Ergoreflex: The essence and mechanisms

Physical load increases sympathetic nervous activity, which results in an increased cardiac output, constriction of peripheral vessels, and elevated systemic blood pressure. These changes are outcomes of two mechanisms: the central command from cerebral structures that trigger voluntary movements to activate the vasomotor center and the reflexes initiated by mechanical and metabolic changes in a working muscle. The latter mechanism of the sympathetic system activation is termed ergoreflex. The main effects of ergoreflex on the indices of systemic hemodynamics are the following: activation of mechanosensitive afferents mainly leads to inhibition of the tonic vagal effects on the heart, which explains the rapid increase in heartbeats upon loading; activation of chemosensitive afferents comes with some delay in pace with metabolite accumulation in muscles and leads to an increase in efferent sympathetic activity and a rise in blood pressure. The metabolic reflex effect is particularly high in the case of muscle fatigue. This review deals with the mechanisms underlying the ergoreflex and their adaptation to hypodynamia, physical training, and some pathologies.