Acute Metformin Ingestion Increases Aerobic Energy Contribution During High-Intensity Exercise: A Randomized, Placebo-Controlled Trial

Abstract

This randomized, placebo-controlled trial investigated the effects of acute metformin ingestion on energy system contributions during high-intensity endurance exercise. Ten recreationally active males (VO2max: 38.6 ± 4.5 mL·kg−1·min−1) completed an incremental cycling test to determine VO2max and maximal workload (Wmax). Using a crossover design, participants performed an exhaustive cycling effort at 110% Wmax one hour after ingesting 500 mg of metformin or placebo. Energy system contributions (aerobic, anaerobic alactic, anaerobic lactic) were estimated using GEDAE-LaB software, based on VO2 and blood lactate kinetics. Total energy expenditure did not significantly differ between conditions (metformin: 165.6 ± 26.3 kJ; placebo: 155.7 ± 30.5 kJ; P = 0.09). The aerobic contribution was significantly greater following metformin ingestion (108.4 ± 25.2 vs. 94.0 ± 25.8 kJ; P < 0.01), however, anaerobic energy contributions were not affected (alactic: 33.3 ± 8.7 vs. 36.5 ± 14.3 kJ, P = 0.37; lactic: 24.0 ± 8.8 vs. 25.3 ± 9.4 kJ, P = 0.62). Acute metformin ingestion increases the aerobic energy contribution during high-intensity endurance exercise without impairing anaerobic energy systems.