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Time-of-day effect on nonthermal control of sweating response to maintained static exercise in humans
Authors:Ken Aoki  Narihiko Kondo  Yoshihiro Shimomura  Koichi Iwanaga  Hajime Harada  Tetsuo Katsuura
Institution:(1) Department of Kinesiology, Graduate School of Science, Tokyo Metropolitan University, 1–1 Minami-ohsawa, Hachioji, Tokyo 192–0397, Japan,;(2) Laboratory for Applied Human Physiology, Faculty of Human Development, Kobe University, Kobe, Japan,;(3) Ergonomics Section, Faculty of Engineering, Chiba University, Chiba, Japan,;(4) Division of Design Science, Graduate School of Science and Technology, Chiba University, Chiba, Japan,;(5) Present address: Tohoku Institute of Technology, Department of Industrial Design, Sendai, Miyagi, Japan,
Abstract:To investigate the influence of nonthermal factors in the time-of-day effect on the sweating response to maintained static exercise, eight healthy male subjects performed handgrip exercise at 20%, 35% and 50% maximal voluntary contraction (MVC) for 60 s at 0600 hours (morning) and at 1800 hours (evening). Oesophageal temperature (T oes) before the experiment showed a diurnal rhythm mean (SEM)] 36.3 (0.1) (morning) compared to 36.8 (0.1) °C (evening), P<0.01]. Experiments were conducted with subjects in a state of mild hyperthermia during which the mean skin temperature (T sk) was kept constant at 35.5–36.5 °C using a water-perfused suit to activate sudomotor responses. The T oes and mean T sk remained stable during the pre-exercise, handgrip exercise and recovery periods. The response in sweating rate (ΔSR) on the chest and forearm to handgrip exercise increased significantly with increasing exercise intensity in both the morning and evening tests (P<0.05). The ΔSR on the palm did not change significantly with increasing exercise intensity in the morning test (P>0.1). During handgrip exercise at 50% MVC only, ΔSR on the chest, forearm and palm in the evening was significantly higher than in the morning (P<0.05). On the other hand, mean arterial blood pressure and the rating of perceived exertion during 50% MVC handgrip exercise were not significantly different between the morning and evening (P>0.1). These results indicate the presence of a time-of-day effect on nonthermal control of the sweating response to isometric handgrip exercise, and that this effect is dependent on exercise intensity. Electronic Publication
Keywords:Circadian variation Nonthermal sweating Isometric exercise Exercise intensity
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