–20 12–25 Hypertrophy 8–12 6–12 6–12 Muscular strength ≤6 ≤6 ≤6 Muscular power Novices n/a Intermediate 3–6 Advanced 1–6 Adapted from Haff GG and Haff EE. Resistance training program design. In: M.H. Malek & J.W. Coburn (eds.) NSCA’s Essentials of Personal Training. Champaign, IL: Human Kinetics, 2012, pp. 359–401; Table 15.13, p. 380. Cluster sets The term “cluster set” has mistakenly become a popular “umbrella” term for any set structure that differs from a traditional set (Tufano et al., 2017a). In tracing the historic roots of the cluster set, the utilisation of interrepetition rest was originally referred to as the “rest–pause” method due to the interspersing of a short rest interval, or a pause, between individual repetitions within the set or what could be considered a period of defined work (Rader, 1958). As time passed the rest–pause terminology morphed into the current cluster set terminology when defining the manipulation of the set structure in order to incorporate inter-repetition (Roll and Omer, 1987; Siff and Verkhoshansky, 1999; Haff et al., 2003) or intra-set rest intervals (Haff et al., 2008a). While Tufano et al. (2017a) incorrectly attribute the cluster set term to Haff et al. (2003), it is important to note that Roll and Omer (1987) utilised the term in their paper published in 1987, which was 16 years prior to the paper published by Haff et al. (2003). In their paper, Roll and Omer (1987) defined the cluster set as performing predetermined sets of 2–6 repetitions with 20–30 seconds’ rest between each repetition in order to ensure that maximal intensity is achieved on each repetition. Siff and Verkoshansky (1999) defined the cluster set as performing one or more repetitions with a 10–20-second rest interval between individual repetitions or groups of repetitions contained within the set structure. They proposed the basic cluster set should be performed for a total 4–6 repetitions with a 5 repetition maximum (RM) load, and that there are two sub-categories of the cluster set: extensive and intensive cluster sets (Siff and Verkhoshansky, 1999). While both sub-categories of cluster sets were performed with 4–6 repetitions, the extensive cluster set was proposed to use a 4–6RM load and a 10-second rest between each repetition or group of repetitions, whereas the intensive cluster set was structured to use a load between 75 and 90% of 1RM with a 20-second rest between each repetition or group of repetitions (Siff and Verkhoshansky, 1999). When carefully examining the work of Siff and Verkoshansky (1999) it is clear that their definition of the cluster set is very similar to definitions presented by Roll and Omer (1987) and Haff et al. (2003). While these authors’ definitions are true to the historic roots of the cluster set concept (Rader, 1958), many contemporary authors have mistakenly tried to make the cluster set terminology into an “umbrella” term describing any manipulation of the set structure (Jukic and Tufano, 2019; Merrigan et al., 2020a; Tufano et al., 2020). While the main alterations to the traditional set have historically been based upon the insertion of inter-repetition or intra-set rest intervals (Haff et al., 2008a), an additional way to modify the set was proposed by Haff et al. (2008a, 2008b) where the loading pattern of each repetition or groups of repetitions contained within the set is modified. Generally, five possible variations to the loading pattern utilised in a set can be constructed: standard, undulating, wave, ascending, and descending cluster set structures (Figure 13.2) (Haff et al., 2008a, 2008b). Example undulating, wave, ascending, and descending cluster sets. Standard cluster sets: The standard cluster set is the most basic modification of the traditional set structure (Haff et al., 2008a, 2008b). With this type of cluster set the load is maintained across all repetitions within the set and only the inter-repetition or intra-set rest interval is modified (Figure 13.1b and 13.1c; Tufano et al., 2017a). Undulating cluster set: The undulating structure is constructed so that the resistance used across the set is increased in a pyramidal fashion (Figure 13.2a; Haff et al., 2003). Depending upon the loading parameters, the repetitions on the descending portion of the pyramid will display a form of post-activation performance enhancement (PAPE), as indicated by increases in the velocity of each repetition (Haff et al., 2003). Wave-loaded cluster set: Another loading strategy is to alternate intensity from repetition to repetition (Figure 13.2b), or between groups of repetitions, in order to create what is termed a wave-loaded cluster set. Similarly to an undulating cluster set, a PAPE response is stimulated by the higher loaded repetitions resulting in higher velocities of movement occurring during repetitions where lower loads are employed. Ascending cluster set: The cluster set structure can be further modified so that the load lifted increases across the set, resulting in the highest intensity being lifted on the last repetition of each set (Figure 13.2c). After the inter-set rest interval, it is hypothesised that higher velocities of movement will occur during the first repetitions of subsequent sets due to the PAPE-inducing effects of the higher-load repetitions. Descending cluster set: The last loading structure that can be programmed to modify the set structure is the descending cluster set where the first repetition of the set is a maximal or near-maximal attempt followed by subsequent repetitions with progressive reduction in repetition loads (Figure 13.2d). It is hypothesised that the increased velocity that occurs as the intensity decreases across the set is a result of a PAPE response stimulated by the heaviest repetition(s) at the start of the set. While these five types of cluster sets have been used in many strength and conditioning settings, much more research is needed to further our understanding of how these loading structures acutely impact movement velocity and translate into chronic training responses. In addition to modifying the loading structure used with the cluster set, the number of repetitions that are completed before inserting a rest interval can be varied to change the training stimulus (Figure 13.3; Haff et al., 2008a, 2008b; Tufano et al., 2017a). For example, three sets of 12 repetitions can be programmed with a 120-second inter-set rest interval and 30 seconds inter-repetition or intra-set rest which is used after every two (Figure 13.3a; Tufano et al., 2016), three (Figure 13.3b), or four repetitions (Figure 14.3c; Haff et al., 2008a). Example cluster set repetition modifications. By modulating the number of repetitions contained within the cluster set the targeted training outcome can be altered. For example, for a given load there will be a greater velocity decline for a cluster set containing four repetitions in comparison to clusters of two repetitions (Tufano et al., 2016). Therefore, using cluster sets with fewer repetitions in each cluster will minimise velocity loss and will therefore be more appropriate for developing neuromuscular power. Conversely, if maximising muscular hypertrophy is the training target, then including more repetitions and higher training loads within the cluster would result in a greater velocity decline across each cluster (Pareja-Blanco et al., 2017) and allow for more time under tension, and greater total work (Tufano et al., 2017b), which may be more effective to stimulate hypertrophy. Interestingly, if the load is aligned with the RM load for the number of repetitions contained within the cluster, velocity loss is similar to that which can occur during high-volume traditional sets (Tufano et al., 2017b). For example, similar velocity declines occur when: (1) 12 repetitions are performed at 60% of 1RM; (2) clusters of four repetitions are performed at 75% of 1RM with 30 seconds’ intra-set rest intervals; and (3) clusters of two repetitions performed at 80% of 1RM with 30 seconds’ intra-set rest intervals (Tufano et al., 2017b). Interestingly, the concentric time under tension is increased when smaller cluster sets are performed with higher intensities when compared to traditional sets. In this case it may be expected that the use of the cluster set will provide a greater stimulus for either hypertrophy or strength, when compared to a traditional set structure. Ultimately, through the manipulation of the number of repetitions within the cluster set, the training stimulus can be varied in a multitude of ways. This equips the strength and conditioning coach with many options for introducing training variation and novelty within an athlete’s training regime (Haff et al., 2008a). Rest–pause method The “rest–pause” terminology was originally used to define what is now referred to as a cluster set, where inter-repetition rest is applied within a pre-defined set (Rader, 1958). However, the modern application of the “rest–pause” set has deviated significantly from this original model. As such, the rest–pause terminology is used when periodic rest is employed to extend the number of repetitions that can be performed within sets performed to failure (Keogh et al., 1999; Marshall, 2011; Marshall et al., 2012; Tufano et al., 2017a). For example, a rest–pause set could be performed to muscular failure, typically with an 8–12RM load, followed by 20 seconds’ interval and another set to failure. A 20-second interval is inserted after each set to failure until a targeted number of repetitions are completed (Marshall, 2011; Marshall et al., 2012; Prestes et al., 2019). While a high volume of training is associated with the modern incarnation of the rest–pause method (Marshall et al., 2012; Prestes et al., 2019), it is important to note that it is not possible to predetermine the number of repetitions that are completed because this method employs a training-tofailure strategy (Tufano et al., 2017a). As such, it is difficult for the strength and conditioning coach to control the volume of training that the athlete performs. The rest–pause set configuration strategy is often used when attempting to increase muscular endurance or maximise hypertrophic gains. While training-to-failure strategies have become popular, recent research has highlighted that training to failure is not necessary to maximise hypertrophic or maximal strength gains (Carroll et al., 2019a, 2019b). In fact, strength and power gains are often muted with the use of training to failure when compared to not training to failure (Izquierdo et al., 2006; Carroll et al., 2019b), which may impact the effectiveness of this cluster set configuration strategy when looking specifically to enhance muscle strength and/or power. Rest–redistribution Recently several authors have proposed the concept of rest–redistribution as an additional cluster set structure (Jukic and Tufano, 2019; Tufano et al., 2020; Merrigan et al., 2020a; Jukic et al., 2020; Merrigan et al., 2020b). With this set structure, the idea is to take the inter-set rest interval and redistribute this rest to either provide inter-repetition or intra-set rest and reduce the time burden associated with the use of cluster sets (Tufano et al., 2020). While at first glance using the cluster set terminology to define this practice seems logical, it is important to note that this set configuration is at odds with the original incarnation of the cluster set (Rader, 1958; Roll and Omer, 1987; Siff and Verkhoshansky, 1999), where the inter-set rest interval applied is similar to what is used when using traditional sets. In reality, the rest–redistribution model should not be considered a cluster set, but instead should be referred to as a short inter-set rest interval strategy. Recently researchers have determined that the rest–redistribution strategy is not as effective at modulating fatigue-induced changes in performance when compared to the implementation of more traditional cluster set protocols (Jukic et al., 2020). It is important to remember that one of the main drivers of the performance gains associated with the cluster set is the additional inter-repetition or intra-set rest allowing for acute performance enhancement (Jukic et al., 2020) via increased movement velocities or allowing higher training loads to be utilised. It appears that while the rest–redistribution strategy has its use as a programming strategy, it does not produce the same outcomes as cluster sets. Due to the aforementioned discrepancies between the rest–redistribution method and cluster sets, it is not appropriate to classify rest–redistribution as a cluster set. SECTION 2 Scientific basis for the cluster set When considering the use of the cluster set as part of the programming process it is important to consider how these novel set structures differ from traditional sets (Haff et al., 2008a, 2008b). The different physiological and performance responses to the traditional and cluster set should assist in informing how the strength and conditioning coach utilises these set configurations as part of a performance-based strength-training programme. Physiological, performance, and psychological responses to traditional sets When examining the traditional set configuration, it is well documented that as the duration of the set is extended there is a concomitant reduction in movement velocity (Gorostiaga et al., 2010; Tufano et al., 2016), power output (Hardee et al., 2012b; Tufano et al., 2016), and technical proficiency (Hardee et al., 2013). These reductions are likely reflective of a fatigue response that occurs due to a combination of central (neural) and peripheral (muscular) factors (Zajac et al., 2015; Enoka and Duchateau, 2016). While fatigue was once thought to be necessary to maximise resistance traininginduced adaptations, there is now an ever-growing body of scientific evidence that has strongly refuted the theory that momentary neuromuscular failure (i.e., RM paradigms) is superior to not training to failure (Folland et al., 2002; Izquierdo et al., 2006; Carroll et al., 2019a, 2019b). When performing resistance training with a traditional set configuration there can be reductions in maximal force-generating capacity, rate of force development, and rate of relaxation within 5–9 maximal contractions (Viitasalo and Komi, 1981). These reductions in performance capacities are likely related to a reduced availability of phosphocreatine (PCr) and the rate of adenosine triphosphate (ATP) resynthesis within the working muscles (Bogdanis et al., 1995, 1996, 1998; Gorostiaga et al., 2012). Supporting this contention, Sahlin and Ren (1989) report that maximal contractions result in significant decreases in ATP and PCr concentrations. In addition to these changes there are typically significant increases in creatine (Cr) and lactate (La) (Gorostiaga et al., 2012) as well as reductions in muscle glycogen (Haff et al., 2000), which are impacted by the number of repetitions contained within the set as well as the load lifted (Robergs et al., 1991). For example, when sets of five repetitions are performed on the leg press, there is a ~26.8% reduction in the concentration of PCr, whilst there is a ~85% reduction when sets of ten are performed (Gorostiaga et al., 2012). As PCr decreases there is a concomitant increase in La accumulation as the utilisation of glycogen increases across the series of sets typically contained with a resistance-training programme. These changes are associated with reductions in peak and mean power output across the series of repetitions, with sets of ten repetitions displaying the greatest declines. Ultimately, the changes in substrate availability across the set partially explain the reductions in movement velocity and the expression of power that are associated with traditional sets. Theoretical and scientific basis for the cluster set The modification of the set to include short inter-repetitions or intra-set rest intervals has been hypothesised to improve the quality of performance of each repetition contained within the set (Haff et al., 2003, 2008a, 2008b). Theoretically, the use of a cluster set allows for: (1) a maintenance or enhancement of training intensity; (2) the maintenance of velocity and force production; and (3) the performance of a greater amount of total work during the set (Haff et al., 2008a, 2008b; Tufano et al., 2017b). These potential benefits are likely a result of the cluster set allowing for partial recovery during the additional rest that is placed within the set structure. It has been hypothesised that the inclusion of 15–30 seconds of interrepetition or intra-set rest may result in the partial replenishment of ATP and PCr that offsets the typical reductions in these substrates seen with the performance of multiple-repetition traditional sets (Haff et al., 2008a, 2008b). The replenishment of ATP occurs rapidly, with 70% of ATP restored in as little as 30 seconds (Hultman et al., 1967), while the resynthesis of PCr is slightly slower, with 50% restoration occurring within 30 seconds (Sahlin and Ren, 1989). The partial replenishment of ATP and PCr associated with inter-repetition or intra-set rest likely results in improvements in performance capacity. For example, Sahlin and Ren (1989) reported that the addition of 15 seconds of rest resulted in one-half of the decrease in force-generating capacity being restored, returning force production to 79.7 ± 2.3% of maximal voluntary contraction (Sahlin and Ren, 1989). Additionally, when 30 seconds of extra rest is employed, less lactate is produced when compared to repetitions that are performed with a traditional set structure (Goto et al., 2005). Collectively, these physiological responses provide the theoretical framework for explaining the performance benefits of cluster sets. An additional benefit of all cluster sets is that they may allow for greater loads to be lifted, which results in a greater time under tension and average force production when compared to traditional sets (Tufano et al., 2017b). Interestingly, when greater loads are lifted with the cluster set, the velocity decline across the set is not different from what is seen with traditional sets performed with lower loads. For example, Tufano et al. (2017b) report that performing three sets of 12 repetitions with cluster sets of two with 80% of 1RM or cluster sets of four with 75% of 1RM, with 30 seconds of intra-set rest, results in a similar decline in velocity across the three sets as seen when performing traditional sets of 12 with 60% of 1RM. In fact, one of the main benefits of the cluster set is that it allows for greater loads to be lifted for more repetitions, which can enhance the hypertrophic and strength gains associated with the training process. It is, however, important to consider that when using higher loads with cluster sets the coach should consider the impact that this will have on cumulative fatigue and delayed-onset muscle soreness. As such it is recommended to consider progressively introducing cluster sets to the athlete’s training programme. Acute responses to cluster sets As noted previously, there is a reduction in movement velocity (Tufano et al., 2016) and power (Gorostiaga et al., 2012) across a traditional set, which can be offset by placing inter-repetition or intra-set rest into the set (Tufano et al., 2017a). This effect is most noted when this practice is employed with lower-body or whole-body resistance-training exercises that are performed with moderate to heavy loads which have the potential to generate significant fatigue (Latella et al., 2019). For example, Haff et al. (2003) report higher movement velocities when performing cluster sets of five repetitions with 30 seconds of inter-repetition rest with clean pulls performed with loads of 90–120% of the 1RM power clean, when compared to traditional sets. Importantly, when the cluster set was utilised with higher loads (i.e., 120% of 1RM power clean), the ability to maintain movement velocity was demonstrated. These findings help strengthen the argument that one of the main benefits of using cluster sets is to allow athletes to lift greater loads and maintain a higher quality of movement (Tufano et al., 2017b). In a series of papers, Hardee et al. (2012a, 2012b, 2013) have provided strong evidence for the positive acute impact of using cluster sets of six repetitions with 20 and 40 seconds of inter-repetition rest with the power clean performed at 80% of 1RM. Specifically, Hardee et al. (2012b) clearly demonstrated that movement velocity during the power clean is better maintained with longer inter-repetition rest intervals (i.e., 40 seconds) when compared to shorter inter-repetition rest intervals (i.e., 20 seconds) or traditional sets. In addition to maintaining movement velocity, the use of cluster sets allowed for a better maintenance of movement quality (Hardee et al., 2013), which can be negatively impacted by changes in motor control that occur when fatigue accumulates (Halil et al., 2009). Importantly, even though athletes were able to perform the power clean with higher velocities and better technique during the two cluster set protocols, the athletes’ rating of perceived exertion was significantly lower than seen when using the traditional set (Hardee et al., 2012a). Collectively, the work of Hardee et al. (2012a, 2012b, 2013) strengthens the argument that cluster sets allow for enhanced acute performance responses which, if repeated consistently, may lead to better-quality training and greater long-term training responses (Hardee et al., 2012a, 2012b, 2013). It is well documented that the load lifted during resistance-training exercise exerts a significant effect on the physiological adaptations that occur in response to a resistance-training programme (Fry, 2004). The ability to consistently train with higher loads may allow for greater strength gains as well as hypertrophic responses (Fry, 2004; Schoenfeld et al., 2016). Based upon these data, it is clear that the cluster set provides a powerful tool for acutely increasing the load that can be used for a given number of repetitions, whilst maintaining the velocity and quality of the repetitions performed (Tufano et al., 2017b). This is important because it clearly shows that the cluster set allows the athlete to acutely train at higher intensities, which is likely to lead to significantly greater longitudinal training effects. Longitudinal responses to cluster sets While a lot of research clearly demonstrates that there are positive acute mechanical and physiological responses to cluster sets, there is far less research examining the impact of the long-term effects of implementing cluster sets within a resistance-training programme (Tufano et al., 2017a; Latella et al., 2019). Due to relatively few longitudinal studies (Hansen et al., 2011; Zarezadeh-Mehrizi et al., 2013; Arazi et al., 2018; Vargas-Molina et al., 2020) that explore the implementation of cluster sets and the vastly different strategies used to create the cluster set in these studies, it is difficult to determine the actual impact of the cluster set on hypertrophy, strength, or power output. Recently, Vargas-Molina et al. (2020) compared the impact of traditional and cluster sets that used 12 repetitions per set. Each cluster set was organised into groups of three repetitions with 3RM loads and 20 seconds of intra-set recovery with squats, deadlifts, and the leg press. The cluster set was associated with greater increases in muscular strength and fat-free mass in the lower body when compared to traditional sets. These findings support the contentions of Tufano et al. (2017b, 2017c), who suggested that the use of cluster sets with high-volume sets would allow for a greater mechanical stimulus that could be translated into increases in muscular strength and hypertrophic gains. Based upon this line of reasoning it seems plausible to suggest that integrating cluster sets within a training programme that targets strength endurance or hypertrophic outcomes may maximise performance outcomes as well as hypertrophic responses. In another longitudinal study, Arazi et al. (2018) examined the integration of cluster sets within a periodised training programme. Across an 8-week training study various standard cluster set structures were performed with 10–30 seconds of inter-repetition rest with squats, bench press, military press, jump squats, and bench press throws. When compared to a group that performed the same training programme with traditional sets, the use of cluster sets resulted in small but significant improvements in vertical jump performance and similar gains in maximal strength. Similarly, Zarezadeh-Mehrizi et al. (2013) implemented cluster sets that utilised 10– 30 seconds of inter-repetition rest or traditional sets with the same relative intensities. After 10 weeks of training there were greater improvements in vertical jump performance and similar strength gains when cluster sets were utilised within the training programme. Collectively, these studies support the contentions of Haff et al. (2008a, 2008b) that cluster sets are best used when attempting to improve performance in ballistic