Stretching & Plyometrics

Dr. MoranEXS 558

December 1, 2005

Lecture Overview 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)

Scientific Basis “The effects of shoulder plyometric training on propioception and

selected muscle preformance characteristics” Workout Integration Plyometric Training Design

CTE (Student Volunteer?)

Review Question #1

What physiological adaptations can be expected from a basketball engaged in a 12 week preseason conditioning program?

↑ 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) Wingate Test(b) Margaria-Palamen Test(c) Sargaent Jump Test

What is difference between anaerobic power and anaerobic capacity?

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

What is the primary reason for increased central blood volume flow during deep water running?

Hydrostatic vascular gradient increases perphiral pressure shunting blood to the central thoracic cavity.

This causes _____ increase in cardiac output at rest?

(a) 15-20%(b) 20-25%(c) 25-30%(d) 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 & PresentationDue 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

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…. 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

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

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 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 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

Sensory Input to CNS

Innervation to muscle fibers

Muscle Spindles (con’t)

Muscle Spindles (con’t)

Your arm is bent at the elbow with your palm up when someone suddenly places a weight in your hand

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

Movement Example (con’t)

γ-motor neurons excite the intramusal fibers Prestretch increases sensitivity to muscle

length changes Unique system because the “GAIN” of system

can be altered through innervation Co-activation

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) 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 Most concur that ruptures occur near

musculotendinous juncture

Muscle Strains 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

Five theoretical arguments why stretching before exercise would not prevent injury1. ↑ compliance suggests a decreased ability of

muscle to absorb energy

2. 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

3. Compliance of resting muscle due to muscle cytoskeleton BUT compliance of acting muscle due to the # of cross-bridges formed

4. Over-stretching (~20%) have damaged resting muscle preparations

5. 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) Countermovement

Part II: Amortization Time between eccentric and concentric contraction

Part III: Concentric Motion Shortening

Plyometrics

Improvement of Force Production 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

PlyometricsCoordination Requirements

Athlete needs to be skilled at movement sequence

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”

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?

PlyometricsWorkout Integration

Types of training for dynamic sports Traditional Resistance Training

High intensity, low velocity of training speed Plyometrics

Rapid acceleration/deceleration of body weight (+med ball)

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)

PlyometricsWorkout Integration

“The optimal training load for the development of dynamic athletic performance”

Wilson et al. (1993)