Plyometric exercises are widely used in the strength and conditioning space to increase the explosive power of athletes. Plyometric exercises refer to those exercises that enable a muscle to reach maximal force in the shortest possible time. Plyometric is actually a combination of two Greek words, plio and metric. Plio means more and metric means measure. (Source: Essentials Of Strength and Conditioning, Fourth Edition, by Haff and Triplett). Simply put, plyometric exercises, or plyos as they are more popularly known in the sporting world, are quick, powerful movements using a pre-stretch or a counter-movement that involve creating a rebound effect in the muscle and generating a powerful catapult.
Football, basketball and badminton players, for example, must make quick powerful movements and perform change of direction in all planes to compete successfully. A basketball centre is required to jump repeatedly for rebounds. He has to out-jump the opposing centre in order to rebound more loose balls. A diving or leaping football goalkeeper save and a tennis jump smash are also great examples of plyometric activities. An elite baseball pitcher routinely throws the ball at 80-100 mph. To reach velocities of this magnitude, the shoulder joint must move at more than 6000 degrees/sec. A fast bowler in cricket must have to face similar demands. Plyometric training of the shoulder joint would not only increase pitching and bowling velocity; it may also help prevent injuries to the shoulder and elbow joints.
Who qualifies for plyometric training? (Safety considerations)
Plyometric training puts great stress on muscles, ligaments, tendons and joint capsules. It is imperative that certain safety parameters are met before an athlete embarks on a plyo programme. Good technique is the biggest safety parameter. For lower body plyos, the athlete must have knowledge of proper landing technique. The shoulders should be over the knees and the knees should be over the toes during landing. Inward movement of the knees is a significant risk factor for knee injuries of all types including patella femoral pain and rupture of the ACL.
Shoulder stability and thoracic spine mobility is a necessary parameter for upper body plyometrics. Balance parameter is also critical. An athlete should be able to stand 30 seconds without falling before starting a plyo programme. An experienced athlete beginning an advanced programme should be able to hold a single leg half squat for 30 seconds. Athletes who weigh more than 100 kg are at increased risk of injury when performing plyometric exercises. Greater weight increases compressive force on joints during the exercises, thereby predisposing these joints to injury. Therefore, athletes weighing more than 100 kg should avoid high volume, high-intensity exercises from heights greater than 18 inches.
An athlete’s previous injuries and joint structures must also be considered and properly examined before commencing a programme. Previous injuries and abnormalities of the spine, lower extremities and upper extremities may increase the athlete’s risk of injury during plyometrics.
Landing surface and training area
In order to prevent injuries, landing surface used for lower body plyos must possess shock-absorbing properties. A grass field, suspended floor or a rubber mat is a good surface choice. Surfaces such as hard wood, concrete and tile are not recommended because they lack shock absorbing qualities.
Most drills will need at least 30m of straightaway and a ceiling height of 3-4m in order to be adequate.
Participants must use shoes with proper ankle and foot support, good lateral stability and wide, non-slip sole. Poor footwear will increase the risk of injuries to the lower extremities.
Finally, a word on supervision. plyos are not inherently dangerous when performed correctly. However, close monitoring and correct prescription is required as like all forms of training, poor form and planning can unnecessarily predispose an athlete to injury.
Click to see the four commonly and popularly used plyometric drills.