Perceptual responses in the heat after brief intravenous versus oral rehydration

Abstract

MARESH, C. M., J. A. HERRERA-SOTO, L. E. ARMSTRONG, D. J. CASA, S. A. KAVOURAS, F. T. HACKER, JR., T. A. ELLIOTT, J. STOPPANI and T. P. SCHEETT. Perceptual responses in the heat after brief intravenous versus oral rehydration. Med. Sci. Sports Exerc., Vol. 33, No. 6, 2001, pp. 1039–1045. The purpose of the study was to compare the effects of a brief period (20 min) of intravenous (IV) fluid rehydration and oral (ORAL) rehydration on ratings of perceived exertion (RPE), thirst, and thermal sensation (TS) during exercise in the heat. After dehydration (−4% of body weight), eight nonacclimated highly trained cyclists (age = 24 ± 1 yr; V̇O2 = 61.4 ± 0.8 mL·kg·min-1) performed three experimental trials. Rehydration (randomized, cross-over design) included: 1) ORAL (0.45% NaCl) equal to 50% of prior dehydration; 2) IV (0.45% NaCl) equal to 50% of prior dehydration; and 3) a control (CON), no fluid trial. Subjects then cycled at 74% V̇O2peak until volitional exhaustion in a hot environment (37°C). Central (C-), local (L-), and overall-RPE (O-RPE) were significantly higher in CON compared to ORAL and IV at minutes 5 and 15 of exercise. C-RPE responses at minute 5 of exercise were lower (P P It was concluded that ORAL resulted in lower RPE, thirst, and TS compared with CON and IV during exercise in the heat.