Carbohydrate oxidation rate is one of the main factors that determine performance in endurance sports. During prolonged exercise, the body’s ability to use carbohydrates as an energy source can be the difference between maintaining pace or entering fatigue. But what actually limits this utilization?
What is carbohydrate oxidation rate
Carbohydrate oxidation rate refers to how quickly the body can use ingested or stored carbohydrates to produce energy during exercise.
In endurance activities, especially at moderate to high intensities, carbohydrates are the primary energy source. However, this utilization is not unlimited and depends on several physiological factors.
Main factors that limit carbohydrate oxidation
Intestinal absorption capacity
One of the main bottlenecks lies in the intestine. There is a limit to how much carbohydrate can be absorbed per hour.
Transporters such as SGLT1 and GLUT5 are responsible for absorbing glucose and fructose. When only a single carbohydrate source is used, absorption tends to reach saturation more quickly.
For this reason, combining different types of carbohydrates can increase absorption rate and, consequently, energy availability.
Gastric emptying
Before being absorbed, carbohydrates need to leave the stomach. This process can be influenced by high carbohydrate concentration, dehydration, and exercise intensity.
When gastric emptying is reduced, energy delivery is also compromised.
Muscle utilization capacity
Even when carbohydrates reach the bloodstream, they still need to be used by the muscle.
Factors such as training status, mitochondrial density, and metabolic adaptations directly influence this capacity.
Trained athletes can oxidize more carbohydrates per hour than untrained individuals.
Glycogen availability
Muscle and liver glycogen stores are also key determinants.
As exercise duration increases, these stores decline, increasing reliance on carbohydrate intake during the activity.
When this intake is insufficient, performance decline is inevitable.
Inadequate nutritional strategy
Consuming too little carbohydrate or at the wrong times directly limits oxidation rate.
Additionally, lack of gut training can reduce tolerance to higher carbohydrate intakes during exercise.
Practical application in endurance
In practice, understanding carbohydrate oxidation rate allows for better adjustment of nutritional strategies.
Athletes can oxidize around 60 g per hour with a single carbohydrate source. When combining different sources, this value can reach 90 g per hour or more.
Intake should be distributed throughout the exercise, and strategies should be tested in training, not only on race day.
Factors such as temperature, intensity, and individual characteristics should also be considered.
Conclusion
Carbohydrate oxidation rate does not depend only on intake, but on the entire process of digestion, absorption, and muscular utilization.
Intestinal absorption, gastric emptying, training adaptation, and nutritional strategy are key factors in maintaining energy supply throughout exercise.
Therefore, well-planned and individualized strategies are essential to optimize performance in endurance events.
Referência
Poulsen, S. B., Fenton, R. A., & Rieg, T. (2015). Sodium-glucose cotransport. Current Opinion in Nephrology and Hypertension, 24(5), 463–469. Disponível em: https://pmc.ncbi.nlm.nih.gov/articles/PMC5364028/
