Human Performance Laboratory, Department of Exercise Metabolism, School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham, UK.
This study compared the effects of ingesting water (WATER), an 8.6% glucose solution (GLU) and an 8.6% glucose+fructose solution (2:1 ratio, GLU+FRU) on gastric emptying (GE), fluid delivery, and markers of hydration status during moderate intensity exercise. Eight male subjects (age=24 +/- 2 years, weight=74.5 +/- 1.2 kg, VO(2max)=62.6 +/- 2.5 mL/kg/min) performed three 120 min cycling bouts at 61% VO(2max)). Subjects ingested GLU, GLU+FRU (both delivering 1.5 g/min carbohydrate), or WATER throughout exercise, ingesting 2.1 L. Serial dye dilution measurements of GE were made throughout exercise and subjects ingested 5.00 g of D(2)O and 150 mg of (13)C-acetate at 60 min to obtain measures of fluid uptake and GE, respectively. GLU+FRU resulted in faster rates of deuterium accumulation, an earlier time to peak in the (13)C enrichment of expired air and a faster rate of GE compared with GLU. GLU+FRU also attenuated the rise in heart rate that occurred in GLU and WATER and resulted in lower ratings of perceived exertion. There was a greater loss in body weight with GLU corrected for fluid intake. These data suggest that ingestion of a combined GLU+FRU solution increases GE and "fluid delivery" compared with a glucose only solution.