Does respiratory
muscle training
improve performance
in high level athletes?
A Systematic Review and Meta-Analysis
RSPT 572
Supervisor: Dr. Darlene Reid
Teryn Buna, Jonathan Coelho, Kyle Freedman,
Trevor Morton, Sheree Palmer, Melissa Toy, Cody Walsh
Outline
 Background
 Objective
 Methods
 Results
 Discussion
 Conclusions
 Implications & Future Directions
Background
Overview
 Competition drives top athletes to seek new ways to gain
an edge
 Top athletes thought to have plateaued their ability to
improve:
 Muscular function
Performance
 Cardiovascular function
 The role of inspiratory muscles (IM) have recently become
a point of consideration in exercise performance research
Respiratory System and
Exercise Performance
 Traditional
 Untrained, healthy respiratory system not a performance
limiting factor 1, 3, 4
 Supported by no change in VO2max and lactate thresholds
following IMT 2, 3
 Focus on O2 transport chain
 Current
 Systemic physiological changes secondary to inspiratory
muscle fatigue (IMF)
Respiratory System and
Exercise Performance
 IMF occurs 2° to demands of work of breathing in 3-12
 Marathon running
 Rowing
 Triathlon
 Cycling
 Swimming
Respiratory System and
Exercise Performance
 IMF effect on performance
 Rating of perceived breathlessness (RPB) 3
 Rating of perceived effort (RPE) 15,16
 Metaboreflex phenomenon
 Redirection of blood flow from the periphery to fatiguing IM 13,14
 Can inspiratory muscle training (IMT) have an impact on
performance?
IMT and Performance
 Debate exists whether IMT can positively contribute to
performance
 3 areas of inconsistency:
1.
Reliable and valid methods for measuring ‘performance’
2.
Variety of IMT protocols and training modalities
3.
Types of athletic performance and level of competition
Tlim vs. TT
Time to limit of volitional
exhaustion (Tlim)
Time Trial
(TT)
Ability to detect small
changes in performance
✔
✖
Constant testing
environments
✔
✖
Ability to mimic
competition
✖
✔
Poor
−
−
✔
Reliability
Valid
3,15,25,31,32
Other study measures
Effects:
Measured by:
1. Ergogenic properties on
performance
Primary performance outcomes
• Time to limit of volitional
exhaustion (Tlim)
• Time Trial (TT)
Secondary performance outcomes
• RPB
• RPE
• VO2max
• Lactate threshold
2. Changes IM function
• PImax = IM strength
• MVV = IM endurance
IMT Protocols
 Types of IMT modalities 25
 Voluntary Normocapnic Hyperpnea (VNH)
 Flow Resistive Loading (FRL)
 Pressure Threshold Loading (PTL)
 Type of IMT protocol chosen based on 25
 Type of adaptations desired
 Factors related to time, cost and ease of use
No current gold standard
Athletic Populations
 Studies have examined four main types of athletes
 Cyclists, rowers and running athletes may  TT with IMT
9,27,30
 Swimming may not be as sensitive to IMT 1
Lack of consistent results between and within
athletic disciplines
IMT Literature
 Other literature on IMT
 Systematic Reviews of COPD and Cystic Fibrosis 45,47
 Favourable results
 IMT as an effective adjunct to general exercise
 3 narrative reviews of IMT in healthy and athletic populations
3,15,25
 No systematic or statistical analysis
Identified a need in the literature for a systematic review
of IMT and performance in high level athletes
Objective
Objective
To conduct a thorough evaluation of the literature and attempt to
answer the following questions pertaining to high level
athletes:
Primary Objective
Does IMT improve performance ?
Secondary Objectives
Does IMT improve IM function ?
Which type of athletes or sports benefit most from IMT?
