Cutaneous blood flow rate in areas with and without arteriovenous anastomoses during exercise

In 10 healthy subjects, skin blood flow rate was measured in the thumb pulp by the heat-washout method, and in the skin fold between the thumb and the forefinger by the 133Xe-washout method. The former but not the latter skin area contains arteriovenous anastomoses (AVAs). In response to 10 min moderate bicycle exercise, an instantaneous decrease in flow was seen in the thumb pulp followed after about 4.6 min by an increase to resting levels. Blood flow in the skin fold remained constant. The results indicate that the initial reduction in blood flow rate and later increase observed in the finger at the onset of moderate exercise take place in the AVAs and not in the capillaries.