Intravenous versus oral rehydration: effects on subsequent
exercise-heat stress.
Castellani, John W., Carl M. Maresh, Lawrence E. Armstrong, Robert W.
Kenefick, Deborah Riebe, Marcos Echegaray, Douglas Casa, V. Daniel
Castracane.
Department of Sport, Leisure, and Exercise Science, and Department
of Physiology and Neurobiology, University of Connecticut, Storrs, CT
06269-1110 and Panhandle Reproductive Research Laboratory, Texas Tech
University Health Sciences Center,, Amarillo, TX 79106-1797
APStracts 3:0533A, 1996.
This study compared the influence of intravenous (IV) vs. oral (ORAL)
rehydration following exercise-induced dehydration (EID) during a
subsequent 90 min exercise bout (EX). It was hypothesized that
cardiovascular, thermoregulatory, and hormonal variables would be the
same between IV and ORAL due to similar restoration of plasma volume
(PV) and osmolality (OSMO). Eight non-heat acclimated males received
three experimental treatments, (counterbalanced design), immediately
following EID (33 C) to -4% body weight loss. Treatments were IV
0.45% NaCl (IV, 25 ml x kg-1), no fluid (NF), and oral saline (ORAL,
25 ml x kg-1). After rehydration and rest (2 h total), subjects
walked at 50% VO2max for up to 90 min at 36 C. The following
observations were made: 1) heart rate (HR) was higher (P < 0.05)
in ORAL vs. IV at minutes 45, 60, and 75 of EX, 2) rectal
temperature, sweat rate, % change in PV, and D plasma OSMO were
similar between IV and ORAL, 3) D plasma norepinephrine decreased
less (P < 0.05) in ORAL compared to IV at minute 45, 4) D plasma
adrenocorticotropic hormone (ACTH) and cortisol (CORT) were similar
between IV and ORAL after exercise was initiated, 5) exercise time
was similar between IV (77.4 +/- 5.4 min) and ORAL (84.2 +/- 2.3
min). These data suggest that following exercise-induced dehydration,
IV and ORAL were equally effective as rehydration treatments.
Thermoregulation, D ACTH, and D CORT were not different between IV
and ORAL after exercise began; this is likely due to similar %DPV and
DOSMO.
Received 6 March 1996; accepted in final form 6 November 1996.
APS Manuscript Number A225-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996