You’ve put in the long runs. You’ve shown up for sunrise speed work. You even turned in early a few nights to make sure you got enough shut-eye.
Today is my day, you think as you approach the starting line.
Not so fast, rumbles your stomach, the archenemy of so many runners.
Take comfort in knowing that you’re not alone in your poop plight. A recently published study in the Human Kinetics Journal found that, during a 30-day period, male runners reported at least one symptom of GI distress on 84 percent of runs. Women, meanwhile, faced GI issues 78.3 percent of the time. Why? Because running, unlike cycling or swimming, includes a whole lot of jostling, says Patrick Wilson, an assistant professor of human motion sciences at Old Dominion University, in Virginia, and the lead author of the paper. “In addition, gut blood flow is compromised during high-intensity and prolonged exercise, which can ultimately cause dysfunction and damage to the GI tract.” The gut-wrenching trio of vigorous movement, compromised blood flow, and race-day nerves signals your body to rid itself of excess weight the only way it knows how. Before you know it, you’re looking for a tree to duck behind.
While GI distress is common—especially in runners—it’s also highly individual, both in how it presents and in how severely you suffer. Wilson says that a range of factors, including anatomy, genetics, propensity for nerves, and even some lifestyle choices such as diet and sleep patterns contribute to your own personal likelihood of uncomfortable (and highly inconvenient) stomach issues. This is why some lucky souls crush burritos at ultra aid stations while others are left to looking on longingly, knowing that even a single bite could wreak havoc on their insides all the way to the finish line.
For races longer than an hour, the research is clear: consuming fuel, especially carbohydrates, improves performance and is key to keeping your body revved. And while racing without fuel may alleviate your GI woes, bonking has its own set of miserable consequences. And the worst part is that you may not know until it’s too late.
Thankfully, there’s hope. According to Wilson, you don’t have to be at the mercy of your intestines. You can, at least to some degree, train your gut like you train your glutes and your lungs. Getting it right, however, takes time, work, and possibly some unpleasant experimentation. Here’s how to do it.
Step One: Play the Long Game
When you exercise, blood is directed away from your intestines to provide oxygen to muscles. Digestion is a lower priority. But how much blood is shunted from your gut can be altered by your level of fitness. Experienced runners lose less blood from their innards than newbies do, according to a couple of studies. In theory, just logging frequent training runs should help soothe your stomach.
Intensity factors in here, too. The harder you’re working, the more blood your legs, heart, and lungs demand. That, in turn, means there’s little left to help keep your digestive system humming. Speed work and racing at peak ability are much more likely to cause GI distress. That's why Eric Orton, an ultrarunning coach and author of The Cool Impossible: Run Beyond Limits, advocates eating during a race when your heart rate isn't approaching “overexcited jackhammer.” Having a good base of fitness means that you can recover much easier and get back below your lactate threshold, to an intensity where you can safely consume food, without jeopardizing your stomach’s ability to handle your fuel of choice.
Step Two: Practice with Carbs
Consuming carbs while training can make it easier to take them in on race day, according to a recent study in Applied Physiology, Nutrition, and Metabolism. Two groups started the experiment by doing a “gut-challenge test,” which paired relatively high-intensity running with the ingestion of carbs. Rates of GI distress were similar in the two groups. One group then spent two weeks training while ingesting mid-run glucose. The other group got a placebo without added fuel. At the end of the two weeks, the groups did a second gut-challenge test, which consisted of running while sucking a gel disk. The group that received the sugar boost in training reported fewer GI symptoms than their placebo-consuming peers, proving that practicing regular mid-workout carb infusions could actually strengthen your stomach. Wilson adds that some limited data shows that your gut can adjust to taking in fluids during exercise, too, although it's important to pick a drink with sugars that help your body function rather than cause further distress.
While the Applied Physiology study used a two-week interval to get runners accustomed to gels, Orton feels that it makes sense to start prepping during the first weeks of your training, when the runs are slower. “These are generally base-building runs, which is the time to try this,” he says, adding that experimenting with gels on a high-intensity-interval day is going to lead to ugly results. In other words, it’s never too early to start practicing even with small doses of mid-race fuel, to give your body ample time to adapt.
Step Three: Be Ready for It to Suck
Because it will. “There was a period when I hated every run, because I was experimenting with fuel. I felt like I was going to vomit every time I went out,” says Crystal Seaver, a Maine ultrarunner and the blogger behind Muscles and Miles. In her first ultra, she felt so sick when she tried to eat that she didn’t take in any fuel at all. “And that was a huge mistake,” she says. She needed a different strategy.
This is another reason why gut conditioning needs to happen early in a training cycle. A string of bad runs in the weeks before a race or even a few DNF results can screw with the mind of any athlete. Seaver says she had to remind herself that these bad runs were not a reflection of her fitness but simply a necessary evil she had to push through.
"It’s trial and error, and it’s not fun,” Seaver says. Orton agrees. A current client hopes to eat pizza at his next event, but his stomach hasn’t quite bought into the idea. “It worked for him one week but didn’t work so great the next week. Which is why you should try these things more than once.”
Step Four: Set Yourself Up for Success
“Poor nutritional choices definitely play a role in GI upset, and there are many potentially problematic strategies,” says Wilson. Too much of anything is one of those. Seaver found she could alleviate her misery if she ate only a single bite of food at a time instead of slamming a bar and powering on.
Not all carb-delivery methods are created equal, either. “Some runners have more issues with carbohydrate gels than liquids, and there is growing research to support the idea that gels cause more symptoms in a select group of athletes,” says Wilson. A 2016 paper in Sports Nutrition and Exercise Metabolism found that triathletes had more GI complaints when taking in gel-based energy instead of liquid fuel. However, there were no performance differences between the two groups.
If, like many endurance athletes, you get gel overload and often find the idea of sucking down one more sticky-sweet packet unbearable, it’s OK to branch out. Seaver knows that she can handle pretzels, and Orton says that chicken soup, broth, and salted potatoes can be reliable options, too. Try a few out at home; it’s really about finding what works for you.
Step Five: Don’t Do Anything Stupid on Race Day
If you’re prone to digestive woes, you’re probably never going to have an iron-clad stomach even with training. In fact, “the most consistent predictor of GI symptoms during a race is a history of those symptoms,” says Wilson. So practice the techniques above, but know that being careful on and before race day is important, too.
Excess fiber, fat, and protein, all of which slow digestion, should probably be avoided close to a race, too, says Wilson. He adds that some runners may also need to avoid Fodmaps, or short-chain carbohydrates that many people struggle to digest well. Surprise: a lot of the foods runners love fall into this category, including things like garlic, onions, wheat, cashews, and many types of fruit. And while coffee is fine before a race, just make sure you drink it early enough to, well, you know.