Yanai Toshimasa
School of Physical Education, University of Otago, PO Box 56, Dunedin, New Zealand.
J Biomech. 2004 May;37(5):605-12. doi: 10.1016/j.jbiomech.2003.10.004.
The present study was conducted to determine the contribution of the turning effect of buoyant force for generating bodyroll and its relationship with the subjects' variability in swimming speed at distance pace and sub-maximal sprinting pace. The performances of front crawl swimming performed by 11 skilled swimmers were recorded with two panning periscopes for three-dimensional analysis. The bodyroll (BR) exhibited by each of the 11 male competitive swimmers was determined for every given instant as the time-integral of the conceptual angular velocity of the entire body about the long-axis, which was computed from the angular momentum and the moment of inertia of entire body. The part of BR generated by the buoyancy torque (BR(BT)) was determined from the moment of inertia of the entire body and the double time-integral of the buoyancy torque. The mean value for the peak-to-peak amplitude of the buoyancy torque was 15 Nm at distance pace and 19 Nm at sub-maximum sprinting speed. The contribution of buoyancy to BR was significantly greater ( P < 0.01) than that of the hydrodynamic forces. The individual swimming speed at sub-maximal sprinting pace was positively correlated ( P < 0.04) with the contribution of buoyancy to BR. These results showed that the skilled swimmers used buoyant force as the primary source of generating BR, and that faster swimmers used buoyant force more effectively to generate BR than slower swimmers. Based on the results and subsequent theoretical analysis, possible patterns of arm-BR coordination that may increase the effectiveness of using buoyant force for BR are discussed.
本研究旨在确定浮力的转动效应在产生身体滚动方面的作用及其与受试者在长距离配速和次最大冲刺配速下游泳速度变异性的关系。使用两个平移潜望镜记录了11名熟练游泳者的自由泳表现，以进行三维分析。对于11名男性竞技游泳者中的每一位，在每个给定时刻，将身体滚动（BR）确定为整个身体围绕长轴的概念角速度的时间积分，该角速度由整个身体的角动量和转动惯量计算得出。由浮力扭矩产生的BR部分（BR(BT)）由整个身体的转动惯量和浮力扭矩的双重时间积分确定。在长距离配速下，浮力扭矩的峰峰值平均为15 Nm，在次最大冲刺速度下为19 Nm。浮力对BR的贡献显著大于（P < 0.01）水动力的贡献。次最大冲刺配速下的个人游泳速度与浮力对BR的贡献呈正相关（P < 0.04）。这些结果表明，熟练的游泳者将浮力作为产生BR的主要来源，并且速度较快的游泳者比速度较慢的游泳者更有效地利用浮力来产生BR。基于这些结果和后续的理论分析，讨论了可能增加利用浮力产生BR有效性的手臂-BR协调模式。
