Sleep after exercise of variable intensity in fit and unfit subjects

Bodily restorative theories of sleep predict that physical exercise results in elevated levels of slow wave sleep (SWS). However the evidence is contradictory. A number of hypotheses have been proposed to accomodate the negative results. Two of these proposals are tested in the present paper. The first argues that under various circumstances stress counteracts the facilitative effect of exercise on SWS. The second, that the facilitative effect is only observed in fit subjects given very intense exercise schedules. Two experiments were conducted in which exercise intensity was systematically varied and in which an attempt was made to minimize stress effects. Physically unfit subjects were used in the first study and fit subjects in the second. Exercise had no effect on SWS under any conditions in either experiment. In addition the failure to observe the effect could not be accounted for by stress. Thus the results of the two experiments offer no support for bodily restorative theories.