Speed and strength are integral components of fitness found in varying degrees in virtually all athletic movements. Simply put the combination of speed and strength is power. For many years, coaches and athletes have sought to improve power in order to enhance performance. Throughout this century and no doubt long before, jumping, bounding and hopping exercises have been used in various ways to enhance athletic performance. In recent years, this distinct method of training for power or explosiveness has been termed plyometrics. Plyometrics is based on the understanding that a concentric muscular contraction is much stronger if it immediately follows an eccentric contraction of the same muscle.
A plyometric exercise comprises of three phases:
- Eccentric phase, or landing phase, involves the pre-loading (energy is stored) of the agonist muscle group
- Amortization phase, or transition phase, is the time between the concentric and eccentric phases. This time needs to be as short as possible otherwise the energy stored during the eccentric phase dissipates, reducing the plyometric effect
- Concentric phase, or take-off phase, uses the stored energy to increase the force of the movement