The effect of exercise intensity on post-exercise skin blood flow control

Abstract

Exercise induces a residual post-exercise increase in the core temperature threshold at which cutaneous vasodilation and sweating begins. The hypothesis that exercise intensity causes a parallel increase in the post-exercise onset threshold for cutaneous vasodilation mediated by an attenuation of active vasodilator activity, was tested in nine subjects. The effect of exercise intensity on the esophageal temperature threshold for the onset of sweating was also evaluated. Esophageal temperature was monitored as an index of core temperature while sweat rate was measured using a ventilated capsule placed on the upper back. Increases in forearm skin blood flow and mean arterial blood pressure were measured and used to calculate cutaneous vascular conductance at two superficial sites, one with intact alpha-adrenergic vasoconstrictor activity and one infused with bretylium tosylate. On four separate days, subjects either remained seated for 35 min or performed 15 min treadmill running at 55, 70 or 85% VO2max followed by 20 min seated recovery. A liquid conditioned suit was used to increase mean skin temperature until cutaneous vasodilation and sweating occurred. It is concluded that intensity of exercise has a prolonged residual effect on the post-exercise vasomotor and sudomotor response by increasing the esophageal temperature at which onset of vasodilation and sweating occurs. Furthermore, the post-exercise increase in onset threshold for vasodilation is likely caused by an attenuation of active vasodilator activity modulated by baroreceptor reflexes in response to post-exercise hypotension.