Hyperthermia and maximal oxygen uptake in men and women

To compare the effect of hyperthermia on maximal oxygen uptake (V̇O_2max) in men and women, V̇O_2max was measured in 11 male and 11 female runners under seven conditions involving various ambient temperatures (T _a at 50% RH) and preheating designed to manipulate the esophageal (T _es) and mean skin \( (\ifmmode\expandafter\bar\else\expandafter\=\fi{T}_{{{\text{sk}}}})\) temperatures at V̇O_2max. The conditions were: 25°C, no preheating (control); 25, 35, 40, and 45°C, with exercise-induced preheating by a 20-min walk at ~33% of control V̇O_2max; 45°C, no preheating; and 45°C, with passive preheating during which T _es and \( \ifmmode\expandafter\bar\else\expandafter\=\fi{T}_{{{\text{sk}}}}\) were increased to the same degree as at the end of the 20-min walk at 45°C. Compared to V̇O_2max (l·min⁻¹) in the control condition (4.52±0.46 in men, 3.01±0.45 in women), V̇O_2max in men and women was reduced with exercise-induced or passive preheating and increased T _a, ~4% at 35°C, ~9% at 40°C and ~18% at 45°C. Percentage reductions (7–36%) in physical performance (treadmill test time to exhaustion) were strongly related to reductions in V̇O_2max (r=0.82–0.84). The effects of hyperthermia on V̇O_2max and physical performance in men and women were almost identical. We conclude that men and women do not differ in their thermal responses to maximal exercise, or in the relationship of hyperthermia to reductions in V̇O_2max and physical performance at high temperature. Data are reported as mean (SD) unless otherwise stated.