[Sub-circadian rhythms as an instrument for the determination of and prediction for the state of the organism].

The paper deals with the analysis of literature concerning the role and hierarchy of circadian rhythms in the structure of rhythmic processes in organism. Substantiation is given to the concept according to which the diagnostic and prognostic value of subcircadian rhythms is predetermined by their wide representation at different levels of the living system organization, high sensitivity to external impacts, and responsiveness to all sorts of shifts in the state of organism. The above considerations are used in the physiology of labor, experimental and clinical medicine. Illustration can be determination of and prediction for the state of patients and subjects exposed to head-down bedrest, g-loads and other debilitating factors based on investigations of subcircadian rhythms. The author presents his own data on determination of and prediction for individual tolerance for passive standing test with account of subcircadian rhythms. Special emphasis is placed on the data about subcircadian rhythms of animals during spaceflight.