Kawai Eisuke, Tsunokawa Takaaki, Takagi Hideki
Doctoral Program in Physical Education, Health and Sport Sciences, University of Tsukuba, Japan.
Coaching of Sports and Budo, National Institute of Fitness and Sports in Kanoya, Japan.
Heliyon. 2018 Dec 28;4(12):e01095. doi: 10.1016/j.heliyon.2018.e01095. eCollection 2018 Dec.
This study investigates the reliability and validity of the estimation of the hydrodynamic forces during eggbeater kicking (a water-treading technique) by pressure distribution analysis (PDA). Our PDA procedure is very similar to that used in a previous study concerning breaststroke kicking (Tsunokawa et al., 2015). In this method, the force estimation is limited to a particular part of the body. However, unlike previous analyses, the PDA method obtains dynamic fluid forces under unsteady flow conditions without requiring cumbersome motion analysis in water. Twelve participants completed the eggbeater kicking activity under four load conditions (0, 1, 2 and 3 weights), and the hydrodynamic forces acting on their right foot are detected by the pressure sensors. To confirm the reliability of our PDA using successive tests, five participants are additionally made to complete the activity under a no-load condition. Further, the PDA is validated in a linear regression analysis of the mean resultant force calculated using the PDA method versus the applied vertical load. The reliability evaluation yields a high degree of coincidence ( = 0.99) and a mean effort of 4.1%. In the validity test, the net vertical loads are significantly correlated with the estimated forces [coefficient of determination ( = 0.91-1.00)]. Therefore, the PDA method is a reliable and valid estimator of eggbeater kicking.
本研究通过压力分布分析（PDA）来探究打蛋器打水（一种踩水技术）过程中流体动力估算的可靠性和有效性。我们的PDA程序与先前一项关于蛙泳打水的研究（Tsunokawa等人，2015年）中所使用的程序非常相似。在这种方法中，力的估算仅限于身体的特定部位。然而，与先前的分析不同，PDA方法在非稳定流动条件下获取动态流体力，而无需在水中进行繁琐的运动分析。12名参与者在四种负荷条件（0、1、2和3块配重）下完成了打蛋器打水活动，作用于他们右脚的流体动力由压力传感器检测。为了通过连续测试确认我们PDA的可靠性，另外5名参与者在无负荷条件下完成了该活动。此外，在对使用PDA方法计算出的平均合力与施加的垂直负荷进行线性回归分析中，对PDA进行了验证。可靠性评估得出高度一致性（=0.99），平均偏差为4.1%。在有效性测试中，净垂直负荷与估算力显著相关[决定系数（=0.91 - 1.00）]。因此，PDA方法是一种可靠且有效的打蛋器打水估算方法。