activities, such as jumping, while traditional sets may be better suited for stimulating strength gains. While this is a logical suggestion, it is necessary to highlight that the use of the same relative training load for both cluster and traditional sets could partially explain the lack of difference in strength gains between set conditions. However, if we consider that one of the main benefits of cluster sets is that higher training loads can be utilised in training when compared to traditional sets, it is likely that if programmed correctly (i.e., this benefit is exploited), the cluster set has the potential to stimulate greater increases in strength, in addition to the noted improvements in ballistic performance. While it appears cluster sets, when programmed correctly, exert positive benefits on hypertrophy, maximal strength, and explosive performance, much more research is needed. It is suggested that future research must consider the load applied to the cluster sets. To add, it is important that researchers consider the ecological validity of how cluster sets are actually programmed in applied resistance-training settings. SECTION 3 Practical applications of cluster sets There are numerous ways to utilise the cluster set in order to align with the training goals established within the periodised training plan (Haff et al., 2008a, 2008b). By manipulating the number of repetitions, inter-repetition or intra-set rest intervals, and loading configurations contained within the cluster set, the athlete can be exposed to a unique training stimulus which can magnify the adaptive responses and performance gains achieved. Programming cluster sets When considering the use of cluster sets it is important to first establish the training outcomes that are being targeted by the periodised training plan (Haff et al., 2008a). Once the training programme outcomes are established, the coach can begin the programming process. The first step in the implementation of cluster sets is to determine which exercises will be aligned with cluster set strategies (Figure 13.4). Suggested exercise alignments for cluster sets. Typically, cluster sets are utilised with ballistic exercises, such as the weightlifting derivatives (i.e., clean/snatch pulls, power clean/snatch), bench press throws, and jump squats (Haff et al., 2008b; Latella et al., 2019). Additionally, cluster sets have been utilised with traditional strengthbased exercises such as the deadlift (Arazi et al., 2018), back squat (Tufano et al., 2017b), and bench press. While all of these exercises could use cluster set strategies it is important to note that not every exercise in a training session needs to or should employ cluster sets. In fact, only 1–2 exercises per training session should be performed with cluster set strategies, whilst the remaining exercises within the session should employ traditional sets, in order to maximise the efficiency of the training session (Table 13.2) (Haff et al., 2008a, 2008b). Table 13.2 Example training session employing cluster sets Exercise Sets × Reps Intensity (% RM) Intensity InterSet type (kg) repetition rest (s) Mid-thigh clean pull* 3 × 5 110% 132 0 Power clean 3 × 5/1 90% 108 20 Back squat 3 × 5 80% 144 0 Traditional Bench press 3 × 5 75% 83 0 Traditional Traditional Standard cluster Note: 5/1 = total repetitions in set/repetitions in cluster. RM, repetition maximum. *Percentage of maximum power clean. Power clean 1RM =120 kg; back squat 5RM = 180 kg; bench press 5RM = 110. An example of this type of planning is presented in Table 13.2 where an individual training session is presented in which a standard cluster set structure is programmed for the power clean and traditional sets are planned for the remaining exercises. After determining which exercises will utilise cluster sets, the second step in the programming process is to align the number of repetitions contained within the set with the overall targeted training goals (Table 13.1). When making this decision, repetition ranges for the entire set are typically structured based upon the ranges commonly used with traditional sets (Haff et al., 2008a). For example, if the coach is designing a training programme that targets hypertrophy, 6–12 repetitions per set are typically programmed, while <6 repetitions are programmed when targeting maximal strength or power development (Haff and Haff, 2012). Once the number of repetitions is determined the third step in the programming process is to determine which type of cluster set will be programmed. This decision is made based upon aligning the cluster set with the mesocycles targeted outcome, such as strength endurance, hypertrophy, strength, or power outcomes (Figure 13.5). Suggested training target/goal set type alignments. When targeting strength/power endurance or hypertrophic training outcomes, the coach can use rest–pause set structures if fatigue management is not an issue. Alternatively, they can manage fatigue and optimise the velocity of movement with the use of standard, ascending, or descending cluster set training strategies. With each of these strategies there will be an increase in the overall volume load of training. For example, standard cluster sets, where training load is held constant and interrepetition or intra-set rest intervals are utilised in conjunction with structured inter-set rest intervals, can be performed to target the desired outcome. Conversely, undulating or wave-loaded cluster sets are more typically utilised during mesocycles that target strength/power or power development in order to capitalise on the PAPE effects of these cluster set configurations (Haff et al., 2008a). Fundamentally, the coach should consider what physiological and performance outcomes are being targeted and then align a cluster set strategy with those goals. Once the exercise, the number of repetitions contained within the set, and the cluster set type are selected, the fourth step in the programming process is to determine the number of sets and how the set is partitioned (Figure 13.6). Cluster sets: set and repetition examples. For example, if a hypertrophy set of 12 repetitions is planned the coach could design a cluster set that places rest after each individual repetition (i.e., 12/1 = total repetitions/cluster repetitions) allowing for a greater maintenance of velocity and technique across the set. Alternatively, the set of 12 repetitions could be created as six pairs of two (i.e., 12/2), four clusters of three repetitions (i.e., 12/3), three clusters of four repetitions (i.e., 12/4) or two clusters of six repetitions (i.e., 12/6). By choosing the number of repetitions contained within the cluster the coach can manipulate the training stimulus and target different outcomes. After the cluster set type is selected, the coach can then prescribe the training load that will be utilised within the set. There are two basic strategies for determining the load used to programme the standard cluster set, with the first method employing the load that would typically be used when performing a set of 12 repetitions. For example, if the coach planned the intensity as 60% of 1RM, this load could be used with a standard cluster set structure. However, this method of loading the cluster set would not draw upon one of the main advantages of cluster sets, which is that higher loads can be performed during the set. The second approach would be to align the training load to the number of repetitions contained in each cluster, where clusters containing fewer repetitions would use higher training loads (Tufano et al., 2017b). For example, standard cluster sets of four repetitions could be programmed to use 75% of 1RM, while cluster sets of two repetitions might be programmed with 80% of 1RM. Ultimately there are infinite ways to load the standard cluster set, but the coach should always consider the relationship between the relative load and the number of repetitions contained within the cluster. When working with undulating, wave, ascending, and descending cluster sets, different loading strategies need to be implemented. Traditionally the coach will select a target intensity for the set and then, depending upon the set structure, craft a loading paradigm (Table 13.3). Table 13.3 Example loading patterns for cluster sets Type of cluster Sets × Repetitions Intensity (% 1RM) Clusters contained in the set (%/repetition) Type of cluster Sets × Repetitions Intensity (% 1RM) Clusters contained in the set (%/repetition) Basic 1–5 × 5/1 85% 85/1 85/1 85/1 85/1 85/1 1–5 × 6/2 80% 80/2 80/2 80/2 1–5 × 5/1 80% 75/1 82/1 88/1 80/1 75/1 1–5 × 6/2 80% 77/2 86/2 77/2 1–5 × 5/1 80% 77/1 85/1 77/1 85/1 77/1 1–5 × 6/2 80% 77/2 86/2 77/2 1–5 × 5/1 80% 70/1 75/1 80/1 85/1 90/1 1–5 × 6/2 80% 75/2 80/2 85/2 1–5 × 5/1 80% 90/1 75/1 80/1 75/1 70/1 1–6 × 6/2 80% 85/2 80/2 75/2 Undulating Wave Ascending Descending Note: 5/1 = 5 total repetitions/cluster repetitions; 6/2 = 6 total repetitions/cluster repetitions. For example, if the coach were to create an undulating cluster set that contains five repetitions and wanted the average intensity across the set to be 80% of 1RM, the repetitions contained in the cluster set would be 75%, 82%, 88%, 80%, and 75% of 1RM (Haff et al., 2003). Ultimately, when working with wave, ascending, and descending cluster sets, a coach should define the average load across the set and then align the individual cluster intensities accordingly. Once the loads used with the cluster set have been selected the coach can then determine the amount of inter-repetition or intra-set rest that is provided within each set (Figure 13.7). Inter-repetition and intra-set rest interval alignments with training phase. If strength/power endurance or hypertrophy is the targeted outcome, shorter inter-repetition or intra-repetition rest between 5 and 15 seconds should be selected. When shifting the training target toward maximal strength the inter-repetition or intra-repetition rest interval contained in the cluster would be lengthened to 15–30 seconds. The longest inter-repetition or intra-repetition rest interval that would be used is 30–40 seconds. Additionally, it is important to remember the shorter the inter-repetition or intra-set rest interval, the greater the focus on endurance, and the longer the interval, the greater the focus on power/strength development (Figure 13.7). Additionally, the more repetitions contained within the cluster, the longer the intra-set rest interval may be required. Challenges to implementing cluster sets While cluster sets are useful and beneficial training tools, they do have practical limitations. The most noted limitation is the increased time needed to complete exercises which employ the cluster set. For example, three traditional sets of 12 repetitions are performed with 120 seconds of inter-set rest, so total time dedicated to rest is 240 seconds. If each set of 12 repetitions is broken into five pairs of two repetitions, each separated by 30 seconds, and the same 120 seconds of inter-set rest is employed, the total rest associated with three sets is now 690 seconds (Tufano et al., 2016). As noted by Jukic and Tufano (ahead of press), increasing the rest associated with a given exercise by this magnitude may not always be feasible from a practical perspective if an athlete has limited total training time. While Jukic and Tufano (ahead of press) are not incorrect about the extension of rest time, it is important to note that not every exercise in a given training session will utilise cluster sets and the coach can manipulate the interrepetition, intra-set, and inter-set rest intervals to allow for the more efficient utilisation of the cluster set. One additional strategy that can be used with team sport athletes is to perform what coach Erin Haff has termed “partner cluster sets” (personal communication, 2018). With “partner cluster sets” athletes can be paired based upon strength levels with one another so that whilst one athlete is resting, another is performing the repetitions contained within the cluster set (Figure 13.8). Partner cluster sets. To lengthen the inter-repetition or intra-set rest interval, the number of athletes partnered could be increased to three, thus allowing each athlete to lift in a rotation until the set is completed. Additionally, partnering athletes’ similar but not exact strength levels could also be used to lengthen the rest interval. One of the additional benefits of the partner cluster set strategy is that it enhances team dynamics as athletes need to learn how to work together to complete the programmed sets, especially if loads have to be altered between clusters such as during undulating, ascending, and descending sets. Additionally, this strategy provides an important opportunity for coaching to occur while athletes wait their turn in the lifting rotation. Periodisation and cluster sets The utilisation of the cluster set within a periodised training programme has not been widely investigated within the scientific literature. When examining the classic applied coaching literature, cluster sets have been employed during the specific preparation and pre-competition phase (i.e., pre-season) (Roll and Omer, 1987). For example, Roll and Omer (1987) suggest using standard cluster sets during the strength/power phase of a resistance-training programme that is associated with the pre-competition periods within an annual training plan for an American College Football team. Similarly, Miller (2011b) recommends using cluster sets during the specific preparation and pre-competition phases of the annual training plan of weightlifters. While it is logical to align cluster sets within the specific and precompetition phases, which often contain strength and power-training blocks of resistance training, various types of cluster set can be aligned with targeted training outcomes which are associated with various phases of the annual training plan (Figure 13.9; Haff et al., 2008a, 2008b). Set alignments with phases of a periodised training plan. For example, standard, ascending, and descending cluster set configurations can be used within the preparation period of the annual training plan, whilst standard, undulating, ascending, or wave-loaded cluster sets can be utilised during the competition period. Ultimately, the alignment of the cluster set with the various periods and phases of an annual training plan should be based upon the resistance-training targets (i.e., strength endurance, hypertrophy, strength and power). Summary The cluster set is not a new concept, but a classic strategy for modifying the set structure to alter the training stimulus and to provide the athlete with a novel training stimulus. The cluster set can be created in numerous ways, through modifying the loading, recovery, and organisational strategies used to create the set. Through manipulating the cluster set type and the recovery duration, the degree of recovery between the repetitions or groups of repetitions contained in the set can be impacted. Cluster sets can be employed to target strength endurance, hypertrophy, strength, and power development. While cluster sets are extremely useful, they should not be used with every exercise in a training session and should be confined to one to two main exercises (i.e., squatting, deadlift, weightlifting derivatives, etc.) per sessions. In team sport situations it may be warranted to create partner cluster sets where groups of athletes perform repetitions in an alternating manner in order to allow for a more efficient use of training time and, more importantly, the development of team dynamics and chemistry. References Arazi, H., Khanmohammadi, A., Asadi, A. & Haff, G.G. 2018. The effect of resistance training set configuration on strength, power, and hormonal adaptation in female volleyball players. Applied Physiology, Nutrition, and Metabolism, 43, 154–164. Bogdanis, G.C., Nevill, M.E., Boobis, L.H. & Lakomy, H.K. 1996. 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Part III Coaching your athlete 14 Movement screening: a systematic approach to assessing movement quality Louis Howe and Chris Bishop DOI: 10.4324/9781003044734-18 SECTION 1 Introduction Movement screening is the process of analysing an athlete’s technical performance across a movement task. Alongside testing measures of athletic qualities, movement screening allows strength and conditioning (S&C) coaches to determine an athlete’s competency for executing fundamental movement patterns during an initial assessment. Consequently, movement screening supports decision making during the gap analysis – a process whereby a coach compares the athlete’s current performance levels against established benchmarks or standards. In this context, movement screening provides S&C coaches with an appreciation for whether an athlete is prepared to progress (via increased mass, movement velocity or coordinative challenge) a relevant movement pattern, to further develop physical skills and capacities that enhance sport performance. In turn, S&C coaches are able to make better-informed decisions at an individual level regarding appropriate exercise prescription. This supports S&C coaches to individualise their approach to athletic development, whilst simultaneously improving athlete safety in the weight room. Although movement screening has limited ability to predict injury incidence (Bahr, 2016; Moran et al., 2017), it can be used to identify athletes at greater injury risk (Hewett et al., 2005; Padua et al., 2015; Hewett, 2016). In this context, athletes who demonstrate specific movement traits during a movement screen would be identified as being at greater injury risk. For example, an athlete who performs a landing task with excessive dynamic knee valgus is at greater risk of developing anterior cruciate ligament injury (Hewett et al., 2005). This would be defined as a movement fault, a coordination strategy that does not align with a pre-defined performance criterion for the task. Although this finding does not guarantee the occurrence of an anterior cruciate ligament injury (Leppänen et al., 2017), it does suggest the athlete is at greater risk (Myer et al., 2007), particularly if other risk factors associated with this injury are present (e.g. sport, gender, previous injury). Another benefit to formally including a movement screen within a testing battery is to provide a baseline indication for an athlete’s movement quality prior to initiating an S&C programme. This will help the S&C coach document improvement following an intervention – whether through appropriate coaching or training. This will be important in instances where an athlete lacks competency across several movement patterns leading to technique being prioritised for a length of time, as may be the case when a physical capacity deficit (i.e. insufficient ability to access a physical quality such as strength or mobility) is the cause of the failed movement screen. For example, if an athlete’s ability to perform full range-of-motion shoulder elevation is poor due to limited thoracic spine mobility, overhead lifting performance will be compromised (Kebaetse et al., 1999). A training programme to improve thoracic extension mobility in some instances will take time to achieve appreciable improvements, resulting in superior overhead lifting technique. The results from the initial screen will support the coach in rationalising the importance of a mobility programme to the athlete, which in turn may enhance the athlete’s motivation to perform the mobility programme regularly. Furthermore, improvements recorded in the subsequent movement screen following engagement with the mobility programme will demonstrate to the athlete and other relevant parties (i.e. technical coach) that the programme resulted in enhanced movement quality. This process reinforces to the athlete the benefits of S&C training, supporting future “buy-in”. The aim of this chapter is to provide the S&C coach with a systematic approach to performing movement screens based on the needs of the athlete and the coach. Key considerations for designing and performing movement screens will be discussed to ensure movement quality is accurately measured. To support the interpretation of the findings, an investigation process will be presented to establish the primary cause of a movement fault, helping S&C coaches problem-solve and individualise their approach to improving movement quality. Finally, in this chapter we present an example for how movement screening can be performed in the practical setting. Selecting movements to screen Specificity for exercise selection is an accepted principle for the transfer of training (Brearley and Bishop, 2019), yet it is rarely discussed in the context of movement screening. Earlier, we proposed that a primary objective of movement screening is to establish an athlete’s competency to perform specific movements, determining their level of preparedness for loading the pattern. As such, patterns that mimic exercises that the S&C coach plans to programme should be prioritised when selecting movements for screening. This ensures each screen establishes what it is supposed to (i.e. movement quality during exercise) and possesses high construct validity (Thomas et al., 2005). Movements that do not replicate the primary exercises likely to be prescribed to develop athletic performance should not be prioritised for screening unless the intended use is for identifying injury risk. For example, although performance of the active straight-leg raise requires an athlete to disassociate hip flexion from spinal motion, its relevance to the performance of a closed-chain hip hinge pattern used to develop posterior-chain strength is limited when compared to the Romanian deadlift screen. Although there are similarities between these tasks, the active straight-leg raise provides no information for how an athlete: (1) maintains balance during the movement; (2) actively develops spinal stiffness in an upright posture; (3) coordinates hip and knee flexion while minimising ankle motion during standing; (4) actively lengthens the hamstring musculature using an eccentric muscle action; and (5) manipulates the location of load so as to minimise spinal forces. As screening a single movement can be time consuming (>3 minutes) and various movement patterns are commonly used in training (e.g. jumping, hopping, squatting, lunging, hinging, pushing, pulling and rotating), coaches are left with little time to qualify movement quality during less relevant tasks. Therefore, it is suggested that practitioners filter their choice of movement screens to ensure findings directly inform training decisions while guaranteeing a time-efficient approach. Specificity is especially relevant when screening movements that are performed at relatively low velocities. In such instances, coaches must recognise that the information gained during low-velocity movement screens provides only a partial representation for how activities with similar coordination features occur at high velocities (Frost et al., 2015a). For example, peak knee abduction angle measured during a bodyweight squat shows only a non-significant moderate association (r = 0.46) with the same measure during a double-leg landing (Donohue et al., 2015). Although several reasons may underpin differences in competency between low- and high-velocity activities, the demands of the task will be the main cause for discrepancies observed. For many athletes, bodyweight squatting presents as a mobility challenge, with considerable demands for hip, knee and ankle motion (Hemmerich et al., 2006). Alternatively, landings require relatively less mobility at the hip and knee joint, but greater eccentric strength and rate of force development to rapidly attenuate landing forces (Montgomery et al., 2012) and preparatory strategies to coordinate the movement prior to ground contact (Hashemi et al., 2010). As a consequence of the conflicting requirements of each task, athletes who possess mobility restrictions will likely demonstrate suboptimal squat mechanics but may still be able to demonstrate appropriate landing technique (Dill et al., 2014). Conversely, athletes with low eccentric strength in the lower extremity are likely to demonstrate poor landing strategies (Lephart et al., 2002; de Marche Baldon, 2011), but may still be able to demonstrate a bodyweight squat. As poor control of the trunk (Zazulak et al., 2007; Dingenen et al., 2014) and lower extremity (Hewett et al., 2005) in the frontal plane during landings increases the risk for knee ligament injuries, screening competency during landing tasks and not through squatting movements becomes even more relevant. This is not to suggest that landing technique must be screened as part of the initial assessment on the first day of coaching a novice athlete. Depending on the circumstances, S&C coaches may choose to organise screening comparable to how training is periodised, so that high-velocity activities (e.g. jump-landing) are screened once a level of competence has been achieved in low-velocity movements (e.g. squat). As previously discussed, movement screening can also be used