Physical exercise accelerates reentrainment of human sleep-wake cycle but not of plasma melatonin rhythm to 8-h phase-advanced sleep schedule

Jan 1, 2010American journal of physiology. Regulatory, integrative and comparative physiology

Physical exercise speeds up adjusting the human sleep-wake cycle but not the melatonin hormone cycle to an 8-hour earlier sleep schedule

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Abstract

The sleep-onset in the exercise group was significantly phase-advanced on the first day of the free-run compared to the control group and baseline.

Seventeen male adults underwent a phase-advanced sleep schedule for 4 days, followed by a 6-day free-run session without time cues.
The exercise group performed 2 hours of physical exercise daily during the waking period, while the control group remained sedentary.
Both groups exhibited a significant phase-delay in their circadian melatonin rhythm, indicating internal desynchronization.
The sleep-wake cycle resynchronized to the melatonin rhythm during the free-run session through phase-advance or phase-delay shifts.
Timed physical exercise may accelerate the reentrainment of the sleep-wake cycle to a phase-advanced schedule, independent of the circadian pacemaker.

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Effects of timed physical exercise were examined on the reentrainment of sleep-wake cycle and circadian rhythms to an 8-h phase-advanced sleep schedule. Seventeen male adults spent 12 days in a temporal isolation facility with dim light conditions (<10 lux). The sleep schedule was phase-advanced by 8 h from their habitual sleep times for 4 days, which was followed by a free-run session for 6 days, during which the subjects were deprived of time cues. During the shift schedule, the exercise group (n = 9) performed physical exercise with a bicycle ergometer in the early and middle waking period for 2 h each. The control group (n = 8) sat on a chair at those times. Their sleep-wake cycles were monitored every day by polysomnography and/or weight sensor equipped with a bed. The circadian rhythm in plasma melatonin was measured on the baseline day before phase shift: on the 4th day of shift schedule and the 5th day of free-run. As a result, the sleep-onset on the first day of free-run in the exercise group was significantly phase-advanced from that in the control and from the baseline. On the other hand, the circadian melatonin rhythm was significantly phase-delayed in the both groups, showing internal desynchronization of the circadian rhythms. The sleep-wake cycle resynchronized to the melatonin rhythm by either phase-advance or phase-delay shifts in the free-run session. These findings indicate that the reentrainment of the sleep-wake cycle to a phase-advanced schedule occurs independent of the circadian pacemaker and is accelerated by timed physical exercise.

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Physical exercise accelerates reentrainment of human sleep-wake cycle but not of plasma melatonin rhythm to 8-h phase-advanced sleep schedule

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