Abstract des Autors

The effects of intravenous injections of atropine and practolol on the thermoregulatory responses to 1 h of exercise on a motordriven treadmill have been investigated on six healthy subjects. The results show that beta-blockade had little effect on thermal responses to work except for a small but significant decrease in mean skin temperature (Tsk) and peripheral tissue heat conductance. In contrast, atropine, particularly at work loads beyond 60 VO2max, raised Tre Tsk and reduced E by approximately 50 . At the highest work loads Tre increased as a linear function of time during the latter part of exercise,and at the 60th min was almost independent of relativestress imposed on the subjects. At the lower work loads the majority of subjects reached thermal equilibrium before the end of exercise by maintaining their convective heat transfer from core to periphery by increasing peripheral blood flow, and raising their heat losses to environment by convection and radiation. Atropine had no effect on M or H but greatly affected work performance. These results demonstrate the ability of the thermoregulatory system to adapt to beta-adrenergicand to parasympathetic blockade during light exercise. (gekuerzt)