Determinants of ability to achieve ballistic stretch-shortening cycle movement. With special reference to strength and power / 体力科学

ABSTRACT

Long jump and high jump, and several types of jumping and footwork with rapid changes in speed and direction of movement in ball games are characterized not only by a combination of eccentric and concentric movement (stretch-shortening cycle movement, SSC) but also a ballistic movement of very short duration (100-200 ms) . This study was conducted to examine the effects of strength and power on ballistic stretch-shortening cycle movement (BSSC) ability to clarify the methods of strength and power training necessary for jumpers and ball game players. The subjects were 99 male college athletes. The index for BSSC ability was RDJ<SUB>index</SUB> [RDJ<SUB>index</SUB> = (1/8⋅g⋅RDJt<SUB>a</SUB><SUP>2</SUP>) /RDJt<SUB>c</SUB>] which was calculated using contact time (RDJt<SUB>c</SUB>) and air time (RDJt<SUB>a</SUB>) in a rebound drop jump from a height of 0.3 m with a small angular range of motion for the knee. The index for strength was maximum leg extension strength exerted in a squat position at a 90° knee angle (Smax/BW) . The index for power was the height of a counter movement jump (CMJh) . Results were summarized as follows;<BR>(1) There were significant correlations between RDJ<SUB>index</SUB>and Smax/BW (r=0.219, p <0.05), RDJ<SUB>index</SUB>and CMJh (r=0.584, p<0.001), and Smax/BW and CMJh (r=0.487, p<0.001), but they were fairly low, suggesting that these indices do not have similar significance for estimating training effects and sports talent.<BR>(2) There was no significant correlation between RDJt<SUB>c</SUB>and RDJt<SUB>a</SUB>, of which the RDJ<SUB>index</SUB>was composed (r=-0.145, ns) . This result suggests that BSSC ability consists of two independent abilities, i. e. the ability to jump higher and the ability to shorten one's movement time.<BR>(3) There were significant correlations between RDJt<SUB>a</SUB>and Smax/BW (r=0.340, p<0.001), RDJt<SUB>a</SUB>and CMJh (r = 0.647, p <0.001), but not RDJt<SUB>c</SUB>and Smax/BW (r=0, 035, ns), or RDJt<SUB>c</SUB>and CMJh (r=-0.187, ns), suggesting that the ability to jump higher is affected by strength and power whereas the ability to shorten one's movement time is not.<BR>(4) When subjects with equal RDJ<SUB>index</SUB>were compared, one subject was dominant in RDJtc and another in RDJt<SUB>a</SUB>. This result suggests that we should consider individual differences based on RDJt<SUB>c</SUB>and RDJt<SUB>a</SUB>in training for increasing the RDJ<SUB>index</SUB>.<BR>These findings seem to be useful to clarifying the methods of strength and power training for jumpers and ball game players who need to improve their ballistic stretch-shortening cycle movement ability.