Relationship between swimming performance and fluid force determined by pressure distribution analysis of breaststroke kicking motion

Abstract

The purpose of this study was to identify the relationship between swimming performance and estimated fluid force by pressure distribution analysis of breaststroke kicking motion. Eleven elite male swimmers participated in the study, and provided written informed consent. Each subject performed the breaststroke kicking motion for 10 seconds without upper limb motion at maximal effort. During the trial, the subjects were connected to a load-cell via a polyethylene rope for measurement of tethered force (F_tethe) at 200 Hz. Eight pressure sensors were attached to the right foot to measure the the distribution of pressure on the foot. Resulting fluid force acting on the foot (F_foot) was calculated from the product of measured pressure values and the area of the foot. Using coordinates of the right foot calculated using the 3D-DLT method, the estimated fluid force, propulsive force (F_prop), vertical force (F_vert) and lateral force (F_later) exerted by the right foot were computed. The competitive swimming velocity (v100) was calculated based on the personal best time over 100 m. Pearson's correlation coefficient (r) was used to investigate relationships among estimated fluid forces, F_tethe and v100. There were no significant correlations for v100 and mean F_tethe. The value of v100 showed significant correlations with the mean F_foot (r=.734, p<.01), mean F_prop (r=−.741, p<.01), impulse of F_foot (r=.742, p<.01), impulse of F_prop (r=−.757, p<.01), peak of F_foot (r=.753, p<.01), and peak of F_prop (r=−.751, p<.01). During the trial, F_vert and F_later corresponded to the kicking motion. These results suggest that there are close relationships between swimming performance and estimating fluid forces acting on the foot. Therefore, the method used for estimating fluid force acting on the foot in this study appears to be a useful tool for evaluation of swimming performance.