Carbohydrate intake during exercise is often seen as something for endurance athletes. In sports like football (soccer) it is often believed that carbohydrate intake is less important. Is this true? Or can carbohydrates play a role in soccer performance?
Can the endurance research be transferred to soccer?
It is true that most evidence of carbohydrate effects is obtained in endurance sports. The increased running endurance capacity may be relevant in soccer and other team sports, but the fact is that running performance is just one of many aspects that will determine the outcome of a game. Other important aspects are skills like accurate passing, shooting, dribbling, timing, heading etc. What is less known (and less researched) is that skills can also be affected by carbohydrate ingestion. Carbohydrate may do this indirectly by delaying fatigue but perhaps also directly by affecting processes in the brain.
Skills performance studies
Five of the seven studies published have reported improvements in soccer players’ shooting, dribbling, and/or passing performance with ingestion of a 6-7.5% carbohydrate solution at an intake rate of 30-61 g/h. These intakes are far higher than what we typically see in soccer matches.
University of Birmingham study
Dr Kevin Currell who is now Head of Performance Nutrition at the English Institute of Sport performed a study at The University of Birmingham as part of his PhD to investigate the effects of carbohydrate feeding on skill performance. He found a significant improvement in dribbling and kicking accuracy with an intake of 55 g carbohydrate/h ingestion versus placebo. In the same study it was found that jumping to head a ball (which involves only a small cognitive component) was not influenced by carbohydrate feeding.
Significant improvement in dribbling and kicking accuracy with an intake of 55 g carbohydrate/h versus placebo
In general, there is a tendency for players’ skill performance to decline during the latter stages of a game with placebo intake. Carbohydrate ingestion can reduce this decline. For example, in a study using an intermittent running protocol there was a 14% reduction in passing performance from pre- to post-test with placebo ingestion and only a 3% reduction with 52 g carbohydrate/h (2).
At the moment there are few studies that have measured skill performance and measuring skill performance is notoriously difficult. Those measurements can have a large variation and are easily influenced by external variables. Therefore they are more difficult to control. If a measurement has a lot of variation it is usually more difficult to detect the effect of an intervention (in this case carbohydrate feeding). I think that this is one of the main reasons why studies show variable results, with some shoring positive effects and some no effects of carbohydrate feeding. There are no studies to my knowledge that show negative effects.
Carbohydrate intake important strategy in soccer
Therefore this is a strategy that should be explored more in soccer, especially at the highest level where small improvements in 11 players could make a difference. There are at least two good moments to ingest carbohydrate: just before the start of a game and at half-time. A target intake of 90 grams for a full game is a good start (45g carbohydrate before and 45g at half-time) based on what we know from the few studies in the literature and from the work in endurance sports, but the reality is that there aren’t enough studies to give very clear guidance on the optimal amount of carbohydrate.
Small improvements in each of the 11 players could make a big difference to overall team performance
Recently a couple of reviews have been published that discuss the effects of carbohydrate intake (and other nutritional interventions) on skill performance in soccer and other team sports in more detail (3, 4).
Phillips SM, Sproule J, and Turner AP. Carbohydrate ingestion during team games exercise: current knowledge and areas for future investigation. Sports Med 41: 559-585, 2011. FREE FULL PAPER