As discussed previously, glycogen—the storage form of carbohydrates—plays a fundamental role in sports performance.1 Glycogen is particularly important during high-intensity exercise (>80% of maximal oxygen uptake), serving as the main energy source, together with phosphocreatine, for actions such as sprints and repeated intense efforts. Moreover, the reduction in glycogen levels after intense exercise has been shown to impair calcium release by the sarcoplasmic reticulum, thereby reducing muscle contractile capacity.2 Maintaining glycogen stores as high as possible is therefore vital in sports dominated by high-intensity actions, including team sports such as football, basketball and handball.
The importance of glycogen in team sports
Although the effects of endurance sports, such as running, cycling and skiing, on glycogen stores—and the benefits of carbohydrate supplementation in these sports—have been studied extensively, much less is known about the effects of team sports on glycogen stores. 15 years ago, a study led by Jens Bangsbo and Peter Krustrup and published in Medicine and Science in Sports and Exercise took quadriceps muscle biopsies from football players in the Danish 4th division before and after a match.3 The researchers found that glycogen levels fell by nearly half (42%) during the match, leaving half of the fibers completely depleted. This decline was also accompanied by a 3% reduction in sprint capacity during the second half compared with the first.3
Similarly, a recent study led by Íñigo San Millán and Julio Calleja analyzed the effect of a football match on muscle glycogen stores in US Major League Soccer players. In this case, glycogen was measured indirectly using ultrasound to estimate levels non-invasively.4 The results showed that, despite the players consuming carbohydrates after the warm-up (40 grams) and during the match (65 grams at half-time), muscle glycogen fell by an average of 20%. Reductions ranged from 6% to 45% between players and were greatest in those with the highest workloads—strikers and midfielders—compared with defenders and the goalkeeper.
Carbohydrate supplementation in team sports
These findings support the importance of carbohydrate supplementation in team sports, especially for players with the highest workloads. A review led by Dr Asker Jeukendrup recommends carbohydrate intake before and during a match (30-60 grams per hour, for example in 0,5 or 1 liter of drink per hour containing 6% carbohydrate), concluding that it appears to improve intermittent high-intensity performance.5 The benefits may extend beyond physical performance. A study in professional football players showed that carbohydrate intake during a simulated match attenuated the decline in shooting speed and accuracy that normally occurs as a match progresses.6
Conclusions
Although the important role of match-day nutrition is often overlooked, carbohydrates can make a major difference to team-sport performance. Glycogen stores become depleted during a match—especially in players with the highest workloads, such as midfielders and strikers—and this is associated with physical fatigue and poorer technical skills, including ball striking. Carbohydrate intake (30-60 grams per hour) before and during a match is therefore recommended, followed by carbohydrate intake after the match to support recovery.
