Nocturnal sleep, cardiovascular function, and adrenal activity following maximum-capacity exercise.

Eight subjects performed a treadmill test of their maximal aerobic capacity (VO2max) to determine whether exercise which is maximally stressful but relatively low in total energy expenditure may affect nocturnal sleep. The test was performed at 16.00 h on day 3 of the study, with day 1 as adaptation, day 2 as baseline and day 4 as a carryover night. Changes observed after exercise included a decrease in the duration of the first REM sleep period, an elevation of heart rate in the first 2 h of sleep, a reduction in norepinephrine excretion and an increased excretion of dopamine. Comparisons of sleep alterations in 4 subjects who exercised regularly (active group) with 4 subjects who took no regular exercise revealed differences in the first sleep cycle. Active subjects displayed an increased duration of SWS coupled with an increased latency to first REM onset. Non-active subjects, by contrast, displayed a shortened REM latency and duration of SWS. These results indicate that short-term maximum exercise may induce significant alteration of the temporal distribution of SWS with differences in response seen between regular exercisers and non-exercisers.