ABSTRACT
Working in shifts may produce several acute and chronic health problems, most of them being related to the sleep-wakefulness and circadian rhythms of the workers involved. Although the effects of physical activity on sleep have been studied extensively, physical exercise as a factor in increasing tolerance to shiftwork is a rather recent finding. Exercise, such as jogging and evening walks, was the most frequently reported factor for promoting sleep and improving its quality. Daytime tiredness was, however, less frequent among subjects exercising at least two to three times a week in comparison with other subjects who exercised less or not at all. There was also a trend towards less frequently perceived negative effects on sleep among those who exercised with light or moderate intensity compared with more intensive training. The effects of exercise on sleep have been described because the most important health consequences of shiftwork concern the sleep and alertness of the workers.
