Abstract

The hypoxic chemoreflex and the arterial baroreflex are implicated in theventilatory response to exercise. It is well known that long-term exercisetraining increases parasympathetic and decreases sympathetic tone, bothprocesses influenced by the arterial baroreflex and hypoxic chemoreflexfunction. Hypobaric hypoxia (i.e., high altitude [HA]) markedly reduces exercisecapacity associated with autonomic reflexes. Indeed, a reduced exercise capacityhas been found, paralleled by a baroreflex-related parasympathetic withdrawaland a pronounced chemoreflex potentiation. Additionally, it is well known thatthe baroreflex and chemoreflex interact, and during activation by hypoxia, thechemoreflex is predominant over the baroreflex. Thus, the baroreflex functionimpairment may likely facilitate the exercise deterioration through the reductionof parasympathetic tone following acute HA exposure, secondary to thechemoreflex activation. Therefore, the main goal of this review is to describethe main physiological mechanisms controlling baro- and chemoreflex functionand their role in exercise capacity during HA exposure.