as a tool to determine an athlete’s injury risk. For this to be accomplished, movements should be selected that share mechanical similarities to the mechanism of the injury. For example, patellofemoral pain syndrome commonly occurs in sports that involve the performance of a high volume of jump-landings (Weiss and Whatman, 2015). As a consequence, double-leg landing technique can indicate which individuals are at greater risk of developing patellofemoral pain syndrome, with sagittal plane knee angle at initial ground contact (Boling et al., 2019) and peak flexion (Boling et al., 2009), along with frontal-plane projection angle (Holden et al., 2017), all shown to be modifiable risk factors. It is therefore suggested that when selecting movement screens S&C coaches consider the injuries that an athlete may be at greater risk of developing through sport participation (Howe, Waldron and Read, 2017). For injuries that demonstrate an incidence and severity rate requiring prevention strategies to be employed, the presence of modifiable risk factors should be assessed during relevant movement screens if applicable so as to inform the training process. An additional consideration for selecting movements to screen is the demands of the sport and the S&C coaches’ approach to developing relevant physical capacities. For example, numerous sports place minimal demand for upper-extremity strength qualities and, consequently, screening upper-limb movement may not be a priority. However, although some athletes may require minimal training for certain regions of the body, coaches may decide to screen movement quality in the area due to the methods employed to improve strength qualities. For instance, a coach seeking to develop explosive strength for a track and field athlete may choose to use variations of weightlifting exercises and medicine ball throws. As many of these lifts require athletes to load the upper extremity overhead, screening the thoracic and cervical spine, scapulothoracic articulation and glenohumeral joint function would be highly relevant (Howe and Blagrove, 2015; Howe and Read, 2015). Therefore, the sport and the approach employed to develop athletic performance by the S&C coach should also influence decision making when selecting movements to screen. As time for movement screening is finite, S&C coaches will likely need to be judicious when selecting movements. This may mean that when deciding on screens to investigate movement quality, coaches group movements where possible. For example, as shoulder elevation capability underpins overhead pulling and pushing exercises, using the bilateral shoulder elevation screen provides an appreciation of an athlete’s ability to optimally orientate the hand overhead (Howe and Blagrove, 2015). Although this approach may sacrifice a degree of specificity, it does preserve time and ensure efficiency is maximised. Other examples for maximising time efficiency during the screening process would be to complete movement screens during performance testing. For example, if the S&C coach would like to screen landing mechanics, video analysis could be used during jump testing to allow coaches to collect multiple forms of information during one test. Therefore, S&C coaches are encouraged to be creative in promoting efficiency when designing movement screens. This must be achieved while assuring a level of reliability to support the interpretation of the results produced through movement screening (discussed later in the chapter). Finally, S&C coaches should also consider the constraints imposed during each movement screen. A common error during movement screening is to have the athlete perform the movement using a technique or start position that fails to accurately replicate the demands of an exercise performed in the weight room. An example of this is having athletes perform an overhead squat screen with the feet facing forward in the sagittal plane (Cook et al., 2014). This constraint does not align with the technical model associated with the overhead squat exercise (Yule, 2007), and will capture a high number of false positives when attempting to determine an individual’s ability to squat with the feet orientated in a self-selected position (McMillian et al., 2016). This occurs as squatting with the feet forward prevents the athlete from accessing the same amount of hip abduction as when some toe-out is allowed. Having the feet facing forwards maximises the length of the femur in the anterior–posterior direction and biases the movement to demand high levels of ankle dorsiflexion range of motion to maintain an upright trunk position (Demers et al., 2018). If toeing out is included in the squat variation being screened, the femur is orientated more towards the frontal plane (relative to the feet-forward position) during the descent via hip abduction. The result is the length of the femur in the anterior–posterior direction decreases, reducing the demand for the ankle to dorsiflex. Although screening the squat with the feet facing forward may be useful for identifying individuals with restricted ankle mobility (Rabin and Kozol, 2017), it is not appropriate for determining an athlete’s ability to squat (McMillian et al., 2016) or whether the individual has adequate ankle mobility to perform the squat as an exercise. Therefore, coaches must ensure, when possible, the movements selected for screening are executed in a similar manner to how the exercise will be performed during training. This in turn will provide greater accuracy when determining an athlete’s readiness for loading the movement pattern. Table 14.1 provides an example menu of movements that may be considered for screening, along with the equipment required, set-up and instructions that should be provided to the participant. Nine screens are included that cover the majority of movement patterns (i.e. jump, hop, squat, hinge, lunge, push and pull) commonly programmed to support the development of physical qualities. However, for efficiency purposes, coaches may choose to only screen movements they anticipate will act as the foundation of the S&C programme. To complement this process, a case study will demonstrate how coaches may design a movement screen to fit athletes and their needs. Table 14.1 Example movement screens, including standardisation procedures Screen Equipment Set-up Instructions Countermovement jump None Stand upright with the feet facing forwards and hip width apart. Hands on hips “Jump as high as possible by dropping to a selfselected depth and then immediately exploding up. Upon landing, maintain balance, while keeping the hands on your hips throughout. Please perform three repetitions.” 75% forward hop Tape measure Tape Two strips of tape are “Hop forward, landing on the same leg with placed on the your big toe just behind the target marker. ground parallel to Upon landing, maintain balance for 2 each other at a seconds. Throughout, keep the hands on the distance of 75% of hips. Please perform three repetitions with maximal hop the same leg. Once finished, complete three distance. repetitions with the other leg.” Stand upright on one leg with the greater toe behind the first marker (taped line). Hands on hips Squat None Stand upright with “Keeping the feet flat on the ground, squat the feet shoulder down as low as you can. Hold the bottom width apart and position for 1 second, and then return to the turned out start. Please perform three continuous approximately 11 repetitions at a controlled pace.” and 1 on a clock face. Fingers are interlinked and the hands are placed behind the head with the elbows pointing to the side. Neutral head position with the eyes looking directly forwards Screen Equipment Set-up Instructions Single-leg squat None Stand upright on one “Keeping the foot flat on the ground, squat leg with the foot down with one leg as low as you can with the facing forwards. arms remaining parallel to the ground. Be The non-stance leg is sure to keep the non-stance knee flexed positioned so the throughout. Hold the bottom position for 1 knee is flexed to second, and then return to the start. Please 90° with the hip in perform three continuous repetitions at a a relatively neutral controlled pace with the same leg. Once position. finished, complete three repetitions with the Shoulders flexed to other leg.” 90° with the elbows extended (arms parallel to the ground). Neutral head position with the eyes looking directly forwards Forward lunge None Lunge distance is “Step forward so the big toe lands just behind normalised to leg the target marker. Upon contact with the length, calculated ground, drop into a lunge, stopping just as the distance before the back knee contacts the ground. between the Please perform three continuous repetitions anterior superior at a controlled pace with the same leg. Once iliac spine of the finished, complete three repetitions with the pelvis and the other leg.” medial malleolus of the tibia (measured in supine lying). Tape is placed on the floor to mark the lunge distance (leg length) between the greater toe of the trail leg and the greater toe of the lead leg. Stand upright with the feet hip width apart and facing directly forwards. Hands on hips. Neutral head position with the eyes looking directly forwards Screen Equipment Set-up Instructions Romanian deadlift Lightweight Stand upright with “Maintaining your spinal alignment, lower the dowel the feet hip-width bar down the front of your thighs as far as approximately apart and facing you can whilst only slightly bending the 30 mm in approximately knees. Hold the bottom position for 1 second, diameter forwards. and then return to the start. Please perform Hold the dowel with three continuous repetitions at a controlled an overhand grip pace.” and the hands just outside of shoulder width. Neutral head position with the eyes looking directly forwards Bilateral shoulder elevation None Stand upright with “Standing tall, lift the arms out to the side until the feet hip-width they are directly above your head, pointing apart. upwards. Keep the elbows extended Arms are by the side throughout the movement and at the top of with the elbows the movement, the palms should face each extended and other. Please perform three continuous palms facing the repetitions at a controlled pace.” side of the thighs. Neutral head position with the eyes looking directly forward Screen Equipment Set-up Inverted row Barbell, power The barbell is rack and positioned in the approximately power rack at a 45-cm box height so that when the athlete lays supine on the floor, only their fingertips can touch the bar. Lying supine, the athlete places their heels on the box with the feet together and facing straight up. The box should be positioned far enough from the bar so that the chest can contact the bar with the body straight. The athlete grips the bar with the hands pronated, just outside of shoulder width. Neutral head position with the eyes looking directly forwards (relative to the body) Instructions “Lift the pelvis so that from the heel to the head, you are a straight line – this is the start position. While maintaining the alignment of your body, pull yourself up to the bar until you feel the bar touch your chest. Hold this position for 1 second before descending until the elbows are fully extended. Please perform three continuous repetitions at a controlled pace.” Screen Equipment Set-up Instructions Push-up None The athlete lies prone “Perform the push-up by pushing the body on the ground with away from the ground until your elbows are the hands directly fully extended. Hold the top position for 1 under the second before returning to the start position. shoulders just Throughout the movement maintain a outside of shoulder straight line from the heels to the head. width. Please perform three continuous repetitions The feet should be at a controlled pace.” together with the knees extended and the toes extended so the balls of the feet contact the ground. Neutral head position with the eyes looking directly forwards (relative to the body) SECTION 2 Designing performance criteria to aid the assessment of movement screens Commercially available movement screens commonly employ a grading system that results in a composite score from a range of screens being calculated to represent an individual’s movement quality (Bennett et al., 2017). However, composite scores provide little value in establishing competency for specific movement patterns (Scibek et al., 2020) and injury risk (Moran et al., 2017). As an alternative approach, the S&C coach should direct their attention to the performance of each test. Additionally, as opposed to scoring movement using a numerical scoring system with levels (i.e. 0–3), it is suggested a pass–fail criterion is used to report performance during screening along with a list of movement faults identified. In this case, a pass would signify that the athlete performed the movement screen using a coordination strategy that satisfied the associated performance criteria. A fail would indicate that discrepancies existed in the performance of the movement screen relative to the performance criteria, or that the athlete experienced pain during the movement. As movement screening is a tool to determine whether an athlete does or does not possess the technique necessary to develop physical qualities using that movement, it is suggested there is no need for a grade beyond pass or fail. The performance criteria represent the technical features that the athlete is expected to display during each movement, guiding the S&C coach as to how the movement should be executed. It is imperative that each component included in the performance criteria is essential for the optimal performance of the movement. Failure to meet the movement standards set by the performance criteria should indicate the athlete demonstrates a strategy that will limit performance or increase injury risk if the movement were to be loaded. Table 14.2 provides an example performance criterion with a brief rationale provided for each component. Table 14.2 Performance criteria for each example screen, including a brief underpinning rationale Screen View Performance criteria Rationale Screen View Countermovement jump (landing phase) Anterior Performance criteria 1. Feet land between hip Rationale Excessive toe-in or -out during landings increases anterior cruciate ligament injury risk (Ishida et al., 2015) and shoulder width apart, facing forward with minimal toein or -out 2. Foot contact is symmetrical 3. Knees remain over the toes Between-limb time discrepancies in ground contact cause asymmetry in peak vertical ground reaction forces (GRF) (Britto et al., 2015) and are suggested as a risk factor for both acute (Hewett et al., 2010) and overuse injuries (Bressel and Cronin, 2005) High knee abduction angle during landings increases anterior cruciate ligament injury risk (Hewett et al., 2005) throughout the landing 4. Pelvis remains level Lateral trunk lean increases peak vertical GRF and peak knee valgus angle for the ipsilateral limb (Hinshaw et al., 2019) and no trunk lean is present Side 5. Forefoot touches down Landing with a plantar flexed ankle reduces peak vertical GRF (Rowley and Richards, 2015) prior to heel contact Increased knee joint flexion results in reduced peak vertical GRF during landings (Zhang et al., 2000) approximately and is associated with reduced injury risk (Boling et 60–90° al., 2009; Leppänen et al., 2017) 6. Knee flexes following ground contact 7. The trunk leans forward >30° A forward trunk lean is associated with increased hip flexion (Blackburn and Padua, 2008) and results in reduced peak vertical GRF (Blackburn and Padua, 2009) Screen View Performance criteria 8. Spine remains in a neutral Rationale Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) position 75% forward hop (landing phase) Anterior 1. Foot lands facing Excessive toe-in or out during landings increases anterior cruciate ligament injury risk (Ishida et al., 2015) forwards with minimal toein or -out 2. The knee remains over High knee abduction angle increases anterior cruciate ligament injury risk (Hewett et al., 2005) the toes throughout the landing 3. Pelvis remains level Lateral trunk lean increases peak vertical GRFs and peak knee valgus angle for the ipsilateral limb (Hinshaw et al., 2019) and no trunk lean is present Side Increased knee joint flexion results in reduced peak vertical GRF during landings (Zhang et al., 2000) approximately and is associated with reduced injury risk (Boling et 60–90° al., 2009; Leppänen et al., 2017) 4. Knee flexes following ground contact 5. The trunk leans forward A forward trunk lean is associated with increased hip flexion (Blackburn and Padua, 2008) resulting in less loading on the knee joint (Dingenen et al., 2015) >30° 6. Spine remains in a neutral Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) position 7. No obvious trunk rotation occurs Poor trunk control during landings is associated with greater loading at the knee joint during landings (Critchley et al., 2019) Screen View Squat Anterior Performance criteria 1. No change in foot position Rationale Excessive toe-out increases medial-lateral knee joint displacement during squatting (Lorenzetti et al., 2018) or alignment 2. Knees remain over the toes throughout the descent Medial knee joint displacement may be associated with hip adduction and internal rotation (Slater & Hart, 2016), which can be a provocative position for femoroacetabular impingement (Lamontagne et al., 2009) and ascent 3. Pelvis and shoulders Lateral trunk lean during squatting may cause asymmetry in force production remain level throughout Side 4. Hip crease descends Represents a minimal standard of range of motion for the movement below the top of the knee 5. Spine remains in a neutral Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) and reduces shear forces (Potvin et al., 1991) position Posterior 6. Pelvis remains centred over the base of support Single-leg squat Anterior 1. No change in foot position Lateral hip shift during closed-chain lower-extremity exercise causes asymmetry in force production (Lally et al., 2017) and may suggest an avoidance strategy (Trulsson et al., 2015). In some instances, this movement presents as an opportunity to improve squat performance by increasing the leg contribution of the (relatively) unloaded limb Excessive toe-in or out during single-leg exercises increases injury risk to passive structures located around the knee joint (Sakurai et al., 2020) or alignment 2. Knees remain over the toes throughout the descent and ascent Maintaining this position reduces knee abduction moments (Herrington et al., 2017). Medial knee displacement may be associated with hip adduction and internal rotation (Slater & Hart, 2016), which can be a provocative position for femoroacetabular impingement (Lamontagne et al., 2009) Screen View Performance criteria 3. Pelvis remains level Rationale Ipsilateral lateral trunk lean during single-leg squatting increases peak knee abduction angles (Nakagawa et al., 2012) and no trunk lean is present Side 4. Knee flexes to Represents a minimal standard of range of motion for the movement ≥ 90° 5. Spine remains in a neutral Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) and reduces shear forces (Potvin et al., 1991) position 6. No obvious trunk rotation Trunk rotation is associated with poor lumbo-pelvic stabilisation during variations of single-leg squatting (Perrott et al., 2010) occurs Forward lunge Anterior 1. Both lead and trail foot face forwards throughout 2. Lead knee remains over Excessive toe-in or out during single-leg exercises increases injury risk to passive structures located around the knee joint (Sakurai et al., 2019). Coaches should be aware that slight toe-in on the lead leg may be advantageous for increasing balance secondary to a greater base of support Maintaining this position during lunging reduces loading on passive structures located around the knee joint (Thijs et al., 2007) the toes throughout 3. Pelvis remains level Adequate lumbo-pelvic stabilisation is required to maintain this position (Whatman et al., 2012) and no trunk lean is present Side 4. Lead foot remains in full contact with the ground following initial ground contact Heel lifting off the ground increases risk of falling due to reduced base of support Screen View Performance criteria 5. Spine remains in a neutral Rationale Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) and reduces shear forces (Potvin et al., 1991) position 6. Knee flexion for the lead Represents equal contribution of the trail and lead leg to producing force and trail leg is approximately 90° Romanian deadlift Anterior 1. Bar descends lower than the Represents a minimal standard of range of motion for the movement patella 2. Bar remains Indicates symmetry in the coordination strategy used level throughout Side 3. Slight knee flexion occurs Signifies a hip flexion strategy is dominant in lowering the load during the descent 4. Tibia remains Minimises ankle dorsiflexion contribution vertical throughout 5. Spine remains in a neutral Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) and reduces shear forces (Potvin et al., 1991) position Posterior 6. Pelvis remains centred over the base of support Lateral hip shift during closed-chain lower-extremity exercise causes asymmetry in force production (Lally et al., 2017) Screen View Bilateral shoulder elevation Anterior Performance criteria 1. Upper arm reaches a Rationale Represents a minimal standard of range of motion for the movement vertical alignment relative to the ground 2. Elbows remain Elbow flexion is a compensatory strategy used to achieve the goal of orientating the hands over the head (Howe and Blagrove, 2015) extended Side 3. Arms remain in the frontal Deviations out of the frontal plane represent a compensatory strategy during the test (Howe and Blagrove, 2015) plane 4. Head does not Poor cervical spine alignment negatively impacts upper-extremity function (Thigpen et al., 2010) change position 5. Spine remains in a neutral alignment Posterior 6. No obvious signs of Excessive thoracic spine flexion impairs scapulothoracic function (Crosbie et al., 2010) and reduces scapular plane abduction strength (Kebaetse et al., 1999) Demonstrates optimal synergy between the scapulothoracic muscles (Ludewig and Reynolds, 2009) shrugging Inverted row Side 1. The chest touches the Represents a minimal standard of range of motion for the movement bar 2. The scapulas fully protract and retract during the descent and ascent, respectively, in a controlled fashion Full scapular retraction and protraction indicate adequate muscular control of the trapezius and rhomboid musculature (Ekstrom et al., 2003) Screen View Performance criteria Rationale 3. The scapula is Demonstrates optimal synergy between the scapulothoracic muscles (Ludewig et al., 2004) not fully elevated or depressed 4. Throughout the Demonstrates adequate lumbo-pelvic control during a pulling movement movement, the body forms a straight line from the heel to the head 5. Spine remains in a neutral Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) alignment Push-up Side 1. Elbows fully extend at the Represents a minimal standard of range of motion for the movement top of the ascent 2. The scapulas fully protract Full scapular retraction and protraction indicates adequate muscular control of the serratus anterior muscle (Ludewig et al., 2004) and retract during the ascent and descent, respectively, in a controlled fashion 3. The scapula is Demonstrates optimal synergy between the scapulothoracic muscles (Ludewig et al., 2004) not fully elevated or depressed Screen View Performance criteria 4. Throughout the Rationale Demonstrates adequate lumbo-pelvic control during a pushing movement movement, the body forms a straight line from the heel to the head 5. Spine remains in a neutral Neutral spine alignment increases tolerance to compressive forces (Gunning et al., 2001) alignment When selecting components of a movement that should be included in a performance criterion, the S&C coach should account for individual variability in the coordination of the movement. For example, variance in anthropometric dimensions will influence the relative contribution of the hip, knee and ankle joints to lowering the centre of mass during squatting (McKean and Burkett, 2012). Visually, this can be observed through varying trunk angles relative to the tibia (shin) angle. A common recommendation for performing a squat movement is to use a technique that maintains a torso angle that is parallel to the tibia (Bishop and Turner, 2017). However, strict adherence to this criterion fails to account for the natural variance that exists between individuals of different statures. Athletes who possess a long torso relative to their femurs will likely squat with a more vertical trunk angle. Conversely, athletes with a shorter torso relative to their femurs will likely adopt greater forward lean during the squat to maintain balance. As a result, S&C coaches may choose to ignore this feature of the movement and focus on other characteristics