~ Annie Bothma, Elite Athlete, IOPN Performance Sports Nutritionist (EQF Level 7. Masters), Running & Strength Coach
Watching the Tour de France, one might wonder how cyclists sustain such immense power and generate watts over three grueling weeks. How do they manage to recover between hard these back-to-back hard efforts over multiple stages?
A significant factor contributing to their success is the increased consumption of exogenous carbohydrates by top athletes worldwide. Intakes exceeding 60-90g per hour are now widely accepted, with some athletes consuming over 120g of carbohydrates per hour.
This blog explains why carbohydrates are crucial and how different carbohydrate sources can help you achieve a greater carbohydrate intake per hour.
The Carbohydrate Journey
The journey of carbohydrates begins when they are consumed and enter the stomach. The process of gastric emptying determines how quickly food leaves the stomach and enters the intestine. This is influenced by various factors, including the volume of food and the nutrient concentration in the gut. Once in the intestine, carbohydrates are absorbed into the bloodstream, with the speed of absorption depending on the type and structure of the carbohydrate consumed.
Different Carbohydrate Sources
Carbohydrates can be classified into two main groups: simple and complex carbohydrates. Simple carbohydrates, such as glucose and fructose, which are rapidly absorbed, while complex carbohydrates, like starches, require more time to be broken down and absorbed. The chemical composition and complexity of these carbohydrates play a role in their digestion and absorption rates, affecting the speed at which they can be utilized for energy during physical activity.
When exercising, the main objective of carbohydrate consumption is to efficiently provide energy to the muscles. Quick digestion of simple carbohydrates allows them to enter the bloodstream rapidly, providing a fast energy boost to the muscles. On the other hand, complex carbohydrates are digested slowly, leading to a more consistent and gradual energy release.
Carbohydrates can be further categorized into two main groups based on their rate of oxidation:
Carbohydrates that undergo rapid oxidation (up to ~60 g/h or 1 g/min), such as glucose, maltose, sucrose, maltodextrin, and amylopectin starch
Carbohydrates that undergo slow oxidation (up to ~30 g/h or 0.5 g/min), including fructose, galactose, isomaltulose, trehalose, and amylose.
Recommended carbohydrate intake per hour
Exercise lasting less than 1-hour: Carbohydrate mouth rinse or nothing, or hydration as needed
Exercise lasting 1-2 hours: 30 - 60g of carbs/hour
Exercise lasting greater than 2-2.5 hours: 60 - 90g of carbs/hour
It is not unusual for elite athletes to consume more than 90 g of carbs/hour. As mentioned earlier, it is increasingly common in high-intensity elite sports to see athletes consuming well over 120 g of carbs/hour.
Before attempting this, it is crucial to slowly raise your carbohydrate consumption while training to prevent stomach issues. Begin at your current level and gradually increase over the weeks leading up to your race.
Multiple Transportable Carbohydrates
Utilizing various transportable carbohydrates involves blending diverse carbohydrate types, such as glucose and fructose, to make use of distinct intestinal transporters. Glucose gets absorbed using the SGLT1 (sodium-glucose co-transporter 1), whereas fructose is absorbed via GLUT5 (glucose transporter type 5).
This combination offers the major advantage of improving the absorption and utilization of carbohydrates, leading to enhanced performance through a steady energy supply and decreased gastrointestinal discomfort during intense physical activity.
Practical Application
For most endurance athletes, the most efficient approach to high carbohydrate intake while exercising remains the combination of glucose and fructose. This strategy enhances the absorption and utilization of carbohydrates, leading to improved performance over time. While newer carbohydrate products like super starch and cluster dextrin have unique features, they may not provide significant advantages over traditional carbohydrate sources for the majority of athletes.
Here are some practical examples of products and foods that provide these carbohydrate sources, suitable for consumption during exercise:
Glucose Sources
Energy Gels: Brands like GU Energy, Cliff Shot, and PowerGel offer gels primarily based on glucose. These are convenient and easy to consume during exercise.
Sports Drinks: Gatorade and Powerade contain high levels of glucose to provide quick energy and hydration.
Fructose Sources
Fruits: Apples, pears, grapes, and watermelon are high in fructose.
Dried Fruit: Dates, raisins, apricots are also rich in fructose.
Honey: Contains a mix of glucose and fructose, but contains a bigger proportion of fructose.
Combined Glucose and Fructose Sources
Energy Gels: Some gels, like those from GU Energy and Cliff Shot, include a mix of glucose and fructose.
Sports Drinks: Certain sports drinks, like Tailwind Nutrition, are designed with both glucose and fructose to enhance absorption.
Energy Chews: Brands like Cliff Blocks and Honey Stinger Chews combine glucose and fructose for balanced energy release.
Energy Bars: Products like Cliff Bars and KIND Bars often combine simple sugars with complex carbohydrates for a sustained energy supply.
Hydrogels like Maurten: This innovative product combines glucose and fructose in a hydrogel, which can enhance carbohydrate absorption and reduce gastrointestinal distress during intense exercise.
Conclusion
To sum up, despite the emergence of new carbohydrate products, the fundamental principles of carbohydrate intake during endurance workouts still emphasize the importance of combining glucose and fructose for efficient absorption and energy provision. Athletes should prioritize what suits their personal requirements and choices, taking into account performance advantages as well as gastrointestinal comfort.
Elevate your own endurance and performance by fueling with multiple transportable carbohydrates and diverse carb sources, ensuring a steady and efficient energy supply throughout your training and races!
References
Baur, D.A., Saunders, M.J. Carbohydrate supplementation: a critical review of recent innovations. Eur J Appl Physiol 121, 23–66 (2021). https://doi.org/10.1007/s00421-020-04534-y
Jeukendrup, A. E. (2010). Carbohydrate and exercise performance: The role of multiple transportable carbohydrates. Current Opinion in Clinical Nutrition & Metabolic Care, 13(4), 452-457. https://doi.org/10.1097/MCO.0b013e328339de9f
Jeukendrup, A. E. (2017). Training the gut for athletes. Sports Medicine, 47(S1), 101-110. https://doi.org/10.1007/s40279-017-0690-6
Hearris, M. A., Hammond, K. M., Fell, J. M., & Morton, J. P. (2017). Regulation of muscle glycogen metabolism during exercise: Implications for endurance performance and training adaptations. Nutrients, 9(6), 584. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371619/
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