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April 28, 2023

Carbohydrates and fluids are crucial to performance. During an intense prolonged race your body may need 90 grams of carbohydrates per hour or even more. At the same time sweat rates can be very high in hot conditions. Therefore fluid intake can be substantial, as it is advised to keep dehydration within 2% of the body weight. Altogether this provides a big challenge for the gastrointestinal (GI) tract to deliver all the required carbohydrates and fluids.

So it is not surprising that many athletes experience GI problems when performing endurance exercise. These problems can range from bloating and cramping to even more serious issues like diarrhea. However, there is good news: the GI system is to an extent trainable, so that those symptoms become less prevalent and the delivery of the nutrients to the relevant parts in the body is improved. This is what usually is called training the gut.

Training the gut is essential for performance

There are a few reasons why it is vital to your performance to train your gut. First of all, to perform optimally, you need a lot of carbohydrates. But to make sure the carbohydrates you take in are actually absorbed by the body and delivered to your muscles, gut training is needed.

Taking a lot of nutrition and fluids in a short period of time can easily cause a bloated feeling. By training the gut this feeling of fullness can be reduced and the gastric emptying can be increased. Together this will help to reduce gastrointestinal issues, which in turn will have a positive effect on your performance.

The graph below summarizes how training the gut can help you.

Training the gut in short. Source: Jeukendrup (2017)

How to train your gut

Now you might think, but what should I do to actually train my gut? Roughly speaking, four training components are involved.

  1. Training your stomach. Getting used to having large volumes of fluids in the stomach to reduce the perception of fullness. This improves the tolerance and comfort.
  2. Increase gastric emptying to reduce stomach discomfort.
  3. Improve the absorption of carbohydrates and the tolerance to ingested carbohydrates. This reduces intestinal discomfort and obviously helps to keep energized.
  4. Practise competition nutrition to find out what nutrition works best for you and to get familiar with timing and nutrition strategy.

The first step: set your goal and know your current intake

Before you start with the four training components mentioned above, it is vital to set your goal and know your current intake. In the EatMyRide app you can already plan your race on beforehand. When planning, you see how many carbohydrates you will need to take per hour, this will usually be between 60 and 90 grams. Also consider what the temperature during the event may be. Is it mid-summer and could it be a hot day? Then training your stomach will be even more important.

Now that you have planned your race, it is time to decide when to start training the gut. Most of the time it is advisable to start training the gut 5 to 10 weeks before competition.

Since training the gut is all about increasing your carbohydrate intake and fluid intake and getting used to that, you need to know at what level you are currently. This involves two parts. First, how many carbohydrates do you usually take during your trainings? In the EatMyRide app you can fill in your actual nutrition intake during trainings. Then, via Profile > Progress you can get more insight into your intake compared to the duration of your rides.

Tip: to track your carbohydrate intake you can use the Carbohydate Burn / Intake Balancer app for Garmin.

The second part is the carbohydrate content of your diet. By logging your nutrition intake on a few training days you get insight into the amount of carbohydrates in your diet, especially on training days. This is important as later on in the process you will specifically need to train with a high-carbohydrate diet.


You now know about the importance of training the gut and how to get started. In Part 2 of the Training The Gut series we will dive deeper into stomach training and improving gastric emptying.



  • Costa, R. J., Miall, A., Khoo, A., Rauch, C., Snipe, R., Camões-Costa, V., & Gibson, P. (2017). Gut-training: The impact of two weeks repetitive gut-challenge during exercise on gastrointestinal status, glucose availability, fuel kinetics, and running performance. Applied Physiology, Nutrition, and Metabolism, 42(5), 547-557.
  • Jeukendrup, A. (2010). Sports Nutrition-From lab to Kitchen. Meyer & Meyer Sport.
  • Jeukendrup, A. E. (2017). Training the gut for athletes. Sports Medicine, 47(Suppl 1), 101-110.


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