Abstract des Autors

Most physiological functions demonstrate rhythmic changes over the course of the solar day and these constitute circadian rhythms. The most prominent include body temperature and subjective alertness which reflect the two major biological timekeepers. Muscular performance measures (grip strength, leg strength, back strength, muscular power) are closely related to the body temperature curve which reaches a peak in the early evening. Self-chosen exercise intensity and coordination tasks may be linked more closely to the sleep-wake cycle. Rhythms in exercise performance persist under sleep loss conditions, which affect coordination more so than gross exercise tasks. The optimal time of day for exercise is not solely determined by endogenous rhythms but depends on the type and intensity of exercise and environmental conditions. Physical fitness influences rhythm amplitude but not its phase, and rhythm characteristics may denote a capability for tolerance to nocturnal shift-work. Rhythms in physical performance are desynchronised when perturbed by nocturnal shift-work or when travelling across multiple time-zones. External synchronisers may be exploited to hasten the adaptation of the body's clocks to such phase shifts. The existence of self-sustaining circadian rhythms in exercise performance should be recognised by practitioners concerned with organising the habitual regimes of athletes. Verf.-Referat