How to Avoid Gastrointestinal Discomfort during a Race?

How to Avoid Gastrointestinal Discomfort during a Race?

In this article, we address a very common problem for which many sportspeople can’t find an answer or solution:

  • How to eat for a race to reduce digestive discomfort?
  • Why does my stomach hurt when I run?

And here are some practical tips to avoid this kind of problem.

What are digestive problems during a race?

When talking about endurance sports training and preparation for medium and long distance events, you need to talk about energy pathways and nutrition.

Good planning will help us to avoid, amongst other things, the typical digestive discomfort that many sportsmen and women suffer during events.

The success of a good training programme, as well as a sporting event, does not depend exclusively on the variables of the training, There are many other factors, some of them limiting, which will directly and indirectly affect the results obtained:

  • Stress management;
  • Intra-session and inter-session rest;
  • Type of lifestyle;
  • Environment; and, of course,
  • The type of diet and food the subject is on.

Gastrointestinal discomfort

These are some of the variables that must be taken into account when planning a sporting event.

Many athletes suffer from this type of ailment, gastrointestinal discomfort and diarrhoea, which prevents them from carrying out the tests efficiently and even from finishing them.

Why does my stomach hurt when I run?

As we have already discussed in previous articles, training the digestive system takes on special importance in a training plan in preparation for a medium, long or ultra-high distance test.

In other words, both the athlete’s normal diet and ergogenic aids, including supplements, must have a plan that accompanies training throughout the different phases of the season.

We are therefore talking about the periodisation of nutrition.

Problems during a competition

Omitting this type of planning and training often results in the immediate mismanagement and inefficient use of the body’s energy substrates at the time of the competition.

Not having an adequate nutritional plan throughout the season and not training the different energy systems properly is one of the most frequent errors.

Runners and popular sportsmen and women present themselves for a long duration without having trained their digestive apparatus, and without having a strategy for supplementation and hydration that is adequate and trained beforehand.

They also take supplements that:

  • They have not trained before.
  • They have not tested how their digestive system responds to amounts of hydrates etc…
  • They do not study the composition of the gels / bars that they will ingest during the test.
  • Excess fibre intake days prior to a race.
  • Dehydration that can cause diarrhoea etc.

What happens then?

If, in itself, a long-duration race involves intense effort and stress to the nervous system, the digestive system and other systems suffer major alterations during this type of competition or demanding training.

Let’s think that, in a race of this type, where we need a continuous flow of oxygen to the lower limbs (especially in cycling and running), the body tries to send all the blood to those muscles so that the muscle contractions can take place, they are irrigated with blood, and there is a good exchange of gases and waste substances.

Digestive problems

The digestive tract is deprived of blood flow and must therefore make greater efforts to digest and separate substances from food.

If you have not also been trained under these conditions, it is most likely that you will have increased gastric motility, discomfort and will not be able to efficiently decompose the substances in the ingested food/drink or assimilate them.

On the other hand, in the case of running, let’s not forget that the repetitive impact causes the intestines to suffer alterations and movements, which can cause not only bad digestions but also too much motility in the digestive system.

How can we avoid gastrointestinal discomfort while running?

Choose the type of supplement

Incorporate the nutritional plan into the training plan and schedule the type of supplementation according to the duration and intensity of the training, simulating the competition.

Important: test what type of supplements each athlete tolerates best, and do not leave it to week before or day of the test.

  • The first thing is to determine the estimated time of your test and intensities, in order to plan an adequate strategy of intake of carbohydrates, mineral salts, electrolytes etc…
  • The choice of the type of supplements, in terms of texture (gel, sticks, powder dissolution in water etc.), will depend not only on how the sportsman or woman tolerates each of them, but also on his or her preferences and tastes.

Although it is recommended that supplements should be as liquid or gel-like as possible, such as HSN’s Evogummys for better assimilation by the body, and not overworking the digestive tract.


There are products in different formats for short, medium and long term tests.

From very sweet gels with a very dense and pasty texture, to powders to be diluted in water with the exact amount of carbohydrates to be ingested per hour

My recommendation is that we always look for what is as natural as possible, easy to digest (remember that we should not overwork the digestive system), preferably liquid rather than solid, and with the right composition.

Adjust the amount of carbohydrates needed

Not all gel bars have the same composition, therefore, the energy contribution can be greater than necessary, or on the contrary, deficient…

That is, the energy requirements are not met.

On the other hand, we must pay attention to what type of carbohydrates – their composition – the gels or bars are, in order to adjust the necessary intakes properly and thus avoid a composition that favours intestinal discomfort. One recommendation is the powdered isotonic drink EvoTonic by HSN.

Isotonic drink evotonic

Many of the intestinal problems suffered by sportspeople are caused by the intake of gels containing only glucose, which are difficult to absorb and assimilate by the body.

It is therefore recommended that the composition of OGH should be glucose + fructose (in a 2:1 ratio) to facilitate absorption and assimilation.

Calculate proportions according to race duration

As the duration of the test increases, so does the intake of both hydrates and isotonic drinks, which will have been trained previously:

As a general rule, a dose of 30 – 60 grams / hour is recommended… bearing in mind that the maximum absorption capacity is around one gram per kilogram of weight per hour.

