Post-exercise rehydration: Comparing the efficacy of three commercial oral rehydration solutions
Donald L. Peden, Mark P. Funnell, Kirsty M. Reynolds, Robert W. Kenefick, Samuel N. Cheuvront, Stephen A. Mears, Lewis J. James
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, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="IM1"><mml:mrow><mml:mover><mml:mi mathvariant="normal">V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math> O 2 peak ∼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 to 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.