Circadian variation in swim performance

• DOI: 10.1152/japplphysiol.00910.2006
• Publication Date: 2006-11-10T01:53:41Z
• Authors: Christopher E. Kline; J. Larry Durstine; J. Mark Davis; Teresa A. Moore; Tina M. Devlin; Mark R. Zielinski; Shawn D. Youngstedt
• Keywords: Time of day

Previous findings of time-of-day differences in athletic performance could be confounded by diurnal fluctuations environmental and behavioral “masking” factors (e.g., sleep, ambient temperature, energy intake). The purpose this study was to examine whether there is a circadian rhythm swim that independent these masking factors. Experienced swimmers ( n = 25) were assessed for 50–55 consecutive hours the laboratory. followed 3-h “ultra-short” sleep-wake cycle, involving 1 h sleep darkness 2 wakefulness dim light, repeated throughout observation. protocol distributes equally across 24-h period. Each swimmer scheduled perform six maximal-effort 200-m trials distributed eight times day 147 trials). trial separated 9 h. A cosine fit intra-aural temperature data established time lowest body (T min ). Swim performances z-transformed compared twelve 2-h intervals relative T . Analysis covariance, controlling number, revealed significant P < 0.001) pattern day. Performance peaked 5–7 before (∼2300) worst from after (∼0500). Mean 169.5 s; variation peak 5.8 s. These suggest effects.