Neurohumoral factor responses to mental (arithmetic) stress and dynamic exercise in normal subjects

We examined the responses of plasma catecholamine and plasma renin activity (PRA) during mental (arithmetic) stress and dynamic exercise in 15 normal subjects. Compared to rest values, there was a significant increase in the plasma epinephrine concentration (E), but not in the plasma norepinephrine concentration (NE) or PRA during mental arithmetic. During dynamic exercise, there were significant increases in both NE and E and in PRA. The ratio of E to NE was significantly higher during mental arithmetic than during dynamic exercise. NE was significantly correlated with PRA at rest, during mental arithmetic and dynamic exercise. No significant correlations were observed between E and PRA. Dynamic exercise primarily induces a sympathetic nervous response, and mental (arithmetic) stress mainly induces an adrenal response. The renin-angiotensin-aldosterone system response may in part be regulated by sympathetic nervous activity during both mental (arithmetic) stress and dynamic exercise.