Rehabilitation Leaps

Paris 2024 Olympics - Beach Volleyball - Eiffel Tower Stadium, Paris, France Andre Loyola Stein of Brazil in action. REUTERS/Arlette Bashizi

Plyometrics involve a series of jumps, hops, bounds, or ballistic-type movements characterized by quick ground contact time and a rapid stretch-shortening cycle (SSC)⁽¹⁾. This rebound activity capitalizes on the neuromuscular and physiological properties of the musculotendon unit (MTU) to increase the muscle’s potential to maximize the force produced within the shortest time possible⁽²⁾. 

Russian national track and field coach Dr Verkhosshanski initially described plyometrics as the shock method or shock training⁽³⁾. Then, the American coach Fred Wilt conceived the term in 1975. The term is derived from the Greek words plyo, which means to increase, and metric, which means to measure, collectively giving the purpose of plyometrics to improve the measurement⁽²⁾. The measurement is any sports performance outcome that can be measured through tests such as jump height, speed, throwing, or serve velocity^(2,4).

Each of these elements requires power development, a key component of plyometric training. Plyometrics mimics specific short-duration high-intensity actions within sports and is critical in strength and conditioning and performance enhancement programs⁽⁵⁾. For example, football and basketball players require rapid direction changes in all planes. Furthermore, endurance runners or cyclists would benefit from plyometric training, allowing their muscles to produce greater force with less energy.

Plyometrics are also beneficial in injury prevention by improving joints’ range of motion and throwing velocity. For example, professional baseball pitchers will reach velocities of 80-100 miles per hour, with their shoulder joints moving more than 6000 degrees/second⁽⁶⁾. Further benefits occur in the terminal phase of rehabilitation, where the aim is to rehabilitate the athlete as quickly as possible and provide a safe return to sports, e.g., plyometric training in anterior cruciate ligament rehabilitation (ACL) can improve force distribution^(7,8).

Plyometric Phases

Plyometrics involve a rapid eccentric (muscle lengthening) contraction, a concentric (muscle shortening) contraction, and a transition in between. Blending these three phases produces the plyometric movement and influences the muscle’s power performance (see figure 1)⁽²⁾.

Eccentric/landing phase: The MTU’s muscle spindle and the non-contractile tissues within the muscle are stretched, causing the MTU to deform under load and eccentrically lengthen.

Transition phase: This is the time to re-bound between the eccentric and concentric phases and equates to the time to overcome the negative work of the pre-stretch to generate force production in the concentric phase. The kinetic energy used in the eccentric phase is transferred and stored as elastic potential energy relative to the degree of tendon stiffness. The muscles are working isometrically. This phase needs to be as short as possible to allow the stored energy to be used efficiently in the transition and avoid dissipating.

Concentric/take-off phase: The stored energy is converted back to kinetic energy to accelerate the muscle contraction and elastic recoil and propel the force of movement into the applied direction. The muscle concentrically contracts explosively.