AUTHOR=Peden Donald L. , Funnell Mark P. , Reynolds Kirsty M. , Kenefick Robert W. , Cheuvront Samuel N. , Mears Stephen A. , James Lewis J. 

TITLE=Post-exercise rehydration: Comparing the efficacy of three commercial oral rehydration solutions

JOURNAL=Frontiers in Sports and Active Living

VOLUME=Volume 5 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/sports-and-active-living/articles/10.3389/fspor.2023.1158167

DOI=10.3389/fspor.2023.1158167

ISSN=2624-9367

ABSTRACT=Introduction: This study compared the efficacy of three commercial oral rehydration solutions (ORS) for restoring fluid and electrolyte balance, after exercise-induced dehydration. 
Method: Healthy, active participants (N=20; ♀=3; age ~27 y, V̇O2peak ~52 ml/kg/min) completed three randomised, counterbalanced trials whereby intermittent exercise in the heat (~36°C, ~50% humidity) induced ~2.5% dehydration. Subsequently, participants rehydrated (125% fluid loss in four equal aliquots at 0, 1, 2, 3 h) with a glucose-based (G-ORS), sugar-free (Z-ORS) or amino acid-based sugar-free (AA-ORS) ORS of varying electrolyte composition]. Urine output was measured hourly and capillary blood samples collected pre-exercise, 0, 2 and 5 h post-exercise. Sodium, potassium, and chloride concentrations in urine, sweat, and blood were determined. 
Results: Net fluid balance peaked at 4 h and was greater in AA-ORS (141 ± 155 mL) and G-ORS (101 ± 195 mL) than Z-ORS (-47 ± 208 mL; P≤0.010). Only AA-ORS achieved positive sodium and chloride balance post-exercise, which were greater for AA-ORS than G-ORS and Z-ORS (P≤0.006), as well as for G-ORS than Z-ORS (P≤0.007) from 1-5 h. 
Conclusion: when provided in a volume equivalent to 125% of exercise-induced fluid loss, AA-ORS produced comparable/superior fluid balance and superior sodium/chloride balance responses to popular glucose-based and sugar-free ORS.