of the squat movement that are required for proficiency in the movement (e.g. maintaining a neutral spine). Alternatively, if the S&C coach believes this feature of the movement will inform their practice, movements that demand this characteristic (e.g. overhead or front squat) should be selected for screening to identify if the athlete has the skill and capacities to demonstrate this coordination strategy. Importantly, the S&C coach must distinguish between movement faults that result in diminished performance or increased injury risk, and variances in performance that do not compromise either. Performing movement screening A common argument against the use of movement screening is that formally performing screens is unnecessary. Instead, observing the way each athlete moves during training sessions will suffice. Although there is merit in this approach, this presents several problems that must at least be considered when attempting to reliably screen an athlete’s movement competency. This section will provide the S&C coach with important considerations for how to perform a movement screen. The primary issue with using training sessions as a movement screen would be a lack of standardisation in the testing procedures (including both screening and assessments), resulting in greater error due to confounding variables diminishing the reliability of the data collected. Reliability is defined as the consistency of a test to provide an outcome measure (Atkinson and Nevill, 1998) and must be established to support the interpretation of the findings. As all testing procedures contain varying levels of associated error, the S&C coach must identify whether changes in results have occurred due to differences in the athlete’s movement competency following training or represent variability in the outcome measure associated with error (Atkinson and Nevill, 1998). To improve reliability when performing movement screens, the S&C coach should ensure the factors presented in Table 14.3 are considered. Table 14.3 Key considerations to improve reliability when screening movement quality Factor Consideration Testing equipment The same testing equipment is used for each testing session and the equipment is set up appropriately and calibrated, as required Clothing and footwear Athletes should wear similar clothing and footwear between testing sessions. Preferably, athletes should wear the same footwear they expect to regularly train in and clothing that allows for unrestricted movement and anatomical landmarks to be observed Facilities and flooring Facilities and flooring should be consistent across testing sessions Circadian variation Time of day and the day relative to the training week should be controlled between test sessions. This will limit the influence of circadian variation and fluctuations in training load across the week, respectively Warm-up If used, the same warm-up protocol should be performed to prevent variability secondary to differences in the level of acute preparedness Instructions and Athletes should be instructed on how to perform the task using a standardised script that demonstrations includes only relevant information. A demonstration should also be provided to ensure the athlete has a clear understanding for how the task should be performed Factor Consideration Familiarisation Athletes should be allowed time to practise the screen to ensure changes in results are not caused by greater familiarity with the task secondary to a learning effect. Sets of three repetitions should initially be performed by the athlete to allow for them to be familiarised with the movements. This should be repeated until the athlete reports they are comfortable with the movement and the coach is confident there is enough consistency between repetitions to ensure reliable results are recorded. Coaches may need to use this time to reinforce elements of the instructions Data collection method For each screen, a camera should be set up so that the optical axis of the camera is perpendicular to the plane of motion being recorded, while ensuring the entire movement is captured. For screens that require footage in both the sagittal and frontal plane, coaches can either use two cameras to record footage simultaneously or if only a single camera is available, the athlete should perform clusters of repetitions at different angles to the camera to allow for footage to be recorded in various planes Performing movement screens in real time has been shown to produce reliable results (Onate et al., 2012). However, investigations establishing the criterion validity for real-time screening demonstrates low accuracy, with the level of agreement being shown to be poor between the evaluation of movement competency in real time and objective measurements recorded using gold-standard methods for measuring movement (i.e. three-dimensional (3D) motion capture analysis) (Whiteside et al., 2016). It has been suggested that disparities in scores between real-time and 3D motion capture are caused by the need for assessors to grade several components of the performance criteria simultaneously in real time during a single repetition (Whiteside et al., 2016). As a result, it is recommended that the S&C coach use video analysis when performing movement screening to improve accuracy. If logistics requires coaches to screen in real time, it is recommended that, for each repetition, only one component of the performance criteria be assessed. This will result in the number of components included in the performance criteria determining how many repetitions to perform for each screen (Gould et al., 2017). As a result, coaches will avoid the error associated with screening movement using a performance criterion that includes several components across only three repetitions in real time. Identifying the causes of movement faults Following the performance of a movement screen, S&C coaches must have a process to interpret the information gathered so as to inform practice. Figure 14.1 illustrates a model that can be used by S&C coaches to establish the cause(s) of movement fault(s) that may present during a movement screen. When an athlete performs a movement screen optimally relative to the performance criteria, the athlete has passed the screen (stage 1). In this instance, the S&C coach can be confident that the athlete has an adequate level of skill and capacities to perform the movement. In this context, skill represents the athlete’s ability to coordinate their body optimally to perform the movement screen using a strategy that matches each component of the performance criteria, while capacities signifies the athlete’s access to a certain physical quality (e.g. strength, mobility, balance, endurance, etc.). As a result of the passed screen, the movement can be programmed to drive adaptations in athletic qualities. Model to establish the cause(s) of movement fault(s). Similar to the medical model used for screening health-related factors (e.g. blood pressure), when an individual fails a movement screen, further investigation through additional assessment is required to identify the cause(s) of the movement fault(s). This requires the S&C coach to adopt a systematic approach to determining the source of the movement fault (Howe and Cushion, 2017). The investigation process for establishing the cause of a failed movement screen should be regarded as crucial for developing movement quality in the pattern screened. Time to train is finite for all athletes and excessive time spent performing corrective exercises will reduce time available to develop physical qualities that will result in enhanced sport performance. This is particularly problematic if S&C coaches apply a scattergun approach to improving movement quality without further investigation, whereby assumed skill, proprioception, balance, strength and mobility issues are addressed through mass prescription of corrective exercises. However, if the cause of the movement fault is identified, corrective strategies can be employed that are effective and time-efficient. Stages 2–4 of the investigation process presented in Figure 14.1 are designed to determine whether the cause of the movement fault is either a skill or capacity issue. To illustrate the practical application of this concept, consider the following example. Two athletes perform the squat screen with excessive forward lean that results in a loss of neutral spine prior to the hip crease descending below the top of the knee joint. Both athletes are made aware of this movement fault and asked to practise squatting without making contact with a wall that is behind them one foot length away from their heels. In this example, the wall acts as a constraint by preventing excessive forward trunk lean and limiting how far the pelvis can deviate posteriorly. Following a short period of practice, one athlete is now able to perform the squat so the hip crease descends below the top of the knee, while preserving a neutral spine. In this instance, the movement fault was caused by a lack of skill. The second athlete is unable to solve the movement problem and, as such, falls forward or limits their range of motion to preserve balance during each attempt. For this athlete, the working hypothesis is the athlete possesses a capacity issue that is limiting their ability to adapt their coordinative strategy and further investigation is required. It should be noted that the distinction provided here is limited, as skills and capacities share an interdependent relationship during the performance of any movement. However, in the context of movement screening and developing corrective strategies, this concept serves the S&C coach in establishing the cause(s) of a movement fault that an athlete demonstrates. When an athlete fails a movement screen, they have either demonstrated movement faults in the coordination strategy used or reported pain during the movement. For the latter, immediate referral to a medical practitioner is required. When movement faults are demonstrated during the initial screen with no pain present, the S&C coach should progress the athlete to stage 2 of the investigation process illustrated in Figure 14.1. At this point, the S&C coach will begin to identify whether a skill issue is the primary cause of the movement fault. A skill deficit would represent the athlete’s failure to coordinate the movement using a strategy the S&C coach regards as optimal. Although coaches could move directly to testing capacities (stage 4 of this process), coaching the athlete on how to perform the movement is the next logical step. This suggestion is based on evidence showing that significant improvements in movement quality occur in short time periods following a basic explanation of the performance criteria (Frost et al. 2015b; Bryson et al., 2018). However, coaching involves more than just providing athletes with a verbal description of a technical model. Verbal feedback, visual demonstrations and techniques that stimulate kinaesthetic awareness can all be strategically applied to facilitate self-correction (Cushion et al., 2017). In the authors’ experience, in many cases this process takes 1–2 minutes for most weight-room-based movements and presents as a time-efficient strategy for identifying the cause of the movement fault following the initial screen. Stage 2 has the additional benefit of helping to establish how “coach-able” an athlete is, as well as their preferred learning style that will serve as a useful tool for future interactions with the athlete. Furthermore, coaches can observe what cues resonate for each athlete in supporting them to appreciate the goal of the task. For athletes possessing the necessary capacities to perform the movement optimally, stage 2 will likely result in the athlete passing the original movement screen. In this instance, the investigation should be ceased and the primary cause of the movement fault has been identified as a skill deficit. The pattern is ready for loading, although additional time spent developing movement skill may be required. It is beyond the scope of this chapter to discuss the science that underpins the variety of approaches available to the S&C coach to improve movement quality through coaching. The interested reader is referred to Cushion et al. (2017). If the movement faults remain, or additional movement faults become apparent as the athlete compensates for the constraints imposed through coaching, the athlete should be progressed to stage 3 of the investigation process. This requires the S&C coach to subtly manipulate the task in order to identify how the athlete can successfully complete the movement. This serves two primary purposes: 1. Provide clues as to the capacity deficits that may be present, whilst ensuring efficiency in the investigation process by ruling out capacity deficits and rendering certain assessments unnecessary. 2. Determine variations in the technique that the athlete can adopt to perform the movement using a strategy that allows the athlete to pass the screen by performing the movement as outlined by the performance criteria. This information may also help the coach identify exercises that the athlete is best suited for. Table 14.4 provides example task manipulations that can be applied to the commonly used overhead squat screen. It should be emphasised that stage 3 should only be employed where the S&C coach sees value in manipulating a task to improve effectiveness during the investigation process. Table 14.4 Example task manipulations for an overhead squat screen that can be applied at stage 3 of the investigation process Task manipulation Rationale Interpretation Task manipulation Rationale Interpretation Elevate the heel using a 10° wedge Reduces the demand for hip flexion (Charlton et al., 2017) and ankle dorsiflexion range of motion (Legg et al., 2017) This manipulation informs the strength and conditioning (S&C) coach what the squat would look like if additional ankle dorsiflexion range of motion were available. If the athlete performs the squat with no movement faults with the addition of the heel wedge, limited hip flexion or ankle dorsiflexion range of motion may be the cause of the movement fault. In this instance, restricted knee flexion range of motion can be ruled out Elevate the forefoot using a 10° wedge Increases the demands for hip flexion and ankle dorsiflexion range of motion (Macrum et al., 2012) This manipulation informs the S&C coach whether the athlete has additional hip flexion they can access during the squat. If the movement fault increases in magnitude, limited ankle dorsiflexion range of motion may be the cause of the movement fault. Additionally, if hip flexion range of motion increases during this movement, it is unlikely hip mobility is a limiting factor as the athlete is able to access greater range of motion at the joint. If squat depth decreases significantly, the S&C coach is unable to rule out limited hip mobility Counterbalanced squat By squatting holding a weight in front of the body (approximately 10% of body mass), the athlete’s centre of mass can move behind their base of support. This decreases the need for ankle dorsiflexion range of motion, while allowing the athlete to display full knee flexion range of motion (Lynn and Noffal, 2012) This manipulation informs the S&C coach whether the athlete possesses adequate knee and hip flexion range of motion to perform the squat. If the athlete can fully flex the knee (hamstrings contact the gastrocnemius) while maintaining a relatively upright trunk and neutral spine, the athlete possesses adequate knee and hip flexion range of motion. In this instance, ankle dorsiflexion range of motion may be the culprit Wide-stance squat Squatting with a wide stance increases hip abduction range of motion (Lorenzetti et al., 2018). This results in a decreased demand for ankle dorsiflexion range of motion (Demers et al., 2018) by reducing the length of the femur in an anterior– posterior direction (Cleather, 2012) This manipulation informs the S&C coach whether the athlete can effectively access their hip abduction range of motion during the squat. If the movement fault decreases in magnitude, limited ankle dorsiflexion range of motion is a potential cause. Alternatively, limited capacity to flex the hip without additional hip abduction may be a source of the movement fault Throughout the investigation process, the S&C coach should form a working hypothesis as to the primary cause of the movement fault. At stage 4, isolated assessments will be performed to test specific capacities that challenge the working hypothesis. The isolated assessments of interest will depend on the movement being screened and how the athlete performed during the preceding stages. Importantly, the results from these assessments should provide the S&C coach with objective data that can be compared to normative data to support the hypothesis that a capacity deficit is present. For example, during squatting, the hip abducts approximately 30° during the descent phase (Hemmerich et al., 2006; Swinton et al., 2012). Assessing hip abduction range of motion using the supine hip abduction test would provide objective data that can be compared directly to the movement to determine whether a capacity deficit exists (Howe and Waldron, 2019). Additionally, as long as the S&C coach has determined the error (e.g. typical error) associated with their testing procedures for each assessment (Howe and Waldron, 2019), changes in the capacity following training can be documented and used to determine true change and the effectiveness of a corrective programme. Table 14.5 provides a brief description of isolated assessments that can be employed to determine deficits in mobility along with the associated movement screen. Normative values are relative to the demands of the corresponding movement pattern to guide the interpretation as part of the investigatory process. However, these values should be interpreted with strong caution due to differences in anthropometric profiles and variability in the coordinative strategies used to perform each movement. Table 14.5 Isolated assessments for mobility testing Test Start position Movement Measurement Normative Relevant values or movement pass screen criteria Test Start position Movement Supine active shoulder flexion test The athlete lies The athlete is supine, with cued to the knees maximally flexed to 90° flex the and the feet shoulder by flat against bringing the the ground. thumbs The athlete towards the is cued to ground above posteriorly the head. rotate the Elbows must pelvis and remain the head extended and should be the lumbar positioned so spine that the face maintained in is looking a flexed towards the position ceiling. The shoulder is flexed to 90°, with the elbows extended, the palms facing each other, and thumbs extended Measurement Normative Relevant values or movement pass screen criteria Prior to testing, the smartphone is zeroed against a vertical reference (e.g. wall). The smartphone is placed along the upper-arm (triceps brachii), just below the medial epicondyle Thumb Bilateral shoulder touches the elevation ground with the elbows extended Test Start position Movement Measurement Normative Relevant values or movement pass screen criteria Supine active shoulder rotation test (internal and external) The athlete lies supine on a plinth, with the knees flexed to 90° and the feet flat against the table. The shoulder is abducted to 90° (upper-arm rests on the plinth), with the elbow flexed to 90° and palm facing towards the feet For glenohumeral external rotation, the athlete is cued to bring the back of the hand towards the floor as far as possible. For glenohumeral internal rotation, the athlete is cued to bring the palm towards the floor as far as possible Prior to testing, the External smartphone is rotation: > zeroed against a 90° vertical Internal reference (e.g. rotation: > wall). For 40° external rotation, the smartphone is placed on the anterior surface of the forearm (flexor side) just below the ulnar styloid process. For internal rotation, the smartphone is placed on the posterior surface of the forearm (extensor side) just below the ulnar styloid process Bilateral shoulder elevation Test Start position Movement Measurement Normative Relevant values or movement pass screen criteria Thoracic spine extension test The athlete leans with their back against a bare wall. The feet should be positioned one-foot length away from the wall, with the knees slightly flexed. The athlete is cued to posteriorly rotate the pelvis to flatten the spine against the wall. The head should be touching the wall and the mouth should be closed Maintaining contact between the head and the wall, the athlete is cued to draw the chin towards the chest as far as possible The distance between the tragus (small pointed eminence covering the auditory meatus (ear canal)) and the wall is measured to the nearest 0.5 cm The corner of the eye should be in line or below the auditory meatus Bilateral shoulder elevation. Romanian deadlift Test Start position Movement Lumbar locked rotation test The athlete The athlete is kneels with cued to rotate the ankles as far as plantar possible in flexed. The the direction athlete sits to the side on their with the arm heels, whilst off the floor, supporting whilst their uppermaintaining a body mass neutral with their alignment of elbows and the cervical forearms spine and the placed on the supporting ground so forearm on the shoulders the floor are flexed to 90°. The athlete flexes the ipsilateral elbow maximally while bringing the forearm off the ground Measurement Normative Relevant values or movement pass screen criteria Prior to testing, the smartphone is zeroed against a vertical reference (e.g. wall). The smartphone is placed on the spine at the level of C7–T1 at the level of the neckline on a traditional crew neck t-shirt > 45° Bilateral shoulder elevation Test Start position Movement Measurement Normative Relevant values or movement pass screen criteria Supine active hip flexion test The athlete lies The athlete is Prior to testing, the > 10° supine on the cued to smartphone is ground, with maximally zeroed against a both knees bring the vertical extended and knee of the reference (e.g. the arms by test limb wall). In the start the athlete’s towards the position, a side ipsilateral horizontal line is shoulder, marked on the while bending athlete’s thigh, 5 the knee cm above the base of the patella. The smartphone is placed proximal to the marked line at the point of maximal hip flexion Squat. Single-leg squat. Forward lunge (lead leg). Countermovement jump. 75% forward hop Test Start position Movement Modified Thomas test The athlete lies While supine on a maintaining plinth so that hip alignment when the for both hips are limbs, the extended, the athlete is back of the instructed to thighs are flex the knee supported by on the test the table, but limb as far as the knee possible does not contact the table. Both hips begin in a flexed position, flattening the lumbar spine. The athlete is instructed to lower the test limb down into hip extension, with the knee extended until the back of the thigh contacts the table Measurement Normative Relevant values or movement pass screen criteria Prior to testing, the < 30° smartphone is zeroed against a vertical reference (e.g. wall). The smartphone is placed on the anterior border of the tibia distal to the tibial tuberosity at the point of maximal knee flexion Forward lunge (trail leg) Test Start position Movement Measurement Normative Relevant values or movement pass screen criteria Supine hip abduction test Athlete lies in a The athlete Prior to testing, the > 40° supine maximally smartphone is position with abducts at the zeroed against a the legs hip (moves vertical extended. the knee reference (e.g. The test leg away from wall). At the is flexed at the midline of point of maximal the hip and the pelvis) hip abduction, knee to 90° while the place the phone coach on the medial stabilises the surface at pelvis, approximately preventing mid-thigh rotation from occurring Squat Active hip rotation test (internal and external) The athlete sits The athlete is Prior to testing, the External on the edge instructed to smartphone is rotation: > of a plinth, maximally zeroed against a 40° with the rotate the foot vertical Internal knees flexed away from reference (e.g. rotation: > at 90° and (hip internal wall) and a 30° the lower rotation) or horizontal line is legs freely towards (hip made 10 cm hanging off external above the the table. For rotation) the inferior tip of the both internal midline of lateral malleolus. and external their body, For both tests, rotation, the while the smartphone non-test leg maintaining a is placed directly is placed 90° flexed proximal to the over the position at the marked line lateral edge knee of the plinth by abducting the hip Squat. Single-leg squat Test Start position Movement Active knee extension test The athlete lies The athlete is supine on the cued to ground, with maximally both legs extend the extended and knee, whilst flat on the maintaining ground and