Influence of exercise intensity and plasma volume on active cutaneous vasodilation in humans

The influence of dynamic exercise on active cutaneous vasodilation was evaluated in eight male subjects. We measured the increase in internal body temperature (esophageal temperature, Tes) required to elicit active cutaneous vasodilation and the slope of the linear relationship between increases in forearm skin vascular conductance (delta FVC) and Tes during indirect heating (legs immersed in 44 degrees C water for 30 min), 30 min of light exercise (LEX; 75 +/- 5 W = 30% maximal oxygen uptake, VO2max), and 20 min of moderate exercise (MEX, 149 +/- 7 W = 60% VO2max). Studies were conducted in the supine position at 30 degrees C (RH < 30%) and mean skin temperature averaged 35.09 +/- 0.12 degrees C. During indirect heating and LEX, cutaneous vasodilation occurred after a similar increase in Tes, 0.03 +/- 0.02 degrees C and 0.11 +/- 0.02 degrees C, respectively. During MEX, Tes increased 0.42 +/- 0.06 degrees C before the onset of cutaneous vasodilation (P < 0.05, different from rest and LEX). The relationship between the increase in Tes threshold for vasodilation and exercise intensity was nonlinear, indicating that some minimal exercise intensity was required to elicit a delay in active cutaneous vasodilation. That minimal exercise intensity was greater than 30% VO2max (75 +/- 5 W). During MEX the increase in Tes threshold for vasodilation was inversely related to resting plasma volume (ml.kg-1) with a larger initial plasma volume associated with a smaller increase in Tes threshold for cutaneous vasodilation (r2 = 0.67, P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)