Effect of carbohydrate ingestion on glucose kinetics and muscle metabolism during intense endurance exercise

1 Department of Physiology, Monash University, Clayton, Victoria 3168; and 2 School of Health Sciences, Deakin University, Burwood, Victoria 3125, Australia There has been recent interest in the potential performance and metabolic effects of carbohydrate ingestion during exercise lasting ~1 h. In this study, 13 well-trained men ingested in randomized order either a 6% glucose solution (CHO trial) or a placebo (Con trial) during exercise to exhaustion at 83 ± 1% peak oxygen uptake. In six subjects, vastus lateralis muscle was sampled at rest, at 32 min, and at exhaustion, and in six subjects, glucose kinetics was determined by infusion of [6,6- 2 H]glucose in both trials and ingestion of [6- 3 H]glucose in the CHO trial. Of the 84 g of glucose ingested during exercise in the CHO trial, only 22 g appeared in the peripheral circulation. This resulted in a small (12 g) but significant ( P