title: Sweat rate and prediction validation during high-altitude treks on Mount Kilimanjaro.
abstract: This study measured sweat rates (m(sw)) during high-altitude summer treks on Mt. Kilimanjaro to evaluate the efficacy of a recently developed fuzzy piecewise sweat prediction equation (Pw,sol) for application to high-altitude conditions. We hypothesized that the Pw,sol equation, adjusted for the barometric pressure (Pb) decreasing steadily at high altitude (Pw,sol+Alt), would allow for a more accurate prediction of m(sw) than Pw,sol unadjusted for altitude (Pw,sol(SL)). Fifteen men (43 ± 16 yr; 80 ± 22 kg) and seven women (46 ± 16 yr; 77 ± 18 kg) wearing hiking clothes (clo ∼1.15; clothing evaporative potential = 0.27) and carrying light loads (9 ± 2 kg), were studied during morning and afternoon treks (∼2-3 h) while ascending from 2,829 m to 3,505 m. After each trek, m(sw) was measured with specific biophysical parameters at 15-min intervals. During the trek day, Pb progressively declined (530 to 504 Torr), as solar radiation and ambient temperature (°C) rose transiently. During all treks, m(sw) ranged from 68 to 393 g·m(-2)·h(-1) (0.14 to 0.79 l/h). For each subject, derived Pw,sol(SL) and Pw,sol+Alt model outputs accurately predicted the morning and afternoon average m(sw) within a root mean square error of 0.145 l/h. No differences were found between Pw,sol(SL) and Pw,sol+Alt values. In conclusion, we report the first m(sw) measured during outdoor high-altitude activities and determined that Pw,sol(SL) equation can be used to predict fluid needs during high-altitude activities without alterations for lower Pb. This model prediction provides a valid water planning tool for outdoor activities at high altitude up to 3,500 m.
authors.affiliation: Biology Department, New Mexico State University, Las Cruces, New Mexico, USA.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Gonzalez
authors.forename: Robert W
authors.initials: RW
authors.lastname: Kenefick
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Muza
authors.forename: Scott W
authors.initials: SW
authors.lastname: Hamilton
authors.forename: Michael N
authors.initials: MN
authors.lastname: Sawka
mesh_terms: D000064:Acclimatization; D000328:Adult; D000531:Altitude; D000704:Analysis of Variance; D001274:Atmospheric Pressure; D004326:Drinking; D004734:Energy Metabolism; D005260:Female; D017143:Fuzzy Logic; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009051:Mountaineering; D015203:Reproducibility of Results; D012621:Seasons; D013546:Sweating; D013696:Temperature; D013997:Time Factors; D014882:Water-Electrolyte Balance