The skin blood flow response to exercise in boys and men and the role of nitric oxide

PurposeChildren thermoregulate effectively during exercise despite sweating rate being consistently lower when compared with adults. The skin blood flow (SkBF) response of children to exercise is inconsistent, when compared with adults. We examined the SkBF response to exercise in children and adults, along with the potential contribution of nitric oxide to the SkBF response.MethodsForearm SkBF during cycling (30 min at 60% V˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}O2max) was investigated in 12 boys (10 ± 1 years) and 12 men (22 ± 2 years) using laser-Doppler flowmetry and Nω-nitro-l-arginine methyl ester (L-NAME) iontophoresis to inhibit nitric oxide synthase.ResultsThe exercise-induced SkBF increase was similar in boys and men (mean ± SD, 540 ± 127 vs. 536 ± 103% baseline, respectively, p = 0.43, d = 0.01 [− 0.8 to 0.8]). However, the total hyperaemic response to exercise (area-under-the-curve, AUC) indicated that boys had a greater vasodilatory response (cutaneous vascular resistance, CVC) (p < 0.01, d = 0.6 [− 1.2 to 2.8] than the men (134,215 ± 29,207 vs. 107,257 ± 20,320 CVC·s−1). L-NAME blunted the SkBF response more in boys than in men (group-by-treatment interaction, p < 0.001) and resulted in smaller AUC in boys (56,411 ± 23,033 CVC·s−1; p < 0.001, d = 1.4 [− 0.4 to 3.2] compared with men (80,556 ± 28,443 CVC·s−1; p = 0.08, d = 0.8 [0.0–1.6]). Boys had a shorter delay from the onset of exercise to onset of SkBF response compared with men (205 ± 48 and 309 ± 71 s, respectively; p < 0.01, d = 1.7 [0.9–2.8]). L-NAME increased the delay in boys and men (to 268 ± 90 and 376 ± 116 s, respectively; p = 0.01, d = 1.0 [0.4–2.1]) but this delay was not significantly different between the groups (p = 0.85).ConclusionsThese findings suggest that boys experience greater vasodilation and faster increases in SkBF during exercise compared with men. The contribution of nitric oxide to the SkBF response to exercise appears to be greater in boys than in men.