Aerobic fitness and exercise: Effect on the sleep of younger and older adults

Abstract

To test a prediction of bodily restorative and energy conservation theories of sleep, the effect of physical exercise and aerobic fitness on the level of slow wave sleep and sleep duration were assessed in younger (average age 22 years) and older (average age 41 years) subjects. The design of the experiment consisted of two levels of fitness (fit and unfit), two age groups and two levels of exercise (exercise and no exercise). However, the design was not a complete factorial as the unfit subjects did not exercise. Two consecutive nights were run in each condition and an extended sleep paradigm was used to assess fully sleep duration. The level of exercise and the fitness of the subjects were selected to maximize the hypothesized effects. The results indicated that exercise did not increase either slow wave sleep or sleep duration; if anything, it disrupted sleep, particularly on the second of the two consecutive exercise nights. Aerobic fitness was associated with increased slow wave sleep and decreased sleep onset latency in both age groups. The data was interpreted as being incompatible with predictions derived from restorative and energy conservation theories.