Effects of ingesting a sports drink during exercise and recovery on subsequent endurance capacity

Abstract

Most rehydration studies prohibit fluid ingestion during the preceding bout of dehydrating exercise. However, an athlete using a widely researched carbohydrate-electrolyte sports drink as a nutritional strategy is likely to consume the fluid both during and after exercise, warranting a study design with administration of test fluids during a preceding exercise bout and recovery. This is further enhanced with the incorporation of wind speed to mimic outdoor conditions. Improved performance, usually extrapolated from improved recovery, was directly quantified in this investigation with an endurance capacity test. Twelve males (mean±s: age 24.3±1.6 years; body fat 14.6±4.0%; V̇O2peak 53.9±8.8 ml · kg-1 · min-1) performed three trials in which they ingested water, placebo or a carbohydrate-electrolyte sports drink during exercise and ensuing recovery to evaluate their efficacy in replacing fluids and carbohydrates, and the effects on subsequent endurance capacity. Double-blind administration of the placebo and sports drink minimized any researcher and participant bias. A total volume equivalent to 150% of sweat loss was ingested during 75 min cycling at 65% peak aerobic capacity (V̇O2peak) in the heat (temperature 32.1±0.3°C; relative humidity 66±1%, wind speed 2.5±0.1 m · s-1) and within 1 h of recovery (temperature=23 °C, relative humidity=60%). An exercise capacity test at 65% V̇O2peak was conducted after a further 4 h of recovery. A paired t-test with Bonferroni correction was used to analyse variation between two trials (P<0.017). Percent fluid retention was higher with the sports drink than the placebo (water 36±10%, placebo 33±9%, sports drink 41±6%; P=0.004). Following rehydration, mean serum sodium concentration was higher with the sports drink (water 136±1 mmol · l-1, placebo 137±1 mmol · l-1, sports drink 138±1 mmol · l-1; P<0.001). Percent change in plasma volume at 5 h of recovery, relative to 0 min of exercise, was greater with the sports drink than with water (water 3±2%, placebo 3± 3%, sports drink 6±3%; P=0.014). Blood glucose concentration was higher with the sports drink at 0 min (water 5.0±0.3 mmol · l-1, placebo 5.0±0.3 mmol · l-1, sports drink 6.2±1.4 mmol · l-1; P<0.017) and 1 h (water 4.8±0.3 mmol · l-1, placebo 4.9±0.3 mmol · l-1, sports drink 7.3±0.7 mmol · l-1; P<0.001) of recovery. Endurance capacity was greater with the sports drink (1.14±0.22 h) than with water (0.85±0.27 h; P<0.001) or placebo (0.92±0.25 h; P=0.013). Ingestion of the sports drink during and after moderate-intensity exercise replaces fluids and energy lost more effectively than water and a placebo, leading to an improvement in subsequent endurance capacity. © 2011 European College of Sport Science.