Effects Of Acute Sodium Ingestion On Water Consumption And Retention, Dehydration, And Exercise Performance In The Heat

PURPOSE: To determine the effects of sodium ingestion on pre-exercise fluid consumption and retention, rates of dehydration, and subsequent exercise performance in the heat. METHODS: Nine male subjects underwent three experimental procedures consuming either 60 mg/kg bm NaCl, (NA), placebo (PL), or no treatment (NT) followed by a 2-hr hydration period in which they consumed water ad-libitum (HP). Subjects began a 1-hr exercise session, followed by a 200 kJ time trial (TT) on a cycle ergometer. Elapsed time to complete TT was used as a performance measure. Blood samples were analyzed for plasma volume (PV). Heart Rate (HR) was obtained at minutes 5 and 50 of the 1-hr ride. RESULTS: Subjects consumed more water during HP in NA compared to PL and NT. Fluid retained at the end of HP was greater in NA compared to PL and NT. NA induced a significantly greater rate of HPE than did PL and NT. Dehydration rate following 1-hr ride was lower in NA compared to PL and NT. The TT was completed faster in NA compared to PL and NT. CONCLUSION: The results suggest acute sodium ingestion enhances voluntary fluid consumption leading to hyperhydration and improved exercise performance in the heat.