Carbohydrate intake can lead to an improvement of performance during endurance exercise. A comprehensive summary of leading nutritionists shows that carbohydrate intake is more important when the effort takes longer.
CARBOHYDRATES AND ENDURANCE SPORTS
Carbohydrates during prolonged exercise are an important fuel for the body. Stellingwerff and Cox examined the impact of the carbohydrate intake on performances of different duration. They looked at the effect of carbohydrates in an effort of less than 1 hour, 1-2 hours, and more than 2 hours. The following is a summary of the most important results and advices about the use of carbohydrates.
EFFORT LESS THAN 1 HOUR
In an effort of less than one hour there is no depletion of glycogen stores in an athlete with a normal diet. Despite the fact that there have been studies in which no effect was found, there are also studies (70% of the analyzed studies) showing that the flushing of (and again spitting out) of carbohydrate-rich beverage may even lead to a performance improvement of about 2.5%.
It is unclear why rinsing with a carbohydrate-rich drink usually leads to performance improvement. Although this method does not guarantee success, it might be good to try. A commonly used method is 5 to 10 seconds, rinsing with 1.5 g of glucose dissolved in 25 mL of water and this to be repeated during the exercise every 8 to 10 minutes.
EFFORT BETWEEN 1 AND 2 HOURS
During an intensive endurance effort of 1 to 2 hours the body makes a serious appeal to the glycogen stores. Depletion of these stocks leads to a negative effect on performance. Out of the large majority of the analyzed studies (83%) shows that the intake of carbohydrates clearly leads to an improvement in performance compared to the taking of a placebo. The intake of 30-60 grams of carbohydrates per hour the performance increases on average by nearly 5%.
EFFORT MORE THAN 2 HOURS
When an intensive effort lasts longer than 2 hours, it is essential to incorporate carbohydrates otherwise glycogen content will become depleted. In 16 of the 17 of the analyzed studies (94%) a positive effect was found of an average of more than 6% of endurance performance when an athlete takes carbohydrates during exercise. In the studies in which a positive effect was found the ingestion varied considerably of 40 to 110 g per hour. It is good to know that the body is not able to absorb much more than about 60 g per hour of one type of carbohydrate. The combination of different types of carbohydrates, such as glucose and fructose can increase the absorption by the body.
The longer the effort takes the more important becomes the role of carbohydrates. This is perhaps not very surprising since the glycogen stores in the body are not inexhaustible. The normal glycogen stores in the body are sufficient to allow for an effort of about 1 hour. Carbohydrates are both to be taken in the form of a beverage, gels or solid food, and the liquid is preferred because the body can absorb this faster. It is important to practice the food / drink during training before an athlete is going to apply it in a race. Because taking too many carbohydrates can lead to stomach / intestinal problems.