In the realm of sports nutrition, the role of carbohydrate (CHO) intake is critical, particularly for athletes involved in high-intensity sports such as soccer. A recent randomized controlled trial published in the International Journal of Sport Nutrition and Exercise Metabolism investigates the effects of two days of moderate versus high carbohydrate intake on both physical and cognitive performance among female team sport players during a simulated soccer match protocol.
The study involved 15 female field-based intermittent team sport players who participated in a double-blind, placebo-controlled, crossover design. Participants consumed either a high carbohydrate diet (6 g·kg body mass [BM]-1·day-1) or an isocaloric moderate carbohydrate diet (3 g·kg BM-1·day-1) for two consecutive days. This dietary intervention was followed by a standardized intermittent exercise protocol lasting approximately 35 minutes.
Performance Assessment
The primary performance assessment was conducted using the Loughborough Intermittent Shuttle Test, which consisted of five 15-minute blocks of intermittent running, followed by a shuttle run to exhaustion. Cognitive performance was evaluated before and after the exercise protocol.
Results indicated no significant difference in time to exhaustion between the high and moderate carbohydrate conditions, with times of 295 ± 137 seconds for the high CHO group and 288 ± 133 seconds for the moderate CHO group (p = .852; g = 0.05). However, sprint times were significantly faster in the high CHO condition during the later blocks of the test, specifically Blocks 3, 4, and 5, with p-values of .021, .035, and < .001, respectively.
Additionally, participants reported lower ratings of perceived exertion during the high carbohydrate condition after the first two blocks of the test (p < .001 for Block 1; p = .018 for Block 2). Cognitive performance, as measured by reaction time in the Task Switching test, improved significantly from pre- to post-exercise in the high carbohydrate condition (p = .017; g = 0.67), while no such improvement was observed in the moderate carbohydrate condition (p = .913; g = 0.05).
What this study does not show
While the study suggests potential benefits of higher carbohydrate intake for female soccer players, it does not establish a direct causal relationship between carbohydrate intake and improved performance outcomes.
Evidence scorecard
- Analytic validity: established
- Clinical validity: established
- Clinical utility: partial
This evidence comes from a human randomized controlled trial.