Effects of muscle metaboreceptor stimulation on cutaneous blood flow from glabrous and nonglabrous skin in mildly heated humans

Given differences in sympathetic innervation to glabrous and nonglabrous skin, we tested the hypothesis that muscle metaboreceptor regulation of cutaneous vascular conductance (CVC) differs between these skin regions. Subjects (n = 21) performed isometric handgrip exercise (IHG; 50% maximal voluntary contraction for 60 s), followed by 2 min of postexercise ischemia. Throughout IHG and postexercise ischemia, CVC was measured from glabrous (palm) and nonglabrous (forearm and chest) regions contralateral to the exercising arm. These procedures were conducted after the subjects had been exposed to an ambient temperature of 35°C and a relative humidity of 50% for 60 min. These thermal conditions were intended to cause slight increases in cutaneous blood flow via sympathetic withdrawal. Esophageal, sublingual, and mean skin temperatures did not change markedly during IHG or postexercise ischemia. During IHG, forearm CVC did not change, chest CVC increased slightly, and palm CVC decreased substantially (from 100 to 34.8 ± 3.5%; P = 0.001). During muscle metaboreceptor stimulation due to postexercise ischemia, CVC from nonglabrous regions returned to preexercise baselines, whereas CVC at the palm remained below preexercise baseline (68.2 ± 4.2%; P = 0.001 relative to preexercise baseline). These results indicate that in mildly heated humans muscle metaboreflex stimulation is capable of modulating CVC in glabrous, but not in nonglabrous, skin.