Carbohydrates during a trail running race: science and practice

Edited by: Dr. Giulio Merlini in cooperation with Trail Running Movement

Preparing for a trail running competition, especially ultra trail events, does not simply mean focusing on physical training. A decisive part of performance lies in how energy is managed during effort, and in particular in carbohydrates during a trail running race.

It is not uncommon to see well-trained athletes experience significant performance drops precisely due to inadequate nutrition.

The reality is that energy availability during competition represents a limiting factor just as much as physical preparation.

In this context, carbohydrates play a central role: understanding how to use them and how to integrate them correctly means being able to sustain effort longer and more efficiently.

In this article, we will analyze the importance of carbohydrates in trail running, how to consume them during a race and how to build an effective nutritional strategy.

Enjoy the reading

TRM Team

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Why carbohydrates during a trail running race are essential

During prolonged activity such as trail running, the body primarily relies on two energy sources:

• lipids
• carbohydrates.

However, as intensity increases or effort is prolonged, carbohydrate availability becomes the determining factor.

Endurance capacity is closely linked to the amount of muscle and liver glycogen available. When these stores are depleted, performance progressively declines, regardless of the athlete’s level (Cermak, Van Loon, 2013).

To better understand their importance, it is useful to consider the functions of carbohydrates during a trail running race:

• they help maintain stable energy availability
• they delay the onset of fatigue
• they support central nervous system function
• they contribute to maintaining hydration.

These aspects clearly show that carbohydrate during a trail running race during a trail running race is not optional, but an essential component of race strategy. Without adequate intake, it becomes difficult to sustain effort effectively over time.

How many carbohydrates during a trail running race

One of the most delicate aspects of building a nutritional strategy concerns the amount of carbohydrates to consume during competition. Available guidelines provide useful indications, but they must always be adapted to the specific context.

Before starting supplementation, it is generally recommended to wait approximately 45 minutes after the start of the activity. This approach helps improve glucose sensitivity and prevents early overload of the digestive system, particularly at the intestinal level.

Once this initial phase is over, the following guidelines can be considered:

• activities up to 150 minutes → about 60 g of carbohydrates per hour
• activities beyond 150 minutes → up to 90 g of carbohydrates per hour
• long-duration activities → maintain a consistent intake close to the upper limit.

This strategy provides several benefits:

• ensures performance continuity, avoiding sudden drops
• improves long-term energy management
• supports hydration, considering that each gram of carbohydrates binds approximately two grams of water (Bisciotti, 2000).

It is important to emphasize that these indications represent general guidelines: individual tolerance and personal experience remain key factors.

Carbohydrate types in trail running: gels or liquid solutions?

One of the most common challenges for long-distance athletes concerns the choice of carbohydrates during a trail running race. The main options are gels and liquid solutions.

Available evidence suggests that liquid formulations may be more favorable in terms of intestinal tolerance compared to gels, reducing the risk of gastrointestinal discomfort (Sareban et al., 2015). However, no significant differences in performance appear to emerge between the different solutions.

To make an informed choice, it is useful to consider the following characteristics:

• liquid carbohydrates → greater tolerance and reduced digestive stress
• gels → practicality and ease of use during running
• combination of both → flexibility to adapt to different phases of the race.

The most effective choice is often the one that takes into account individual preferences and the ability to manage the product during effort.

How to build an effective nutritional strategy

An effective nutritional strategy cannot be improvised on race day. On the contrary, it requires a period of experimentation during training, allowing athletes to evaluate their individual response to different types of supplementation.

This process helps reduce uncertainty and ensures a more structured and reliable approach on race day.

To build a truly effective plan, it is important to consider:

• the timing of carbohydrates during a trail running race
• the hourly intake to maintain
• the type of product used
• digestive system tolerance.

A particularly relevant aspect is the so-called “gut training” which refers to the ability to progressively adapt the body to absorb increasing amounts of carbohydrates during exercise.

This adaptation is a key factor in improving race management and reducing the risk of gastrointestinal issues.

Practical example of intake of carbohydrates during a trail running race

To make the principles described so far more concrete, it is useful to observe how a nutritional strategy could be structured during a long-distance trail race (approximately 5–6 hours).

The goal is to maintain a constant carbohydrate intake, avoiding both energy deficits and digestive overload.

The following table represents an indicative example, which must be adapted based on the athlete’s level, individual tolerance and race characteristics.

