ELECTROLYTES ARE THE PRIMARY DRIVER FOR FLUID RETENTION
Osterberg, K. L., Horswill, C. A., Pallardy, S. E., & Murray, R. (2008). Carbohydrate exerts a mild influence but electrolytes are the primary driver of fluid retention following exercise-induced dehydration. ACSM 55th Annual Meeting Indianapolis, Presentation Number 888.
This study determined the effect of graded levels of carbohydrate on fluid retention. Heat-acclimatized men (N = 15) exercised in the heat for 90 minutes with no fluid to induce 2-3% dehydration. After a 30-minute rest, Ss ingested one of five test beverages equal to 100% of body weight loss. The volume was administered every 10 minutes for 60 minutes in aliquots equal to 25, 25, 12.5, 12.5, 12.5, and 12.5% of body weight loss. The experimental beverages consisted of an artificially flavored placebo with no electrolytes, a similar placebo with electrolytes, 3%, 6%, and 12% carbohydrate solutions with electrolytes. All beverages contained the same type and concentration of electrolytes. After rehydrating, Ss voided their bladders at 60, 90, 120, 180, and 240 minutes post-exercise and urine specific gravity and urine volume were measured. A final body weight was taken at 240 minutes to calculate percent fluid retained.
Dehydration as percent of body weight loss, sweat loss, and total fluid intake did not differ between trials. Urine specific gravity was significantly higher for 6 and 12% carbohydrate at all time points following rehydration compared to placebo and placebo + electrolyte. Cumulative urine loss was significantly greater for placebo compared to all carbohydrate beverages. Fluid retention was significantly better for all carbohydrate beverages compared to placebo. Placebo + electrolytes did not differ to water, 3% electrolytes, or 6% electrolytes but was significantly less than 12% electrolytes.
Implication. Carbohydrate exerted a mild influence on rehydration. Electrolytes in 3, 6, and 12% concentrations were the primary driver for fluid retention and the completeness of rehydration.
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