Exercise training and response to stress: insights from an animal model.

Abstract

The effect of training on the sympathoadrenal and cardiovascular responses to stress was examined in borderline hypertensive rats (BHRs). Animals trained with swimming showed reduced heart rates and plasma norepinephrine and epinephrine levels in response to novel foot shock stress. In contrast, systolic blood pressure was significantly higher in trained BHRs during the stress. Parasympathetic blockade with atropine sulfate (1 mg.kg-1 IV) had little effect on heart rate during stress in untrained rats but significantly elevated the stress-induced heart rate of trained animals. The reduction in stress reactivity produced by exercise training is not manifested in all physiological variables and increases in parasympathetic tone contribute strongly to the attenuated reactivity in heart rate.