Exercise and human sleep

Abstract

IT has been proposed that slow wave sleep (SWS) in humans is associated with somatic restitution¹, and findings of increased plasma somatotrophin during SWS², and of the greater amounts of SWS following exercise^3,4 support this proposal. Others have, however, failed to show any exercise effects of sleep^5,6. Exercise has been found to increase sleep somatotrophin levels, but not SWS⁷. These contradictory findings may in part be attributed to the large interstudy variations of administered exercise and fitness of subjects (in no study has exercise been standardised against individual work capacity); the time of day of exercise; the need for further qualification of SWS, defined⁸ here as sleep stages 3 and 4, respectively containing 20–50% by time of delta activity, and more than 50% delta activity. Up to 20% delta activity is included in the non-SWS stage 2. We have investigated the effects of the time of day of individually standardised amounts of exercise on subsequent sleep in which stage 2 was subdivided further between 10% and 20% delta activity (2ii).