Stretching & Plyometrics
Dr. Moran
EXS 558
December 1, 2005
Lecture Overview
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Review Questions
Review Paper
Brief PowerPoint Demo
Stretching (partial Ch. 13)
 Muscle Spindles
 GTO
 Type of Stretches
 Muscular Adaptations to Stretching
 “Stretching Before Exercise Does Not Reduce the Risk of Local Muscle
Injury: A Critical Review of the Clinical and Basic Science Literature”
 Plyometrics (partial Ch. 12)
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Scientific Basis
 “The effects of shoulder plyometric training on propioception and
selected muscle preformance characteristics”
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 CTE
Workout Integration
Plyometric Training Design
(Student Volunteer?)
Review Question #1
 What physiological adaptations can be
expected from a basketball engaged in a 12
week preseason conditioning program?
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↑ transformation of type II fibers to a more glycolytic subtype (spectrum)
↑ elevations of glycolytic enzymes (e.g. PFK)
↑ in maximum blood lactate concentrations
↑ [blood lactate] during submax exercise intensities
Improved buffering capacity
Review Question #2-3
 Which of the following is NOT a method for
measuring anaerobic power?
(a)
(b)
(c)
Wingate Test
Margaria-Palamen Test
Sargaent Jump Test
 What is difference between anaerobic power
and anaerobic capacity?
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Anaerobic capacity is the maximum amount of ATP resynthesized during a
short duration anaerobic activity and is usually measured by maximal blood
lactate levels. Anaerobic power is defined as the maximal capacity to produce
to produce ATP via a combination of the ATP-CP and glycolytic systems. It is
measured in watts.
Review Question #4
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What is the primary reason for increased central
blood volume flow during deep water running?
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Hydrostatic vascular gradient increases perphiral
pressure shunting blood to the central thoracic
cavity.
This causes _____ increase in cardiac output at
rest?
(a)
(b)
(c)
(d)
15-20%
20-25%
25-30%
30-35%
Review Question #5
 What is the major differences for an untrained
versus trained population that are utilizing a
deep water training program? What are the
biggest differences in the expected outcomes
in these two groups?

The relevant research shows that trained runners
can use DWR to MAINTAIN but not IMPROVE
aerobic capacity for up to 3 weeks, BUT untrained
athletes can actually IMPROVE aerobic capacity
through a DWR training program.
Review Paper & Presentation
Due Wednesday December 7
 Things to Remember - PRESENTATION
 Powerpoint: make slides available to classmates
 Email before 5pm on Wednesday to Dr. Moran OR
 Bring on a JumpDrive
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Presentation should be at least 15 minutes long with 5 minutes for
questions
Each class member will ask at least one question following presentation
Each class member will also evaluate each presentation in a # of
categories and offer constructive criticism
 Some Key Points – PAPER
 Title Page – don’t forget this
 Avoid paragraph after paragraph of summarizing research articles. A
CRITICAL review forces you to synthesize material not just regurgitate
 Avoid statement:
 In 2004 Moran’s study on….
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First sentence of paragraph should explain that entire paragraph.
Scientific writing should be simple and easy for the reader to follow
 Brief PowerPoint DEMO
Stretching – Is it advised?
 Does stretching before exercise reduce injury rates?
 How does stretching increase flexibility?
 No basic science articles have directly examined the effect of
stretching on injury prevention
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Many believe stretching to improve ROM
 Improved performance
 Reduced Injuries?
 “Stretching-Induced Strength Deficit”: preexercise stretching
may compromise the ability of a muscle to maximally contract.
How is muscle stretch detected?
 Muscle Propioceptors
 Golgi Tendon Organs (GTO)
 Muscle Spindles
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These are all sensory neural fibers that relay
information about musculotendon stretch to the
upper CNS
Muscle Spindles
 These structures let other neurons know about the LENGTH
and VELOCITY of muscle fibers
 Scattered among muscle fibers in large quantities
 Between regular skeletal muscle fibers (extrafusal)
 Within each spindle – specialized muscle fibers
 Intrafusal: attached to either extrafusal fibers or tendionous ligaments, so
that when extrafusal fibers change length the intrafusal fibers are stretched
or shortened
 Bag Fibers: refers to distribution of nuclei in fiber
 Static
 Dynamic
 Chain Fibers: refers to distribution of nuclei in fiber
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These fibers are myelinated with diameters ranging from 12-20 μm (AP
velocity of 120 m/s)
Central region can not contract b/c contain few actin or myosin filaments
Nerve endings are wrapped around this central portion
Muscle Spindles (con’t)
 Two types of sensory endings
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Primary (Ia): in all intrafusal fibers
Secondary (II): seen in chain fibers and static bag fibers, but
NOT dynamic bag fibers
 Intrafusal Fibers controlled by γ-motor
neurons
 Extrafusal fibers controlled by α–motor
neurons
Muscle Spindles (con’t)
Innervation
to muscle
fibers
Sensory
Input to CNS
Muscle Spindles (con’t)
Movement Example
 Your arm is bent at the elbow with your palm
up when someone suddenly places a weight
in your hand
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Muscle Stretch (biceps brachi): this stretches the
muscle spindles
This sends a signal to the CNS which stimulates
the α–motor neurons
Muscle force increased in biceps to overcome
forearm drop and stabilize weight
Movement Example (con’t)
 γ-motor neurons excite the intramusal fibers
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Prestretch  increases sensitivity to muscle
length changes
Unique system because the “GAIN” of system
can be altered through innervation
 Co-activation
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γ-motor neurons are also contracted when α–
motor neurons are stimulated to contract
extrafusal fibers
 This increases muscle force production
 Integral to the field of motor control
Golgi Tendon Organs (GTO)
 Located proximal to the tendon fibers
attachment to the muscle fibers

