It has been well established that carbohydrate (CHO) ingestion during prolonged, moderate- to high-intensity endurance-type exercise can delay the onset of fatigue and enhance exercise performance. Interestingly, several studies have reported that CHO ingestion can also improve performance during more intense exercise of short duration—less than 45-60 min. However, there is no apparent metabolic explanation for this improvement, because endogenous CHO stores should not limit exercise performance during short duration exercise tasks. To examine exogenous and endogenous glucose kinetics during high-intensity cycling exercise, Carter and colleagues tested 6 endurance athletes for 1 h at 75% Wmax while infusing either 20% glucose or 0.9% saline. Despite greater plasma glucose availability in the glucose-infusion trial, total CHO oxidation rates did not differ between treatments. Moreover, no performance benefits were observed after intravenous glucose administration. Consequently, the authors suggested that CHO ingestion during high-intensity exercise of short duration might exert its ergogenic effect by acting through the central nervous system, possibly mediated by glucose receptors in the mouth or gastrointestinal tract.