Glucose and Fructose Hydrogel Enhances Running Performance, Exogenous Carbohydrate Oxidation, and Gastrointestinal Tolerance.
Level 2 - randomized trial
Randomized double-blind crossover trial
PubMed 34334720 · doi:10.1249/MSS.0000000000002764
What was done
Eleven trained male runners completed three experimental sessions consisting of a 120-minute steady-state run at 68% VO2max followed by a 5-km time trial in a randomized, double-blind crossover design. During the 120-minute run, participants ingested 90 g/h of 13C-enriched 2:1 glucose-fructose formulated as a sodium alginate and pectin hydrogel, a standard nonhydrogel carbohydrate solution, or a carbohydrate-free placebo. Fat, total, and exogenous carbohydrate oxidation, plasma glucose oxidation, and endogenous glucose oxidation from liver and muscle glycogen were measured via indirect calorimetry and isotope ratio mass spectrometry, alongside gastrointestinal (GI) symptoms.
What was found
Time-trial performance was 7.6% faster after hydrogel (19:29 ± 2:24 min:s, P < 0.001) and 5.6% faster after nonhydrogel (19:54 ± 2:23 min:s, P = 0.002) compared to placebo (21:05 ± 2:34 min:s). The hydrogel condition was 2.1% faster than nonhydrogel (P = 0.033). Absolute and relative exogenous carbohydrate oxidation was higher with hydrogel (68.6 ± 10.8 g, 31.9% ± 2.7%) than nonhydrogel (63.4 ± 8.1 g, 29.3% ± 2.0%; P = 0.01 and P = 0.003, respectively). Absolute and relative endogenous carbohydrate oxidation decreased similarly in both carbohydrate trials compared to placebo (P < 0.001), with no difference between carbohydrate conditions in liver glucose or muscle glycogen oxidation. Total GI symptoms were higher in the nonhydrogel condition than in placebo and hydrogel (P < 0.001), but did not differ between hydrogel and placebo.
Why it matters
This study shows that encapsulating high-dose glucose and fructose within an alginate-pectin hydrogel can enhance exogenous carbohydrate oxidation and subsequent running performance while attenuating GI distress.
Limits
The sample size was small (n = 11) and restricted entirely to trained male runners, limiting generalizability to female runners or broader fitness levels. The protocol tested a single carbohydrate dose (90 g/h) under controlled laboratory treadmill conditions, which may not capture variable pacing, race-day conditions, or different nutritional regimens.
Cited by
- contradicts Consuming 120 grams of carbohydrates per hour during prolonged strenuous exercise suppresses fat metabolism to approximately 10% of total energy expenditure and shifts over 85% of fuel utilization to glucose, primarily from muscle glycogen.