DETERMINANTS OF THE MAXIMAL MECHANICAL POWER DEVELOPED DURING THE COUNTERMOVEMENT JUMP (CMJ)
AbstractINTRODUCTION A countermovement (a preparatory movement in the direction opposite to that of the goal) increases performance in explosive movements such as the CMJ. The height of jump and the maximal power relative to body weight have been reported to be significantly correlated. Our previous observations has suggested the take-off technique (the countermovement depth) to affect power rather than height of jump. The purpose of the present study was to determine the influence of the height of jump, of the countermovement depth and of body mass on the maximal mechanical power developed during the positive take-off phase. METHODS Untrained students (56 female and 38 male) volunteered to take part in the CMJ jumping test consisting of 3 jumps performed with one-minute intervals on the computerized Kistler force plate. The subjects were requested to jump on the maximal height possible. Results of the highest jump were selected for each subject for further processing. The following variables were included into statistical analysis: the maximal mechanical power (PmaJ developed during the take-off, the height of jump (H), lowering of the body mass center before the take-off (L). and body mass (mb)' The Shapiro-Wilk test was used to examine the distributions of the tested variables. Pearson's correlation matrix and multiple regression analysis were employed to identity the parameters of the Pmax statistical model. Dolittle's method was used to estimate the contribution of the selected jump variables to the Pmax. RESULTS In both female and male groups the multiple regression procedure (the forward stepwise method) employed all the independent variables studied to construct the regressions equations. both of them proving very highly significant (p<0.OO1). The following equations describing the P".. dependencies upon H. Land mb in both groups were obtained: for females: Pmu=0.627.H-O.326.L+16.6.mb-61 0, for males: PIllu=0.640•H-O.474-L+37.7.mb-1972. The obtained models explained 80.8% and 88.4% of the Pma variance, respectively. Neither the countermovement depth, nor body mass were correlated with the height of jump. CONCLUSIONS The correlation between the maximal mechanical power developed during the take-off and the height of jump becomes highly significant, when the countermovement depth is taken to consideration. The countermovement depth significantly influences the maximal power developed, having no effect on the height of jump. The maximal mechanical power can be easily and accurately estimated by using simple parameters, which can be measured without any sophisticated equipment REFERENCES Bobert et al. In: Book of Abstract. XV ISB Congress. Jyväskylä, 1995 Dowling J.J., Vamos L. J.Appl. Biomech. 9:95-110,1993. Viitasalo J. Res. Q Exer. Sport 59:9-13, 1988.
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