Muscle metabolism during prolonged exercise in humans: Influence of carbohydrate availability

Abstract

Eight endurance-trained men cycled to volitional exhaustion at 69 ± 1% peak oxygen uptake on two occasions to examine the effect of carbohydrate supplementation during exercise on muscle energy metabolism. Subjects ingested an 8% carbohydrate solution (CHO trial) or a sweet placebo (Con trial) in a double-blind, randomized order, with vastus lateralis muscle biopsies (n = 7) obtained before and immediately after exercise. No differences in oxygen uptake, heart rate, or respiratory exchange ratio during exercise were observed between the trials. Exercise time to exhaustion was increased by ~30% when carbohydrate was ingested [199 ± 21 vs. 152 ± 9 (SE) min, P < 0.05]. Plasma glucose and insuli..