Bearing in mind that the maximum absorption of glucose is estimated at one gram per hour and that to this can be added the absorption of up to 30g of fructose per hour by another route of absorption (which could reach, if there is good adaptation, around 90g of carbohydrate per hour).


In any case, the intakes will vary depending on the subject and the total duration of the test.

In races or training sessions lasting less than 70 minutes, no extra intake of hydrates is necessary, and even a simple mouthwash with a drink containing hydrates would help. To learn more about this strategy, visit this link.

Plan supplies

Once you have trained and planned your nutritional strategy during the training for the competition, it is time to write down your plan for the race and also to study and analyse the food supplies for the race.

If the gels and/or bars offered by the organiser of the event are the same brand as those you take, you can be sure that, if necessary, you know in advance that your body will tolerate them well.

My recommendation is always that you have everything prepared before, during and after the race, without just depending on what the organisation gives you.

Yes, it is important to know WHERE – AND ALL OF THE LOCATIONS of the refreshment points so that you can replenish your water bottle, drink water and even take some supplements or fruit just in case.

What food to have

The diet in the week prior to the competition must also be planned and, depending on the type and duration of the event, what is commonly called “Hydrate loading” is usually carried out 2-3 days prior to the race in order to have good glycogen deposits.

Although, this carbohydrate load should not be excessive, but incorporate a little more of this type of macro-nutrients to the usual diet (some rice, pasta, potato, sweet potato …).

What food should we avoid before the race?

Basically we should avoid anything rich in fibre in the prior days, precisely to avoid possible digestive problems on the day of the race. In other words, vegetables, wholemeal foods and other foods rich in fibre should be avoided on the two or three days prior to the competition.

We must also avoid excessively high-fat and ultra-processed foods, precisely to prevent the digestive system from working too hard, as this type of ultra-processed food requires greater digestion.

Practical example

Before I started to train in an orderly way the nutrition in training and in competitions, both before, during and after them, I did not keep track of what I drank or of the gels I consumed.

Fatigue came early, recovery after training was poor, and I suffered from dehydration.

Once I started training and planning my intake – both fluid and hydrate intake – the results were incredible. I was giving the body intermittent and planned intakes to maintain the intensity of the session without suffering stomach problems, hydration etc…

I give you, for example, the supplementation strategy that I usually take in a 5 hour medium distance triathlon event.

Preparation and Breakfast

  • Bottles: 2 x 750 ml, one with 90g of hydrates to be drunk in the first hour and a half of the test, and another with an isotonic drink.
  • Breakfast: the usual 90 minutes before the test.

Before Starting

  • Caffeinated gel 5 minutes before the start of the race – swimming segment (duration approximately 35 minutes with transition)

Cycle segment

  • Mouthwash: only water after getting on the bike (we have swallowed some sea water, and we let the body adapt and assimilate the cycling for a while).
  • Every 10 minutes: small intake of water with electrolytes.
  • After 45 minutes: first HCO gel
  • From then on: intake of a gel every 20-30 minutes for the first 2 hours.
  • In the last hour:I replace the gel with a natural energy bar with a soft texture that is easy to digest / half a banana (if given by the organisation at the refreshment points).
10 minutes before the start of the race segment: new intake of gel with caffeine

Race period

  • Take 1 gel in the 60 to 90 minute period.

Post Competition

  • Right at the end: Recovery drink with carbohydrates and proteins
  • Post meal: containing healthy protein, carbohydrates and fats.

Avoiding junk food, which is difficult to assimilate and lacks essential nutrients for the body.

Supplementation strategy

It is also important to maintain good post-competition hydration in the two days following the event.

This is my strategy, individualised and previously tested; both in training and in competitions. Develop and test your own!

Other tips to try to avoid gastrointestinal discomfort

  • Try gels, bars, isotonic drinks… everything related to supplementation in the months before your event.
  • Test the nutritional plan during your long training sessions and at competitive times.
  • Analyse the composition of the gels in grams of hydration, remember that we should consume at least 30 grams per hour (most gels have 24 grams).
  • Don’t forget to hydrate and replace the salt – electrolytes, especially if there is environmental humidity.
  • Liquid textures or the softest and easiest to digest and assimilate by the body.
  • 2:1 ratio of glucose:fructose for better assimilation.

Bibliographic references

  1. Cardona C, Cejuela A, Esteve J. Manual para Deportes de Resistencia. All in Your Mind Training System. (2019).
  2. Hopkins, W., & Word, M. (2006). The Optimum Composition for Endurance Sports Drinks. Sports Science(10), 59-82.
  3. Shirreffs, S., Armstrong , L., & Cheuvron, S. (January de 2014). Fluid and electrolyte needs for preparation and recovery from training and competition. Journal of Sports sciences, 57-63.
  4. Jeukendrup A, Gleeson M. Nutrición Deportiva. Ediciones Tutor (2019).

Related Entries

  • If you are an Endurance Sportsperson and want to know more about the Type of Food that suits you best, we recommend you visit this post.
  • Do you know the Best Supplements for Running? We tell you what the science says if you click here.
  • There are different types of Sports Drinks: isotonic, hypotonic and hypertonic; each of them is used… keep reading.
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About Isabel del Barrio
Isabel del Barrio
Isabel del Barrio really loves sport, demonstrating it from a very young age and sharing her enthusiasm and knowledge to this day
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