Running and Gastrointestinal Distress

Tips to Avoid Runner's Trots

Gastrointestinal distress, also called runner’s trots or runner’s diarrhoea, is quite common in endurance activities. Whether you’re running a marathon or an ultra, tackling an Ironman, riding a sportive or having a multi-day trek, those all too familiar rumblings, that bloated feeling, waves of nausea, cramps and desperate dashes to relieve yourself out of either end, can turn even the most amazing event into an extended bout of sheer misery.

As this begins, your tempo may be reduced to a crawl and, with your stomach rejecting anything you try to take onboard, you’ll quickly run out of fuel. Turning the situation round can be near to impossible, and in a lot of cases leads to a DNF against your name.

In search of a cause, many runners consider the obvious and blame what they consumed during or just before the activity. Even though this may be the cause, there is a wide range of factors that can lead to gastrointestinal distress. Read further to learn what you can do to avoid gut problems.

couple jogging
The most common cause of gastrointestinal distress probably lies in getting your pacing wrong.


The most common cause of gastrointestinal distress probably lies in getting your pacing wrong, going too hard and not matching your nutrition to those demands. You only have a limited blood volume and if you’re pushing the tempo, much of of it will be shunted to your working muscles. Because of this your digestive system will have a limited blood supply, won’t be able to deal with what you’re putting in and will shut down. If you try to consume more food or fluid, especially solids, this will just sit in your stomach, resulting in that familiar bloated feeling. Ultimately, if you hold trying to push on, your stomach will just eject its contents.


Like with all aspects of performance, you have to practice your nutritional strategy in training so that along with your pacing you’re 100% confident with it on race day. Ensure that your systems are in place to allow easy fueling. Are your gels easy to reach in your pack or are you confident removing a bar from your jersey and eating it while riding? All of these things should be practiced and refined in training. Find out how much fuel you can tolerate at race pace. This is pretty much an individual thing, a usual range is 30-60 g of carbohydrate per hour, but elite runners train themselves to tolerate 90-100g. Practice with different amounts and discover what suits you best.

energy gel_Gastrointestinal Distress
A common mistake is to train on one brand of products and then at an event use the brand provided at aid stations with disastrous results.


Once you’ve discovered what works for you, stick with it. A common mistake is to train on one brand of products and then at an event use the brand provided at aid stations with disastrous results. Do some research to find out what’s on offer, try it in training and, if you don’t get on with it, develop a more self-sufficient approach. Even minor differences, such as a higher proportion of fructose than you’re used to, can cause distress, so don’t risk it. Additionally, if you know that two gels per hour works for you in training, don’t switch to one or three on race day. Set an alarm on your watch or bike computer and follow your tried and tested routine.


It doesn’t matter if you’re running or riding, you don’t want to be consume anything during difficult climbs. At higher intensities your body won’t cope with it. It’s better to fuel on flat or downhill sections, so gather information about the route. Don’t forget that even the fastest acting gels will take 10-15 minutes to start working, so take this into account. Eat little and often from the beginning of a long race and don’t let excitement cause you to miss early feeds. If you want to catch up later, this is often a recipe for stomach problems. Set an alarm as a reminder. In triathlons, especially in long course and Ironman events, much of your day’s calories should be consumed during riding. Work on this yourself, because it’s very likely your body won’t tolerate solids on the run and you’ll be relying on those bike-banked calories.


Finding a pre-race meal that works for you is something that you have to practice in training. Avoid anything that could slow down the transit of food through your gut. Avoid high levels of fat, so if you go for the endurance athlete’s staple of pasta, don’t decide for red meat, creamy or cheesy sauces. Reduce fibre and don’t eat large quantities of gas producing vegetables such as cabbage, broccoli or cauliflower. You can consume some lean protein, such as chicken or turkey but in moderate amounts. In addition, you should avoid heavily spiced food: a pre-event curry is rarely a good idea.


This in another aspect of your race day nutrition strategy that you havo to nail in training. All of what applies to your night before meal applies to your breakfast. Make sure you leave enough time for your breakfast to digest. Two to three hours is best, and the more intense your race, the more important this period of time is.

Hygiene is highly important_Gastrointestinal Distress
Hygiene is highly important.


Hygiene is highly important. Don’t forget to clean and sterilize your water bottles or bladder after every use, especially if you drank a sugary energy drink. Don’t leave them in the back of your car or your pack to ferment, but clean them as soon as you get home. On the bike, road spray can contaminate your bottle so if the roads are very dirty, squeeze a small amount of liquid out before you drink to clear the nozzle and squirt into your mouth rather than sucking. Heavy endurance training can decrease your immunity so be careful and always wash your hands, particularly in public places. Carrying a small bottle of anti-bacterial hand gel may appear excessive to you but if you’ve put in months of training, picking up a bug could easily ruin your event. Both vitamins D and C can give your immune system a bit of a boost. If you’re travelling to a race abroad, all the usual rules for avoiding bugs apply. Avoid salads and buffets and avoid everything you can’t boil, cook or peel.

If you find yourself still experiencing gastrointestinal distress after having followed all these tips, you should go to see the doctor. You may need to rule out conditions such as IBS, Coeliac or Chrohn’s disease.

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Written by Kyra Williams

Kyra Williams likes to say in a joke that she preferred running to walking already as a child. Regular running has always been part of her life and she has joined several running events. She loves long runs with her loyal playful companion Vicky, Brittany Spaniel, in the early morning or in the evening.


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