Effects of dynamic leg exercise on subcutaneous blood flow rate in the lower limb of man.

Subcutaneous blood flow (SBF) was studied simultaneously in the upper arm at heart level and in the lower limb during positional changes and during leg exercise in seven healthy males. SBF was estimated by local clearance of 133Xenon registered by portable cadmium telluride detectors. Venous pressure was recorded directly on dorsum on the foot. Changing the position from supine to head-up tilt, SBF decreased by 43% (P less than 0.01) at the arm level, 40% at the thigh (P less than 0.01), 47% at the calf (P less than 0.01) and decreased by 51% at the ankle level (P less than 0.01). Performing 20 heel-raisings per min in nearly erect posture, SBF increased by 96% at the thigh (P less than 0.01), 25% at the calf (P greater than 0.1) and increased by 18% at the ankle level (P greater than 0.01). At 40 heel-raisings per min SBF increased by 99% at the thigh (P less than 0.01), 121% at the calf (P less than 0.01), but only 44% at the ankle level (P greater than 0.1). During leg exercise subcutaneous vascular resistance was significantly increased at arm and ankle levels. In contrast, a vasodilatory response was noticed at the thigh and calf levels and seemed associated with a decrease in local venous pressure to below the trigger level of the sympathetic veno-arteriolar reflex mechanism. In conclusion, SBF in the lower limb of man was increased during exercise. The increase in SBF could only partly be ascribed to the concomitant increase in perfusion pressure. The local blood flow response seemed modified by changes in sympathetic nervous activity and metabolic rate.