Plyometrics
Plyometrics, also known as plyos, are exercises in which muscles exert maximum force in short intervals of time, and activating a rapid stretch-shortening cycle. While commonly associated with jumping, plyometrics can include explosive upper-body movements, such as plyometric push-ups and switch-ups, with the goal of increasing muscular power (speed-strength).
This training focuses on learning to move from a muscle extension to a contraction in a rapid or "explosive" manner, such as in specialized repeated jumping. The amortization phase (transition from extension to contraction) must be very brief, as a slow transition will not fully release elastic energy stored in eccentric phase, and instead some stored energy leaks away as heat. For example, a person lands after jumping and absorbs any shock. The thigh (quadricep) muscles extend during this process. The amortization phase begins which involves the reorientating and channeling of the stored muscular energy from the landing and shock absorption, into the preparatory and preloading action for the jump. This energy is then subsequently channeled into the main jumping action which involves the thigh muscles contracting. In plyometrics, it is important that the amortization phase is completed as quickly as possible in order to maximise the potential to bridge between the landing and jumping actions and transfer energy between them. Describing the changes as occurring between phases of muscle extension and contraction is a simplification of the overall process which is more complex and involves a system of simultaneously occurring and interconnected muscle extensions and contractions.
Stretch shortening cycle training loads tendons elastically and when done properly, it can yield benefits including improved landing mechanics, force absorption, joint stability and greater force and power output, with transferability to many athletic activities, such as sprinting, where similar repetitive movements are required. Progressive plyometric training can also help to reduce the chances of injury, especially to the lower leg, ankle and foot.
Plyometrics are frequently used by athletes, especially martial artists, sprinters and high jumpers, to improve performance, and are used in the general fitness field to a lesser degree.