Plyometrics in Rehabilitation

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. 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