Interaction of the Circadian Rhythm with the Effects of Continuous Work and Sleep-II

Abstract

The synthetic-work approach was employed in an investigation of the effects of continuous work and sleep loss on sustained performance. Two crews of five subjects each worked continuously for 36 hr., slept 4 hr., and then returned to work 8 hr. per day. During the continuous-work period, one crew began work at 0400 hr. and the other at 1600 hr. Performance decrements were found to be significantly larger (33% as compared to 11%) and recovery to be less complete for the crew whose continuous work began during the low portion of the subjects' circadian rhythm (i.e., the crew beginning at 0400 hr.). Comparisons of these data with other continuous-work investigations (in which the continuous-work periods began at other points of the subjects' circadian rhythm) indicate that the circadian rhythm constitutes a primary determiner of man's ability to work continuously for extended periods of time and to recover from the effects of continuous work and sleep loss.