Maximum Skin Wettedness following Aerobic Training with and without Heat Acclimation.

PURPOSE: To quantify how maximum skin wettedness ([omega]max), i.e. the determinant of the boundary between compensable and uncompensable heat stress, is i) altered by aerobic training in previously unfit individuals, and ii) further augmented by heat acclimation. METHODS: Eight untrained individuals completed an 8-week aerobic training program immediately followed by 8 days of hot/humid (38[degrees]C, 65%RH) heat acclimation. Participants completed a humidity ramp protocol pre-training (PRE-TRN), post-training (POST-TRN), and post-heat acclimation (POST-HA), involving treadmill marching at a heat production of 450 W for 105 mins in 37.5[degrees]C, 2.0 kPa (35%RH). After attaining a steady-state esophageal temperature (Tes), humidity increased 0.04 kPa[middle dot]min-1. An upward inflection in Tes indicated the upper limit of physiological compensability (Pcrit), which was then used to quantify [omega]max. Local sweat rate (LSR), activated sweat gland density (ASGD) and sweat gland output (SGO) on the back and arm were simultaneously measured throughout. RESULTS: Peak aerobic capacity increased POST-TRN by ~14% (PRE-TRN:45.8+/-11.8 ml[middle dot]kg-1[middle dot]min-1; POST-TRN:52.0+/-11.1 ml[middle dot]kg-1[middle dot]min-1, P

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