Frequent Carbohydrate Intake Delays Fatigue in Runners

Delaying the onset of fatigue in continuous sports, especially endurance sports, is one of the objectives sought by both coaches and nutritionists. In this way, it is known that a low intake of dietary carbohydrates can have a negative effect on sports performance.

For this reason, the importance of carbohydrate intake during prolonged exercise is increasingly recognized among athletes. However, how important can the timing of these intakes be during exercise?

That is why a study by Menzies et al. (2020) investigated the effect of frequent or single carbohydrate intake during physical exercise. This study had a cross-over design, in which a total of 6 highly trained runners were subjected to 2 experimental conditions on a randomized basis: i) single carbohydrate intake, in which they ingested 75g of sucrose after 75 minutes of running; and ii) frequent carbohydrate intake, in which they ingested 15 intakes of 5g of sucrose every 5 minutes of running (75g total). In both experimental conditions, the participants carried out a prolonged run until exhaustion.

In this study, it was observed that the frequent and continuous intake of carbohydrates throughout the race had various benefits in terms of performance such as the increase in the time to exhaustion, the decrease in the subjective perception of effort and a reduced muscle glycogen use during the race.  In addition, no differences were observed in terms of the oxidation of energy substrates during physical exercise (carbohydrates and fats), or in the circulating levels of glucose, lactate or free fatty acids.

Conclusions: Frequent carbohydrate intake maintains glycogen stores and delays fatigue in runners.

Practical implications: in long-term training or competition sessions, carbohydrate intake recommendations should be focused on spreading the recommended amounts continuously throughout the event. In addition, it will be important to avoid ingesting all carbohydrates in a single dose. With this, it will be possible to optimize the intake of these carbohydrates with the consequent increase in performance in endurance disciplines.

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Reference:

Menzies, C., Wood, M., Thomas, J., Hengist, A., Walhin, J. P., Jones, R., Tsintzas, K., Gonzalez, J. T, & Betts, J. A. (2020). Frequent carbohydrate ingestion reduces muscle glycogen depletion and postpones fatigue relative to a single bolus. International journal of sport nutrition and exercise metabolism, 30(3), 203-209.