PRACTICAL SIGNIFICANCE
This study demonstrated that combining oral and intravenous rehydration facilitates recovery from exercise dehydration compared to single modes of rehydration. When intravenous fluid is necessary, the addition of simultaneous oral rehydration accentuates recovery.

STUDY BACKGROUND
Dehydration as a result of exercise participation is common in athletics. Previous investigations have compared intravenous (IV) and oral fluid replacement during a brief period. Surprisingly, minimal significant differences are identified between rehydration methods. None of these studies included a trial where subjects consumed fluids ad libitum (AL), or a combination of IV and oral (IV+OR) fluid rehydration.  Furthermore, no previous studies focused on recovery following exercise dehydration (EXDE).

OBJECTIVE
To determine differences in thermoregulatory and stress recovery from exercise dehydration comparing no fluid (NF), AL, OR, IV, and IV+OR rehydration modes.

DESIGN AND SETTING
A repeated measures design was used to compare five treatment groups (rehydration mode) across time intervals (pre, 5 min, 15 min, 30 min, 45 min, 60 min).  This study took place in the Human Performance Laboratory at the University of Connecticut.

SUBJECTS
Twelve physically active subjects (23 ± 4 yrs, 81.3 ± 3.7 kg, 180 ± 6 cm, 56.9 ± 4.4 mL·min-1·kg-1 VO2max, 7.9 ± 3 % body fat) voluntarily participated in five randomly ordered experiments.

MEASUREMENTS
Body mass, rectal temperature, 4-site mean weighted skin temperature, sweat rate, plasma cortisol concentration [CORT], thermal sensation and Environmental Symptoms Questionnaire (ESQ) score.

RESULTS
Subjects were hypohydrated (-4.23% body mass) post-EXDE and were REHY to -2.13 ± 0.47% for all but NF and AL trials.  Subjects partially REHY during AL, returning to only -2.13 ± 1.3% body mass. NF rectal temperature was significantly greater than IV (p=.023) at REHY30, and significantly greater than OR, IV, and IV+OR (p>.009), but not AL (p=.068) at REHY60.  Mean weighted skin temperature during AL was significantly less than IV+OR at REHY5 (p = .019).  Sweat rate throughout REHY and seated recovery did not differ between REHY mode and averaged 0.96 ± 0.18 L.hr-1 (p=.699).  AL demonstrated increased plasma [CORT] compared to IV+OR, independent of time (p=.015).  Thermal sensation showed a significant decrease over time (p<.05), without a significant between trial difference (p=.324).  NF ESQ score was significantly greater than IV+OR at REHY60 (p=.012), but no other significant differences existed.

CONCLUSIONS
IV and combined IV+OR REHY offered some short-term thermoregulatory advantages over NF and AL REHY, beyond those of OR REHY.  These benefits were equivocal after 30-min of recovery. IV+OR attenuated environmental symptoms more effectively than other REHY modes. Combining IV+OR REHY stimulates multiple mechanisms of thermoregulatory and stress recovery following EXDE.

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