Electrolyte Supplementation Prior to Prolonged Submaximal Exercise Results in Decreased PCO2 and tCO2 During Exercise and Recovery

Abstract

IntroductionElectrolyte supplementation prior to exercise is known to benefit both performance and recovery; however its effects on acid‐base status remain not well characterized. The purpose of this study was to use the physicochemical approach to provide a comprehensive time‐course of the acid‐base alterations that occur following pre‐exercise electrolyte supplementation in horses. It was hypothesized that electrolyte supplementation will attenuate the alkalosis occurring with prolonged moderate intensity exercise.MethodsIn a randomized crossover experiment four conditioned mares were given, via nasogastric tube, 3 L of a commercial electrolyte solution (ES; designed to fully replace sweat electrolyte and fluid losses), or water alone (Control), 1 hour before they exercised on a treadmill at 30% VO2max until voluntary fatigue (inability to keep pace with belt speed). Blood was sampled from jugular venous catheters at frequent intervals before, during, and until 20 h of exercise recovery, and analyzed for all dependent and independent plasma acid‐base variables. Differences (P<0.05) over time and between groups were assessed by 1‐ or 2‐way repeated measures ANOVA.ResultsHorses exercised for 57.5 ± 10.3 and 72.5 ± 17.0 min and lost 2.73 ± 0.82 and 4.63 ± 1.35 L in Control and ES trials, respectively. ES horses had lower pCO2 and total carbon dioxide (TCO2) concentrations during exercise and early recovery. Control horses exhibited decreased [H+]. pCO2 was the primary contributor to changes in [H+] and [TCO2], while there were no differences in strong ion difference ([SID]) or total weak acid concentration ([Atot]).ConclusionsElectrolyte supplementation prior to prolonged exercise leads to sustained effects on equine acid‐base variables, even in the absence of significant changes in plasma electrolytes or hydration.Ethical Animal ResearchThe experiments and use of animals were approved by the University of Guelph Animal Care Committee, in accordance with the guidelines of the Canadian Council on Animal Care. Sources of funding: Ontario Horse Racing Industry Association and the Natural Sciences and Engineering Research Council of Canada. Competing interests: none.