Sweating distribution and active sweat glands on the scalp of young males in hot-dry and hot-humid environments

Purpose We investigated the effects of humidity on regional sweating secretion and active sweat gland density on the scalp during passive heating in hot environments. Methods Eight male subjects shaved their heads prior to expose to dry (30%RH; H30%) and humid (85%RH; H85%) conditions at an air temperature of 32 °C. Total sweat rate, local sweat rates (frontal, vertex, temporal, and occipital regions), active sweat glands on the scalp (2 frontal, 2 parietal, 2 temporal, 1 occipital, and 1 vertex), and rectal and skin temperatures were measured during leg immersion in 42 °C water for 60 min. Results (1) Total sweat rates were greater for H30% (179.4 ± 35.6 g h −1 ) than for H85% (148.1 ± 27.2 g h −1 ) ( P