The aim of this study was to test the hypothesis that the maximal instantaneous muscular power of humans (w_ p) is affected by the negative work performed immediately before the jump (wn), 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_ p, the average power (w_ a) and wn 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 wn was higher in CM than in SQ and in FF than in CM and SQ. The w_ p was 3.51 ± 0.54 kW in SQ and did not vary in CM and FF. The w_ a increased with increasing wn (1.70 ± 0.30; 1.85 ± 0.34; 1.99 ± 0.31 kW in SQ, CM and FF, respectively, p