Plyometric drills decrease the reaction time of the nervous system in response to external stimuli. This allows the muscles to contract faster to prevent falling or twisting an ankle. The technique was first used during the 1960's and 70's by eastern European athletes, who organised hopping and jumping techniques into specific plyometric drills.
As the athlete plants their foot before jumping, the muscle that will produce the jump is stretched. As the muscle contracts, the pre-stretched energy is released, producing kinetic energy (movement) which enhances muscle power. By doing plyometric drills the time taken for the stretch to be converted into kinetic energy is decreased.
Before initiating plyometric activities there must be a sound strength base, otherwise the risk of injury is increased. As a general rule the athlete should be comfortable in squatting 60% of their body weight, at a rate of 5 repetitions in 5 seconds, before these exercises are commenced. The athlete should be able to stand on one leg, with eyes both open and shut, for 30 seconds and should be able to long jump the distance of their own height.
Ideally, plyometric training should be done under the supervision of a trainer or chartered physiotherapist.