EFFECT OF WORK LOAD ON CUTANEOUS VASCULAR-RESPONSE TO EXERCISE

The purpose of the present study was to examine whether intensity of exercise affects skin blood flow response to exercise. For this purpose, six healthy men cycled, in a random order on different days, for 15 min at 50, 60, 70, 80, and 90% of their maximum oxygen consumption (VO2max) at a room temperature of 25-degrees-C. At the end of exercise, esophageal temperature (T(es)) averaged 37.4 +/- 0.2, 37.7 +/- 0.2, 37.9 +/- 0.2, 38.6 +/- 0.3, and 38.9 +/- 0.4-degrees-C (SE) at the 50, 60, 70, 80, and 90% work loads, respectively. At the two highest work loads, no steady state was observed in T(es). Skin blood flow was estimated by measuring forearm blood flow (FBF) with strain-gauge plethysmography and by laser-Doppler flowmetry on the upper back. Both techniques showed that skin blood flow response to rising T(es) was markedly reduced at the 90% work load compared with other work loads. At the end of exercise, FBF averaged 7.5 +/- 1.7, 10.7 +/- 3.1, 9.6 +/- 2.1, 11.3 +/- 2.6, and 5.4 +/- 1.3 (SE) ml.min-1.100 ml-1 (P < 0.01) at the 50, 60, 70, 80, and 90% VO2max work loads, respectively. The corresponding values for T(es) threshold for cutaneous vasodilation (FBF) were 37.42 +/- 0.16, 37.48 +/- 0.13, 37.59 +/- 0.13, 37.79 +/- 0.19, and 38.20 +/- 0.22-degrees-C (P < 0.05) at 50, 60, 70, 80, and 90% VO2max, respectively. In two subjects, no cutaneous vasodilation was observed at the 90% work load. It was suggested that cutaneous vascular response to dynamic exercise is significantly attenuated at high relative work loads. In our subjects the critical intensity was above 80% VO2max.