Nakazono Yusaku, Shimojo Hirofumi, Sengoku Yasuo, Takagi Hideki, Tsunokawa Takaaki
Graduate School of Comprehensive Human Sciences, Doctoral Program in Physical Education, Health and Sport Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, Japan.
Department of Health and Sports, Niigata University of Health and Welfare, Niigata, Japan.
J Biomech. 2024 Mar;165:112020. doi: 10.1016/j.jbiomech.2024.112020. Epub 2024 Feb 24.
Increasing the velocity of the lower-limb movement is crucial for improving underwater undulatory swimming (UUS) velocity. However, the underlying mechanism of how these movements influence swimming velocity have remained unclear. This study aimed to clarify the relationship between changes in swimming movement and the resulting changes in flow field as a result of changes in test flow velocity (U) in a water flume. A male student swimmer was tested with the following three U settings 0.8, 1.0 and 1.2 m/s. The lower-limb movements and wake flow behind the swimmer were compared. A motion capture system was employed for motion analysis, and a stereo PIV for visualizing the flow field. The findings revealed that, as U increased, the velocity vectors of the flow field in all directions (u, v, w) increased, as did the toe velocity. It was also suggested that with increasing U, the outward change in the toe velocity vector down-kick and the inward change in the toe velocity vector up-kick may have a positive effect on the vortices, contributing to an increase in the velocity vectors in the flow field. Furthermore, the high U, vortex re-capturing occurred during the transition from down-kick to up-kick, indicating that this might contribute to increased momentum. This suggests that the transition from the down-kick to the up-kick is necessary for gaining greater momentum. Notably, this study is the first to identify the factors that increase the swimming velocity of the UUS in the context of movement and flow field.
提高下肢运动速度对于提升水下波动式游泳（UUS）速度至关重要。然而，这些运动如何影响游泳速度的潜在机制仍不清楚。本研究旨在阐明在水槽中，测试水流速度（U）变化导致的游泳运动变化与流场变化之间的关系。一名男性学生游泳运动员在以下三种U设置下接受测试：0.8、1.0和1.2米/秒。比较了游泳运动员的下肢运动和身后的尾流。采用运动捕捉系统进行运动分析，并使用立体粒子图像测速技术（PIV）来可视化流场。研究结果表明，随着U的增加，流场在所有方向（u、v、w）上的速度矢量增加，脚趾速度也增加。还表明随着U的增加，脚趾速度矢量向下踢时的向外变化和向上踢时的向内变化可能对涡旋有积极影响，有助于增加流场中的速度矢量。此外，在高U时，从向下踢到向上踢的过渡过程中会发生涡旋重新捕获，这表明这可能有助于增加动量。这表明从向下踢到向上踢的过渡对于获得更大的动量是必要的。值得注意的是，本研究首次在运动和流场的背景下确定了提高UUS游泳速度的因素。
