Effects of vigorous late-night exercise on sleep quality and cardiac autonomic activity

Sleep is the most important period for recovery from daily load. Regular physical activity enhances overall sleep quality, but the effects of acute exercise on sleep are not well defined. In sleep hygiene recommendations, intensive exercising is not suggested within the last 3 h before bed time, but this recommendation has not been adequately tested experimentally. Therefore, the effects of vigorous late-night exercise on sleep were examined by measuring polysomnographic, actigraphic and subjective sleep quality, as well as cardiac autonomic activity. Eleven (seven men, four women) physically fit young adults (VO2max 54 +/- 8 mL.kg(-1).min(-1), age 26 +/- 3 years) were monitored in a sleep laboratory twice in a counterbalanced order: (1) after vigorous late-night exercise; and (2) after a control day without exercise. The incremental cycle ergometer exercise until voluntary exhaustion started at 21:00 +/- 00:28 hours, lasted for 35 +/- 3 min, and ended 2:13 +/- 00:19 hours before bed time. The proportion of non-rapid eye movement sleep was greater after the exercise day than the control day (P < 0.01), while no differences were seen in actigraphic or subjective sleep quality. During the whole sleep, no differences were found in heart rate (HR) variability, whereas HR was higher after the exercise day than the control day (54 +/- 7 versus 51 +/- 7, P < 0.01), and especially during the first three sleeping hours. The results indicate that vigorous late-night exercise does not disturb sleep quality. However, it may have effects on cardiac autonomic control of heart during the first sleeping hours.