ABSTRACT
Individuals who regularly work on abnormal work schedules are more prone to fatigue than typical day workers. This is due in large part to restricted opportunities for rest, recovery and sleep, which may impact on the performance at work and the likelihood of them making a mistake, possibly resulting in an accident. Many of the fatigue-related problems that shift workers encounter stem from their disrupted biological rhythms. These rhythms have evolved in response to the periodic changes in the environment, such as the day–night cycle. From a fatigue perspective, one of the most important biological rhythms is the sleep–wake cycle. A key issue is whether workers should regularly "rotate" between different shifts or whether they should always work the same shift. In rotating shift systems, changing from one type of shift to another entails altering the timing of the sleep and most other aspects of daily routine.