This distribution highlights several key principles:

• the importance of starting gradually
• the need to progressively increase intake
• the key role of variety in carbohydrate sources.

It is important to emphasize that there is no one-size-fits-all strategy. This scheme represents a reference model, useful for understanding the underlying logic, but it must be tested and adapted over time through training, especially during long runs.

Most common mistakes in management of carbohydrates during a trail running race

Despite the availability of clear guidelines, many athletes make mistakes that compromise the effectiveness of their nutritional strategy. These are often the result of limited experience or insufficient planning.

Understanding these mistakes helps avoid them and improves overall preparation quality.

The most frequent ones include:

• consuming carbohydrates during a trail running race only when feeling hungry
• starting supplementation too late
• not testing products during training
• always using the same type of supplementation
• ignoring signals from the digestive system.

These behaviors can lead to sudden energy drops or gastrointestinal issues, negatively affecting performance even when physical preparation is adequate.

The role of other nutrients

Before concluding, it is important to consider the role of other nutrients during competition. In particular, some formulations combine carbohydrates with proteins.

However, scientific evidence suggests that proteins do not play a significant ergogenic role during prolonged exercise (McLellan, Pasiakos, Lieberman, 2014; Antonio et al., 2008).

During a race, it is therefore advisable to focus on:

• adequate intake of carbohydrates during a trail running race
• proper hydration management
• a simple and sustainable strategy.

Proteins remain important in recovery and in pre- and post-exercise nutrition, but they are not a priority during competition.

Conclusion

Carbohydrates during a trail running race is one of the most critical factors for performance. It is not simply about following general guidelines, but about building a personalized strategy based on experience and adaptation.

The difference between an effective performance and a sudden drop in energy is often directly linked to the ability to maintain a consistent energy supply over time.

Training this component, testing different solutions, and developing a consolidated routine allows athletes to turn theory into practice. It is precisely through this process that a more solid, conscious, and sustainable performance is built over time.

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Want to improve your race-day carbohydrate fueling strategy?

Choose one of our TRM Nutrition Plans and get

a concrete and personalized nutrition plan developed by the TRM Team nutritionists

tailored to your level, your goals, and the races you are preparing for

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Frequently Asked Questions (FAQ)

1. How many carbohydrates should I take during a trail race?
It depends on race duration and intensity, but generally ranges from about 60 g/hour up to 90 g/hour in longer events. The key is not only the amount, but the ability to sustain it over time.

2. Are gels or liquid carbohydrates better?
Both are valid options, but liquid carbohydrates tend to be better tolerated at the intestinal level. The best choice is the one you can manage comfortably during effort.

3. When I should start taking carbohydrates during a trail running race?
Not necessarily. In many cases, it is useful to wait around 45 minutes before starting to improve metabolic response and reduce digestive stress.

4. Is it really necessary to train the gut?
Yes, and it is one of the most overlooked aspects. Consuming carbohydrates during training helps the body adapt, reducing the risk of gastrointestinal issues in race conditions.

5. What happens if I consume too few carbohydrates during a trail running race?
The main risk is a progressive energy drop, leading to a significant decline in performance, especially in the final stages of the race.

6. Are proteins useful during a race?
Not significantly for performance. They are important for recovery, but during exercise the priority remains carbohydrate intake.

7. How do I know if my fueling strategy is correct?
If you can maintain stable energy, avoid major crises, and manage fatigue well in the later stages, you are likely on the right track. Otherwise, it may be necessary to adjust timing, quantity, or carbohydrate type.

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REFERENCES

1. Antonio et al. (2008), Essentials of Sports Nutritionand Supplements, ISSN; p. 333
2. Bisciotti GN (2000), Teoria e metodologia del movimento umano, Teknosport, Ancona
3. Cermak NM, Van Loon LJ (2013). The use of carbohydrates during exercise as an ergogenic aid, Sports Med; 43 (11): 1139-1155
4. Mc Lellan TM, Pasiakos SM, Lieberman HR (2014). Effects of protein in combination with carbohydrate supplements on acute or repeat endurance exercise performance: a systematic review, Sports Med; 44(4): 535-550
5. Sareban et al. (2015). Carbohydrate Intake in Form of Gel is Associated With Increased Gastrointestinal Distress but Not With Performance Differences When Compared to Liquid Carbohydrate Ingestion During Simulated Long-Distance Triathlon, Int J Sport Nutr Exerc Metab