Control of forearm venous volume during exercise and body heating

Abstract

Subjects ate ice to cool sufficiently to constrict the superficial forearm veins. After ice-eating, esophageal temperature (Tes) recovered from local cooling in 10-15 min, and thereafter reflected body core temperature. Eight skin temperatures (Tsk) were measured, and a weighted mean (Tsk) computed. The left wrist was suspended 5-6 in. above shoulder level, and left forearm skin temperature was maintained at 35 degrees C with a controlled-temperature air stream. Forearm venous volume (FVV) w-s the volume difference between the forearm drained by gravity and the forearm congested by a pneumatic cuff inflated to 32 Torr. Subjects were warmed either by storage of resting metabolic heat or by cycle exercise at 40-45% of maximal O2 consumption. Exercise experiments were conducted in ambient temperatures of 15, 25, and 35 degrees C, and resting experiments in 25 and 35 degrees C. FVV rose linearly with Tes, but during exercise FVV was lower than at the same Tes and Tsk during rest, and the difference was greater at high Tsk and FVV. Our data fit the equation FVV-FVV0 = (a1 Tes + a2 Tsk - b).[1 - phi (W).(Tsk - T-sk0)], where phi (W) is a function of exercise, and phi (W) = 0 at rest.