1. Plyometrics in Rehabilitation
Rehabilitation Techniques for Sports Medicine and Athletic Training
William E. Prentice

2. What is Plyometric Exercise
Specificity is an important parameter of an exercise training program
Jumping movement is inherent in most sports
Running is a repeated series of jump-landing cycles
Therefore, jump training should be used in the design and implementation of the overall training program and rehabilitation

3. What is Plyometric Exercise
Success in most activities is dependent upon the speed at which muscular force and power is generated.
Power combines strength and speed
Can be increased by increasing the amount of work or force that is produced and decreasing the amount of time required to produce force
Plyometrics is a form of training that attempts to combine speed of movement with strength

4. What is Plyometric Exercise
Plyometrics=quick, powerful movement involving pre-stretching of muscle and activating the stretch-shortening cycle to produce a subsequently stronger concentric contraction.
Takes advantage of stretch-shortening cycle (SSC) to increase muscular power

5. What is Plyometric Exercise
Main purpose of plyometric training is to heighten the excitability of the nervous system for improved reactive ability of the neuromuscular system

6. Plyometric Exercise
Myotatic stretch reflex used to produce powerful response of contracting muscles
Upon landing muscles undergo a lengthening eccentric contraction to decelerate movement and pre-stretch the muscles
Pre-stretch energy is then immediately released in an equal and opposite reaction
Produces kinetic energy
Neuromuscular system must react quickly to produce concentric shortening contraction to produce upward change in direction

7. Plyometric Exercise
Plyometric exercise should be used to prepare athletes for return to activity
Train specific movements in a biomechanically accurate position
Specific functional exercise used to emphasize the rapid change of direction
Can be used for upper and lower extremities
Whether athlete is jumping or throwing the musculature around the joint must first stretch and then contract to produce explosive movements

8. Biomechanical and Physiological Principles
Stretch-shortening cycle:
Coupling of eccentric-concentric muscle contraction
Movement rarely begins from static position
Preceded by eccentric pre-stretch that loads muscle and prepares for concentric contraction
2 components work together to produce response:
Proprioceptive reflexes
Mechanical: Elastic properties of muscle fibers

9. Mechanical Characteristics of a Muscle
Three component model
Contractile component (CC)
Series Elastic Component (SEC)
Parallel Elastic Component (PEC)
All interact to produce a force output
CC focal point of motor control, however SEC & PEC provide stability and integrity to fibers as muscle is lengthened
During lengthening energy is stored within the musculature in the form of kinetic energy

10. Mechanical Characteristics of a Muscle
When a stretch is applied , potential energy is stored
That energy is applied as it returns to its normal length when the stretch is released
Analogy: stretching a rubber band
Significant increases in concentric muscle force production has been documented when immediately preceded by an eccentric contraction
Uses the elastic energy stored during eccentric contraction

11. Mechanical Characteristics of a Muscle
Ability to use stored elastic energy affected by 3 variables
Time
Magnitude of the stretch
Velocity of the stretch
In order to increase concentric force production eccentric contraction must be of short range and performed quickly without delay
If large range, slow, with delay stored energy will be lost

12. Neurophysiological Mechanisms
Proprioceptive stretch reflex:
Involve the mechanoreceptors in the muscle:
Muscle spindle:
When muscle spindle is stretched sensory response sent to CNS and neurological impulses sent back to muscle causing motor response
Strength of muscle spindle response is determined by rate of stretch
More rapidly load applied, greater firing frequency of the spindle and stronger muscle contraction

13. Neurophysiological Mechanisms
Golgi Tendon Organ:
Inhibitory effect by contributing a tension limiting reflex, restricting the amount of force that can be produced
Theorized that Plyometrics desensitizes GTO and allows more force to be produced

14. Neurophysiological Mechanisms
Dependent on time frame between eccentric and concentric contraction
Amortization phase
Electromechanical delay between eccentric and concentric contractions when muscle must switch from overcoming work to acceleration in opposite direction
Increased amortization phase leads to decrease in force production and vice versa
Neurophysiological Mechanisms
Increased force production seen during SSC due to combined effects of stored elastic energy and the Myotatic stretch reflex
Increased amount of force production dependent upon the time frame between eccentric and concentric contractions
Defined as Amortization Phase
Electromechanical delay between eccentric and concentric contractions
Muscle must switch from overcoming work to acceleration in opposite direction
Increased time in amortization phase will lead to decrease in force production

15. Neuromuscular Considerations
Plyometric training can promote changes within the neuromuscular system
Allow individual to have better control of contracting muscle and synergists
Can increase performance by enhancing nervous system to become more automatic

16. Program Development
Should begin with establishing adequate strength base
Allow body to withstand large stress placed on it (Safety)
Allow for greater force production
Increase in CSD of muscle will increase potential to store greater amounts of elastic energy

17. Plyometric Pre -requisites
Biomechanical Examination
Functional movement screening
Strength test
Poor strength and mechanics will result in loss of stability and increased stress absorbed in wt. bearing tissue
Decrease performance and increase risk of injury
Stability Test
Static and Dynamic Balance Test

18. Plyometric Pre -requisites
Dynamic Movement Test
Single Leg Hop test-LE
Seated chest pass or sit up and throw test -UE
Flexibility
General and specific flexibility
High amount of stress applied to musculoskeletal system
Should do general and specific warm up before plyometric exercise

19. Plyometric Pre -requisites
Classify individual as beginner, intermediate or advanced
Dependent on information found through biomechanical, stability, and dynamic testing
Will determine where athlete begins plyometric program
Take into consideration tissue healing if post-injury
Take into consideration sport so Plyometric training can be specific to athletes position
SAID Principle!!!!!

20. Plyometric Program Development
Direction of Body Movement
Weight of Patient
Speed of Execution
External Load
Intensity
Volume
Frequency
Training Age
Recovery

21. Plyometric Program Development
Beginning of plyometric program emphasize technique and principles of Plyometrics
For example, the importance of short amortization phase
Minimal time on ground, reverse the landing as quickly as possible
Focus on body, control, posture and mechanics
As intensity increases, volume should decrease
Plyometrics should be used in later phases of rehabilitation.
After appropriate strength base established and athlete has performed closed chain exercises

22. Guidelines for Plyometric Programs
Sound, technical foundation
Force reduction and force production should be absorbed throughout entire body
Ankle, knee, hip, trunk, arms
Time and coordination of these body segments will yield positive ground reaction and high rate of force production

23. Guidelines for Plyometric Programs
Specific to individual goals of athlete
Quality of work more important than Quantity
Greater intensity the greater recovery time required
Low to medium intensity if done at conclusion of workout, high if done before
When to fatigued to maintain proper technique exercise should stop

24. Guidelines for Plyometric Programs
Progressive in nature
Only 2 to 3 times a week depending on periodization
Dynamic testing on regular basis to provide motivational feedback
Proper equipment: footwear, landing surface, external loads…Safety First!!

25. Plyometrics in Rehabilitation
Involve loading of the healing tissue
Medial and Lateral Loading
Ability to accept weight on injured extremity and change direction
Imperative to return to sport with cutting maneuvers (Most Sports)
Rotational Loading
Same as above
Shock Absorption (Deceleration Loading)
Eccentric load of muscle and tendon
Increase in tensile strength

26. Specific Plyometric Exercises
Double extremity to Single Extremity
Vertical Hops to Lateral Hops to Diagonal Hops
Flat surface to box jumps
Non weighted to weighted
Jumps to Hops to Bounding
Manipulate Volume, frequency, and intensity to advance program appropriately
Re-evaluate and re-assess athlete to prevent injury and provide motivational feedback