[Biorhythm structure as one of the criteria of the body's capacity for physiologic adaptation].

In order to establish the criteria of the organism's ability for adaptation, we examined 16 healthy subjects, 10 of whom were able to very well adapt themselves to changes in environment, whereas 6 subjects could not do that well enough. In the background examinations (and for the well-adapting subjects in examinations made after meridian crossing in flight), the blood pressure, heart rate, and capillaroscopic picture were recorded during 3 days 5 times a day. Apart from that, the biorhythmic structure of the natural nocturnal sleep EEG was analysed. The data obtained showed that the well-adapting subjects had these characteristics of the biorhythms structure: relatively higher mean values of the parameters under study, a major dispersion of these values over different hours of the day and night, and clear temporal structure of the 24-hr curve as expressed by occurrence of the maximal and the minimal values of the functions at the same hours.