Cardiovascular regulation during exercise - Contribution of peripheral reflexes

Static and dynamic exercise is accompanied by increases in arterial blood pressure, heart rate and sympathetic nerve activity. It has been hypothesized that these cardiovascular responses are mediated by central command as well as by feedback mechanisms operating via afferent nerves (group III and IV fibers) that arise from skeletal muscles, are sensitive to mechanical (the so-called muscle mechanoreflex) and metabolic changes (the so-called muscle metaboreflex), and are modulated by arterial and cardiopulmonary baroreflexes. In this review, discussion is focused on the roles of the arterial baroreflex and muscle metaboreflex in cardiovascular regulation during exercise. In the first part of the review, brief discussion is made of the functions of these two reflexes during exercise; in the second part, their interactions are looked at in more detail. It is thought that during heavy exercise, the arterial baroreflex and the muscle metaboreflex are both activated, and interact in ways that lead to modulation of the primary cardiovascular reflex responses. Two types of interaction have been demonstrated. In the first, the arterial baroreflex acts to oppose pressor responses induced via the muscle metaboreflex. The second type of interaction involves the modulation of arterial baroreflex function during muscle metaboreflex activation. The authors offer commentary on these two types of interaction, including recent knowledge.