View
219
Download
1
Tags:
Embed Size (px)
Citation preview
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)