Male and female highly trained runners adapted comparably to seven 60-min heat-acclimation runs at a fixed easy pace (40 °C): no significant sex difference in how fast or how far core temperature, heart rate and sweat rate changed, in a randomised crossover of 18 runners (8 M / 10 F); heat gave larger falls in core temperature and heart rate and a larger rise in sweat rate than the same runs at 22 °C, and plasma volume changed in neither

Keefe and colleagues asked whether the course and size of heat adaptation differ between male and female highly trained endurance runners, and how heat acclimation compares with the same training in temperate air.

Eighteen runners (8 men, 10 women) each completed two blocks of seven sessions in a randomised, counterbalanced order: one at 40 °C and one at 22 °C, both at 35% humidity, each session 60 min of running at 50% of the velocity at VO2max. Adaptation was the change from the first session in core temperature, skin temperature, heart rate, whole-body sweat rate and plasma volume.

There was no intervention × sex × session interaction for core temperature, heart rate or sweat rate, and no sex difference in the overall size of any heat adaptation. The heat block lowered mean and peak core temperature and baseline, mean and peak heart rate more, and raised sweat rate more, than the temperate block; plasma volume did not change after either.

The authors conclude that men and women adapt comparably to this protocol, and that temperate training gives part of the adaptation while heat adds to its size without changing its course by sex.