~5-25 muscle fibers are usually connected with each
GTO
 Sensitive to tension within musculotendon complex
 Acts like a strain gauge
 Inhibitory
 Inhibit agonist and excited antagonist muscle groups
 Researchers believe reducing the role of GTO
would allow a more powerful muscle contraction
Types of Stretching Techniques
 Slow Static
 Ballistic
 Proprioceptive Neuromuscular Facilitation (PNF)
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All 3 techniques improve ROM but PNF is most
effective (Wallin et al., 1985)
PNF is a type of flexibility exercise which combines
muscle contraction and relaxation with passive and
partner-assisted stretching
Explaining Theory: by performing a sub-max
isometric contraction of an antagonist muscle group
a reflex facilitation occurs and subsequent
contraction of agonist muscles. Thus this
suppresses the contraction of the muscles being
stretched.
Research Article #1
 “Stretching Before Exercise Does Not Reduce
the Risk of Local Muscle Injury: A Critical
Review of the Clinical and Basic Science
Literature”
 Ian Shrier (1999)
Stretching
Basic Science Evidence
 Acute Muscle Injuries
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Most concur that ruptures occur near
musculotendinous juncture
 Muscle Strains
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Occur when actin and myosin filaments are
stretched beyond overlap
Sarcomeres attached to tendon stretch the least
Typically during eccentric contractions (“active
lengthening”)
Stretching
Basic Science Evidence
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Five theoretical arguments why
stretching before exercise would not
prevent injury
1.
2.
3.
4.
5.
↑ compliance suggests a decreased ability of
muscle to absorb energy
Energy absorption by muscles is most important
variable regarding muscle injuries. Sarcomere
length is related to most exercise-related muscle
strains rather than total muscle length
Compliance of resting muscle due to muscle
cytoskeleton BUT compliance of acting muscle due
to the # of cross-bridges formed
Over-stretching (~20%) have damaged resting
muscle preparations
Masking of pain
*PNF stretching
*Stretching tolerance but no change in tissue
compliance
Plyometrics
 “stretch-shortening” exercises
 History
 1960’s Dr. Margaria (Italy)
 these exercises first used within
sport (track & field) in the
1960’s (Yuri Verkhoshanski a
Soviet jumping coach)
 Fred Wilt was the first to bring
plyometrics to the US (1970s)
 Online resource
 Plyometrics  greek word coming
from greater, longer, wider and to
measure, to appraise, to compare
Plyometrics (continued)
 Part I: Rapid stretch (eccentric contraction)
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Countermovement
 Part II: Amortization
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Time between eccentric and concentric contraction
 Part III: Concentric Motion
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Shortening
Plyometrics
 Improvement of Force Production
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Pre-stretch (countermovement) improved vertical
jumps by 18-20% (Bosco et al., 1982)
 Reasons:
1.) greater stored elastic energy from Part I
2.) greater neural stimulation (Schmidtbleicher et
al., 1988)
3.) increased joint moment (i.e., torsional spring)
Bobbert et al. (1996) suggested this was the
greatest contribution to improved jump
performance
Plyometrics
Coordination Requirements
 Athlete needs to be skilled at movement
sequence
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Finely tuned coordination of agonist, antagonist
and synergistic muscle groups
Beginners should proceed slowly and
incrementally when new to plyometric exercises
 This is done to prevent injuries
Research Article #2
 “The effects of shoulder plyometric training on
propioception and selected muscle
preformance characteristics”



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Swanik et al. (2002)
Why is a decreased amortization time a positive adaptation?
Do you want a desensitized GTO? Why or why not?
“The results of this study support the rationale that plyometric training
may NOT be the most effective activity to enhance torque
development”. From the results of this study do you believe this
statement?
Does this type of training increase the chance of glenohumeral
instability?
Plyometrics
Workout Integration
 Types of training for dynamic sports
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Traditional Resistance Training
 High intensity, low velocity of training speed
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Plyometrics
 Rapid acceleration/deceleration of body weight
(+med ball)
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Ballistic Training
 Combination of traditional resistance and plyometric
training methods
“Effects of ballistic training on preseason preparation of elite volleyball players”
Newton et al. (1999)
Plyometrics
Workout Integration
“The optimal training load for the development of
dynamic athletic performance”
Wilson et al. (1993)