INTRODUCTION: A method was developed to predict hydrodynamic forces acting on the hand in swimming (H) based on the pressure distribution of the hand (Kudo et al., 2008). However, a method to predict propulsive forces exerted by the hand using the pressure method during swimming has not been developed. Thus, the aim of this study is to develop a method to predict propulsive forces exerted by the hand using the pressure method during swimming. METHODS: A portable data logger with 12 pressure sensors was developed to measure pressures and synchronized with an underwater motion capture system. A subject was asked to swim the front crawl stroke in a sub-maximal effort for 18 m. Different sets of best-fit equations including the best-fit equation from the previous study (B-Eq1) and the first order of best-fit equations (B-Eq2) were used to predict H to see if there is a considerable effect of multicollinearity on the prediction. Propulsions exerted by the swimmer`s hand were computed using H predicted and kinematic data from the camera. RESULTS: Mean propulsive forces exerted by the hand predicted by B-Eq1 over a stroke was 15 ± 11 N. Mean propulsive forces exerted by the hand predicted by B-Eq2 over a stroke was 33 ± 24 N. The contribution of drag and lift forces to the propulsive force predicted by B-Eq2 was 55% and 45%, respectively. Mean hand speed over a stroke was 2.3 ± 0.3 ms-1. The angle of attack (AP) changed from 24º to 85º. The sweepback angle (SB) changed from 73º to 254º over a stroke. DISCUSSION: A method to predict propulsive forces by the hand in swimming was developed. Feedback of the predicted propulsive forces by the hand can be provided to the swimmer and coach within a few hours by combining the pressure method with kinematic data from the motion capture system. Additionally, the contribution of drag and lift forces to the propulsion by the hand can be provided. The prediction of H by the best-fit equation in the previous study (B-Eq1) may experience error due to multicollinearity. The erroneous effect on the prediction of H can be detected using the information on the magnitude of H, kinematics of hand, as well as AP and SB, and be minimized by choosing the first order of the polynomial best-fit equations. REFERENCES: 1. Kudo, S., Yanai, T., Wilson, B., Takagi, H., & Vennell, R. (2008). Prediction of fluid forces acting on a hand model in unsteady flow conditions. Journal of Biomechanics, 41, 31-1136.
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