hip alignment the arms by the athlete’s side. The test limb is then flexed at the hip and knee to 90° and foot positioned in a neutral alignment Modified weightbearing lunge test The athlete The athlete is Prior to testing, the > 40° starts in a instructed to smartphone is half-kneeling reach the zeroed against a position, knee forward vertical with the as far as reference (e.g. pelvis facing possible, wall). At the forwards and while keeping point of maximal the trunk the knee over ankle relatively the foot, the dorsiflexion just upright heel down prior to heel lift, (some against the the smartphone forward lean ground and should be placed is allowed). the pelvis on the anterior The test foot facing border of the is positioned forward tibia distal to the half a foot tibial tuberosity length ahead of the knee of the nontest leg, with the knee aligned directly over the foot on the test limb Practical applications: a case study Measurement Prior to testing, the smartphone is zeroed against a vertical reference (e.g. wall). At the point of maximal knee extension, the smartphone is placed on the anterior border of the tibia distal to the tibial tuberosity Normative Relevant values or movement pass screen < 20° Romanian deadlift criteria Squat. Single-leg squat. Countermovement jump. 75% forward hop This section will now provide a “real-world” example for how the approach discussed in this chapter can be applied. A 19-year-old international female distance runner, with no previous experience of S&C training, presented for an initial testing session prior to commencing a structured S&C programme ahead of the competitive season. Physical capacity and tissue tolerance testing were performed alongside movement screening (stage 1 only) in a single testing session, while physiological testing and gait analysis were completed elsewhere by other members of the interdisciplinary team. Findings from the movement screen, along with the investigatory process previously discussed in this chapter, are presented in Table 14.6. Table 14.6 Movement screen findings and associated investigatory process for an international distance runner Order Movement screen Stage 1 (screen movement) Stage 2 (coach) 1 Squat Pass 2 Forward lunge Fail: Knee Athlete passed the valgus screen with practice (patella following: inside of 1. Verbal greater toe) feedback and demonstrated cueing on the lead leg following 2. Additional ground demonstrations contact on both sides 3 Romanian deadlift Fail: Excessive knee flexion and neutral spine alignment are not maintained prior to the bar reaching the patella Athlete passed the screen with practice following: 1. Verbal feedback and cueing 2. Additional demonstrations 3. Practice with changes in environmental constraints 4 Bilateral shoulder elevation Pass Stage 3 Stage 4 (task (isolated manipulation) assessments) Order Movement screen Stage 1 (screen movement) Stage 2 (coach) Stage 3 Stage 4 (task (isolated manipulation) assessments) 5 Countermovement jump (landing phase) Pass 6 75% forward hop (landing phase) Fail: Knee Athlete was unable to Single-leg squat: valgus pass the screen with Excessive spine (patella practice following: flexion during inside of the descent and 1. Verbal greater toe) knee flexion did feedback and and limited not reach 90°. cueing knee flexion Counterbalanced are single-leg squat 2. Additional demonstrated (5 kg): Athlete demonstrations following was able to ground maintain a 3. Video contact on neutral spine feedback on both sides alignment and her achieve >90° knee flexion performance Modified weightbearing lunge test: Right = 44° Left = 42° Movement screening was performed in a fresh state, prior to physical capacity and tissue tolerance assessment, with the exception of landing movements. In this instance, double-leg landing competency was screened using the same test for assessment of explosive strength (i.e. countermovement jump). Similarly, movement quality during single-leg landings was screened following the performance of a maximal hop test used to determine between-limbs symmetry in strength. Movement screens were primarily selected based on their distinct mechanical similarities to the range of exercises that would likely be prescribed as part of the S&C programme, with the exception of the bilateral shoulder elevation screen. This movement was chosen to assess competency for achieving an overhead position in preparation of ballistic (i.e. weightlifting and medicine ball throws) and supplementary (i.e. trunk and upper-body exercises) training modalities. All screens were recorded for video analysis, with a single camera (sampling rate 60 frames per second) set-up using the procedures outlined in Howe et al. (2020). To allow for accurate comparison against the performance criteria, the athlete was required to complete clusters of three repetitions at the necessary angles relative to the camera. A demonstration and standardised instructions (Table 14.1) were provided prior to familiarisation to ensure the athlete understood the task demands. No warm-up was used for the squat, forward lunge, Romanian deadlift or bilateral shoulder elevation screens. A standardised warm-up was performed prior to the countermovement jump and 75% forward hop screen. As reported in Table 14.6, the athlete failed three of the six movement screens, demonstrating movement faults for the forward lunge, Romanian deadlift and 75% forward hop screen. During the subsequent training session, the athlete was coached (stage 2) for each movement. This began with allowing the athlete to practise the movement following additional demonstrations and verbal feedback with an emphasis on highlighting her specific movement fault(s). For the 75% forward hop screen, showing the athlete video footage of her performance was also adopted as a coaching strategy. While the athlete was able to pass the forward lunge screen immediately following a demonstration and feedback on performance, the Romanian deadlift required the manipulation of environmental constraints to develop hip–spine disassociation. This was achieved initially by having the athlete perform the movement with both tibias directly in front of a training bench to prevent a “knee-dominant” strategy being accessed, whilst directing the athlete towards a “hip-dominant” pattern. Following additional practice, a dowel was held along the athlete’s spine to provide kinaesthetic feedback for spinal alignment and help the athlete maintain a neutral spine position. This strategy resulted in the athlete passing the Romanian deadlift screen. As the forward lunge and Romanian deadlift screen were passed following coaching, a lack of skill was the primary culprit for the failed screens and no further investigation was required. To reinforce the corrections for these patterns, frontal-plane control of the lower extremity and hip–spine disassociation were emphasised in the design of the dynamic warm-up for subsequent S&C sessions. Following a short period coaching the 75% forward hop screen, significant improvements in technique were not observed. As the movement faults were not corrected following practice, a contributing factor may be muscle strength. Weakness in the leg extensor muscles has been shown to be associated with stiffer landing strategies (Fisher et al., 2016). Additionally, when less knee flexion is present during landings, peak knee valgus angles may increase (Pollard et al., 2010). Physical capacity testing performed during the initial testing session had already revealed low levels of leg extensor strength during tests such as one repetition maximum (1RM) single-leg leg press (right = 0.89 kg/body mass; left = 0.85 kg/body mass) and countermovement jump (22 cm) when compared to normative data (Blagrove, 2015). Therefore, based on the findings of this investigatory process, it was hypothesised that diminished leg extensor strength was a primary driver for the movement fault. However, the contribution of mobility restrictions could not be excluded at this point. Further investigation was performed with the single-leg squat to establish whether the athlete had the capacity to access the required knee flexion during a less dynamic variant (stage 3). As the athlete also demonstrated sub-optimal technique for this movement, failing to flex the hip, knee and ankle joints whilst maintaining a neutral spine position, a mobility restriction was considered alongside insufficient strength levels. To direct the isolated assessments, a counterbalanced single-leg squat was performed to determine whether hip and knee flexion range of motion was sufficient. Using approximately 10% of the athlete’s body mass, the athlete was now able to squat beyond the acceptable depth (i.e. > 90°) whilst maintaining a neutral spine and controlling knee alignment in the frontal plane. As adequate hip and knee flexion range of motion was displayed during the counterbalanced single-leg squat, restricted ankle dorsiflexion range of motion relative to the movement demands was hypothesised. However, as counterbalanced squats reduce loading at the knee joint (Lynn and Noffal, 2012), muscle weakness could not be ruled out. Studies have shown that restrictions in ankle dorsiflexion range of motion negatively affect landing mechanics by reducing sagittal-plane knee joint displacement (Dowling et al., 2018; Howe et al., 2019) and increasing knee valgus (Malloy et al., 2015). To challenge the working hypothesis and assess ankle dorsiflexion range of motion, the modified weight-bearing lunge test was administered as an isolated assessment (Table 14.5). As the athlete demonstrated sufficient ankle dorsiflexion range of motion relative to the requirements of the movement (e.g. approximately 35°; Horan et al., 2014), ankle joint hypomobility was not believed to be the primary cause of the failed 75% forward hop screen. This process provided the following information: 1. The athlete had sufficient physical capacities to perform the squat, forward lunge, Romanian deadlift and countermovement jump exercises to an acceptable level. 2. Overhead lifting exercises would not be limited by mobility restrictions. 3. Sufficient mobility was present to perform lower-extremity strength exercises. 4. To improve single-leg landing mechanics, leg extensor strength would need to be prioritised. Conclusion Movement screening should be administered prior to designing a training programme so as to: (1) identify an athlete’s movement competency during patterns that will be loaded during the training of the athlete; and (2) determine injury risk. This should be performed formally, allowing coaches to document the training process with accurate data, evidencing the success and failures of the programme. In order to support the accurate collection of data, procedures should be standardised to ensure the methods used to screen a movement are reliable. This includes the use of a clearly defined and well-rationalised performance criterion to support the identification of movement faults. When movement faults are displayed during a screen, S&C coaches should systematically investigate the pattern to establish the potential causes of the error. This chapter presented a four-stage model that supports coaches in recognising the source of the movement fault, by determining the contribution movement skill and physical capacities have on the performance of the screen. This process begins by coaching the athlete on the movement. When an athlete passes the screen following coaching, a lack of skill is the cause of the fault. 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Range of motion The ROM performed during an exercise describes the displacement of an athlete’s body mass and/or the external load being lifted. When prescribing exercises for athletes, practitioners must focus not only on the ability of the athlete to perform the exercise, but teaching them to perform each exercise through a ROM that permits the safe/correct execution of the exercise that will ultimately elicit the desired training adaptations. There is little debate that performing an exercise with proper technique is more important than the weight that may be lifted; however, some athletes may sacrifice the ROM performed in order to “claim” that they lifted a heavier load. While this practice may only occur during “max-out” sessions, it should not be encouraged due to the training implications that may result from chronic use (e.g., training-to-failure mindset, developing poor technical habits, etc.). Instead, practitioners should promote the execution of exercises through the full ROM an athlete is able to perform, considering existing constraints such as the athlete’s safety, flexibility, anthropometrics, and previous injuries that may hinder performance. By promoting such a practice, it is more likely that athletes will develop good training habits and positive training adaptations (e.g., increased strength and power, decreased injury risk, and improved/maintained ROM at the involved joints). Squatting variations (e.g., back squat, front squat, goblet squat, etc.) are some of the most commonly prescribed exercises within resistance-training programs. Regardless of the variation, the method in which it is performed is often the subject of discussion when it comes to the desired ROM performed by athletes. Based on a practitioner’s coaching philosophy, he or she may desire that the athletes perform full squats, parallel squats, halfsquats, quarter-squats, or any combination of those previously listed. Certain squat depths may be considered by some to be “more positionspecific” or “safer”; however, the desired adaptations being sought may dictate the ROM performed. For example, previous research has indicated that training with deep squats produced greater increases in quadriceps muscle cross-sectional area, lower-extremity lean body mass, isometric knee extension strength, and jump height compared to shallow squats (Bloomquist et al., 2013). In addition, Hartmann et al. (2012) indicated that training with deep front and back squats elicited greater vertical jump adaptations compared to quarter-squats. However, the results of additional research have indicated that training with quarter-squats produced greater sprint speed adaptations compared to full squats (Rhea et al., 2016). Interestingly, Bazyler et al. (2014) indicated that a combination of both full ROM squats and partial squats may produce greater maximal strength and rapid force production characteristics than performing only full ROM squats. It is important to note that the ROM performed during an exercise may dictate the activation of specific musculature, the training adaptations elicited, or the specificity to a sport movement. Previous researchers have indicated that greater gluteus maximus activation occurs during deeper squats, but found no differences between partial, parallel, or deep squats in vastus medialis, vastus lateralis, or biceps femoris activation (Caterisano et al., 2002). Similarly, Gorsuch et al. (2013) displayed that greater activation of the rectus femoris and erector spinae muscles was produced during parallel squats compared to partial squats, but noted no differences in biceps femoris or lateral gastrocnemius activation between squat variations. The results of additional research also support these findings for the rectus femoris (Pereira et al., 2010). Moreover, Bryanton et al. (2012) suggested that greater relative muscular effort was produced at greater squat depths for both hip and knee extensors. Table 15.1 summarizes the effects squat depth has on load, muscle activation, joint loading, and transference to dynamic movements. Table 15.1 Potential training effects of partial and deep squat variations While practitioners may have their opinions on what ROM should be performed, the decision to increase or decrease the ROM performed may be justified if the athlete is returning from injury or within specific training periods where larger or smaller volume loads may be needed to elicit specific training adaptations. Kotani and Hori (2017) have recommended that athletes should perform deep squats during the majority of the training year. However, the authors also mentioned that shallow squats may be implemented to emphasize power output and rate of force development (RFD) if the preparation period exceeds 10 weeks. A further description of this approach will be discussed in Section 2 below. Grip and stance variation The grip or stance used during a given exercise may modify the training stimulus by changing the muscle activation patterns of the muscles being trained. For example, a wider grip during a bench press may increase the amount of activation of the sternoclavicular portion of the pectoralis major while decreasing the activation of the triceps brachii and anterior deltoid (Barnett et al., 1995; Lehman, 2005); however, such a grip may increase the risk of shoulder injuries. Similarly, a wider squat stance may increase the activation of the adductor muscles (McCaw and Melrose, 1999), while a wider deadlift stance may increase vastus medialis, vastus lateralis, and tibialis anterior activation (Escamilla et al., 2002). Whether referring to a bench press, squat, or deadlift variation, different activation patterns may alter the extent to which the musculature is activated, which may ultimately affect potential architectural or neuromuscular adaptations. This idea has been explored in greater detail in other literature, for the bench press (Green and Comfort, 2007) and pull-up/lateral pull-down (Leslie and Comfort, 2013) exercises. Another grip consideration that has been previously discussed is the use of the “hook grip” (Favre and Peterson, 2012). The hook grip is frequently used during traditional weightlifting movements (e.g. snatch, clean and jerk) and their derivatives (e.g. clean pull from the floor, hang power snatch, mid-thigh pull, etc.). The idea behind the hook grip is that by wrapping additional fingers around the thumb, athletes may prevent their grip from being a limiting factor when it comes to the weight that can be lifted for single and multiple repetitions. The findings of recent literature suggest that one repetition maximum (1RM) power clean, peak velocity, power, force, and catch height may all be improved by using the hook grip (Oranchuk et al., 2019). Mechanical demands of exercises Force–velocity characteristics The nature of each exercise partially determines the force–velocity characteristics that an athlete trains. For example, the back squat serves as a force-dominant exercise in which the primary goal is to develop muscular strength. In contrast, the jump squat is a velocity-dominant exercise that may be used to develop high-velocity characteristics. Cormie et al. (2010a) showed that relatively weak men may improve their athletic performance by training with either a strength or ballistic training emphasis. However, the authors also noted specific adaptations based on the type of training used (e.g., greater relative back squat strength adaptations with strength emphasis training and greater sprint speed adaptations with ballistic emphasis). While it is important to emphasize high-force movements or high-velocity movements during certain periods of the training year, the use of combined loading has previously been recommended where athletes train and develop both the force and velocity sides of their force–velocity profile, albeit with an emphasis on one aspect (Haff and Nimphius, 2012). Training in such a manner may ultimately lead to favorable adaptations in RFD and power (Cormie et al., 2007). A recent review discussed how this method of training can be implemented using a sequenced progression of weightlifting derivatives (Suchomel et al., 2017) (Also see Chapter 16.) Assessments which may indicate whether force production or movement velocity should be emphasized are explored in Chapters 10 and 11. Stretch-shortening cycle The inclusion/exclusion of the stretch-shortening cycle (SSC) within a movement may impact the training stimulus an athlete receives. The SSC may allow for the activation of the stretch reflex, optimization of length– tension muscle factors, optimization of muscle activation, and the concentric muscle action beginning at a higher force output (Komi, 1986, 2000; Aagaard et al., 2000; Cormie et al., 2010b). By using the SSC, an athlete may produce greater magnitudes and rates of force production, potentially allowing for heavier loads to be lifted and a given load being lifted at a higher velocity. In contrast, movements that exclude the SSC may require unique neuromuscular demands. For example, an exercise performed using a static start position may require a greater RFD compared to a movement that includes the SSC because an athlete must overcome the inertia of the training load from a dead-stop position compared to having developed a given magnitude of force previously. Such observations have been reported for weightlifting derivatives (Comfort et al., 2011a, 2011b). The inclusion/exclusion of the SSC may place varying demands on athletes (Meechan et al., 2020a, 2020b), with an increased eccentric demand when utilizing the SSC, due to the braking phase that is required and thus, practitioners should consider each athlete’s sport/event when programming exercises to allow for maximum transfer of training. Load placement The placement of load during different exercise variations (e.g., front squat vs. back squat) may modify the activation of specific musculature. One study indicated that the front squat produced greater vastus lateralis activation during the ascending phase and entire movement, while the back squat produced greater semitendinosus activation during the ascending phase (Yavuz et al., 2015). In contrast, two other studies reported no differences in muscle activation between the front squat and back squat (Gullett et al., 2009; Yavuz et al., 2015; Contreras et al., 2016a). Additional research demonstrated that greater peak force, velocity, and power were achieved using a hexagonal bar deadlift compared to a traditional deadlift (Swinton et al., 2011). While the previous example includes exercises that are typically used for strength development, similar results have been shown with ballistic jumping movements. The acute kinetic and kinematic differences between the jump squat and hexagonal bar jump indicate that greater force, RFD, and jump heights are achieved during the hexagonal bar jump, across several different loads (Swinton et al., 2012). In both studies, Swinton et al. (2011, 2012) noted that the differences displayed may have been due to more favorable moment arms based on the load being closer to the lifter’s center of mass, ultimately allowing for more efficient vertical force production. A more recent study expanded upon previous literature and compared both the jump squat and hexagonal bar jump with the jump shrug exercise (Suchomel et al., 2019). Suchomel et al. (2019) supported the findings that the hexagonal bar jump produced a greater training stimulus compared to the jump squat, but also concluded that the jump shrug produced superior kinetic magnitudes compared to the jump squat as well. Furthermore, although no differences existed between the hexagonal bar jump and jump shrug, it was concluded that the exercises may best serve the athlete as strength-speed (moderate-high-load power) and speedstrength (low-moderate-load power) movements, respectively. Force production vectors Muscular strength has been defined as the ability to produce force against an external resistance; however, when it comes to exercise selection, the direction in which the force is produced may alter an athlete’s training outcomes. Previous research has examined the effects of training with exercises that emphasize more vertical force vectors compared to horizontal (Contreras et al., 2016b) or unilateral–multidirectional (Gonzalo-Skok et al., 2017). Contreras et al. (2016b) indicated that adolescent rugby and rowing athletes who trained with either the front squat or barbell hip thrust for 6 weeks demonstrated greater improvements in the vertical jump and horizontal jump and 10- and 20-m sprint times, respectively. Similarly, Gonzalo-Skok et al. (2017) indicated that amateur/semi-professional teamsport athletes who trained with squats produced greater improvements in unilateral and bilateral vertical jumps and 25-m sprints compared to those who trained with unilateral–multidirectional versapulley. In addition, those who trained using the versapulley demonstrated greater improvements in lateral and horizontal jumps and change-of-direction tasks. It should be noted, however, that the results of Jarvis et al. (2019) contradict the previous findings as the authors concluded that training with barbell hip thrusts did not enhance 10-, 20-, 30-, or 40-m sprint times. Similar findings were displayed by Fitzpatrick et al. (2019), who showed that despite improvements in 3RM hip thrust, there were no differences in the magnitude of improvement between vertical and horizontal jumping. The authors of the latter study suggested that the force-vector theory may be flawed based on