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Why does my stomach hurt when I’m running?

I will be bold enough to submit that EVERY runner’s greatest fear (even before loose dogs and speeding cars) is stomach trouble. Side stitches, vomiting, diarrhea, cramps; nothing can make a good race go south quite like your guts. Some people are more prone to stomach upset than others, but few, if any, are immune. 

Exercise causes blood flow to be redirected from your digestive system to your muscles. This, along with changes in hormones and gastric movement rates are the main culprits in stomach sensitivity while running. There’s not much you can do about these physical factors so you have to find the right way to cater to your irate belly. Fortunately, there are ways to mitigate the bubble guts while exercising. 

Nix the NSAIDs

While Non-steroidal anti-inflammatory drugs (such as Advil or Motrin) may help you temporarily with achy joints and muscle pain, they can do a number on your stomach. They act by blocking certain enzymes that lead to inflammation, but these enzymes also play a role in protecting your gut lining. Regular use of NSAIDS can lead to bacterial imbalances and even ulcers in your stomach. If you have to take them, wait until after your race.

Hydrate properly

The smooth muscles of your stomach and intestines cannot function without being hydrated. It can get a little bit tricky though. Too much water can actually irritate your stomach more when you are really putting the pedal to the metal on a run. Make sure to hydrate throughout the day and use an electrolyte drink before, during and after your run. 

Keep up with your electrolytes

You know that you sweat out electrolytes and need to replace them to perform your best. Electrolytes are key to your gut’s ability to absorb hydration. Many sports drinks are too high in sugars and too low in electrolytes to move fluid effectively through your gut and out into your bloodstream. Remember learning about osmosis in high school? Molecules (like electrolytes) in a solvent tend to pass through membranes (like your gut lining) from a less concentrated solution into a more concentrated one. Too much sugar in your gut can actually draw fluid INTO your stomach, where you don’t want it.

Don’t eat a big meal within 2 hours of racing

This can mean that you might actually need to get up earlier before a race to eat. (As an added bonus this will give you more quality time with the bathroom and possibly keep you from having to stand in a massive line at the race start porta potties) You’ll also want to stick to foods that aren’t too spicy, greasy, high in fiber or fat the night before your race.  Choose foods that are familiar and that you know will make you feel good the next day. How do you know what those foods are? 

Practice your fueling strategy

Use the nutrition you plan to race with on every long run. EVERY LONG RUN. Even if you are trying to cut back on your overall calories, fuel for your long runs is not the place to cut. Learn how to avoid the bonk. Not only will this help you determine what does and does not work for your stomach, it also helps your body get used to fueling on the go. Practice will help you figure out your ideal fuel timing too. Pay attention during training to how the meals you eat the day before affect today’s workouts. Everyone’s nutritional needs vary, so it’s important to figure out exactly what works best for you. 

Know your sugars

Not all sports nutrition products are created equal. Pay attention to the type of sugar they contain. Some may aggravate your gut. Sucrose is the scientific name for sugar, typically derived from sugar cane or sugar beets. Fructose and glucose are the simple sugars (monosaccharides)  that make up sucrose, however; they act differently in your body. Glucose in processed foods is frequently added in the form of Dextrose which is derived from corn. Some studies have shown that Fructose may be the most harmful of the processed sugars. It can increase the risk of type 2 diabetes and may even increase the hunger hormone ghrelin. 

Be a label reader and compare the way different varieties of sugar affect your stomach and performance. 

  Keeping your stomach happy while running hard definitely takes some trial and error. Be your own scientist during training and see what helps you the most. It may vary some based on your race distance and environmental factors like heat and humidity. It’s always a good idea to control what you can. And if all else fails, here’s a piece of advice I received early in my running career and have followed since: Always pack an extra pair of shorts. 

By USAT Level 1 Coach Kara Sasser