2.3. Study Variables
thirst, Euhydration, Thirst
For all trials, participants were asked to confirm their adherence to the instructed pre-trial fluid intake protocol and major deviations from the protocol resulted in the trial being rescheduled. Upon arrival at all trials, hydration was assessed through urine analysis. Participants provided a urine sample upon arrival and urine specific gravity (USG) was assessed using a hand-held refractometer (Ketotek, Hangzhou, China) and urine color was assessed through comparison with a urine color chart (Hydration Check, Human Hydration, VA, USA). Euhydration was defined as a USG of less than 1.020 [Before beginning and immediately following exercise, nude body mass (WB800S Tanita, IL, USA), thirst, and rating of perceived exertion were assessed. To assess nude body mass, participants entered a private and locked room where they removed all clothing and dried off with a towel (after exercise) to obtain a body mass. Thirst was assessed by asking the participants to rate their sensation of thirst on a 9-point Likert scale with 1 indicating “Not thirsty at all” and 9 indicating “Very, Very Thirsty” [Rate of perceived exertion was recorded according to a Borg scale (6–20). Average heart rate and total duration were monitored in both trials using wrist-worn GPS and heart rate devices (Garmin Forerunner 245, Olathe, KR, USA). The trials took place over three different days at the same time of day (1500–1700) to accommodate the participants’ schedules. Environmental conditions were assessed at the beginning of each trial using the Kestrel 3000HS Heat Stress Meter (Kestrel, Boothwyn, PA, USA).