Although maximum height (H(max)), muscle force (F), and power output (P), have been routinely obtained from maximum vertical jumps for various purposes, a possible role of the countermovement depth (H(cmd)) on the same variables remains largely unexplored. Here we hypothesized that (1) the optimum H(cmd) for maximizing H(max) exists, while (2) an increase in H(cmd) would be associated with a decrease in both F and P. Professional male basketball players (N=11) preformed maximum countermovement jumps with and without arm swing while varying H(cmd)±25 cm from its preferred value. Although regression models revealed a presence of optimum H(cmd) for maximizing H(max), H(max) revealed only small changes within a wide range of H(cmd). The preferred H(cmd) was markedly below its optimum value (p < .05). However, both F and P sharply decreased with H(cmd), while F also revealed a minimum for H(cmd) close to its highest values. Therefore, we conclude that although the optimum H(cmd) should exists, the magnitude of its effect on H(max) should be only minimal within a typical H(cmd) range. Conversely, F and P of leg muscles assessed through maximum vertical jumps should be taken with caution since both of them could be markedly confounded by H(cmd).
Keywords: Arm swing; Ground reaction force; Jump height; Power output; Regression.
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