Body size and countermovement depth confound relationship between muscle power output and jumping performance

A number of studies based on maximum vertical jumps have presumed that the maximum jump height reveals the maximum power of lower limb muscles, as well as the tested muscle power output predicts the jumping performance. The objective of the study was to test the hypothesis that both the body size and countermovement depth confound the relationship between the muscle power output and performance of maximum vertical jumps. Sixty young and physically active males were tested on the maximum countermovement (CMJ) and squat jumps (SJ). The jumping performance (H-max), peak (P-peak) and the average power output (P-avg) during the concentric phase, countermovement depth (only in CMJ) and body mass as an index of body size were assessed. To assess the power-performance relationship, the correlations between H-max with both P-peak and P-avg were calculated without and with controlling for the effects of body mass, as well as for the countermovement depth. The results revealed moderate poliver-performance relationships (range .55<.64) that were comparable for CMJ and SJ jumps. When controlled for body mass, the same values were markedly higher (.61<.82; p<.05 for P-peak of both jumps). When controlled for both the body mass and countermovement depth, CMJ revealed r=.88 and r=.77 for P-peak and Pan, respectively. Both jumps revealed stronger relationships with P-peak than with P-avg (p<.05) when controlled for either body mass or both body mass and countermovement depth. We conclude that both body size (in CMJ and Si) and countermovement depth (in CMJ) confound the relationship between the muscle power output with the performance of maximum vertical jumps. Regarding routine assessments of muscle power from jumping performance and vice versa, the use of CMJ is recommended, while P-peak, rather than P-avg, should be the variable of choice. (C) 2013 Elsevier B.V. All rights reserved.