No matter what schedules are required and what conditions are present in the work environment, the most effective strategy for minimizing fatigue on the job is, of course, to ensure adequate sleep prior to the duty period. It also has been established that reducing the amount of sleep to only four hours or less rapidly leads to serious uncontrolled 'sleep attacks' that often occur without the knowledge of the victim. Average the sleep hours across this period of time, and you will develop a good idea of your basic physiological sleep requirement. This is the amount of sleep that is necessary for optimal alertness, performance, and physical and mental well-being. The importance of aerobic exercise to restful sleep has been clearly established in the scientific literature. Daytime napping can be a wonderful fatigue countermeasure in situations where adequate consolidated sleep opportunities are unavailable.