Brief hourly exercise during night work can help maintain workers' performance.

Increased night work is an important issue because of its implications on workers' health, safety and performance. This study examined the effects of brief hourly exercise as a countermeasure against the adverse effects of night work, especially for workers requiring sustained attention while working in a prolonged sitting posture. During simulated night work (22:00-08:00), participants were required to follow an hourly schedule comprising a 30-min task, 15-min test and 15-min break. The study included 2 experimental conditions: (1) hourly exercise (HE; hourly exercise for 3 min during breaks) and (2) control (without exercise during breaks). Throughout the test period, work performance in the last 10 min of each 30-min task was better under the HE condition than under the control condition (p<0.01). During the second half of the test period, exercise showed an effect on sustained attention (p=0.02). Parasympathetic nerve activity under the HE condition was less than that under the control condition (p<0.01). However, exercise was not effective in reducing subjective fatigue and sleepiness. These results suggest that brief hourly exercise acts as a restraint on parasympathetic nerve activity and is capable of sustaining attention levels during the circadian rhythm nadir that occurs during early morning.