Contribution of limbs’ actions to the four competitive swimming strokes: a nonlinear approach

ABSTRACT

The aim of our study was to assess the effect of the limbs’ actions on the nonlinear properties of the four competitive swimming strokes. Forty-nine swimmers performed all-out sprints at front-crawl, backstroke, breaststroke and butterfly, each one at full stroke (FS), only the arms’ stroke (AS), and only leg kicking (LK), in a total of 12 bouts, 6 per day. A speedo-meter cable was attached to the swimmer’s hip, to collect the speed-time raw data (f = 50Hz). Velocity, speed fluctuation, sample entropy and fractal dimension were derived from the speed-time series. Significant and moderate-strong effects were noted for both stroke and condition in all variables in the study (p ≤ 0.001; 0,560<η² < 0,952). The four competitive strokes and their three conditions exhibited nonlinear properties. The swimming pattern was less complex and more predictable for LK in comparison to AS and FS. Breaststroke and butterfly have more complex but more predictable patterns than backstroke and front-crawl.

KEYWORDS:

• Swimming
• dynamical systems
• nonlinear variables
• sample entropy
• fractal dimension

Acknowledgements

The authors would like to express their sincere gratitude to: i) all the coaches for their support and the swimmers who participated in this study, and; ii) Dr. Márcio Carocho for the assistance in reviewing the English language.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This project was supported by the National Funds through FCT - Portuguese Foundation for Science and Technology (UID/DTP/04045/2013) - and the European Fund for regional development (FEDER) allocated by European Union through the COMPETE 2020 Programme (POCI-01-0145-FEDER-006969); European Regional Development Fund [POCI-01-0145-FEDER-006969]; Fundação para a Ciência e a Tecnologia [UID/DTP/04045/2013].