Effects of Physical Activity on Circadian Rhythms in the Elderly

Abstract

Aging is usually associated with a disruption of the chronobiological cycle. However, physical activity could act as a non-photic zeitgeber (external cue) for the internal clock, and thus reduce this disruption. In young participants, an effect of exercise on phase shift of circadian rhythms has sometimes been reported. A link between physical status and the circadian rhythm amplitudes has also been shown. Thus, rhythmicity alterations observed in aging could be explained by sedentary lifestyles in older adults. Few studies have explored the effects of physical activity on the circadian rhythm in the elderly. However, the biological clock seems to be enhanced in older participants with a higher level of physical capacity. The amplitude of core temperature is higher in elderly persons with a high level of aerobic capacity. A few months of physical training seems to promote circadian rhythmicity in the elderly. After training, a reduction in the fragmentation of the rest-activity rhythm, an increase in amplitude of activity-rest and core temperature rhythms, and enhancement of sleep and diurnal vigilance have been reported. We may suppose that the exercise-mediated increase in core temperature and/or melatonin and/or pupil size (increased information on light fed into the retinal-hypothalamic tract) would be the underlying zeitgeber. Another hypothesis could be that the vestibular system, when strongly stimulated by physical activity, could act as an actimeter, providing information on motion during the wake period which could then act as a zeitgeber.