Topic 1. Carbohydrate, sports drinks and performance: strategies for Olympic sports

Résumé 0

For Olympic endurance events lasting 30 minutes or longer carbohydrate intake during exercise is an important determinant of performance. Although this is true for most sports, this review will focus mostly on endurance activities and less on stop-and-go sports. An individualized nutritional strategy can be developed that aims to deliver carbohydrate to the working muscle at a rate that is dependent on the absolute exercise intensity as well as the duration of the event. Although it has been known since the 1980s that carbohydrate ingestion during exercise can improve endurance exercise performance, it is only in the past ten years that we are getting a better understanding of the optimal amounts and types of carbohydrates to ingest. Studies in the 1980s and 1990s demonstrated that carbohydrate ingested during exercise was oxidized at rates up to 60 g/h. Carbohydrates could be separated into two categories: slowly oxidized carbohydrates such as fructose, galactose and insoluble starch and rapidly oxidized carbohydrates such as glucose, sucrose, maltose and maltodextrins. However, even with very high-carbohydrate intake, exogenous carbohydrate oxidation did not exceed 250 kcal/h whilst energy expenditure during activities could easily amount up to 1000 kcal/h. It became obvious that intestinal absorption was the main limitation to providing exogenous carbohydrate to the working muscle. This can at least partly be overcome by making use of multiple transportable carbohydrates. Ingestion of these carbohydrates may result in higher intestinal absorption rates and has been shown to lead to higher rates of exogenous carbohydrate oxidation (up to 105 g/h), which can also result in better endurance performance. In the past few years, studies have emerged to demonstrate a dose–response relationship between exogenous carbohydrate oxidation rates and performance suggesting that higher intake rates result in superior performance. This is reflected in practical recommendation: carbohydrate intakes of 90 g/h for events longer than 2.5 h as a balance between practicalities and ergogenic effects. It also seems possible to increase the absorptive capacity of the intestine by adapting to a high-carbohydrate diet. Although there are still many unanswered questions, it is clear that there are ample opportunities to develop strategies that enhance the delivery of carbohydrates and thereby improve endurance performance. These strategies should also include aiming to maintain hydration status (avoid >2% loss in body mass) to contribute to the prevention of fatigue, especially when exercising in warm-hot environments.