• The Contribution of Nitric Oxide to the Skin Blood Flow Response to Exercise in Boys and Men

      Woloschuk, Alexandra; Applied Health Sciences Program
      In response to heat stress, children sweat less than adults. However, little is known about their skin blood flow (SkBF) response. We investigated child-adult differences in SkBF during exercise (30 min at 60% VO2max) and local heating (44℃) in 12 boys (9.71.2 y) and 12 men (22.22.0 y) using laser-Doppler flowmetry and L-NAME to inhibit nitric oxide (NO). The exercise-induced SkBF increase was greater in boys versus men (p=0.03). L-NAME blunted SkBF response during exercise in boys and men (p<0.01) (758±201 to 429±229 percent change from baseline vs. 541.6±167 to 352±109 percent change from baseline, respectively). Boys had a shorter time delay between the onset of exercise and onset of SkBF response compared with men (p<0.01) and L-NAME increased the time delay in boys and men (205±48 to 268±90 s vs. 309±71 to 376±116 s, respectively) (p=0.01). During local heating, SkBF increases were greater in boys versus men (p<0.01) and L-NAME blunted the SkBF response in boys and men (2594±939 to 1630±791 percent change from baseline vs. 1600±605 to 1046±345 percent change from baseline, respectively) (p<0.01). These data suggest that boys experience greater and faster increases in SkBF during exercise and local skin heating compared with men. NO influence on microvasculature and thermoregulatory function was not different between boys and men.
    • Quantifying the Relationship of Bilateral Blood Flow in Glabrous Skin at Rest and During Sympathetic Perturbations

      McNabb, Leed; Applied Health Sciences Program
      Sympathetic nervous system regulation of blood flow within glabrous skin occurs through control of vasoconstrictor tone, with vasodilation being a passive process. As bursts of sympathetic vasoconstrictor activity occur simultaneously at separate sites of the body, blood flow patterns should also be closely matched due to the direct connection between sympathetic nerves and peripheral microvessels. With sympathetic activity difficult and invasive to measure directly, the possibility of using blood conductance as an indirect measure seems promising. We investigated the relationship of bilateral blood conductance recordings of both middle fingers in ten (7M, 3F) healthy participants, while at rest and in response to perturbations known to elicit sympathetic activity. Cutaneous vascular conductance was measured from both middle fingers via laser Doppler flowmetry, while at rest in a thermoneutral room for 20 minutes and in response to 4 randomized sympathetic perturbations (2 breath holds and 2 cold stimuli) while centrally vasodilated via heating of the back. Correlation coefficients while at thermoneutral rest were high (0.80 ± 0.22) demonstrating a strong temporal relationship for blood conductance in both fingers. During the sympathetic perturbations, blood conductance in both fingers were more related during (0.93 ± 0.11) and post (0.87 ± 0.11) administration of the sympathetic perturbation than prior (0.67 ± 0.25) to the administration (p = 0.002). Taken together, these findings indicate that blood conductance patterns at separate sites of the body are significantly more related during vasoconstrictor activity and that blood conductance may have potential as a non-invasive measure of sympathetic activity.