ABSTRACT

Large changes in skin blood flow occur with exercise. Most studies have dealt with changes in cutaneous flow at sites distant from vigorous exercise. Thus, hemodynamic effects and changes in core body temperature are the dominant influences on measurements obtained. It has been technically difficult to determine skin blood flow at sites near vigorous muscular activity. We have developed a technique to carry out dynamic exercise of an extremity while maintaining the site of blood flow measurement motionless. Therefore, we are able to obtain valid readings using Laser Doppler technology, free from motion artifact.

Using this technique we measured skin blood flow on the paw on the Wistar-Kyoto rat during dynamic limb exercise induced by electrocutaneous stimulation. We contrasted results on the planter surface of the paw, which has a high density of arteriovenous anastomoses (AVA), with measurements on the dorsal surface, which has a nutritive (NUTR) perfusion (NUTR). At basal skin temperature, the average maximal flow reached at the planter paw surface was 46 + 4 mVmin 100 gm compared to 33 + 2rnl/min/100 gm at the paw dorsum. With application of heat, there was no change in the mean maximal flow attained during exercise at the paw dorsum. At the planter paw surface, there was a small increase to 68 + 10 ml/min/100 am. Expressed as a percentage of increase, exercise induced an increment over preexercise baseline of 992 + 100% at the planter paw surface at basal temperature, but only 30 + 3% at 44 C. In contrast, there was a sixfold increase in mean maximal flow at the paw dorsum with exercise both at basal temperature and at 44 C. At the dorsal surface, the increase was mediated by an equivalent increase in microvascular volume and red blood cell velocity. In contrast, at the planter surface, the increase was chiefly one of red blood cell velocity. Distant exercise raises skin blood flow through increased heart action and reflex vasodilation due to core body thermogenesis. In contrast, local exercise appears to act by a direct physical action.

For more information on this topic, click here!