mechanical inconsistencies. Instead, the authors suggested using dynamic correspondence as the method of exercise selection. Thus, it is important that practitioners understand the orientation of the athlete when they are generating force (Figure 15.1). Considering the above results, practitioners may also note that the application of force during various exercises may produce specific adaptations. DeWeese et al. (2016) discussed this idea regarding resistance training practices for developing sprint speed. Ground reaction forces (orange arrow) and local coordinate frames (blue arrows) during a sprint acceleration. Ballistic and non-ballistic exercises The nature of the exercise(s) performed may result in a different training stimulus experienced by the athlete based on the intent of the movement. As noted in Chapter 2, this may include modifications in the force–velocity characteristics of the exercise. The results of previous work by Lake et al. (2012) and Suchomel et al. (2018), as well as Newton et al. (1996), have highlighted the differences between lower- and upper-body exercises performed in a ballistic manner (i.e., acceleration throughout the entire movement) and exercises performed quickly (i.e., intentionally fast with a negative acceleration at the end of the movement), respectively. Taken together, the results of these studies indicate that exercises performed in a ballistic manner produced greater force, velocity, power, and muscle activation compared to the same exercises performed quickly. Practitioners may choose from a variety of ballistic exercises that may provide an effective training stimulus. Regarding the development of lowerbody explosive strength, the exercises that first come to mind may be the weightlifting movements and their derivatives due to their ability to improve force–velocity characteristics to a greater extent compared to other training methods (Tricoli et al., 2005; Channell and Barfield, 2008; Arabatzi and Kellis, 2012; Otto III et al., 2012; Chaouachi et al., 2014;Teo et al., 2016). This is likely due to movement specificity, but also the ability to accelerate a moderate-heavy load in a jumping movement with ballistic intent. Greater detail on how practitioners can use weightlifting movements to enhance sport performance will be covered in Chapter 16. While weightlifting movements provide an effective ballistic training stimulus, it should be noted that exercises like the jump squat (Cormie et al., 2010a), hexagonal bar jump (Swinton et al., 2012; Suchomel et al., 2019), kettlebell swing (Lake and Lauder, 2012), and ballistic squat can also provide an effective training stimulus for the improvement of lower-body explosive strength. Practitioners may be more limited with their exercise selection regarding ballistic upper-body exercises. Typical upper-body ballistic exercises may include the bench press throw, plyometric push-up, and medicine ball throw. Newton et al. (1996) indicated that a ballistic bench press throw may produce greater force, power, and muscle activation compared to a bench press performed quickly. The extent of these differences can be explained by the velocity of the movement throughout its completion. The results of the previous study indicated that the ballistic bench press throw was accelerated throughout the entire movement whereas the traditional bench press resulted in deceleration at the end of the movement (~45% of the ROM). Taking these results into account, the traditional bench press may serve as more of a foundational exercise to develop strength, while the bench press throw may be used to develop RFD and power characteristics (Soriano et al., 2017). Similarly, Vossen et al. (2000) indicated that plyometric push-ups result in greater improvements in strength and power compared to traditional push-ups. The ability of ballistic exercises to improve a strength/power training stimulus is well documented. An additional benefit of ballistic exercises may be their ability to be used as a potentiation stimulus, as noted by Maloney et al. (2014). Previous researchers indicated that ballistic concentric-only half-squats produced a larger and faster potentiation effect compared to those performed in a non-ballistic manner (Suchomel et al., 2016c, 2016d). This may be due to the ability of ballistic exercises to recruit high-threshold motor units (van Cutsem et al., 1998), which display greater potentiation compared to smaller, lower-threshold motor units (Hamada et al., 2000). Rest intervals Inter-set rest intervals It has previously been suggested that rest intervals as short as 30 seconds (Sheppard and Triplett, 2016) or 1 minute (Kraemer et al., 2002) may be used to stimulate adaptations in muscle hypertrophy. While a greater metabolic demand may be present following high-volume exercise sets (Gorostiaga et al., 2010, 2012), an athlete’s ability to recover during a short rest interval is limited and thus, their capacity to tolerate the same loads or heavier loads becomes diminished as the number of sets increases (Buresh et al., 2009; de Salles et al., 2009). This is likely due to decreased adenosine triphosphate (ATP), phosphocreatine (PCr), and glycogen concentrations as well as increases in hydrogen concentrations due to repetitive high-volume sets (Gorostiaga et al., 2010, 2012). Despite previous recommendations, additional research findings indicate that longer rest intervals (1.5–3 minutes) may produce superior muscle hypertrophy and strength adaptations compared to shorter inter-set rest intervals (0.5–1 minute) (Robinson et al., 1995; Schoenfeld et al., 2016; Longo et al., 2020). This may be due to several factors (e.g., neural, metabolic, etc.); however, one must consider not only the quantity of work, but the quality of work. For example, researchers indicated that subjects were unable to complete four sets of ten repetitions during the back squat with 70% 1RM and 2 minutes of inter-set rest (Oliver et al., 2016). In response to the failed sets, the authors noted that they decreased the load performed within the remaining sets, which likely decreased the overload placed on the athlete. Longer inter-set rest periods may allow for athletes to replenish their ATP stores and lessen the metabolic fatigue experienced to a greater extent prior to a subsequent set compared to shorter rest periods. Ultimately, this may lead to a higher quality and volume of work performed through the continued use of the prescribed loads, and possible increased loads, during all sets, potentially leading to greater physiological adaptations (e.g., work capacity and muscle cross-sectional area) (Longo et al., 2020). Collectively, it appears that while shorter rest intervals have the potential to produce a hypertrophic response, peak adaptations in trained individuals may be limited due to the loads/volume that may be maintained over multiple exercise sets. Moreover, if the ultimate goal is to increase the muscular power of the athlete, training with shorter rest intervals may result in an endurance effect, which may interfere with long-term hypertrophy adaptations (Baar, 2006; Hawley, 2009). It should be noted that if practitioners are concerned with the increase in the overall training time associated with longer inter-set rest intervals, they may consider short rest intervals within a set to split up and maintain the work performed. Such an approach to training, termed cluster set training (Haff et al., 2008), will be briefly discussed below and covered in greater detail in Chapter 13. Much of the existing evidence suggests that longer rest intervals may produce superior adaptations in muscular strength and power. Robinson et al. (1995) indicated that longer rest intervals (1.5–3.0 minutes) produced greater strength and power adaptations during a high-volume program. Additional researchers have indicated that longer rest intervals (2.5–5.0 minutes) resulted in a greater volume of work performed during a workout (Willardson and Burkett, 2005, 2008), greater ability to train with heavier loads (Willardson and Burkett, 2006), and greater strength increases (Robinson et al., 1995; Pincivero et al., 1997; de Salles et al., 2010) compared to shorter rest intervals (0.5–2.0 minutes). While another study indicated that no statistical differences in strength gains were found between 2- and 4-minute rest intervals (Willardson and Burkett, 2008), those who trained using longer rest intervals produced a larger practical effect compared to those who trained with shorter rest intervals (i.e., Cohen’s d = 2.96, very large vs. d = 1.96, large) (Hopkins, 2014). The discussed research is in line with previous rest interval recommendations for improving muscular strength and power (i.e., 2–5 minutes) (Kraemer et al., 2002; de Salles et al., 2009; Sheppard and Triplett, 2016). It should be noted that the range in rest interval length may exist due to the training age (Willardson and Burkett, 2008), fiber-type composition of the athletes, and the loads implemented in training. Rest interval recommendations are summarized in Table 15.2. Table 15.2 Rest interval length to achieve specific training goals Training goal Rest interval length Hypertrophy 1.5–3 minutes Strength 2–5 minutes Power 2–5 minutes Note: Rest interval length may vary based on the type of exercise, load, repetition scheme, and training status of the athlete. Intra-set/inter-repetition rest intervals A growing body of literature has been published regarding inter-repetition rest within a set of exercise. Specifically, researchers have examined the effect that cluster sets (Haff et al., 2008) have on kinetic, kinematic, and technique characteristics during various repetition schemes. A cluster set may be defined as a traditional exercise set that is split into smaller sets of repetitions (i.e., clusters) that are separated by rest intervals. One of the first studies examining cluster sets investigated the effect of various set configurations (i.e., traditional, undulating, and cluster) on clean pull performance (Haff et al., 2003). The results indicated that a cluster set configuration may result in greater barbell velocity and displacement and power-generating capacity across an entire set. A similar series of studies examined the effect of rest interval length between repetitions within several sets on various power clean performance variables (Hardee et al., 2012a, 2012b, 2013). Collectively, the results indicated that cluster set configurations using 20–40 seconds of rest between repetitions allowed subjects to maintain power output and technique and lower their perceived exertion. Researchers have also examined the effect of cluster set configurations on higher repetition sets that focus on muscle hypertrophy. In a series of studies, researchers reported that high repetition sets with inter-repetition rest resulted in greater increases in strength and power, while producing similar increases in lean body mass (Oliver et al., 2013), greater total volume load and power, similar anabolic hormonal response, decreased metabolic stress (Oliver et al., 2015), and maintenance of force, velocity, and power (Oliver et al., 2016) compared to traditional sets. It is important that practitioners note the amount of total training time required if certain rest intervals are implemented within cluster set configurations. For example, researchers noted that performing six two-repetition clusters for a set of 12 total repetitions may take longer than performing three fourrepetition clusters (Tufano et al., 2016). Smaller clusters require a longer training time due to the increased amount of rest taken within a set. From a practical standpoint, using antagonistic supersets (e.g., bench press and bent-over row) may be an efficient method of performing cluster sets, where the second exercises of the superset are performed during the rest period for the previous exercise. It should be noted that a paucity of research exists on antagonistic supersets. Considering that some sport governing bodies set strict guidelines on the amount of time for team activities, it is important for practitioners interested in using cluster sets to choose cluster set configurations that are both time-efficient and effective at managing fatigue. For a more thorough discussion on the theoretical and practical applications of cluster sets, readers are directed to Chapter 13. Cluster set rest interval recommendations are summarized in Table 15.3. Table 15.3 Cluster set rest interval length to achieve specific training goals Training goal Rest interval length Hypertrophy 5–15 seconds Strength 20–25 seconds Power 30–40 seconds Adapted from Tufano et al. (2017). Potentiation complex rest intervals While the previously discussed rest intervals may be specific to traditional resistance-training exercises, unique rest intervals may exist when implementing potentiation complexes. A number of factors may affect the magnitude of potentiation expressed (Tillin and Bishop, 2009; Suchomel et al., 2016a). However, a portion of the existing potentiation literature has focused on examining the effect that various rest intervals have on the magnitude of potentiation expressed. Following a potentiating stimulus, both a state of fatigue and potentiation exist (Rassier and Macintosh, 2000; Sale, 2002; Fowles and Green, 2003; Hodgson et al., 2005). The interplay between fatigue and potentiation may be acutely modeled on the fitness– fatigue paradigm (Zatsiorsky, 1995), where the subsequent performance is the result of the interaction between fatigue and the fitness after-effects that are the result of an exercise stimulus. While meta-analyses indicated that rest intervals ranging between 3–7 minutes, 7–10 minutes (Wilson et al., 2013), and 8–12 minutes (Gouvêa et al., 2013) produced positive moderate practical effects, additional literature indicated that the type, intensity, and duration of the exercise may determine whether fatigue or potentiation is dominant over the other (Masiulis et al., 2007). Thus, it should come as no surprise that certain protocols may produce positive moderate practical effects as early as 2 minutes post-stimulus (Suchomel et al., 2016c) or as late as 15 or 20 minutes post-stimulus (Gilbert and Lees, 2005). Therefore, practitioners should consider that each individual potentiation complex possesses unique characteristics and may therefore have its own “optimal” rest interval. Another factor that may affect the rest interval during various potentiation complexes is the relative strength of the individuals completing the protocol. The results of previous literature have indicated that strong relationships exist between an individual’s relative strength and the magnitude of potentiation expressed (Seitz et al., 2014; Suchomel et al., 2016b, 2016d). This idea is supported by the notion that stronger individuals may be able to tolerate a more fatiguing protocol given their frequent exposure to high-intensity loading during training (Stone et al., 2008). Moreover, researchers have noted that stronger individuals potentiate earlier and to a greater extent compared to weaker individuals (Jo et al., 2010; Seitz et al., 2014; Suchomel et al., 2016d). Thus, when designing potentiation complexes for athletes, practitioners should ensure that they take the athlete’s relative strength into account. It should be noted that researchers have recently attempted to distinguish the differences between post-activation potentiation (PAP) and post-activation performance enhancement (PAPE) (Blazevich and Babault, 2019); however, further research is needed to determine if these characteristics are truly distinct from one another. SECTION 2 Practical applications Modifications for appropriate exercise performance Appropriate modifications/alternatives may need to be made in order for an athlete to safely perform a specific exercise or receive a given training stimulus. Whether it may be inexperience with an exercise or a lack of quality coaching, some athletes have difficulty performing certain exercises. Thus, it is important to provide athletes with consistent coaching modifications to help them learn and/or improve their technique in order to perform exercises correctly. Previous recommendations were made to maximize leg muscle activation and minimize the risk of injury during the back squat (Comfort et al., 2018). Briefly, an athlete’s feet should be wider than shoulder-width apart with a natural foot position (Ninos et al., 1997; McCaw and Melrose, 1999), unrestricted movement of the knees while the heels maintain contact with the floor (Fry et al., 2003), a forward or upward gaze (Donnelly et al., 2006), and full ROM (115–125° of knee flexion) (Ninos et al., 1997; Caterisano et al., 2002), as long as the athlete is able to maintain a lordotic curve/neutral spine. Some athletes may have difficulty reaching the desired squat depth due to several potential issues (e.g., inexperience, stance, lack of flexibility, balance, etc.). Some common methods to implement that may help athletes achieve the desired squat depth may be to modify their stance width and/or rotating their toes out (i.e., hip external rotation). These modifications will open up the hip joints and allow for greater displacement of the athlete’s body. While the above provides one example, additional technique recommendations have been made for the bench press (Green and Comfort, 2007) and pull-up/lateral pull-down (Leslie and Comfort, 2013) exercises. Footwear While some athletes may be able to effectively squat to the desired depth by adjusting their stance width or turning their toes out, a pre-existing anatomical limitation or lack of flexibility within the ankle may still prevent an athlete from performing a good squat. An additional consideration may be to slightly elevate the heels of athletes in order to lessen the effect that this limitation has on their squat performance. This may be accomplished by placing small weights under an athlete’s heels or by purchasing weightlifting shoes. The results of previous research have indicated that weightlifting shoes may allow for a greater squat depth, an upright torso, and greater stability to be achieved (Hughes and Prescott, 2015; Legg et al., 2017). Further work has suggested that weightlifting shoes may reduce the forward trunk lean of individuals, reducing potential shear stress in the spine, and also increase knee extensor muscle activation compared to running shoes (Sato et al., 2012). While the addition of weightlifting shoes will not inherently fix poor squat technique, the resulting acute changes in technique may lead to chronic improvements in strength and potential reductions in injuries. Weightlifting movements The weightlifting movements (i.e., snatch and clean and jerk) and their derivatives are popular exercises within resistance-training programs. However, they are often described as technically complex movements that are difficult to teach and for athletes to learn. Practitioners may find that some of their athletes may have difficulty learning an aspect of a full weightlifting movement (e.g., performing the first pull to the knee, transitioning to the second pull starting position, properly executing the catch phase, etc.). While this may deter some practitioners from prescribing weightlifting movements within their athletes’ training programs, it should be noted that a number of derivatives exist that serve as effective substitutes (Suchomel et al., 2017). Scenarios that a practitioner may face when it comes to choosing an alternative weightlifting movement are displayed in Figures 15.2 and 15.3. Scenario requiring weightlifting alternatives for the snatch: (a) range of motion must be reduced and the bar raised for the start of the lift; (b) if planning to use a catching variation in subsequent phases a catching variation at 80–95% 1RM may be advantageous to reinforce technique; (c) if the athlete cannot catch (e.g. due to injury or limited range of motion) and/or higher loads (≥100% 1RM power snatch) are desired pulling derivatives may be advantageous. Scenario requiring weightlifting alternatives for the hang power clean. Unilateral training alternatives Although the back squat exercise is a popular choice for lower-extremity strength development, it is not without its limitations. As mentioned above, it is possible that the back squat may result in a greater forward lean compared to the front squat. Moreover, this may result in greater shear forces in the spine experienced by athletes. While proper technique modifications with the potential assistance of weightlifting shoes may mediate these issues, practitioners should also note that unilateral exercises, such as the rear-foot elevated split squat, may serve as effective exercise alternatives. While some research findings have indicated that unilateral training results in similar improvements in strength and power adaptations (McCurdy et al., 2005) as well as sprint speed and agility (Speirs et al., 2016), additional research has shown similar improvements in sprint performance between unilateral and bilateral training, but greater improvements in change-of-direction performance following bilateral training (Appleby et al., 2020). Further research findings indicate that a modified split squat resulted in greater gluteus medius, hamstring, and quadriceps activation compared to a bilateral squat (McCurdy et al., 2010). These authors also noted that the modified split squat also maintained a more upright torso, which may potentially decrease shear force stress in an athlete’s lower back. This notion is supported by large effect size differences in left and right erector spinae activation between the rear-foot elevated split squat and back squat exercise (Bellon et al., 2013). Collectively, the evidence indicates that unilateral exercises may be suitable alternatives for practitioners to prescribe (Appleby et al., 2019), especially if an athlete is hampered by lower-back pain. However, it should be noted that unilateral exercises may be best implemented as assistance exercises to bilateral movements (Ramirez-Campillo et al., 2018). This conclusion is based on the physiological stimulus that bilateral exercises can provide (Appleby et al., 2020), but also the decreased stability that is characteristic of unilateral exercises. Cueing and feedback Sport and strength and conditioning coaches traditionally have their own methods of cueing and providing feedback to athletes. While this is done to get athletes to perform an exercise or task in a certain manner, practitioners should note that how they provide cues and feedback may have a profound effect on the training stimulus that athletes receive. Cueing Previous work by Wulf (2007) indicates that cues and feedback that are external (i.e., athlete focuses on movement effect) are much more effective than those that are internal (i.e., athlete focuses on his or her body movements) when it comes to how motor skills are performed, learned, and retained. In a recent review, the authors discussed instructions and cues for improving sprint performance echoed these sentiments, suggesting that cueing should provide an external focus for the athlete (Benz et al., 2016). The authors suggested that coaches should consider providing external and/or neutral cues at 100% frequency while keeping the quantity of instructions low. A similar strategy may be applied when cueing athletes in the weight room. For example, if an athlete is performing an overhead press and the training emphasis is speed-strength, an appropriate external cue may be: “Make the bar rattle at the top,” compared to an internal cue of: “Contract your arms faster to push the weight.” From the athlete’s perspective, the external cue gives them the goal based on a sound that would indicate that they moved the weight quickly. As athletes become more experienced, smaller cueing phrases may be used. At this point, an athlete and their coach understand what a specific cue means for them compared to another athlete. A common cue used in the weight room that can be applied to many scenarios is: “Stay tight!” As previously mentioned, this cue may be sufficient for a more experienced athlete; however, it may also mean something different to two different athletes. It is recommended that practitioners apply an external focus strategy when it comes to cueing exercises, keeping in mind that the amount of information provided should be concise and specific to each athlete. Coaching instruction and cueing are discussed further in Chapter 20. Feedback Like coaching cues, research findings support the use of providing external feedback to athletes as opposed to internal feedback. Coaches can provide feedback in a variety of ways, including audio (e.g., verbal discussions), visual (e.g., video analysis and/or demonstrations), and quantitative (e.g., data display). Previous research has demonstrated that augmented feedback (included coaching and two-dimensional video analysis) resulted in greater kinetic and kinematic adaptations during the power snatch exercise compared to a control group (Winchester et al., 2009). While this method was effective, another study