Intersegmental dynamics of the lower limb in vertical jumps

The purpose of this study was to investigate changes in intersegmental dynamics of the lower limb at the instant of push-off in vertical jumps. Using a mathematical model including dynamic equations, the net joint moment (NET) was decomposed into a muscle moment (MUS), gravitational moment, and interaction moment (INT) in terms of joint acceleration and velocity. Ten subjects performed two submaximal jumps (60% and 80% of maximal height) and one maximal jump. Results showed that the hip and ankle joints mainly utilized MUS to generate NET at the push-off instant, while the knee joint primarily used INT at the instant of push-off. The hip MUS increased with increasing jump height because the deep countermovement (larger flexion angle of hip and knee joint at the push-off instant) in maximal jump was a disadvantage from intersegmental dynamics, but may be neurophysiologically advantageous.