The goal of carb loading is to maximize the glycogen stored in the muscles prior to competition. It is most usually performed by endurance athletes who perform in exercise for more than 90min. However, it is something that more athletes are looking at.
Carb loading started in 1967 in Sweden when researchers found that four days of exhaustive exercise and an extremely low carb diet followed by three days of little exercise and a high carb diet resulted in substantial increases in the muscle glycogen stores of the body. However, there were some problems. The first stage was very difficult to complete with the exercise and low carb intake while the second stage resulted in stomach upset and increased muscular water storage, making athletes feel ‘heavy’.
Further research has modified the process to be less extreme. The first stage, depletion stage, is recommended to follow a diet of 5g of carbs/kg body weight daily, or about 50% of total energy intake. Exercise during this stage consists of one day of 90min of hard training, followed by 2 days of 40min of hard training. The second stage, repletion stage, consists of a high carb diet with consumption of 10gm of carbs/kg of body weight daily for 3 days before competition. There should only be 20min of exercise each of the first two days and then a rest day on the third day.
It is important to ensure adequate water intake during the entire process.
Like all diet recommendations, carb loading is something to individualize with both the levels of carbs and types of food consumed, and the levels and types of exercise throughout the process.
Carb loading is not needed during the regular weeks of a season, and should not be done continuously. It is something to do with an important competition, tournament, or event, and these should be longer events or multiple events in a day or weekend.