Glycogen and soccer

Glycogen: the soccer “fuel”

The short explosive actions that characterize a game of soccer rely mainly on the players’ fast muscle fibers. These fibers are capable of producing a large “energy flow” and a rapid increase in muscle tension. The fast muscle fibers take sugars from the blood to generate the necessary energy. When the glycogen reserves in the liver and the muscles are exhausted and the blood sugar level falls, fast muscle fibers are no longer capable of performing work. The player can continue to work for some time by making use of the slow muscle fibers. However, those fibers work less quickly and strongly, because they mainly derive their energy from fat. The intensity and strength of one player’s exertions therefore decrease. The player simply becomes fatiqued. Although other factors can play a role(decreased motivation if a team is losing, or change of tactics for the purpose of defending a lead), exhausted glycogen reserves are viewed as the most important cause of fatique in soccer players. The “soccer fuel tank” is empty. Player with larger glycogen reserves can sprint more.

The influence of glycogen on soccer performance

The influence of glycogen on the work capacity of soccer players was studied in Sweden as long ago as 1973. Five soccer players(one defender, two midfielders and two attackers) started a game with maximum glycogen reserves. Four other players(one defender, two midfielders and one attacker) only had half of their maximum reserve(they had carried out tiring exercises the day before game). A film analysis of the game was made, with the aim of determining how much work each player carried out during the game. All of the players did less work in the second half. The decrease was lower for the players who started with maximum glycogen reserves. They covered a total of 19% more ground. A bigger difference was found in the intensity. The players with less glycogen covered 50% of the distance at walking pace and 15% at a sprint. The figures for the other group were 24% and 25% respectively. The conclusion was that more glycogen enabled the players to carry out more(sprint) work. Sprinting is a key performance factor in contemporary soccer. Such experiments were carried out another ten times, and each time the result was the same. Soccer players become fatiqued because they have exhausted their glycogen reserves. At lower levels of play, less discomfort is experienced when the glycogen reserves are spent. The logical explanation is that less sprint work is carried out at lower levels. On the other hand, the players have smaller glycogen reserves and therefore exhaust them more quickly. Selective nutrition only becomes important at the level of the second class Dutch Soccer Association leagues. In the lower classes it is important that the players should not eat too much fat. The intake of specific carbohydrate preparations is then less critical.

“Conditioning for soccer”  Raymond Verheijen