Assessment of accuracy, reliability and force measurement errors for a tethered swimming apparatus

Researchers frequently use purpose-built devices to calculate propulsive forces during tethered swimming. Although such devices are subject to force measurement errors, no specific methods have been suggested in the swimming literature for the estimation of these errors. The purpose of this study was to access the accuracy and reliability of a portable device that is used to measure propulsive forces in tethered swimming, and to estimate the errors caused by hysteresis, sensitivity and linearity. The force values recorded during a maximum front crawl test of an international level swimmer were used to provide an example of the extent to which measurement errors could affect the values collected during a tethered swimming study. The calculations revealed small and acceptable errors. When summing the errors from all sources, the total errors affecting the minimum, average and peak forces recorded during the case study were 1.15%, 0.94% and 0.86% respectively. It is recommended that investigators always calculate and report such errors for tethered swimming studies. The methods used in the present study are reasonably simple and not time-consuming, and could be used when assessing errors for similar tethered swimming devices.