Carbohydrates and Sports Performance

Carbohydrates and Sports: Energy Metabolism

Carbohydrates play a crucial role in providing the energy needed for high-intensity sports performance. They are the primary energy source for the brain and nervous system, and they are quickly broken down and used during high-intensity exercise when fast-twitch muscle fibers are primarily relied upon.

High-Intensity Exercise and Carbohydrates

During high-intensity sports lasting approximately 1 hour, small amounts of carbohydrate, including mouth-rinsing, can enhance performance through central nervous system effects. The optimal amount of carbohydrate intake for sports is 30-60 g per hour. For endurance events lasting more than 2.5 hours, athletes may require up to 90 g of carbohydrate per hour.

Glycogen and Muscle Energy

Carbohydrates are stored in the body as glycogen, which is a complex carbohydrate found in the liver and muscles. Glycogen stores in the human body are limited, providing at best a 24-hour supply of glycogen. At rest or during light exercise, fat is the primary energy source. However, as exercise intensity increases, the body needs a more immediate source of energy. At moderate to high intensity exercise, carbohydrate is used almost exclusively.

Pre-Exercise Meals and Carbohydrates

The choice of carbohydrate in pre-competition meals can have an effect on performance. High glycemic index carbohydrates, which produce a large increase in blood glucose concentration, are classified as having a high glycemic index. On the other hand, low glycemic index carbohydrates have a slower effect on blood glucose levels. One study found that low glycemic index carbohydrates appeared to improve endurance capacity to a greater extent than high glycemic index carbohydrates.

Recovery and Carbohydrate Replacement

Recovery from exercise is not a passive process. Tissues undergo repair and reproduction, fluid balance is restored, and substrate stores are replaced. Carbohydrate replacement is one of the most important events during recovery. During periods of daily training or competition, a normal mixed diet containing approximately 4 to 5 g/kg body weight of carbohydrate is sufficient to replace muscle glycogen.

Low-Carbohydrate Diets and Performance

Low-carbohydrate diets have been shown to impair sport performance and can impact an athlete's ability to train effectively. One panelist cited a recent study of world-class race walkers who consumed a low-carbohydrate, high-fat diet for three weeks and experienced a loss of exercise economy, resulting in a decrement in performance gains.

In summary, carbohydrates are essential for high-intensity sports performance. They are the primary energy source for the brain and nervous system and are quickly broken down and used during high-intensity exercise. The optimal amount of carbohydrate intake depends on the duration and intensity of the sport, and the choice of carbohydrate in pre-competition meals can have an effect on performance. Recovery from exercise is also important, and carbohydrate replacement is crucial during recovery. Low-carbohydrate diets have been shown to impair sport performance, and athletes should aim to maintain adequate carbohydrate availability for optimal performance.