Plyometrics

How Plyometric Exercises Work
A muscle that is stretched before a concentric contraction, will contract more forcefully and more rapidly (4,5). A classic example is a “dip" just prior to a vertical jump. By lowering the center of gravity quickly, the muscles involved in the jump are momentarily stretched producing a more powerful movement. But why does this occur?

Plyometrics & Injury
Strength and conditioning specialists are often cautious in their prescription of plyometrics due to what they believe is an inherent risk of injury. However, there is limited data to either confirm or reject this claim.
Several researchers have explicitly stated that no injuries occurred during their plyometric studies (13,33,34). Most do not mention whether injuries occurred or not or to what extent.
As a precaution it has been suggested that athletes have a substantial strength training background. The criteria often cited is that the athlete should be able to back squat 1.5-2x bodyweight (2,3,35) for lower body plyometrics and bench press 1x bodyweight for upper body plyometrics (3,35).
If injuries are more likely to occur with this form of training it may be due to improper landing, landing surface or depth jumps from too great a height (1). Several studies have measured the height of depth jumps on vertical jump performance. Depth jumps from both 50cm (19.7) and 80cm (31.5in) both improved power to the same extent (13). The same results were found between jumps of 75cm and 110cm (31) and between jumps of 50cm and 100cm (16). This suggests that there may be little or no added benefits of jumping from heights above 50cm (19.7in) even though the risk of injury is likely to rise.
Finally, landing surface is an important component of the plyometrics session. It should posses adequate shock absorbing properties such as grass, rubber mats and a suspended floor. Concrete, tiles, hardwood and crash mats are not suitable (35).

References

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