examined the use of the method of amplification of error (MAE) and how it affected snatch performance compared to traditional coaching feedback (Milanese et al., 2017). Briefly, MAE allows athletes to learn to correct their movements by understanding how to perform the movement incorrectly. The authors indicated that the MAE group produced greater kinematic improvements of snatch technique compared to direct instruction only. Finally, a practical example of quantitative feedback may be through the use of velocity-based training (Mann et al., 2015). In order to achieve a specific velocity during training, the athlete may need to be provided with immediate velocity feedback. Using current technologies, an athlete may see the velocity they produced and adjust the weight accordingly in order to meet the goal of that training session. The amount of feedback given to an athlete may be based on their training age. However, practitioners should be cautious as to how much feedback is provided at any given time. Athletes may not be able to receive multiple pieces of information and perform an exercise effectively, especially if feedback is provided after every repetition. In order to effectively provide feedback to an athlete, practitioners should choose one point of emphasis that an athlete can work on during subsequent training sets. Practitioners should focus on the most important aspect that is hindering appropriate exercise performance before fine-tuning technique with smaller corrections. This is especially true if an athlete is putting themselves at risk for injury. Range-of-motion specificity example While practitioners may have their opinions on what ROM should be performed (full or partial), the decision to increase or decrease the ROM may be justified if the athlete is returning from injury or training within specific training periods when larger or smaller volume loads may be needed to elicit specific training adaptations. The most obvious instance would include an athlete’s return from an injury. In this situation, practitioners may not be as focused on improvements that will transfer to the athlete’s sport/event, but instead may be focused on having the athlete regain the competency of an exercise using a reduced ROM. Some of this training may be dictated by the sports medicine staff; however, strength and conditioning practitioners should be aware and involved in some capacity as well. Ultimately, once an athlete again achieves the desired ROM during a given exercise, strength and conditioning practitioners may take over and transition the athlete into a return to fitness phase. While the above scenario certainly occurs, it should be noted that it may be practical to reduce the ROM of a given exercise during certain times of the training year in order to maintain certain abilities or reach peak adaptations. For example, it may be preferable during certain times of year to perform half-squats or quarter-squats in order to dissipate any accumulated fatigue and peak for a certain event. If a practitioner is working with a sprinter, reducing the ROM of the work sets may be advantageous from multiple aspects. For example, it may be practical to progress a sprinter from performing full squats and adding in half-squats and quarter-squats during certain phases of training (Bazyler et al., 2014). Using a progression may not only reduce an athlete’s neuromuscular fatigue due to less eccentric work performed, but partial squats may also increase the mechanical specificity of their training for maximum velocity. This notion is supported by recent research that indicated that training with quarter-squats resulted in greater improvements in 40-yard sprint time and vertical jump height compared to training with full and half-squats (Rhea et al., 2016). However, it should be noted that additional literature has suggested that the complete removal of full-ROM squats in trained individuals may result in a plateau and possible reductions in 1RM strength (Harris et al., 2000; Painter et al., 2012). Thus, practitioners should consider prescribing a combination of both full and partial ROM squats in order to improve/maintain overall and angle-specific strength. Summary While there are several factors that a practitioner must consider when prescribing resistance-training exercises to their athletes, each individual factor should not be overlooked. Exercise technique considerations such as the ROM performed and the grip/stance used may alter the training stimulus for athletes. In addition, practitioners must consider mechanical demands of each exercise, including their force–velocity characteristics, the inclusion/exclusion of the SSC, load placement, direction in which the force is produced, and ballistic/non-ballistic nature. Finally, the rest intervals used, whether they are inter-set, intra-set, or within potentiation complexes, should be specific to the characteristics that are being developed within each phase of training. From a practical standpoint, practitioners should implement appropriate modifications to exercises in order to provide an effective training stimulus for their athletes. 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Suchomel and Paul Comfort DOI: 10.4324/9781003044734-20 SECTION 2 The effectiveness of weightlifting movements The term ‘weightlifting’ refers to the sport in which competitors perform the snatch and the clean and jerk, attempting to lift the maximum amount of weight. Weightlifting in this sense is different from the general term ‘resistance training’, which refers to all other forms of training in which an individual is moving against a resistive load. However, weightlifting movements (i.e. snatch, clean and jerk) and their derivatives may also be used within resistance-training programmes in order to train the strength and power characteristics of athletes who are not competing in the sport of weightlifting. While both weightlifting and other forms of resistance training may improve an athlete’s lower-body strength and power, research suggests that weightlifting movements and their derivatives may provide superior training effects compared to other methods (Hoffman et al., 2004; Tricoli et al., 2005; Channell and Barfield, 2008; Arabatzi and Kellis, 2012; Otto III et al., 2012; Chaouachi et al., 2014; Teo et al., 2016). These findings are attributed to two primary reasons: movement specificity and the overload that the athlete can be subjected to. Movement specificity The most common movement in sports is the coordinated extension of the hip, knee and ankle joints (plantar flexion), termed ‘triple extension’. Jumping, sprinting and change-of-direction tasks require the completion of the triple extension movement. A similar coordinated triple extension movement takes place during the second pull phase of weightlifting movements (see the section ‘Weightlifting technique’, below), which allows these movements to transfer to sports performance. Due to the similarities between the triple extension of sports movements and the second pull of weightlifting movements, it should come as no surprise that better performance of weightlifting movements is related to better performance during sprinting and jumping (Carlock et al., 2004; Hori et al., 2008). Overload Weightlifting exercises are coordinated movements in which an athlete moves a moderate-heavy load with ballistic intent. While other resistancetraining methods may be used to train lower-body strength and power (e.g. free weights, plyometrics, kettlebells, etc.), these methods are typically not performed in the same manner as weightlifting movements. For example, training with the back squat may produce high forces but with less velocity, whereas plyometric exercise may produce high velocities but with less force. This is supported by previous literature that has demonstrated that the power outputs of the snatch, clean and jerk were superior to core exercises (primary compound exercises) such as the squat and deadlift (Garhammer, 1980, 1991). Additional literature indicated that standard resistance-training exercises (e.g. bench press, squat, etc.) result in reduced force production (i.e. deceleration) during as much as 45% of the range of motion. Weightlifting technique During the snatch in a weightlifting competition, the lifter must lift the barbell from the floor to an overhead position, receiving the weight with the arms fully extended, in one continuous motion. The clean is characterised by lifting the barbell from the floor to a resting position across the front of the lifter’s shoulders. As a continuation of the clean, the jerk is completed by lifting the barbell from the shoulders to an overhead position, receiving the weight with the arms fully extended. The technique of each lift is described below. Snatch/clean first pull The first pull refers to the initial movement of the barbell from the floor to a position just above the knee. The starting position of each athlete will be based on their anthropometric characteristics such as their height, body mass and somatotype as well as their range of motion and flexibility. Athletes should position themselves so that they are centred on the bar with their feet flat and positioned about hip-width apart and the barbell positioned over the middle of their feet. The recommended grip to use with weightlifting movements is the hook grip as this increases grip strength (Figure 16.1). Whether performing a clean or snatch variation, the hands may be positioned more closely together or further apart, respectively. While the appropriate distance between the hands will vary based on an individual’s anthropometrics, an easy method to determine this distance involves placing the individual in a position where the second pull of the snatch or clean starts (i.e. mid-thigh/power position) (Figure 16.2). From here, the hands may be narrowed or spread further apart to ensure the proper second pull position. The elbows should be pointed outward to prevent excess elbow flexion that may hinder the transfer of force to the barbell. The barbell should almost be in contact with the athlete’s lower leg, their knees should be in line with their feet and their hips should be slightly higher than their knees. The position of the upper body should include extended arms, shoulders in front of the bar, an elevated chest, shoulder blades pulled back and a slightly arched (natural curve) or flat back. Finally, the athlete’s head should be neutral with the eyes looking forward (Figure 16.3). Hook grip – (a) thumb wraps under the bar with (b) the fingers wrapped around the thumb and bar. Clean (top) and snatch (bottom) grip spacing. Starting position for (left) the snatch and (right) clean. After reaching the correct starting position, athletes should inhale to increase their intra-abdominal pressure and remove any slack that may still exist within their arms. The athlete should then begin the lift by pushing into the ground through the centre of their feet while elevating their hips and shoulders at the same rate and maintaining the angle of their back, shoulders over the barbell, and fully extended arms. While elevating the barbell, the knees move backward while the lower legs reach a near-vertical position, resulting in a shift of the centre of pressure from the mid-foot to the heels (Figure 16.4). The end of the first pull for (left) the snatch and (right) clean. Snatch/clean transition The transition phase refers to the movement of the barbell from a position just above the knee to the mid-thigh ‘power’ position in preparation for the second pull. An effective transition phase requires the athlete to re-bend the knees to a position in front of the barbell as it moves from the knee to the mid-thigh, shifting the centre of pressure from the heels to the mid-foot. The athlete’s hips should move over the ankles, resulting in a vertical torso, extended arms and knees bent to approximately 125–145° (Figure 16.5). Mid-thigh position side view for (left) the snatch and (right) clean. Snatch/clean second pull Upon reaching the mid-thigh position, athletes perform the second pull movement by pushing into the ground and rapidly extending their hips, knees and ankles (plantar flexion) and shrugging their shoulders (Figure 16.6). This movement causes the barbell to rise vertically and results in the greatest force, rate of force development (RFD), velocity and power (Enoka, 1979; Garhammer, 1980, 1982). Athletes should keep their arms extended for as long as possible during the second pull to ensure maximum force transfer to the barbell. However, the athlete’s arms will bend due to the upward momentum of the barbell and the failure to elevate the torso any higher. It should be noted that while the second pull results in the completion of certain weightlifting derivatives (see the section ‘Weightlifting derivatives’, below), others require the athlete to catch or receive the weight. Second pull of (left) the snatch and (right) clean. Snatch/clean catch Following the second pull, a snatch variation requires the athlete to rotate the hands and elbows around the barbell, moving from a vertical position above the barbell into a position below the barbell. Simultaneously, the athlete will flex the hips, knees and ankles (dorsiflexion), drop and pull themselves into an overhead squat position while their feet may move slightly outward to a more stable position. The athlete should receive the barbell in an overhead squat position with their elbows locked out whilst at the same time their feet land flat on the ground in the desired squat depth while maintaining an upright torso and normal lumbar curve (Figure 16.7). Catch position of the snatch (left) and clean (right). (Modified from DeWeese et al., 2014.) A clean variation requires the athlete to rotate the elbows around the barbell from a position above the barbell into a horizontal position in front of the barbell. The athlete will flex their hips, knees and ankles (dorsiflexion), drop and pull themselves into a front squat position while their feet may move slightly outward to a more stable position. The athlete should receive the barbell in a front squat position on the front of their shoulders with their elbows pointed forward, their upper arm nearly parallel with the ground and a relaxed grip, while at the same time their feet land flat on the ground in the desired squat depth while maintaining an upright torso and normal lumbar curve (Figure 16.7). Figure 16.8 displays a power clean and power snatch catch variation. Power snatch (left) and power clean (right) catch positions. Snatch/clean recovery After becoming stable in the desired squat depth for snatch and clean variations, the recovery phase requires the athlete to return to a standing position maintaining the overhead or front squat position (Figure 16.9). The athlete should maintain an upright torso while extending the hips and knees to return to a standing position. Recovery position for the snatch (left) and clean (right). Jerk starting position As a continuation of the clean exercise, or from a rack or training blocks, the athlete should start in standing position with the feet approximately shoulder-width apart, an upright torso and the barbell racked across the front of their shoulders with their upper arms nearly parallel to the floor. The athlete’s eyes should be forward and their chin tucked (Figure 16.10). An alternative variation would allow the athletes to start with the barbell resting on their upper back, similar to a back squat. Starting position for a jerk variation. Jerk dip Before the athlete begins the lift, the athlete should take a deep breath in order to elevate the rib cage, brace the other trunk musculature and create intra-abdominal pressure. Following the breath, the athlete will simultaneously flex their hip and knee joints and descend to a quarter-squat position where the knees are flexed to approximately 125–145° (Figure 16.11). While slightly shifting backwards during the dip, the athlete’s weight should be distributed between their mid-foot and heels. As the athlete descends, they should keep their elbows elevated to prevent the barbell from moving away from their centre of mass. This common error may result in the athlete pushing the barbell more forward rather than vertically during the drive phase. In addition, it is important to maintain the centre of pressure through the mid-foot to heel. The dip phase should be completed rapidly without pausing in the bottom position in order to receive the greatest stretch-shortening cycle benefits (i.e. greater use of stored elastic energy and less force dissipation). Completion of the dip phase of the jerk. Jerk drive Upon reaching the bottom of the dip phase, the athlete should immediately, without pausing, rapidly extend the hip, knee and ankle joints in order to drive the barbell up vertically (Figure 16.12). The triple extension movement should cause the barbell to elevate off the athlete’s shoulders and pass in front of their face. It is important to remind the athlete to tuck their chin during the drive phase in order to prevent possible injury. As the barbell continues to elevate, the athlete should grasp it with an overhand grip. Simultaneously, the athlete’s feet are beginning to split either forward and backward (split jerk) or laterally (power jerk). The athlete’s torso should remain upright and rigid in preparation for receiving the load overhead. The drive phase of the jerk. Jerk receiving positions Depending on the variation used, split jerk or power jerk, the athlete’s feet will continue to split forward and backward or laterally. Coaches should note that the splitting of the feet should not be a jumping motion, but rather a continuation of the drive phase. During the split jerk (Figure 16.13), the athlete should ‘jab’ the front foot forward so that it is flat on the ground with the pressure on the heel. The athlete’s front knee should flex and remain in line with their toes. Simultaneously, the athlete’s back foot moves backward and is planted on the ball of their foot with their heel off the ground. The back leg should be slightly bent to allow for the absorption of force as the load is received overhead. As the athlete splits their legs, they should also continue the drive phase by pushing the barbell vertically and receiving it overhead with their elbows in a locked position. The barbell should be received with a braced torso in a position where the barbell is directly above the back of the head (Figure 16.13). The split distance of the athlete’s legs will be individualised based on anthropometrics, flexibility and strength. Split jerk receiving position. A power jerk variation follows a similar sequence of movements through the drive phase. Instead of splitting the feet forward and backward, the athlete moves their feet slightly laterally and flexes their hips and knees into a quarter-squat position. At this point, the athlete continues to drive the barbell upward before receiving in the previously described overhead position (Figure 16.14). Power jerk receiving position. Jerk recovery In order to recover from a split jerk position, the athlete should first step backwards with their front foot until it is close to the body and then step forward with the back foot until the legs are together all while maintaining an upright posture and the barbell held overhead with locked arms (Figure 16.15). The movements of the legs should be completed in this order to allow for the centre of mass to be moved backwards against a braced back leg rather than creating forward momentum by moving towards the front leg. Once in a stable receiving position during the power jerk, the athlete should extend their hips and knees while maintaining an upright torso and holding the barbell overhead with locked arms to return to a standing position (Figure 16.15). Jerk recovery. Weightlifting derivatives As mentioned above, the primary weightlifting movements are the snatch, clean and jerk. However, it should be noted that there are several partial lifts (i.e. weightlifting derivatives) that exclude part of the full snatch, clean or jerk movements. Despite removing an aspect of the lift, weightlifting derivatives may also be effectively implemented into resistance-training programmes for athletes. It should be noted that weightlifting derivatives may be further sub-divided into weightlifting catching and pulling derivatives. Weightlifting catching derivatives Weightlifting catching derivatives are defined as weightlifting movements that involve the catch phase of the snatch or clean, but omit a portion of the traditional snatch or clean movement (e.g. full squat catch, lifting the barbell off the floor, etc.). In addition to producing high-power outputs during the triple extension movement, it is generally believed that weightlifting catching derivatives will train an athlete to decelerate an external load, which is an important characteristic for athletes in sports such as rugby, American football and wrestling. Previous research has indicated that weightlifting catching derivatives may be used as a training tool to improve landing characteristics, as loading during the catch was comparable to that observed during a drop jump landing (Moolyk et al., 2013). As with any exercise, the athlete’s technique is vital to receive the optimal training stimulus while minimising the risk of injury. This is especially true when it comes to weightlifting movements and their derivatives as they are highly complex regarding technique. Several studies have examined factors that may influence the proper completion of the snatch and clean and jerk exercises. Researchers have examined the effect that loading has on snatch and clean and jerk technique (Häkkinen et al., 1984), snatch technique of weightlifters at different levels (Kauhanen et al., 1984; Harbili and Alptekin, 2014), technique changes following feedback (Winchester et al., 2009) and the technique differences between successful and unsuccessful snatch attempts (Stone et al., 1998; Gourgoulis et al., 2009) and power clean repetitions (Kipp and Meinerz, 2017). The findings from this literature are beneficial in that they may help improve coaching cues and the focus on critical aspects of each lift. The most common snatch and clean derivatives prescribed are the power clean/snatch and hang power clean/snatch. Thus, to aid practitioners and their programming decisions, researchers have examined these exercises by attempting to find the load that produces the greatest magnitude of power (i.e. the optimal load). This research has indicated that loads ranging from 70% to 80% one repetition maximum (1RM) may provide the optimal training load for the power clean (Comfort et al., 2012a) and hang power clean (Kawamori et al., 2005; Kilduff et al., 2007). Interestingly, a paucity of research has examined the optimal training load for snatch catching derivatives. However, the information presented within the literature surrounding the optimal training loads of weightlifting catching derivatives is important for practitioners when it comes to prescribing loads during various training phases. Furthermore, it is important that practitioners understand that the optimal load may be specific to the device used to measure power output (e.g. force plate, linear position transducer, etc.) (Hori et al., 2005; Cormie et al., 2007; McBride et al., 2011; Lake et al., 2012). Practitioners should also determine which magnitude of power is specific to the athlete’s sport/event. For example, power applied to the barbell is essential for weightlifters, whereas power applied to the system is arguably more important in terms of assessing the development of lowerbody power. A review has discussed optimal loading ranges for lower-body exercises and concluded that a range of loads should be prescribed when training for maximal power output (Soriano et al., 2015). This notion is supported by additional literature (Newton and Kraemer, 1994; Newton et al., 2002; Haff and Nimphius, 2012). A third aspect of the extant literature focuses on different cluster set configurations when it comes to implementing weightlifting catching derivatives. The results of these studies indicate that the use of cluster sets offset the increase in perceived effort (Hardee et al., 2012a), allowed for technique to be maintained (Hardee et al., 2013) and also allowed power output to be maintained throughout the set (Hardee et al., 2012b). From a practical standpoint, it appears that 20–40 seconds of inter-repetition rest may allow the athlete to experience a better training stimulus when training with the clean derivatives. See Chapter 13 for a detailed discussion of the use of cluster sets. Weightlifting pulling derivatives Weightlifting pulling derivatives, as the name suggests, are weightlifting derivatives that remove the catch phase and finish with the completion of the second pull (Figure 16.6). Examples of weightlifting pulling derivatives discussed within the literature include the clean/snatch mid-thigh pull, pull from the knee, hang pull, pull from the floor, countermovement shrug, hang high pull and jump