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Circadian Cycles and Restorative Power of Naps.

NIOSH 1981 Jul:693-720
The recuperative power of a 2 hour nap after either 45 or 53 hours of a vigil was studied. Subjects were 15 young sailors in the 45 hour study (group-I) and eight in the 53 hour study (group-II). The experiment started at 0700 hours on Tuesday and continued until 0400 on Thursday. This was followed by a 2 hour nap. The recuperative power of the nap was tested every 2 hours. At 1200 on Thursday, subjects took the second nap and then resumed their task until midnight. In Phase 2, subjects worked until they took a 2 hour mid day nap on Thursday. Task sessions included 45 biosessions containing 14 tasks, 13 chore sessions with four tasks, and eight watch sessions in Wilkinson auditory vigilance test (WAVT). Statistically significant circadian rhythms (CR) were detected in baseline data of all 12 dependent variables. The 95 percent confidence ellipses in CR tended to be larger for data collected during the vigil. Performance minima for response alternation performance 1 (TRAP 1) and memory and search test were at 0507 and similar profiles which changed together. The profiles of both groups were combined, and omnibus testing of all possible contrasts among conditions indicated there were no significant differences among conditions for the following dependent measures: pulse rate, diastolic blood pressure, TRAP 1 measure, four choice serial reaction time, and average reaction time in WAVT. Forty five hours of sleep loss produced a significant change from baseline in subjective ratings of sleepiness. The results indicated that early morning nap had no recuperative power. The author concludes that the results suggest that the recuperative power of naps depends on number of hours of prior wakefulness, time of napping, and duration of the nap.
Sleep-deprivation; Circadian-rhythms; Physical-stress; Mental-fatigue; Mental-stress; Biological-effects; Psychological-testing; Psychophysiology;
Publication Date
Document Type
Conference/Symposia Proceedings;
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
(NIOSH) 81-127
NIOSH Division
Source Name
The Twenty-Four Hour Workday: Proceedings of a Symposium on Variations in Work-Sleep Schedules, Division of Biomedical and Behavioral Science, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, DHHS (NIOSH) Publication No. 81-127