Effect of fluid replacement on endurance performance

The purpose of this study was to examine the effects of fluid replacement on power output (PO), rating of perceived exertion (RPE), heart rate (HR), body weight (BW) and urine osmolarity and electrolyte concentration ([Na⁺], [K⁺], [Cl^-]). Following a 5 min. warm-up at 50 Watts, 10 physically active males (n=4) and females (n=6), (X age 29 ± 7 yr), were asked to generate their highest PO during 60 min. of cycling on a cycle ergometer under three randomized conditions: Ingestion of I) no fluid, II) 1200 mL of distilled water, and III) 1200 mL of Gatorade®. BW and urine volume were measured before and after the ride to determine sweat rate (SR). Repeated measures ANOVAs indicated that there were no significant differences between treatments for PO, RPE, HR, and SR, however, urine [Na⁺] and [Cl^-] were significantly (p <.02) lower after the ride for all three treatments. There was a significant difference for BW post exercise for treatments II and III when compared to the no fluid treatment. These results suggest that during a 1 h ride, fluid intake does not significantly affect performance, but may help maintain BW.