1. Sweat sodium concentration during exercise in the heat in aerobically trained and untrained humans.
- Author
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Hamouti, Nassim, Del Coso, Juan, Ortega, Juan, Mora-Rodriguez, Ricardo, and Ortega, Juan F
- Subjects
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PERSPIRATION , *EXERCISE intensity , *SERUM , *SODIUM in the body , *EXERCISE , *CROSS-sectional method , *SODIUM metabolism , *BIOCHEMISTRY , *BODY temperature , *BODY temperature regulation , *COMPARATIVE studies , *HEAT , *HUMIDITY , *PHENOMENOLOGY , *RESEARCH methodology , *MEDICAL cooperation , *PHYSICAL education , *PHYSICAL fitness , *RESEARCH , *STATISTICAL sampling , *SODIUM , *WATER-electrolyte balance (Physiology) , *EVALUATION research , *RANDOMIZED controlled trials , *OSMOLAR concentration , *METABOLISM , *PHYSIOLOGY - Abstract
The purpose of this study was to determine whether sweat sodium concentration ([Na(+)](sweat)) during exercise in the heat differs between aerobically trained and untrained individuals. On three occasions, ten endurance-trained (Tr) and ten untrained (UTr) subjects (VO2peak = 4.0 ± 0.8 vs. 3.4 ± 0.7 L min(-1), respectively; P < 0.05) cycled in a hot-ventilated environment (36 ± 1°C; 25 ± 2% humidity, airflow 2.5 m s(-1)) at three workloads (i.e., 40, 60, and 80% VO2peak). Whole-body (SR(WB)) and back sweat rates (SR(BACK)) were measured. At the conclusion of the study, Na(+) in sweat and blood samples was analyzed to calculate Na(+) secretion and reabsorption rates. SR(WB) and SR(BACK) were highly correlated in Tr and UTr (r = 0.74 and 0.79, respectively; P < 0.0001). In both groups, SR(BACK) increased with the increases in exercise intensity (P < 0.05). Likewise, [Na(+)](sweat) increased with the exercise intensity in both groups (P < 0.05) and it tended to be higher in Tr than in UTr at 60 and 80% VO2peak (~22 mmol L(-1) higher; P = 0.06). However, when normalized for SR(BACK), [Na(+)](sweat) was not different between groups. In both groups, Na(+) secretion and reabsorption rates increased with the increases in SR(BACK) (P < 0.05). However, Na(+) reabsorption rate was lower in the Tr than in the UTr (mean slope = 48 vs. 82 ηmol cm(-2) min(-1); P = 0.03). In conclusion, using a cross-sectional study design, our data suggest that aerobic fitness level does not reduce sweat Na(+) secretion or enhance Na(+) reabsorption during prolonged exercise in the heat that induced high sweat rates. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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