Effectiveness of Rotating Versus Fixed Three‐Section Watchkeeping Schedules on Crews' Well‐Being, Cognitive Performance, Sleep and Salivary Cortisol in the Navy

When 24 h-work needs to be distributed among crew members on ships, on-watch duty times can be either stable over time or can vary on a regular basis. Research suggests that adaptation to permanent night shift might be less disruptive to humans' innate circadian rhythms than rotating schedules when external and social influences are minimized, such as when working on ships. Since the research on the question of rotation in the design of watchkeeping schedules is still not conclusively answered, the present research investigated the effects of a fixed and a daily rotating three-section watchkeeping schedule on crew members' vigilance performance, well-being, salivary cortisol and sleep quantity and continuity in five underways on board a German frigate. Results revealed better vigilance performance, less acute disruptions in salivary cortisol and less subjective sleepiness in the rotating watchkeeping schedule, especially for the night watch (watch on duty from 00 to 04). In contrast, sleep continuity was better in the fixed watchkeeping schedule. In sum, results favour rotating three-section watchkeeping schedules for cognitive functioning and well-being, but also suggest fixed three-section watchkeeping schedules are more suitable to maintain restorative sleep.