HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 102/5/1899    most recent 00920.2006v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Kenefick, R. W. Articles by Castellani, J. W. Search for Related Content PubMed PubMed Citation Articles by Kenefick, R. W. Articles by Castellani, J. W.

Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat

¹Departments of Kinesiology, University of Connecticut, Storrs, Connecticut; ²Department of Kinesiology, University of Rhode Island, Kingston, Rhode Island; ³Department of Biology, University of Puerto Rico at Cayey, Cayey, Puerto Rico; and ⁴US Army Research Institute of Environmental Medicine, Natick, Massachusetts

Submitted 21 August 2006 ; accepted in final form 15 February 2007

This study examined the effects of rehydration (Rehy) with fluids of varying tonicities and routes of administration after exercise-induced hypohydration on exercise performance, fluid regulatory hormone responses, and cardiovascular and thermoregulatory strain during subsequent exercise in the heat. On four occasions, eight men performed an exercise-dehydration protocol of 185 min (33°C) to establish a 4% reduction in body weight. Following dehydration, 2% of the fluid lost was replaced during the first 45 min of a 100-min rest period by one of three random Rehy treatments (0.9% saline intravenous; 0.45% saline intravenous; 0.45% saline oral) or no Rehy (no fluid) treatment. Subjects then stood for 20 min at 36°C and then walked at 50% maximal oxygen consumption for 90 min. Subsequent to dehydration, plasma Na⁺, osmolality, aldosterone, and arginine vasopressin concentrations were elevated (P < 0.05) in each trial, accompanied by a –4% hemoconcentration. Following Rehy, there were no differences (P > 0.05) in fluid volume restored, post-rehydration (Post-Rehy) body weight, or urine volume. Percent change in plasma volume was 5% above pre-Rehy values, and plasma Na⁺, osmolality, and fluid regulatory hormones were lower compared with no fluid. During exercise, skin and core temperatures, heart rate, and exercise time were not different (P > 0.05) among the Rehy treatments. Plasma osmolality, Na⁺, percent change in plasma volume, and fluid regulatory hormones responded similarly among all Rehy treatments. Neither a fluid of greater tonicity nor the route of administration resulted in a more rapid or greater fluid retention, nor did it enhance heat tolerance or diminish physiological strain during subsequent exercise in the heat.

fluid regulation; hydration state; dehydration; environment; osmotic load