Experimental trials
thirst
HEAT, COLD, BLOOD
Participants ingested a CorTemp Sensor (HQInc, Palmetto, FL) the evening prior to experimental visits, 10–12 h before arriving to the laboratory. Likewise, participants consumed 6 mL·kgExperimental trials.Participants were then seated in an upright position and fitted with a heart rate monitor (Polar® FT4M). Baseline measures of core temperature, skin temperature, heart rate, thermal sensation and subjective ratings of thirst were recorded. Thermal sensation was assessed using a 9‐point Likert scale, ranging from −4 (Unbearably Cold), to +4 (Unbearably Hot) with 0 (Comfortable) anchored at the midpoint. Perceived thirst was measured using a 100 mm long psychometric response scale with verbal anchors at assigned distances to quantify subjective measures. Thereafter, the first blood sample was drawn from the antecubital space. Participants did not eat or drink until all experimental data collection was completed.Following baseline measurements, participants entered the environmental chamber (40°C, 60% RH) to begin 60 min of seated passive heat exposure. Participants wore a standardized outfit (i.e., t‐shirt, shorts, socks, and shoes) while in the chamber for every experimental condition. Once inside, measures of core temperature, skin temperature, thermal sensation, and heart rate were measured in 15‐min intervals. Blood was drawn inside the chamber at min 30 and 60. Breath measurements were collected from 0 to5 min, 25 to 30 min, and 55 to 60 min. Metabolic heat production was calculated using measures of gas exchange (i.e., VOAfter 60 min of passive heat exposure, participants exited the chamber. Immediately afterward, participants completed their subjective measure of thirst, then toweled dry to provide their post‐heat exposure nude body weight. Thereafter, participants were seated and passively recovered in a thermoneutral room (23°C, 50% RH) for 30 min before the final blood draw.