Purpose: The purpose of the study was to compare the effects of a brief per
iod (20 min) of intravenous (IV) fluid rehydration and oral (ORAL) rehydrat
ion on ratings of perceived exertion (RPE), thirst, and thermal sensation (
TS) during exercise in the heat. Methods: After dehydration (-4% of body we
ight), eight nonacclimated highly trained cyclists (age = 24 +/- 1 yr; VO2
= 61.4 +/- 0.8 mL.kg.min(-1)) performed three experimental trials. Rehydrat
ion (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 dehydra
tion; and 3) a control (CON), no fluid trial. Subjects then cycled at 74% V
O(2)peak until volitional exhaustion in a hot environment (37 degreesC). Re
sults: 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-R
PE responses at minute 5 of exercise were lower (P < 0.05) during ORAL comp
ared with IV, and C-RPE and O-RPE responses at minute 15 were lower (P < 0.
05) during ORAL compared with IV. TS responses during CON were higher (P <
0.05) than ORAL and IV at minute 5, and TS was higher (P < 0.05) during IV
versus ORAL at minute 15. TS were significantly correlated with all RPE res
ponses at minute 15 in all trials. Thirst ratings were lower (P ( 0.05) dur
ing ORAL compared with CON and IV at minutes 0, 5, and 15. Conclusion: It w
as concluded that ORAL resulted in lower RPE, thirst, and TS compared with
CON and IV during exercise in the heat.