Self-paced work in sleep deprived subjects.

The effect of sleep deprivation and physical fatigue on self-paced work was determined in two experiments simulating sustained combat engineer operations. In experiment A, four subjects went without sleep for 69 hours. During this period they performed only four physically demanding tasks, three of them in the last 24 hours. Continuous recordings of heart rate (HR) indicated that sleep deprivation, in the absence of physical fatigue, had no effect on work intensity and the period of fatiguing work (HR above 120 beats min−1). In experiment B, six subjects carried out a full schedule of physically demanding tasks during a period of sleep deprivation lasting 47 hours. Some of the tasks were repeated at least once so that the effects of sleep loss and physical fatigue could be assessed. For the first 14 hours of experiment B, the subjects worked at an average hr of 120 beats min−1, equivalent to an energy expenditure of 35-40% of maximal oxygen uptake in fit young men. In the remainder of the sustained operat...