Modification of the skin blood flow body temperature relationship by upright exercise

To determine whether skin is relatively vasoconstricted during upright exercise in the heat and to determine the roles of upright posture and exercise on the relationship of skin blood flow (SkBF) to internal temperature, increments in forearm SkBF (plethysmography), and esophageal temperature, [T(es)] were measured in six men during upright exercise, supine exercise, urpight rest, and supine rest. Skin temperature, [T(sk)], was held at 38°C in all studies with water perfused suits. Exercise loads were chosen to yield heart rates of 120 to 130 beats/min during supine exercise at neutral T(sk). Both upright posture and exercise per se consistently caused reduced (SkBF at a given T(es) as compared to supine rest. Major alterations of the slope of SkBF to T(es) relationship also accompanied upright posture or exercise. It is concluded that skin is relatively vasoconstricted during heat stress with exercise or upright posture, and that the greatest effect occurs when these stresses are combined.