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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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!!!!!

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

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

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

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

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!!

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

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