Methods
PICO
P
Healthy, high level athletes aged 18-40
I
Inspiratory muscle training: Voluntary Normocapnic
Hyperpnea (VNH), Flow Resistive Loading (FRL),
Pressure Threshold Loading (PTL)
C
Control, sham
O
Physical performance: Tlim, TT, VO2max,
Pulmonary function: PImax, MVV, FEV1
Physiological measures: Lactate, RPE, RPB
Operational Definitions
Inspiratory Muscle Training (IMT): an intervention that used
either a VNH, FRL or PTL
Healthy: fully able-bodied humans, non-injured and without
chronic disease
High level: an athlete competing at a varsity, national,
international or professional level, OR has a VO2max level
designated by Wilmore and Costill, 2005
VO2 max
Search Strategy
Medline, SPORTDiscus, CINAHL,
All EBM reviews, PEDro , Web of
Science, Grey Literature, Google Scholar
INCLUDED: 68
Eliminated doubles
INCLUDED: 26
Full text screen
INCLUDED: 15
* Found up to March 30, 2010 *
Search Strategy
 Following procedures performed by 2 independent reviewers
 Article screening
 Title and abstract screening
 Screening tool
 Inclusion/exclusion criteria
 Quality assessment
 PEDro scale +
 Oxford Level of Evidence +
 van Tulder
 Data abstraction
 Third party reviewer was used when required
Study Inclusion
 Articles were included if:
(1) Participants were high level, healthy athletes (mean age of 1840 years)
(2) Compared IMT to another comparison group
(3) An RCT or crossover study design
(4) Includes measures of respiratory muscle adaptation with
reliable and valid outcome measures
(5) English
Included Studies
 14 articles
 Note: Romer et al, 2002A and Romer et al, 2002B same study
data
 Sports
 Cycling
 Endurance running
 Intermittent sprint: Soccer, Rugby, Field Hockey, Basketball
 Rowing
 Swimming
Quality Assessment
Meta-Analysis
 RevMan 5.0.24 for meta-analyses48
 Randomized effects model:
 Does not assume a common treatment effect exists
 Allows for variation by assuming that effects follow a distribution
across all studies
 Standardized mean differences: Summary statistic when the
studies assess the same outcome but measure it in variety of ways
 Used to standardize to a uniform scale
 Express the size of the intervention effect relative to the variability
observed
 Equivalent of ‘effect size’ in social science studies
Meta-Analysis
 RevMan 5.0.24 48
 Heterogeneity: The extent to which the results of studies are
consistent
 I2: assesses whether observed differences in results are
compatible with chance alone
 P <0.1 was considered significant for heterogeneity
Meta-Analysis
 Analysis done on primary and secondary outcomes
 Sport based sub-group analysis was performed
 Cycling
 Endurance Running
 Intermittent Sprint (Soccer, Rugby, Field Hockey, Basketball)
 Rowing
 Swimming
Results
Primary Outcomes
# studies
Z= / P =
I2 = / P=
Overall performance
9
Z = 3.55 P= <0.001
I2=24% P=0.23
Swimmers
1
Z = 0.61 P= 0.54
n/a
Intermittent Sprint
Sports
3
Z = 2.95 P= 0.003
I2= 0% P=0.61
Cyclists
1
Z =2.41 P= 0.02
n/a
Rowers
3
Z = 1.29 P= 0.20
I2=63% P=0.07
Endurance Runners
1
Z = 0.36 P= 0.72
n/a
Primary Outcomes
# studies
Z= / P =
I2 = / P=
Overall performance
9
Z = 3.55 P= <0.001
I2=24% P=0.23
Swimmers
1
Z = 0.61 P= 0.54
n/a
Intermittent Sprint
Sports
3
Z = 2.95 P= 0.003
I2= 0% P=0.61
Cyclists
1
Z =2.41 P= 0.02
n/a
Rowers
3
Z = 1.29 P= 0.20
I2=63% P=0.07
Endurance Runners
1
Z = 0.36 P= 0.72
n/a
Swimming
Intermittent Sprint
Sports
Cycling
Figure 1: Meta-analysis
results comparing
targeted or threshold
resistive IMT versus sham
or control in whole body
athletic performance
Rowing
Special Forces
Overall Performance
Favours IMT
Favours control/sham
Secondary Outcomes
# studies
/14
Z= / P =
I2 = / P=
Lactate
5 (3)
Z= 0.50 P = 0.62
I² = 56% P = 0.04
RPE
3 (1)
Z=1.58 P= 0.12
I2 = 0% P =0.39
RPB
7 (1)
Z=2.54 P=0.01
I²=0% P=0.86
VO2 max
7 (1)
Z= 1.01 P= 0.31
I²=0% P= 0.31
FEV1
9 (0)
Z=0.53 P=0.59
I2 =0% P=0.97
MVV
5(0)
Z = 2.84 P=0.005
I2 = 0% P=0.45
Pimax
- Resting
12 (0)
Z=4.34 P<0.001
I2 = 81% P< 0.001
- Post Performance
4 (0)
Z=12.57 P<0.001
I2 = 73% P= 0.01
(#) = the number of studies that mentioned the
outcome but did not provide numerical data
Secondary Outcomes
# studies
Z= / P =
I2 = / P=
Lactate
5 (3)
Z= 0.50 P = 0.62
I² = 56% P = 0.04
RPE
3 (1)
Z=1.58 P= 0.12
I2 = 0% P =0.39
RPB
7 (1)
Z=2.54 P=0.01
I²=0% P=0.86
VO2 max
7 (1)
Z= 1.01 P= 0.31
I²=0% P= 0.31
FEV1
9 (0)
Z=0.53 P=0.59
I2 =0% P=0.97
MVV
5(0)
Z = 2.84 P=0.005
I2 = 0% P=0.45
Pimax
- Resting
12 (0)
Z=4.34 P<0.001
I2 = 81% P< 0.001
- Post Performance
4 (0)
Z=12.57 P<0.001
I2 = 73% P= 0.01
Discussion
Summary of Findings
 Primary Outcome:
 Overall = Meta- analysis found that IMT does have an
ergogenic effect on performance
Sport based sub-group analysis revealed….
