Plasma catecholamine response to acute psychological stress in humans: relation to aerobic fitness and exercise training.

Existing cross-sectional studies on plasma catecholamine activity provide no support for the concept that a markedly high level of aerobic fitness modifies sympathoadrenal response to an acute psychological challenge in humans. In contrast, compromised sympathetic nervous system activity has been observed in individuals with low aerobic fitness and the relationship probably reflects a global deconditioning syndrome involving both psychological and physiological processes. The relationship between low levels of fitness and plasma norepinephrine may appear as a blunted or augmented response depending upon the nature of the task. Short-term (3-4 months) exercise training studies conducted with humans have not indicated a substantial adaptation in the relative plasma catecholamine change from a preexisting baseline during exposure to acute psychological stress. Exercise training can lower basal circulating plasma norepinephrine, resulting in lower absolute concentrations during an acute challenge, but the studies in this area lack consistency and the absolute change tends to be modest. There is no evidence that fitness or exercise training is significantly associated with plasma epinephrine activity during short-term psychological stress.