Sex-related differences in evaporative heat loss: the importance of metabolic heat production

We evaluated the hypothesis that different rates of metabolic heat production between sexes, during exercise at the same percentage of maximum oxygen consumption \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left( {\dot{V}{\text{O}}_{2\max } } \right), $$\end{document} give proportional differences in evaporative heat loss. Seven males and seven females, exercised at 41.3 ± 2.7% \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}{\text{O}}_{2\max } $$\end{document} for 60-min at 40°C and 30% relative humidity. Whole-body direct air calorimetry measured rate of whole-body evaporative heat loss \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left( {\dot{H}_{\text{E}} } \right), $$\end{document} while metabolic heat production \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left( {\dot{M} - \dot{W}} \right) $$\end{document} was measured by indirect calorimetry. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{M} - \dot{W} $$\end{document} was greater in males (243 ± 18 W m−2) relative to females (201 ± 4 W m−2) (P ≤ 0.05) throughout exercise. This was paralleled by a greater \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{H}_{\text{E}} $$\end{document} at end-exercise in males (207 ± 51 W m−2) relative to females (180 ± 3 W m−2) (P ≤ 0.05). Differences in metabolic heat production between sexes during exercise at a fixed percentage of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}{\text{O}}_{2\max } $$\end{document} give differences in evaporative heat loss. To compare thermoregulatory function between sexes, differences in metabolic heat production must therefore be accounted for.