Not all sports are equal!
 Intermittent sprint sports and cycling benefited from IMT
performance
 Swimming, rowing and endurance running were not found to
benefit
Discussion
 Significance of Primary Outcomes
 IMT could be used as an adjunct to regular training to
enhance performance in high-level athletes
 Only in certain sports disciplines
Discussion
 Secondary Outcomes
 Improvements in PImax and MVV across all studies
 Improvements in RPB across all studies
 Significance
 Highly trained athletes are able to improve their IM function
 All protocols effective in eliciting training effect
 Attenuation of dyspnea is supported as a response to
improvements in IM function
Discussion
 Improvement in performance with cycling and
intermittent sprint sports
 Correlated with
IM
function
 PImax and MVV
 Reduction in RPB

RPB
Better
performance
Discussion
Why does this not translate to rowing, swimming and
endurance running performances?
 Rowing 9,52
 Dual function of IM = stabilization of the thorax + ventilation
 “Entrained” breathing
 Different ventilatory mechanics and IM physiological
demands
 ? Negate or confound IMT related improvements?
Discussion
Why does this not translate to rowing, swimming and
endurance running performances?
 Swimming 3,33,50
 Respond with smaller  in PImax following IMT
interventions
 IM trained by water submersion
 Swimmer IM already near function plateau
 Unable to gain performance effects from IMT
Discussion
Why does this not translate to rowing, swimming and
endurance running performances?
 Endurance Runners 51
 German Special Forces = Not elite athletes within a specific
sporting discipline
 ‘Generalist’ characteristics + non-specific performance test
Discussion
Why does this not translate to rowing, swimming and
endurance running performances?
 Individual characteristics
 Each athlete limited by different physiologic or psychologic
factors
 Some may be more limited by IM function than others
 Mix of responders and non-responders within a small sample
could affect the effect size
Discussion
 Individual characteristics
 Highlights the need to consider the unique characteristics of
each athlete prior to choosing a training intervention
Discussion
 Other secondary measures
 FEV1
 VO2 max
 Blood lactate
 RPE
 Consistent with the literature
 FEV1 limited by airway diameter not IM strength
 VO2 max does not respond to IMT
 Blood lactate postulated to decrease
 More recent studies have failed to support this argument
Discussion
 Lack of positive RPE findings contrasts current literature
 Data analyzed on end of test measures
 RPE  post IMT for similar workouts during incremental
testing
 Future studies should examine exercise performance
measures during fixed workload tasks vs. end-points of
exercise performance
Limitations
 Small number of studies with sample sizes
 Definition of “high-level” athletes
 Data abstracted graphs via hand and ruler measurements
 McMahon (2002) removed from the analysis
 Data could not be reliably extracted from the graph
 Attempts to contact the author failed
Conclusion
Conclusion
 IMT improves performance in intermittent sprint and
cycling NOT rowing, swimming or endurance running
 Where IM serve a dual function (rowing) or already
stimulated with regular training (swimming) may not
benefit vs. sports in which the sole function of the RM is
ventilation
 High level athletes able to  IM function with IMT
 Can translate into performance improvements
 Limited strength of claim
Implications
 Consider IMT as a possible adjunct to regular athletic
training
 It is cheap and time effective
 Must consider the individual characteristics
 Must consider type of athletic performance
Future Direction
 Call for more, higher quality studies
 Studies should examine:
 Most effective IMT protocols
 Specific sport
 Apply IMT in a non-research/field setting with a
team/athletic group to determine feasibility and
adherence
Acknowledgements
THANK YOU!
Dr. Darlene Reid
Marc Roig
Dr. Bill Sheel
Dr. Allison McConnell
Charlotte Beck
Dean Guistini
Dr. Theresa Lui-Ambrose
Dr. Lara Boyd
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Questions?