Circadian Variation in Swim Performance

Abstract

Previous findings of time-of-day differences in athletic performance could be confounded by diurnal fluctuations in environmental and behavioral "masking" factors (e.g., sleep, ambient temperature, and energy intake). The purpose of this study was to examine whether there is a circadian rhythm in swim performance that is independent of these masking factors. Experienced swimmers (n ϭ 25) were assessed for 50 -55 consecutive hours in the laboratory. The swimmers followed a 3-h "ultra-short" sleep-wake cycle, involving 1 h of sleep in darkness and 2 h of wakefulness in dim light, that was repeated throughout the observation. The protocol distributes behavioral and environmental masking factors equally across the 24-h period. Each swimmer was scheduled to perform six maximal-effort 200-m swim trials that were distributed equally across eight times of day (n ϭ 147 trials). Each trial was separated by 9 h. A cosine fit of intra-aural temperature data established the time of the lowest body temperature (T min). Swim performances were z-transformed and compared across the eight times of day and across twelve 2-h intervals relative to Tmin. Analysis of covariance, controlling for trial number, revealed a significant (P Ͻ 0.001) pattern in swim performance relative to environmental and circadian times of day. Performance peaked 5-7 h before Tmin (ϳ2300) and was worst from 1 h before to 1 h after Tmin (ϳ0500). Mean swim performance was 169.5 s; circadian variation from peak to worst performance was 5.8 s. These data suggest a circadian rhythm in athletic performance independent of environmental and behavioral masking effects. body temperature rhythm; swimming; ultra-short sleep-wake cycle CIRCADIAN RHYTHMS ARE INTERNALLY generated phenomena with periodicity of ϳ24 h (3). Most mammalian circadian rhythms originate from an endogenous pacemaker located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus (37). Neural and humoral outputs from the SCN communicate with other centers in the hypothalamus and the endocrine system. These centers drive a multitude of behavioral and physiological rhythms (17).Demonstration of circadian rhythms requires chronobiological techniques that separate the measurement of circadian rhythms from environmental and behavioral factors that might "mask" the measurement (e.g., energy intake, activity, posture, sleep, ambient temperature, and light) (21). These "unmasking" techniques have included the constant routine (21), data purification (51), forced desynchrony (19), and ultra-short sleep-wake protocols (15).There has been speculation that there may be a circadian rhythm in athletic performance. The theoretical rationale for

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“…What is more, the athletes in the LH travel group were still competing against each other for places on the Australian World Cup skeleton team. The inclusion of a mood state questionnaire would have allowed for a closer inspection of the inXuence of the athlete's competitive perception on performance similar to the methods used by Kline et al (2007). We believe though that by creating a competitive environment we enhanced the ecological validity of this study for athletes travelling to compete overseas in maximal intensity tasks.…”

“…Short duration (<4 min) athletic performance has been clearly demonstrated to have a circadian rhythm (Kline et al 2007) while maximal voluntary strength in both dynamic and isometric conditions has also been shown to be aVected by the body's circadian rhythm (Bernard et al 1998;Coldwells et al 1994;Gauthier et al 2001;Martin et al 1999;Sedilak et al 2008). Since circadian rhythms are driven internally following rapid transmeridian travel, optimal athletic performance may depend upon the time of competition relative to the circadian system (Youngstedt and O'Connor 1999).…”

Stress, Sleep and Recovery in Elite Soccer: A Critical Review of the Literature

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

“…The aim of this study was to analyze stroke parameters and arm coordination to better explain time-of-day effects in swim performance during a test of maximum velocity using the front Circadian variations in swim performance have previously been shown in other studies comparing maximum swimming performance at different times of the day Kline et al 2007;Martin et al 2007;Zarrouk et al 2012), these studies observing significantly superior performance in the evening compared with the morning. For example, Baxter and Reilly (1983) observed evening improvements of 3.5% in 100 m and 2.5% in 400 m swim performance.The present study confirms the better performance in the evening than the morning.…”

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