Why Proper Carbohydrate Fueling is Crucial
Carbohydrates are the body's primary and most efficient fuel source for moderate to high-intensity exercise. When you exercise, your muscles and liver rely on stored carbohydrates, called glycogen, for energy. For exercise bouts exceeding 60 to 90 minutes, these glycogen stores can become significantly depleted, leading to profound fatigue often referred to as 'hitting the wall' or 'bonking'. By ingesting carbohydrates during exercise, you provide a continuous source of energy that helps sustain blood glucose levels, delays fatigue, and allows for consistent high performance.
The Specific Recommendation for 1-2.5 Hours
For physical activity lasting between 1 and 2.5 hours, current sports nutrition recommendations advise consuming 30 to 60 grams of carbohydrates per hour. The specific amount within this range depends on the intensity of the workout. For example, during a 90-minute high-intensity interval session, an athlete might aim for the higher end of the scale (closer to 60g/hr) to keep up with the rapid energy expenditure. In contrast, during a two-hour moderate-intensity trail run, a lower intake of around 30-40g/hr may be sufficient to prevent energy crashes.
Practical examples of 30-60g of Carbohydrates
- 30g of carbs: 1 standard energy gel, 500ml of a 6% sports drink, or a medium banana.
- 60g of carbs: 2 standard energy gels, 1 litre of a 6% sports drink, or an energy bar.
Fueling Strategy: Products vs. Whole Foods
Athletes can use a variety of sources to meet their hourly carbohydrate needs. The choice between commercial sports products and whole foods often depends on personal preference, convenience, and stomach tolerance. Sports products are designed for rapid absorption with minimal gastrointestinal distress, while whole foods can be gentler on the stomach for some individuals.
Commercial Products
- Sports Gels: Highly concentrated, pre-portioned sources of simple carbohydrates, offering quick energy. A single gel typically provides 20-30g of carbs.
- Sports Drinks: Combine carbohydrates with electrolytes, aiding both fuel delivery and hydration. A standard 6% carbohydrate drink provides around 6g of carbs per 100ml.
- Chews & Blocks: Provide a chewable alternative to gels, with each serving containing a set amount of carbohydrates, typically 20-30g.
Whole Foods
- Bananas: One medium banana contains approximately 25g of carbs, along with potassium.
- Dates: Medjool dates are a great source of quick-absorbing sugar. Two medium dates can provide around 30g of carbs.
- Dried Fruit: Raisins, apricots, or other dried fruits can be a simple, portable source of energy.
The Role of Multiple Transportable Carbohydrates
For exercise lasting longer than 2 hours, using multiple transportable carbohydrates, such as a glucose-fructose mix, is beneficial, even within the 1-2.5 hour window. Glucose uses a specific transporter (SGLT1) for absorption, which can become saturated at around 60 grams per hour. Fructose, however, uses a different transporter (GLUT5), allowing the body to absorb a higher total amount of carbohydrates per hour without overwhelming a single absorption pathway. While most crucial for events over 2.5 hours, this strategy can help prevent gastric distress and optimize delivery for high-endurance efforts within the 1-2.5 hour window.
Comparison of Fueling Strategies
| Feature | Single Carbohydrate Source (e.g., Glucose) | Multiple Transportable Carbohydrates (e.g., Glucose-Fructose) |
|---|---|---|
| Absorption Rate | Maxes out around 60 g/hr due to single transporter saturation. | Higher absorption rate (up to 90g/hr) due to utilizing different transport proteins. |
| Performance Impact | Effective for sustaining energy within the 1-2.5 hour range, especially at lower intensities. | Superior for higher intensity and longer duration efforts within the 1-2.5 hour range by maximizing carbohydrate delivery. |
| Gastrointestinal Tolerance | Generally well-tolerated at intakes of 30-60 g/hr. | Excellent tolerance at higher intake rates (60-90 g/hr) by reducing load on a single pathway. |
| Typical Use Case | Sufficient for exercise up to 2 hours at moderate intensities. | Optimal for high-intensity efforts approaching 2.5 hours or for individuals prone to GI issues. |
Training Your Gut
Consuming carbohydrates during exercise is a skill that must be practiced, much like any other aspect of training. The gut is a highly adaptable organ, and its ability to absorb and tolerate carbohydrates can be trained over time. Athletes should experiment with different types and quantities of fuel during training sessions to determine what works best for their body. This helps minimize the risk of gastrointestinal discomfort on race day or during important events. Starting with smaller amounts and gradually increasing intake can help your system adapt to higher fueling rates.
Conclusion: Fuel Smart for Optimal Performance
For exercise ranging from 1 to 2.5 hours, the general recommendation for carbohydrate intake is a practical range of 30 to 60 grams per hour. The ideal amount depends on the intensity of the effort, with higher rates more beneficial for more demanding workouts. A mix of glucose and fructose can enhance absorption and performance, particularly as you approach the 2.5-hour mark. By experimenting during training and listening to your body, you can create a fueling strategy that sustains your energy, prevents fatigue, and helps you achieve peak performance in your endurance activities. For further information on broader nutrition strategies for athletes, the Gatorade Sports Science Institute offers valuable resources on dietary carbohydrates and endurance performance.
The Science of Fueling: A Guide for Endurance Athletes
- Summary: Fueling guidelines depend on exercise duration, with recommendations for 30-60g/hr for activities of 1-2.5 hours and up to 90g/hr for longer efforts. Mixing carbohydrate types can improve absorption at higher intakes.
- Relevance: Directly confirms the 30-60g/hr recommendation and explains the mechanism behind using multiple transportable carbs.
DIETARY CARBOHYDRATE AND THE ENDURANCE ATHLETE
- Summary: Comprehensive overview of carb needs for endurance athletes, including pre-exercise fueling, in-workout intake (30-90g/hr), and the benefits of glucose-fructose mixes. It emphasizes the importance of periodized nutrition.
- Relevance: Provides authoritative scientific backing for the fueling guidelines discussed, highlighting the role of different carb types.
How many carbs per hour do you need?
- Summary: A detailed guide on determining individual carbohydrate needs based on exercise intensity and duration. Confirms the 30-60g/hr window for 1-2 hours of exercise and offers practical examples of food sources.
- Relevance: Offers practical, user-friendly examples and confirms the core recommendation, making it highly useful for readers.
Carbohydrate Intake During Exercise
- Summary: This article reviews advances in carb intake science, highlighting that single carb sources max out around 60g/hr absorption, while multiple transportable carbs can raise that limit. It also emphasizes that practice is key for gut tolerance.
- Relevance: Explains the physiological reasons behind absorption limits and the benefits of mixed carb sources, reinforcing the advice provided.
Nutrition guide for endurance athletes
- Summary: General nutrition advice for endurance athletes covering daily intake, pre-exercise meals, and during-exercise fueling. Explicitly recommends 30-60g/hr for exercise lasting 1-2.5 hours.
- Relevance: Provides confirmation from another reputable source on the specific hourly intake recommendation for the target duration.
