title: Possible biphasic sweating response during short-term heat acclimation protocol for tropical natives.
abstract: The aim of the present study was to evaluate the sweat loss response during short-term heat acclimation in tropical natives. Six healthy young male subjects, inhabitants of a tropical region, were heat acclimated by means of nine days of one-hour heat-exercise treatments (40+/-0 degrees C and 32+/-1% relative humidity; 50% (.)VO(2peak) on a cycle ergometer). On days 1 to 9 of heat acclimation whole-body sweat loss was calculated by body weight variation corrected for body surface area. On days 1 and 9 rectal temperature (T(re)) and heart rate (HR) were measured continuously, and rating of perceived exertion (RPE) every 4 minutes. Heat acclimation was confirmed by reduced HR (day 1 rest: 77+/-5 b.min(-1); day 9 rest: 68+/-3 b.min(-1); day 1 final exercise: 161+/-15 b.min(-1); day 9 final exercise: 145+/-11 b.min(-1), p<0.05), RPE (13 vs. 11, p<0.05) and T(re) (day 1 rest: 37.2+/-0.2 degrees C; day 9 rest: 37.0+/-0.2 degrees C; day 1 final exercise: 38.2+/-0.2 degrees C; day 9 final exercise: 37.9+/-0.1 degrees C, p<0.05). The main finding was that whole-body sweat loss increased in days 5 and 7 (9.49+/-1.84 and 9.56+/-1.86 g.m(-2).min(-1), respectively) compared to day 1 (8.31+/-1.31 g.m(-2).min(-1), p<0.05) and was not different in day 9 (8.48+/-1.02 g.m(-2).min(-1)) compared to day 1 (p>0.05) of the protocol. These findings are consistent with the heat acclimation induced adaptations and suggest a biphasic sweat response (an increase in the sweat rate in the middle of the protocol followed by return to initial values by the end of it) during short-term heat acclimation in tropical natives.
authors.affiliation: Laboratório de Fisiologia do Exercicio, Escola de Educação Física Fisioterapia e Terapia Ocupacional, Universidade Federal de Minas Gerais, Brazil.
authors.forename: Flávio de Castro
authors.initials: Fde C
authors.lastname: Magalhães
authors.forename: Christiano Antônio
authors.initials: CA
authors.lastname: Machado-Moreira
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Vimieiro-Gomes
authors.forename: Emerson
authors.initials: E
authors.lastname: Silami-Garcia
authors.forename: Nilo Resende Viana
authors.initials: NR
authors.lastname: Lima
authors.forename: Luiz Oswaldo Carneiro
authors.initials: LO
authors.lastname: Rodrigues
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000328:Adult; D001831:Body Temperature / Q000502:physiology; D001938:Brazil; D015444:Exercise / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D044382:Population Groups; D013546:Sweating / Q000502:physiology*; D014329:Tropical Climate