BAROREFLEX REGULATION OF FOREARM VASCULAR-RESISTANCE AFTER EXERCISE IN HYPERTENSIVE AND NORMOTENSIVE HUMANS

The mechanisms underlying the antihypertensive period following a bout of exercise are not well understood. We examined the aftereffects of exercise on the linear relationship between forearm vascular resistance (FVR) and estimated central venous pressure (CVP) during leg raising and lower body negative pressure to determine whether an alteration of the baroreflex control of FVR was associated with the decreased blood pressure. Blood pressure, forearm blood flow (FBF), and estimated CVP were obtained in 13 hypertensive and 9 normotensive subjects evaluated in a randomized crossover fashion after 30 min of cycle ergometer exercise and after a nonexercise control period. In hypertensive subjects, the reduced blood pressure was accompanied by an increased baseline FBF after exercise. This resulted in a downward shift of the FVR-CVP relationship, while the slope was unchanged. In normotensive subjects, blood pressure and baroreflex control of FVR were unaffected by prior exercise. Four of the hypertensive subjects performed an additional study in which forearm skin was vasodilated with local heating to FVR levels similar to those observed after exercise. Results suggested that the aftereffects of exercise could not be attributed to changes in cutaneous blood flow. We speculate that modulation of the baroreflex control of FVR after exercise contributes to its antihypertensive effect.