Carbohydrate Ingestion and Performance

1 KEY POINTS • Carbohydrate feeding during moderate intensity endurance exercise is well known to delay fatigue and improve performance. • The mechanisms responsible are thought to involve maintenance of blood glucose levels and carbohydrate oxidation rates and sparing of liver, and perhaps, muscle glycogen. • The majority of studies investigating high intensity (>75%VO 2 max) endurance exercise (30-60 min) have also reported a performance benefit with exogenous carbohydrate. • Traditional metabolic pathways are unlikely to account for the ergogenic effect because endogenous stores of carbohydrate are not limiting and exogenous carbohydrate oxidation is minimal. • A growing number of studies have now shown that rinsing the mouth with a carbohydrate-containing solution is associated with improved high intensity endurance exercise performance. • The consistent performance benefits of 2-3% occur without any ingestion of carbohydrate but are similar in magnitude to those reported when carbohydrate is ingested. • Brain imaging studies have identified areas of the brain activated when carbohydrate is in the mouth, and it is likely that mouth rinsing carbohydrate results in afferent signals capable of modifying motor output. • The effects appear more profound after an overnight fast, but performance benefits are still present even after ingestion of a meal. • Further research is warranted to fully understand the separate taste transduction pathways for various carbohydrates, the practical implications for athletes as well as the impact on different sporting events.