Effects on sleep stages and EEG power density of different degrees of exercise in fit subjects

In order to study the effects of exercise on sleep, 6 fit male subjects between 30 and 35 years of age were exposed to 4 conditions--sleep after a day with no running, sleep after a day with a moderate training run (15-20 km), the first night after an extremely exacting race (30 or 43 km), the second night after the race. All measurements were obtained in the respective homes of the subjects. The main effects of the race condition were a delay and decrease of REM sleep, an increase of stage 2 sleep and a weak decrease of SWS latency. Spectral analysis (FFT) of the EEG showed an increase of total power density as well as power in the delta band. The increase was significant also within SWS. By the second night all values had returned to baseline. The training run had virtually no effect on the sleep parameters although the values usually fell between baseline and race night values. Catecholamine excretion during the night and heart rate at bed-time and rising increased with increasing prior exertion. Subjective ratings showed no significant differences between the conditions. It was concluded that exercise effects mainly REM sleep, but although no SWS response was found in this age group, the increase of EEG power density after physical activity could lend some support to a hypothesized recovery theory.