Glucose and Fructose Hydrogel Enhances Running Performance, Exogenous Carbohydrate Oxidation and Gastrointestinal Tolerance

PURPOSE: Beneficial effects of carbohydrate (CHO) ingestion on exogenous CHO oxidation and endurance performance require a well-functioning gastrointestinal (GI) tract. However, GI complaints are common during endurance running. This study investigated the effect of a CHO solution-containing sodium alginate and pectin (hydrogel) on endurance running performance, exogenous and endogenous CHO oxidation and GI symptoms. METHODS: Eleven trained male runners, using a randomised, double-blind design, completed three 120-minute steady state runs at 68% V̇O2max, followed by a 5-km time-trial. Participants ingested 90 g·h-1 of 2:1 glucose:fructose (13C enriched) either as a CHO hydrogel, a standard CHO solution (non-hydrogel), or a CHO-free placebo during the 120 minutes. Fat oxidation, total and exogenous CHO oxidation, plasma glucose oxidation and endogenous glucose oxidation from liver and muscle glycogen were calculated using indirect calorimetry and isotope ratio mass spectrometry. GI symptoms were recorded throughout the trial. RESULTS: Time-trial performance was 7.6% and 5.6% faster after hydrogel ([minutes:seconds]19:29±2:24; p<0.001) and non-hydrogel (19:54±2:23, p=0.002), respectively, versus placebo (21:05±2:34). Time-trial performance after hydrogel was 2.1% faster (p=0.033) than non-hydrogel. Absolute and relative exogenous CHO oxidation was greater with hydrogel (68.6±10.8g, 31.9±2.7%; p=0.01) versus non-hydrogel (63.4±8.1g, 29.3±2.0%; p=0.003). Absolute and relative endogenous CHO oxidation were lower in both CHO conditions compared with placebo (p<0.001), with no difference between CHO conditions. Absolute and relative liver glucose and muscle glycogen oxidation were not different between CHO conditions. Total GI symptoms were not different between hydrogel and placebo, but GI symptoms was higher in non-hydrogel compared with placebo and hydrogel (p<0.001). CONCLUSION: Ingestion of glucose and fructose in hydrogel form during running benefited endurance performance, exogenous CHO oxidation and GI symptoms, compared with a standard CHO solution.