Faculty of Physical Education, International Budo University, Katsuura, Chiba, Japan.
Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Sports Biomech. 2023 Oct;22(10):1319-1333. doi: 10.1080/14763141.2020.1797152. Epub 2020 Aug 4.
The purpose of this study was to characterise the unsteady propulsive force during eggbeater kicking by a fluid force estimation method based on pressure distribution analysis. The eggbeater kick was performed by six male water polo players. The participants' eggbeater kicking motions were recorded by three cameras, and the kinematic foot variables were analysed. The pressure distributions around the foot were measured by four pairs of pressure sensors attached to the dorsal and plantar surfaces of the participants' right foot. The resultant fluid force acting on the foot was estimated from the measured pressure and area of the foot. The calculated propulsive force increased with the pressure difference between the plantar and dorsal sides of the foot, which was mainly related to the decrease in pressure on the dorsal side, and peaked when the foot passed its maximum velocity and began to decelerate. These results cannot be elucidated only by conventional biomechanical theories of swimming propulsion (Newton's laws of motion and the quasi-steady approach) but instead indicate a high possibility that the exerted propulsive force is induced by the effects of unsteady water flow.
本研究旨在通过基于压力分布分析的流体力估算方法来描述打蛋器踢腿时的非稳态推进力。六位男性水球运动员进行了打蛋器踢腿。参与者的打蛋器踢腿动作由三台摄像机记录，分析运动学脚部变量。通过将四对压力传感器附着在参与者右脚的脚背和足底表面，测量了脚部周围的压力分布。根据测量的压力和脚部面积估算作用在脚部的流体合力。计算出的推进力随脚部足底和脚背之间的压差而增加，这主要与脚背的压力降低有关，当脚部达到最大速度并开始减速时达到峰值。这些结果仅通过游泳推进的传统生物力学理论（牛顿运动定律和准稳态方法）无法解释，而是表明施加的推进力很可能是由非稳态水流的影响引起的。
