Plyometrics

Plyometrics, also known as plyos, are exercises in which muscles exert maximum force in short intervals of time, and activate a rapid stretch-shortening cycle where muscles quickly alternate between states of extension and contraction. While commonly associated with jumping, plyometrics can also include explosive upper-body movements, such as plyometric push-ups, with the goal of increasing upper-body 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 the eccentric phase, and instead some stored energy leaks away as heat. For example, a person lands after jumping, safely absorbs any shock, and immediately recovers balance and energy. As the leg bends, the thigh (quadricep) muscles extend. The amortization phase begins which involves the reorientating and channelling of the stored muscular energy from the landing, shock absorption and immediate recovery phase into the preparatory and preloading action for the jump. This energy is then subsequently channelled 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. The rapid changes of a plyometric jump cycle are designed to harness the body's stretch-shortening cycle to a greater extent than would be possible otherwise. 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.

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