Post-Exercise Fructose-Maltodextrin Ingestion Enhances Subsequent Endurance Capacity

PURPOSE: Restoring muscle and liver glycogen content during short-term (<6 h) recovery from prolonged exercise is pertinent for athletes seeking to maximize performance in repeated exercise bouts. Previous research suggests co-ingestion of fructose-glucose carbohydrate sources augments liver and has equivalent effects on muscle glycogen storage during short-term recovery from prolonged exercise compared to isoenergetic glucose ingestion. The aim of the present investigation was to determine if this has a discernible effect on subsequent exercise capacity. METHODS: Eight trained endurance runners and triathletes performed two experimental trials in a single-blind, randomised, and counterbalanced cross-over design. Trials involved treadmill running to exhaustion at 70 %V[Combining Dot Above]O2max, a four-hour recovery with 90 g.h-1 of glucose-maltodextrin (GLU) or fructose-maltodextrin (FRU) ingestion (1:1.5 ratio), and a second bout of treadmill running to exhaustion at 70 %V[Combining Dot Above]O2max. Indirect calorimetry and stable isotope methods were employed to estimate substrate oxidation and ingested carbohydrate oxidation. RESULTS: Endurance capacity in the second exercise bout was significantly greater with FRU (81.4 ± 22.3 vs. 61.4 ± 9.6 min, P = 0.02), a large magnitude effect (ES = 1.84 ± 1.12, 32.4 ± 19.9 %). Total carbohydrate oxidation rates were not significantly different between-trials at given time-points, although the total amount of carbohydrate oxidised in the second exercise bout was significantly greater with FRU (223 ± 66 vs. 157 ± 26 g, P = 0.02). Ingested carbohydrate oxidation rates, representing carbohydrate stored during recovery and/or that derived from ongoing absorption, were greater during bout two with FRU (P = 0.001). Plasma glucose and non-esterified fatty acid concentrations were not significantly different between-trials. Plasma lactate concentrations were significantly greater during recovery with FRU (P = 0.001). Self-reported nausea and stomach fullness during bout two were marginally in favour of FRU. CONCLUSION: Short-term recovery of endurance capacity was significantly enhanced with fructose-maltodextrin vs. glucose-maltodextrin ingestion during recovery.