Plyometric exercise is used in sport-specific training to enhance power and performance. Plyometrics is defined as activities that enable a muscle to reach maximal force in the shortest amount of time, according to the National Strength and Conditional Association. Essentially, plyometric exercises enhance the series elastic component and the stretch reflex by using movements similar to those used in the athlete's sport.
Series Elastic Component
The series elastic component, or SEC, is primarily made up of tendons and some muscle tissue. When the SEC is stretched or lengthened, as in an eccentric muscle action, it acts in a similar fashion to a spring and stores energy as it is lengthened. Eccentric action is the lengthening of a muscle such as during the extension of a biceps curl; concentric action is the shortening of a muscle, such as in the flexion of a biceps curl. When the eccentric muscle action is immediately followed by a concentric muscle action, the stored energy is released, resulting in an explosive movement, such as in a jump.
There is also a neurophysiological model of plyometric exercise known as the stretch reflex. This involves the change in force-velocity of a muscle, caused by the stretch of the concentric muscle action. The stretch reflex happens when a quick stretch is detected in the muscles and an involuntary response occurs to prevent overstretching and injury, according to Phil Davies of Sports Fitness Advisor. During plyometric exercise, this results in a powerful concentric muscle action, such as when your feet leave the ground in a squat jump.
Types of Exercise
Plyometrics exercise can be used for upper- or lower-body drills and are typically high intensity. Lower-body plyometric drills might include squat jumps, bounds or box drills. Box drills require the athlete to jump on or off a box. The height of the box and landing surface of the box can vary in size, and box drills may involve the use of both legs or just one leg. Upper-body plyometric drills might consist of medicine ball throws and catches or clap pushups.
Because plyometric exercises are high intensity and high impact, those with osteoporosis or who are susceptible to breaking bones should not perform them. If you are a beginner, establish a solid base of strength, speed and balance prior to learning the proper techniques of plyometric drills. Proper warmup is also necessary before plyometric drills. To reduce the risk of injury, do plyometric workouts no more than two times a week on nonconsecutive days.