Effects of physical exercise on human circadian rhythms

概要

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Bright light is the principal zeitgeber for the biological clock in mammals, including humans. Butthere is a line of evidence that non-photic stimuli such as physical activity play an important role inentrainment. Scheduled physical activity, such as wheel and forced treadmill running, has beenreported to phase-shift and entrain the circadian rhythm in rodent species. In humans, several studieshave reported the phase-shifting effects of physical exercise. A single bout of physical exerciseat night was demonstrated to phase-delay the circadian rhythm in plasma melatonin. However, forthe entrainment of human circadian rhythm, a phase-advance shift is needed. Previously, we demonstratedthat scheduled physical exercise in the waking period facilitated the entrainment ofplasma melatonin rhythm to the sleep/wake schedule of 23 h 40 min. This result suggested thattimed physical exercise produced phase-advance shifts. A regular physical exercise also facilitatedentrainment of the circadian rhythms associated with acute phase-delay shifts of the sleep/wakeand light/dark schedule. These findings suggest that physical exercise is useful to adjust the circadianrhythm to external time cues, especially for totally blind people and elderly people.