Diurnal variation in stroke parameters and motor organization in front-crawl swimmers

Abstract

The aim of the present study was to examine the effects of time of day on stroke parameters and motor organization in front-crawl swimmers. In a randomized order, fourteen regional swimmers (age: 18.7 ± 1.6 years) performed maximal front crawls over 12.5 m during two experimental sessions; the morning sessions were conducted between 07:00 and 09:00 h and the evening experiments were conducted between 17:00 and 19:00 h. Stroke parameters (swim velocity, stroke rate [SR], and stroke length), motor organization (arm stroke phases and arm coordination) were calculated from aerial and underwater side-view cameras. Arm coordination was quantified in terms of an index of coordination (Idc). Results showed that oral temperature was significantly higher in the evening 36.8 ± 0.2 °C than in the morning 36.1 ± 0.2 °C (p < 0.001), with a morning–evening difference of −0.7 ± 0.1 °C. Performance was also higher in the evening (7.4 ± 0.6 s) than in the morning (8.0 ± 0.8 s) (p < 0.001), with a morning–evening difference of 0.55 ± 0.30 s. Likewise, values of swim velocity and SR were higher in the evening than in the morning (p < 0.001) with morning–evening differences of −0.10 ± 0.04 m s⁻¹ and −3.99 ± 2.91 cycles min⁻¹, respectively. Percentage Idc increased significantly (p < 0.01) between the morning (−5.1 ± 6.5%) and evening (−1.6 ± 7.0%). It is concluded that maximal swimming trials are performed better in the evening than the morning, and that this might be explained by better stroke parameters and motor organization at this time.

Keywords:

• circadian
• swimming
• stroke parameters
• motor organization

Acknowledgement

We would like to express our gratitude to the swimmers who volunteered for this study.

Disclosure statement

No potential conflict of interest was reported by the authors.