

Gastrointestinal issues and gut training
Gastrointestinal (GI) problems affect many athletes in endurance events, and it's a major cause of DNFs in races.
You may be surprised that GI distress manifests in many different ways. For starters, we can split the GI tract into two sections: upper and lower.
The upper GI tract includes the mouth, oesophagus, stomach and the first part of the small intestine - the duodenum. Upper GI symptoms can include stomach pain and/or cramps, heart burn, regurgitation, and burping.
The lower GI tract includes the rest of the small intestine, the large intestine, right until, well ... the end.
Lower GI symptoms could be abdominal pain, bloating, or diarrhoea. Further related symptoms such as dizziness, nausea, and an inability to keep down food can make a race a nightmarish experience.
There are many factors that exacerbate GI issues. Some are extrinsic to you - such as the type of exercise (the running motion can be more upsetting than cycling, for example), the climate, and the intensity and duration of your exercise.
Medicines like aspirin and ibuprofen can damage the gut lining. And of course, various foods can upset your stomach too.
Then there are intrinsic aspects: your current fitness, whether you've had a recent gastrointestinal infection, or you have an inflammatory disorder or disease of the digestive tract.
When we exercise, our digestive tract is put under a stress of sorts. First, blood flow to the abdomen is reduce, because your muscles are competing for blood and oxygen. Your body also releases stress hormones which reduce the wave-like motion in your small intestine. That is, your digestion slows.
Over the duration of prolonged exercise, this will cause an injury to your gut inner lining and will impact your body's ability to digest and absorb nutrients. This leads to all the symptoms we talked about earlier like stomach or abdominal pain, bloating, and so on.
The good news is that it's possible to 'train your gut' to reduce GI issues and improve the absorption and delivery of nutrients to your muscles.
Gut Training Advice
Happy training!
Other resources
We're here to help you on your sports nutrition journey.
For more tips on Nutrition and Recipes, check out the dedicated corner of our Journal here.
Read more on recent research into the area of gut training.
And if you're planning your nutrition for a long endurance sports event, this is a must read.