A STUDY OF SOME POTENTIAL CORRELATES OF THE HYPOTENSIVE EFFECTS OF PROLONGED SUBMAXIMAL EXERCISE IN NORMOTENSIVE MEN

This study was undertaken (1) to examine the relation of plasma catecholamine and insulin levels to the blood pressure response during and after submaximal exercise, (2) to verify whether the blood pressure response to an epinephrine infusion is associated with the blood pressure response to a prolonged submaximal exercise, and (3) to study some potential correlates of the hypotensive effect of prolonged aerobic exercise. Nine normotensive young men (mean age 22.0 +/- 1.4 years) were subjected to a 1-h epinephrine infusion protocol and a 1-h submaximal exercise test on a cycle ergometer. The two tests were performed 1 week apart. The physiological and hormonal responses observed during the submaximal exercise test were generally greater than those observed during the epinephrine infusion test. Blood pressure responses in both tests showed no significant association with changes in plasma insulin levels. Changes in plasma norepinephrine concentration were positively correlated with changes in systolic blood pressure during the submaximal exercise test but not during the epinephrine infusion. Results also showed that the blood pressure response to epinephrine infusion was not correlated with the blood pressure response to submaximal exercise. However, post-exercise and post-infusion systolic blood pressure responses (differences between "post-test" and "resting" values) were significantly associated (r = 0.81, p < 0.01). In addition, a significant hypotensive effect of submaximal exercise was observed for both systolic and diastolic blood pressure. However, the individual difference observed in the hypotensive effect of aerobic exercise appeared to be more related to variations in vascular sensitivity than to exercise-induced variations in plasma insulin and catecholamine levels, at least in this sample of healthy normotensive young men.