A shipboard study of a four-crew rotating watchkeeping system

Abstract

Body-temperatures and subjective alertness ratings were obtained at 2-hourly intervals in a shipboard study of six subjects watchkeeping on a rapidly rotating system with a 4-day cycle. The results were compared with those from an earlier study of this system conducted on land in ‘laboratory’ conditions. The similarity of the temperature curves from the two studies indicated that prolonged exposure to shipboard conditions made no difference to the underlying circadian rhythm in this variable, which appeared to be near-normal in form. Subjective alertness showed a clear rhythm of considerable amplitude; the phasing of this rhythm suggested that, under the present system, operational effectiveness is likely to be reduced in watches held in night hours. Further analyses indicated that it was also likely to be reduced in daytime hours following these night watches, because of the disruption of sleep that results from them. An alternative ‘fixed hours’ watchkeeping system is proposed to overcome these unwanted effects.

Keywords:

• Watchkeeping
• Circadian rhythms
• Body temperature
• Subjective alertness
• Performance efficiency