Lately, William and I have been taking weekend adventure runs, meaning we’ve been getting out of town for a good part of the day to run somewhere new. Often this is followed by a picnic with a very runner-favorite spread: PB&J sandwiches, fruit, and tortilla chips. A couple weekends ago, the route I chose was based on being new and not far to drive, and as such it was on a course that’s designed more for mountain biking. After three miles of steady running upwards amidst the giant forest foxgloves and complete peace that is running away from civilization, we got to our summit and the single-track mountain biking descent. It started out as a really fun, fairly technical terrain with lots of creek rocks, tree roots, twisty trails and garden-gnome spotting. But there were also steady, heavy mountain biking moguls, making every bit of downhill come with nearly the same in little uphill rollers.
By about halfway through the downhill, I had this experiential memory of being on a carnival ride, and I was unsurprised to find my digestive system was feeling jostled in just the same way. By the end of the fourth and final mile of downhill, I realized I’d taken for granted that the norm for runners is to cruise and ‘wheee!’ downhill once the climbing is done. And I’d gladly take that steady climb over the tumbling in my lower GI and the muscle fatigue setting in from all those rollers.
My carnival belly largely went away for the day once I stopped running and had a meal, but it was mildly painful and upset for a day or two afterwards. Relatedly, this week our annual relay team has taken the very different challenge of racing the 2020 relay race virtually, and because this race coincides with the hottest stretches of heat year after year (and no different this year), I had that same mild carnival belly throughout the day yesterday after a hard race effort in the morning heat that was quickly becoming uncomfortable. Similarly to the week before, the discomfort was mostly gone again within a few hours.
So What’s With the Carnival Belly From Exercise, and in Running Particularly?
When we exercise, our body directs blood flow away from the gastrointestinal tract and to the working muscles. This reduction in blood flow, accompanied by an increased release of stress hormones during higher intensity or long exercise efforts, as well as the high impact of running (just visualize the internal organs being jostled up and down as we run), all combine to cause damage to the cheesecloth-thin lining to the gut, leading to all sorts of uncomfortable symptoms, as well as impaired digestion and absorption of food and drinks.
And yes, all of this is fairly normal in small amounts given the nature of doing long or hard exercise bouts. When we are dehydrated (a big topic in itself for another day) and/or exercise in the heat or to an extent that we have a high body temperature, we further reduce blood flow to the GI system, increasing stress hormone release, and develop a higher likelihood of digestive distress. But what might be a small amount of discomfort and upset sometimes should not lead to or be confused with frequently occurring and/or greater than mild GI symptoms.
What Can We Do For MILD GI upset?
Rather than grimace and bear it, there are many nutritional and training strategies we can do to minimize GI distress. Primary strategies include being properly hydrated in the 24 hours before / after exercising, especially in the summer heat, as well as training the gut. Just like other aspects of the body, we can train our gut to tolerate different types of foods, fuels, and amounts. Other helpful tactics include avoiding NSAIDS around exercise (as frequent use negatively impacts the gut), and eating and drinking smaller and more frequent amounts during exercise–this method alone helps alot with optimizing absorption and reducing upset.
But what about when that GI ‘offness’ or tummy upset isn’t just mild, and it continues long-term or occurs frequently?
That’s what I’d love to ask about today. Having chronic or frequent digestive symptoms including nausea, GI pain or cramping, reflux, lack of appetite (in general or after exercise), bloating, gas, diarrhea, constipation, loose stools with undigested food, or limited food choices due to reacting to many foods are all big warning signs, kind of like our body’s version of a flashing yellow or red light telling us to proceed with caution, or just plain stop and seek to understand what’s going on.
Rather than address any of those symptoms individually or all together, I’d actually first like to know how common those symptoms are–so I’ve created an anonymous survey for you to tell me about them.
If you’ve followed along here longer term, you’ll know I write about digestion a lot as it’s one of a few factors that finally pushed me into clinical nutrition, and it’s honestly my favorite nutrition topic to help others with–partly due to my own challenges over the years, but also because it can be complicated and I love a good challenge.
So if you’d please, fill out the quick survey for me and I’ll see if I can share about any of those flashing yellow or red symptoms that can cause us distress in or out of exercise in the coming weeks.
Costa, R.J.S., Miall, A., Khoo, A., Rauch, C., Snipe, R.,…and 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.
Costa, R.J.S., Snipe, R., Kitic, C.M., and Gibson, P.R. (2017). Systematic Review: Exercise-induced gastrointestinal syndrome-implications for health and intestinal disease.
Snipe, R. (2018). Exertional heat stress-induced gastrointestinal perturbations: Prevention and management strategies.