ABSTRACT
As was generally alluded to in the preceding chapter, there are basic physiological factors that determine the level of alertness at any given time in the daily 24-hour cycle. Two of these factors are particularly relevant for a discussion of general sleep needs and shift work, but a third will be briefly included as well for reasons that will become apparent later on. When attempting to understand the basic nature of fatigue, the impact of each of these factors must be considered.
