[Dynamics of the human heart rate during changes of posture under various climatic conditions]

The time course of the heart rate (15-sec-periods) during active orthostasis (10 min) was investigated according to types found by Drischel et al. under different climatic conditions in 51 female and 50 male subjects. Constant types were observed in each subject in 3 repeated tests on different days at 20 degrees C and 55% R.H., the types remaining constant even at 25 and 90% R.H. The increase in environmental temperature from 15 to 30 and 45 degrees C showed a significant alteration from type A via different transitional types to type B. At 45 degrees C, an additional type was observed called superhigh type B, functionally being a precollapse type. The variation in typology includes the dynamics of the initial process of the active orthostasis as well as the deviation between the steady-state of the heart rate in erect and in supine position. The physiological mechanisms eliciting the changes in the dynamic behaviour and the correlations with the effective temperature are discussed.