The effects of negative work on the maximal instantaneous muscular power of humans during vertical jumps

摘要

The aim of this study was to test the hypothesis that the maximal instantaneous muscular power of humans (w˙w˙ p) is affected by the negative work performed immediately before the jump (w n), possibly due to the recoil of elastic strain energy stored in previously stretched series-elastic elements of the muscle–tendon complex. Twenty-seven Bantu subjects (age 25.1 +- 4.3 years, body mass 67.5 +- 7.8 kg) were investigated. The w˙w˙ p, the average power (w˙w˙ a) and w n were determined during maximal vertical jumps off both feet on a force platform. Three jumping conditions were studied: squat jumps (SQ), countermovement jumps (CM), and jumps preceded by a free fall (FF) from a height of 0.3 m above the platform surface. The w n was higher in CM than in SQ and in FF than in CM and SQ. The w˙w˙ p was 3.51 +- 0.54 kW in SQ and did not vary in CM and FF. The w˙w˙ a increased with increasing w n (1.70 +- 0.30; 1.85 +- 0.34; 1.99 +- 0.31 kW in SQ, CM and FF, respectively, p < 0.05). The greater was the w n, the higher was the force at the start of the positive push phase, and thus the maximal force attained during the push phase. In conclusion, w˙w˙ p was independent of wn, whereas w˙w˙ a was affected, because a greater force was developed over a shorter time during the push. The independence of w˙w˙ p of w n leads to refutation of the tested hypothesis.