Seldom-Used Words

...a type of exercise training designed to produce fast, powerful movements, and improve the functions of the nervous system, generally for the purpose of improving performance in sports. Plyometric exercises may also be referred to as explosive exercises. Plyometric movements, in which a muscle is loaded and then contracted in rapid sequence, use the strength, elasticity and innervation of muscle and surrounding tissues to jump higher, run faster, throw farther, or hit harder, depending on the desired training goal. Plyometrics is used to increase the speed or force of muscular contractions, providing explosiveness for a variety of sport-specific activities. Plyometrics has been shown across the literature to be beneficial to a variety of athletes. Benefits range from injury prevention, power development and sprint performance amongst others...


Muscle-tendon component:
For a muscle to cause movement, it must shorten; this is known as a concentric contraction. There is a maximum amount of force with which a certain muscle can concentrically contract. However, if the muscle is lengthened while loaded (eccentric contraction) just prior to the contraction, it will produce greater force through the storage of elastic energy. The quick transition from the eccentric to the concentric phase is known as the stretch shortening cycle (SSC), and is one of the underlying mechanisms of plyometric training.The force created by the muscled-tendon during the SSC is determined by the muscle's length and compliance. To increase power through plyometrics two integral controlling aspects are required. These aspects include “a more rapid initial stretch, which generates more power in the muscle group moving in the opposite direction in the second phase of the action; and a shorter time between eccentric and concentric contractions (SSC)".

Nearly all animals have different types of muscles to produce different types of reactions. Humans have three different types of muscle fibers: slow-twitch (Type I), fast-twitch A (Type IIa), and fast-twitch B (Type IIb). Type I muscle fibers are recruited for aerobic activities, so therefore contract slowly, but are very resistant to fatigue. Type IIa muscle fibers have both endurance and power characteristics and are recruited for long anaerobic activities. They lie in the middle of Type I and Type IIb muscle fibers as they are more fatigue resistant than Type IIb muscle fibers, but less fatigue resistant than Type I muscle fibers. Type IIb muscle fibers are recruited only for short intense activities like lifting heavy objects, sprinting and jumping. Exercising fast twitch muscles to produce quicker reactions is the basis of plyometrics.

Although each type of muscle fiber cannot be converted into another (i.e. fast-twitch to slow-twitch), specific types of training can increase the area occupied by the targeted muscle fiber. Fast twitch muscle fibers have a greater ability to hypertrophy, therefore specified training targeting fast twitch muscle fibers can increase the area in the muscle that fast twitch muscle fibers will occupy. For example if the occupancy of fast twitch to slow twitch muscle fibers is 50-50, with the right training regiment, fast twitch muscle fibers may increase to occupy 75% of that muscle.

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