[The wakefulness-sleep cycle during antiorthostatic hypokinesia]

Studies on the wake-sleep cycle with participation of eight female volunteers were performed before, during, and after a 120-day bed rest with the head-end of bed tilted down at 6 degrees (HDT). Methods of polysomnography and actography were applied. The test-subjects were assigned into 2 groups. Group A was prescribed to use countermeasures throughout the experiment; no countermeasures was administered by group B. Evidence of significant alteration in sleep structure at different time points in HDT is given in comparison with data about females of the control group under the conditions of everyday activity. Sleep deviations in the subjects were reordered at each of the three points of investigation and differed from those in control. HDT was shown to modify the sleep structure in experimental groups A and B. A supposition is made that under these conditions the dynamics of physical activity during night sleep had an adaptive character.