Fluid Tolerance while Running: Effect of Repeated Trials

This study assessed tolerance to fluid ingestion with repeated sessions of drinking while running. Runners (n = 7; age 22 +/- 2yr; (V)over dotO(2max) = 54.4 +/- 7.1 ml/kg/min) performed six 90-min runs (65% (V) over dotO(2max); separated by 7-11 days). During run 1, Subjects drank a glucose-electrolyte solution ad libitum for 1 min every 10 min. During runs 2-6, subjects drank a volume of the solution every 10 min equal to their sweat production over 10 min during run 1. Stomach comfort (1-4 scale) and gastrointestinal symptoms were also assessed every 10 min. Gastric emptying rate was determined in runs 2 and 6. Subjects consumed more (p < 0.05) fluid during runs 2-6 (mean SD; 1247 +/- 162 ml), than during run 1 (508 +/- 476 ml). Stomach comfort improved (p < 0.05) on runs 5 and 6 (1.7 +/- 0.5 mean ranks) compared to run 2 (2.3 +/- 0.5 mean ranks). Gastric emptying rate was not different between runs 2 and 6 (12.0 +/- 1.9 ml/min vs. 12.3 +/- 2.3 ml/min, respectively). These results indicate repeated sessions of drinking at a rate matching sweat rate improves stomach comfort, however, gastric emptying rate does not change under Such conditions.