Carbohydrate ingestion during exercise: An aid to endurance performance

The effects of carbohydrate ingestion on prolonged exercise performance have been extensively studied. Particularly, many studies have paid specific attention to the effect of carbohydrate ingestion on time to fatigue, the effect on the respiratory exchange ratio (RER), the effect that the time at which the carbohydrate is ingested may have on performance, and the optimal amount of carbohydrate to be ingested. In addition, the effect of different types of carbohydrate and the influence of exercise intensity has been studied, including the influence on hepatic glycogenolysis and on ratings of perceived exertion (RPE). The most important findings have been that there is a beneficial effect from ingestion of carbohydrate during prolonged exercise due to prevention of hypoglycaemia, the provision of blood glucose for oxidation late in exercise, and that there is a hepatic glycogen sparing effect as a result ingesting carbohydrate. Importantly, the majority of carbohydrate types are oxidised at similar rates when ingested singularly. However, a mixture of specific carbohydrates ingested together are oxidised at a much higher rate. Despite the volume of research in this area, some questions remain unclear, specifically information pertaining to feedforward control mechanisms in the brain that integrate exercise performance on the basis of feedback from different body organs, and the role that carbohydrate ingestion may have on this control, including the effect of body carbohydrate reserves.