Effect of fatigue on the intra-cycle acceleration in front crawl swimming: A time-frequency analysis

TL;DR

This study investigates how fatigue affects intra-cycle acceleration in front crawl swimming by applying time-frequency analysis, revealing significant reductions in acceleration amplitude and spectral features after fatigue.

Contribution

It introduces a Fourier analysis approach to quantify intra-cycle acceleration changes due to fatigue in swimmers, enhancing understanding of propulsive force alterations.

Findings

RMS decreased by 67.5% after fatigue

Peak power and spectrum area reduced significantly

Fourier analysis provides detailed insights into propulsive force changes

Abstract

The present study analyzes the changes in acceleration produced by swimmers before and after fatiguing effort. The subjects (n=15) performed a 25-meter crawl series at maximum speed without fatigue, and a second series with fatigue. The data were registered with a synchronized system that consisted in a position transducer (1 kHz) and a video photogrametry (50Hz). The acceleration (ms-2) was obtained by the derivative analysis of the variation of the position with time. The amplitude in the time domain was calculated with the root mean square (RMS); while the peak power (PP), the peak power frequency (PPF) and the spectrum area (SA) was calculated in the frequency domain with Fourier analysis. On one hand, the results of the temporal domain show that the RMS change percentage between series was 67.5% (p<0.001). On the other hand, PP, PPF, and SA show significant changes (p<0.001). PP and SA were reduced by 63.1% and 59.5%, respectively. Our results show that the acceleration analysis of the swimmer with Fourier analysis permits a more precise understanding of which propulsive forces contribute to the swimmer performance before and after fatigue appears.