[Characteristics of human sleep, circadian periodicity of physiological functions and of work capacity indices in the 1st 24 hours after the transition from an altered to a usual sleep and wakefulness cycle].

Twelve male test subjects, aged 28 to 40, took part in the studies, in which a normal work-rest cycle was preceded by three types of an altered cycle, to investigate their adaptation-readaptation reactions. The return to the normal work-rest cycle was accompanied by slight changes in physiological functions, work changes was correlated with the type of altered work-rest cycles and with the degree of men's adaptation to them. The return to the normal work-rest cycle proceeded more readily, if adaptation to an altered cycle was incomplete. It is concluded that the required level of work capacity of men that have to vary their work-rest cycles frequently can be maintained by short-term (for 1 to 3 days) cycle alterations.