shrug (Suchomel et al., 2017a). Some of the benefits of the above derivatives include decreased exercise complexity regarding technique, a potential decreased learning and teaching time for the movements, a potential reduction of impact on specific joints and a greater ability to overload the triple extension movement (Suchomel et al., 2015b). Due to the number of benefits that may enhance the abilities of athletes, research has examined weightlifting pulling derivatives in several capacities, including comparisons with weightlifting catching derivatives, loading effects and different set configurations. Cross-sectional comparisons with weightlifting catching derivatives have shown that weightlifting pulling derivatives may produce a comparable (Comfort et al., 2011a, 2011b) or superior (Suchomel et al., 2014b; Suchomel and Sole, 2017a, 2017b; Kipp et al., 2018; Kipp et al., 2019a, 2019b; Takei et al., 2020) training stimulus compared to weightlifting catching derivatives with regard to peak force, velocity, power, RFD and impulse. Further research indicated that the load acceptance demands (work, mean force, duration) of weightlifting pulling derivatives are similar or greater compared to weightlifting catching derivatives (Comfort et al., 2017; Suchomel et al., 2017b, 2018a, 2020b). While the above studies display the cross-sectional differences between weightlifting catching and pulling derivatives, research that displays longitudinal strength-power adaptations may be more beneficial. Comfort et al. (2018) examined the differences of training for 8 weeks with either weightlifting catching or pulling derivatives that were load-matched. Their findings showed no differences in 1RM power clean, isometric mid-thigh pull force production characteristics or countermovement jump performance between groups, indicating that either catching or pulling derivatives may be used to improve strength-power adaptations. Interestingly, two recent studies (Suchomel et al., 2020a, 2020b) expanded on the study by Comfort et al. (2018) and added a third group that trained using weightlifting pulling derivatives that included phase-specific loading to provide a force (loads >100% 1RM) or velocity (loads <50% 1RM) overload stimulus. The findings from the recent studies showed that training with weightlifting pulling derivatives that include a force and velocity overload stimulus may produce greater dynamic and isometric strength, sprint and change-of-direction adaptations (Suchomel et al., 2020a), as well as greater squat jump and countermovement jump propulsive force adaptations (Suchomel et al., 2020b). The results of the latter two training studies suggest that the ability to expand the loading spectrum using weightlifting pulling derivatives may allow for more favourable strengthpower adaptations. Similar to weightlifting catching derivatives, much of the research that focuses on weightlifting pulling derivatives has examined the effect that the external load has on various kinetic and kinematic variables. Through examining different loads, sport scientists and practitioners can determine which loads provide the optimal training stimulus for athletes within the context of each exercise. Furthermore, these findings may then be applied within resistance-training programmes. For example, the goals of maximal strength and absolute strength-training blocks are to enhance the maximal force production capacity of the athlete and to begin the initial stages of enhancing their RFD characteristics against heavy external loads. Thus, weightlifting pulling derivatives that allow for the use of heavier training loads may aid in the development of the desired characteristics. Researchers have shown that the mid-thigh pull (Comfort et al., 2012b, 2015; Meechan et al., 2020b), countermovement shrug (Meechan et al., 2020b), pull from the knee/hang pull (Meechan et al., 2020a) and pull from the floor (Haff et al., 2003) may use loads in excess of an athlete’s 1RM power clean because these derivatives do not require athletes to drop under the barbell and catch the load. Specifically, practitioners may prescribe loads up to approximately 120–140% of their 1RM power clean, as long as proper technique is maintained. Based on these findings, it is clear that weightlifting pulling derivatives may enhance an athlete’s force production characteristics. In fact, previous research indicated that implementing weightlifting pulling derivatives such as the mid-thigh pull, countermovement shrug and pull from the floor produced greater peak force production adaptations compared to only implementing weightlifting catching derivatives (Suchomel et al., 2020a). Another example would be selecting exercises that maximise power production during speed-strength-training blocks. While high-force production is emphasised during maximal strength and absolute strengthtraining blocks, the goals of a speed-strength-training block are to peak the RFD and power characteristics of athletes prior to competition. Thus, weightlifting pulling derivatives that are the most ballistic in nature may be useful exercises that may aid in the development of these characteristics. Previous research has examined the effect that load has on the jump shrug (Suchomel et al., 2013) and hang high pull (Suchomel et al., 2015a). The results of these loading studies indicated that the lightest loads examined (i.e. 30 and 45% of 1RM hang power clean) produced the greatest magnitudes of velocity and power. It should be noted that athletes may not always perform a 1RM catching derivative and may thus require another method to prescribe loads for weightlifting pulling derivatives. A recent study indicated that loads from 20–40% body mass or 10–20% of a back squat 1RM may be used to optimise power output for the jump shrug (Suchomel et al., 2019). However, practitioners should use caution when prescribing loads based on body mass or from a 1RM squat because relative strength may alter the performance of weightlifting movements. In contrast to exercises such as the mid-thigh pull and pull from the floor, it is clear that the jump shrug and hang high pull may fall on the opposite end of the loading spectrum, but may still be useful during certain phases of training (Suchomel et al., 2017a). It should be noted that unpublished data support the notion that exercise-specific loading with weightlifting pulling derivatives may also produce greater rapid force production (e.g. force at 50–200 ms) adaptations compared to submaximally loaded weightlifting catching and pulling derivatives. A third area of research on weightlifting pulling derivatives is research that examines different set configurations. For example, the aforementioned studies may provide the practitioner with the choice of exercise and the potential loads that coincide as an effective training stimulus; however, the performance of each repetition may be modified based on the set structure. Previous research has examined different set configurations (traditional, undulating and cluster) when performing the clean pull from the floor (Haff et al., 2003). The results of this study indicated that the use of a cluster set may result in greater barbell velocity and displacement during the clean pull from the floor compared to a traditional set. More recent research examined the effect of rest redistribution sets that modified the traditional set structure by taking the total amount of rest between sets and distributing it between smaller sets of the clean pull from the floor (Jukic and Tufano, 2019, 2020). The results from this research indicated that rest redistribution sets allowed for the maintenance of movement velocity and power (Jukic and Tufano, 2019) as well as lower perceived and mechanical fatigue (Jukic and Tufano, 2020). Further detail on different set configurations is discussed in Chapter 13. SECTION 2 Practical applications Developing an athlete’s force–velocity profile As described in Chapter 2, one of the primary goals of a strength and conditioning practitioner is to develop the force–velocity profile of their athletes in order to enhance important force production characteristics such as impulse, RFD and power. Haff and Nimphius (2012) indicated that the most effective way to develop an athlete’s force–velocity profile is through the use of training methods that will develop both the force and velocity ends of the spectrum. While this process can be completed using different set and repetition schemes, warm-up and warm-down sets, and various intensities during core exercises (squat, bench press, etc.), a sequenced progression of weightlifting derivatives may also develop the entire force– velocity profile of an athlete (Suchomel et al., 2017a). Figure 16.16 displays the theoretical force–velocity relationship specific to weightlifting derivatives. Force–velocity curve for weightlifting exercises. 1RM, one repetition maximum; HPC, hang power clean; PC, power clean. The previously discussed literature supports the notion that weightlifting derivatives such as the mid-thigh pull, countermovement shrug, pull from the knee, hang pull and pull from the floor may all be used to develop highforce production characteristics due to the decreased displacement of the load during each movement. On the opposite end of the force–velocity curve are weightlifting derivatives that are characterised by higher velocities. The jump shrug, hang high pull, mid-thigh clean/snatch and countermovement (hang) clean/snatch are weightlifting derivatives that are highly ballistic and are typically programmed with low-moderate loads (<60% 1RM). While the placement of derivatives within Figure 16.16 is supported by evidence, it should be noted that the load prescribed may influence the position of each exercise on the force–velocity curve. For example, while the mid-thigh pull enables athletes to use the heaviest loads (i.e. 140% of 1RM power clean), power production and velocity were maximised with the lightest load (i.e. 40% of 1RM power clean) (Comfort et al., 2012b, 2015). However, recent research from Meechan et al. (2020b) indicated that the addition of a countermovement (e.g. countermovement shrug) may allow peak power to occur across a spectrum of loads (i.e. 80– 120% of 1RM power clean) based on the trade-off between force and movement velocity with a change in load. As discussed in Chapter 7, previous literature suggests that a sequenced progression of training phases promotes the optimal development of an athlete’s force–velocity profile (Stone et al., 1982; Minetti, 2002; Zamparo et al., 2002). Briefly, increases in work capacity and muscle cross-sectional area produced during a strength-endurance (hypertrophy) phase enhance an athlete’s ability to increase their muscular strength. From here, increases in muscular strength will then enhance an athlete’s potential to improve their RFD and power characteristics. A similar approach can be taken when prescribing weightlifting derivatives because certain lifts place greater emphasis on either force or velocity. Thus, specific weightlifting catching and pulling derivatives may be prescribed during resistance-training phases in order to meet the goals of each phase and develop the force–velocity profile of the athlete. The following will discuss the implementation of weightlifting derivatives into various resistance training phases to promote the optimal development of an athlete’s force–velocity profile. Strength-endurance The strength-endurance phase is characterised by a high volume of repetitions (usually 8–12) in exercises that use moderately heavy loads (60– 70% 1RM). The purpose of this phase is to increase the athlete’s work capacity, stimulate increases in muscle cross-sectional area and refine exercise technique for subsequent training phases. Regarding the use of weightlifting derivatives within this phase, it is suggested that practitioners implement the clean/snatch pull from the floor, pull to the knee and clean grip shoulder shrug for several reasons. First, the suggested derivatives serve as foundation exercises that enable the progression to more complex weightlifting movements. The inability to perform these exercises may lead to improper exercise technique of more complex derivatives, potentially impacting the training stimulus. Second, the clean/snatch pull from the floor enables athletes to overload the triple extension movement without experiencing the additional stress and complexity of performing the catch phase every repetition as fatigue develops. While the catch phase of certain weightlifting derivatives may enable the athlete to develop additional performance characteristics as mentioned above, the high volume experienced during the strength-endurance phase may lead to a deterioration in form due to acute fatigue. Moreover, a decline in technique may alter catch phase mechanics and increase the likelihood of injury or compression stress. Finally, the suggested derivatives enable the development of important lower- and upper-body musculature that will be used to enhance the force–velocity profile during later training phases in tandem with exercises such as squatting, pressing and pulling movements. Recent training studies have displayed how to effectively implement pulling derivatives within a higher-volume training phase (Suchomel et al., 2020a, 2020b). It should be noted that the athletic population may dictate which weightlifting movements are prescribed in a strength-endurance-training block. For example, the clean/snatch pull from the floor may only be implemented with an athletic population whose technique is more consistent and resilient to fatigue. Practitioners may also consider prescribing cluster sets of either two or five repetitions for the clean/snatch pull from the floor due to the high volume within the strength-endurance phase. As discussed in Chapter 13, the use of cluster sets or rest redistribution sets may enable the athlete to maintain technique, force production and power output throughout each set (Jukic and Tufano, 2019, 2020) leading to high-quality work, enhanced work capacity and force production adaptations with a high volume of repetitions. Moreover, the inter-repetition rest interval may allow the coach to provide additional feedback to the athlete. Maximal strength A maximal-strength phase is used to increase an athlete’s force production capacity using sets of 4–6 repetitions and moderately heavy to heavy loads (i.e. 80–90% 1RM, although potentially slightly higher with pulling derivatives). During this phase, practitioners should shift their focus to exercises that emphasise force production and enable the use of heavier loads. A limitation to weightlifting catching derivatives is that practitioners cannot prescribe loads greater than the athlete’s 1RM. This, however, is not the case for weightlifting pulling derivatives as exercises such as the clean/snatch pull from the floor, pull from the knee and mid-thigh pull allow for loads greater than the athlete’s 1RM to be used due to the elimination of the catch phase and decreased displacement of the load. The use of these exercises combined with heavier loads will emphasise force production and train the high-force portion of the force–velocity curve. Absolute strength Similar to the maximal-strength phase, the goals of the absolute-strength phase are to enhance the athlete’s low-repetition (e.g. 1–3) force production (both magnitude and rate) characteristics using near-maximal loads (90– 95% 1RM or potentially as high as 120–140% 1RM with pulling derivatives). While the same exercises from the maximal-strength phase may be prescribed to retain the athlete’s capacity for high-force production, additional derivatives that include a strength-speed component should be introduced to begin the enhancement of RFD. These exercises might include the hang power clean/snatch (Suchomel et al., 2014a), power clean/snatch, mid-thigh clean/snatch (Comfort et al., 2011a, 2011b) and the full clean/snatch. The combination of high-force movements and introducing high-velocity movements will ultimately contribute to the athlete’s ability to further develop impulse, RFD and power characteristics. Strength-speed The primary goals of the strength-speed phase are to further increase RFD and power, while also maintaining or potentially increasing the athlete’s strength. Because previous literature has indicated that RFD and power are two of the most important characteristics regarding an athlete’s performance (Morrissey et al., 1995; Stone et al., 2002), it is important to prepare the athlete to maximise these adaptations using the previously discussed training phases. Based on the phasic progression of resistance-training phases, increases in muscular strength (Suchomel et al., 2016b, 2018b) and RFD (Taber et al., 2016) from the previous training phases should, in theory, enhance the athlete’s ability to augment their power characteristics. Regarding the programming of weightlifting derivatives during the strength-speed phase, RFD and power characteristics may be enhanced using a combination of heavy and light loads. However, the emphasis within this phase is to move relatively heavy loads quickly in order to enhance RFD characteristics. Thus, the mid-thigh clean/snatch, countermovement clean/snatch and power clean/snatch from the knee (Suchomel et al., 2016a) may be used to develop the high-velocity portion of the force–velocity curve, while the power clean, clean/snatch pulls from the floor, knee and mid-thigh may develop the high-force end of the force– velocity curve. Speed-strength The goals of the speed-strength phase are to produce peak adaptations in RFD and power prior to competition. In order to peak these abilities, a wide variety of weightlifting derivatives may be prescribed. Many of the previously described derivatives may be prescribed; however, the speed at which the movement is performed, and therefore the load, must be considered. For this reason, the jump shrug and hang high pull may be highlighted during the speed-strength phase due to their ballistic nature. A combined approach of prescribing heavy- and light-loaded derivatives should be implemented to optimise RFD and power adaptations. Thus, practitioners may prescribe a combination of the clean/snatch mid-thigh pull or pull from the floor and the jump shrug and hang high pull to focus on training each end of the force–velocity curve. Varying neurological demands will be placed on the athlete as the above combination will simulate overcoming the inertia of an external load from a static start (e.g. mid-thigh pull) and using the stretch-shortening cycle (e.g. jump shrug), allowing them to optimise impulse, RFD and power characteristics. Another aspect to consider during the speed-strength phase is the load implemented with each exercise. Previous literature has suggested that training at or near the loads that maximise power may produce favourable strength-power adaptations (Kawamori and Haff, 2004). As discussed above, loads of approximately 70–80% 1RM may provide the optimal training load for the power clean and hang power clean, while lighter loads (i.e. 30–45% 1RM of hang power clean) may serve as an optimal training stimulus for the jump shrug and hang high pull. Additional literature has indicated that loads of approximately 90% of an athlete’s 1RM power clean (Haff et al., 2003) or full clean/snatch (Ermakov, 1980) may optimise the training stimulus for the clean/snatch pull from the floor, while loads of 100% and 120% 1RM power clean may maximise power during the pull from the knee/hang clean pull (Meechan et al., 2020a) and countermovement shrug (Meechan et al., 2020b), respectively. Speed development A sequenced progression of programming weightlifting derivatives may aid in the development of an athlete’s speed characteristics (DeWeese et al., 2016). Using the methods described above, specific weightlifting derivatives may be programmed during specific strength-training phases that coincide with speed development phases (Figure 16.17). The following will discuss the rationale of prescribing a sequenced progression of weightlifting derivatives to enhance an athlete’s sprint speed. Sequenced progressions of speed and strength-power development with the weightlifting derivatives that may be used within each phase. CM, countermovement. (Modified from DeWeese et al., 2014.) General preparation phase As displayed in Figure 16.17, the general preparation phase is focused on improving the accelerative abilities of an athlete. Coaches may choose to program resisted runs (i.e. incline sprints and towing) at this point to develop high propulsive forces into the ground, while in the weight room a strength-endurance phase serves to develop the athlete’s work capacity and cross-sectional area in order to enhance their muscular strength and power in later training phases (Stone et al., 1982). As mentioned above, practitioners may program the clean/snatch pull to knee, pull from the floor and shoulder shrug. Each of these movements can be used to strengthen the athlete’s musculature at specific angles that relate to their posture during various acceleration phases. For example, the first pull requires athletes to start from a knee angle of approximately 90° and extend the knees to about 120°, which are angles that coincide with a sprinter’s knee angles in the starting blocks. Special preparation phase Upon entering the special preparation phase of training, the training emphasis builds upon the enhanced acceleration characteristics from the previous phase to build top speed characteristics. Coaches may program running drills such as acceleration holds, low-load resisted runs and longer segment accelerations during this phase before introducing maximumvelocity sprinting drills (e.g. fly-in sprints and in-and-outs). Concurrently in the weight room, the focus of training shifts to improving the athlete’s strength characteristics. The clean/snatch pull from the floor, pull from the knee and mid-thigh pull exercises serve to develop vertical force production through the ranges of motion experienced during the acceleration and transition to upright running phases. Moreover, these movements overload the athlete in a position that is relative to top speed mechanics (i.e. 125– 145° knee angle, upright torso and shortened range of motion) (DeWeese et al., 2015). In addition, exercises like the hang power clean/snatch, power clean/snatch, mid-thigh clean/snatch and the full clean and snatch may be programmed during this phase to introduce a strength-speed component that will aid in the development of the athlete’s RFD characteristics. Early-mid competition phase Leading into the start of the season, coaches will typically prescribe drills that will retain an athlete’s accelerative and top speed abilities through short sprint work as well as training sessions specific to the sprint distances of the athlete’s sport/event. Within the weight room, an early emphasis should be placed on strength-speed. Thus, weightlifting derivatives that focus on moving heavier loads quickly should be programmed. The suggested exercises within this phase include the mid-thigh pull, countermovement shrug and the power clean/snatch. The mid-thigh pull and countermovement shrug in this case will maintain high-force production characteristics as practitioners may program up to 140% 1RM, while the power clean/snatch enables athletes to utilise the stretch-shortening cycle that occurs during the double-knee bend, as described above. The latter will allow athletes to generate large vertical forces in an upright position that may counteract those experienced during the stance phase of sprinting. Finally, the emphasis may shift to incorporating speed-strength exercises which move lighter loads quickly. Such exercises may include the countermovement clean/snatch, mid-thigh clean/snatch, hang high pull and jump shrug. Late competition/taper phase Upon reaching the latter stages of competition, the emphasis in weight room training aims to emphasise speed-strength characteristics while retaining strength-speed characteristics. Practitioners may elect to implement a variety of ballistic movements such as potentiation complexes, light-weighted jump squats, plyometrics, etc. However, regarding weightlifting derivatives, the countermovement clean/snatch, mid-thigh clean/snatch, hang high pull and jump shrug should be implemented during this phase of training. In addition, practitioners may consider implementing the mid-thigh pull to continue to retain strength-speed qualities. In fact, the mid-thigh pull could be programmed prior to one of the previously mentioned exercises in order to potentiate the power output of the latter exercise. Summary Weightlifting movements and their derivatives are effective training tools that may be used to enhance an athlete’s lower-body ‘explosiveness’ and load acceptance/braking characteristics. Weightlifting catching and pulling derivatives both provide useful training stimuli and may be programmed to meet the specific goals of various resistance-training phases. 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