Effects of circadian rhythms on night-time swimming during the Olympics: will performance be affected? – A pilot study for Rio 2016

Abstract

Introduction
The impact of Circadian rhythms (CRs), among other factors, on sporting performance is already known (Cappert T, 1999). Unlike the usual timings for international events, the swimming competitions in the 2016 Olympics will be held between 22.00 and 00.30. Therefore, the aim of this study was to analyse sleep quality (SQ), heart rate variability (HRV), heart rate recovery (HRR) and the total mood disturbance (TMD) index during a week of night-time training and the influence they have on the state of overreaching.
Methods
Three male swimmers, qualified to the 2016 Olympics in Rio, were monitored during a week of night-time training sessions to correspond with the timings of Rio’s semi-finals and finals. Assessments of SQ was calculated using actigraphy (Sensewear, Bodymedia USA), HRR, HRV (Minicardio, Hosand – Italy) and TMD were conducted five times during the whole simulation exercise with intervals of two days and once on the habituation day. All athletes answered a “morningness/eveningness” questionnaire in relation to the chronotype profile.The CRs were made to shift by five hours, such that the athletes woke up at 11.00 and retired for the day at 02.00, while their nutritional intake was integrated with Tryptophan in order to improve SQ.

Results

The Univariate ANOVA showed that, for HRV, which was classified in terms of Very Low Frequency (VLF), Low Frequency (LF) or High Frequency (HF), SQ showed significant effects between each time period (T0-T1-T2-T3-T4): F=9.481 and p=0.002, F=6.603 and p=0.007, F=9.209 and p=0.002, F=19.189 and p<0.0001, respectively. Conversely, the Univariate ANOVA showed no significant effect on HRR, (F=0.817 and p=0.542). Finally, TMD was very low at the start (5.50±3.51) respect 81.00±18.90 during the last session (p=0.031).
Discussion
The main findings indicated that there are effects on HRV, SQ and TMD. The data suggest that training late at night increased sleep disturbance, fatigue and changes in autonomic functioning hinted at the onset of an overreached state.
More than two days under “late night” conditions can inhibit the performance of athletes, with a major impact on their “morningness” profile. In order to reduce such an impact, greater emphasis must be placed on identifying the nutritional and sleep needs of elite swimmers, in order to put together adequate recovery strategies that will help them train effectively to maximize performance outcomes.

References
Sleep in Elite Athletes and Nutritional Interventions to Enhance Sleep – Halson S. – Sports Med. 2014
Review: Time of Day Effect on Athletic Performance: An Update – Cappaert T. – J. Strength. Cond. Res. 1999
Circadian Rhythms in Sports Performance: An Update – Drust B. et al. – Chronobiol. Int. 2005
Sleep, Circadian Rhythms, and Athletic Performance – Thun E. et al. – Sleep Med. Rev. 2015
Contact
Gian Mario Migliaccio [info@sportsciencelab.uk]