Cardiac autonomic regulation during hypoxic exercise

摘要

autonomic nervous system regulation of the heart and vascu-lature plays a key role in enabling the tight coupling between oxygen consumption of exercising skeletal muscles and oxygen delivery. The withdrawal of cardiac parasympathetic nerve activity and elevation in cardiac sympathetic nerve activity facilitate the exercise intensity-dependent increase in heart rate, ventricular contractility, stroke volume, and cardiac output (5). Robinson et al. (10) laid the foundations for the present understanding of cardiac autonomic regulation in exercising humans with the demonstration that administration of atropine (to block cholinergic muscarinic receptors) markedly diminishes elevations in heart rate only during low-to-moderate intensity dynamic exercise, whereas administration of propran-olol (to block beta-adrenergic receptors) principally attenuates the cardiac acceleration during strenuous dynamic exercise. In the current issue of the American Journal of Physiology-Heart and Circulatory Physiology, Siebenmann et al. (12) use a similar methodological approach to provide new insights into cardiac autonomic regulation during hypoxic exercise in humans.