Let’s face it — constipation sucks bad, even when you’re not training for an epic event. But when you’re headed to the starting line, feeling weighed down, lethargic and cramped isn’t just a bummer — it can directly interfere with your training progress, leading your pace to drag and your endurance to sputter.

“Constipation may also signal to your brain, via the gut-brain axis, that there is an imbalance. This may cause the body to continue to release hormones to the digestive tract rather than to your muscles to support exercise,” says Kelly Jones MS, RD, CSSD, LDN. And that means you won’t be at your best. The gut-brain relationship can also impact your stress level, making it harder to zone out and do your thing.

What’s Behind The Back Up?

Any number of things can cause constipation, making it hard to consistently prevent it. “Constipation can be a symptom of a digestive disorder, or it can be due to low fluid intake, low fiber intake, reduced activity level, too little sleep, changes in schedule due to traveling, high stress, and many medications,” says Jones.

If you’re racing in a new city, arrive as many days early as you can, to give your system time to acclimate. “It’s also helpful to train at the time you’ll be racing, so your body is primed for racing versus digesting at that time of day,” she says.

Get Your System Rolling Before The Race

If you need to get things moving and have at least a day, increase your water intake — by a lot. Constipation is often due to low fluid intake, keeping food from moving through the digestive tract effectively. “If your body doesn’t have access to the water it needs, it will pull it from the food waste in your large intestine. This results in harder stools that are difficult to pass,” says Sam Presicci, MCN, RD, LD, CPT, Lead Registered Dietitian at Snap Kitchen. Women should aim to slug at least 90 ounces daily and men about 120 ounces. (You read that right.)

And eat fibrous foods, like grains, greens, apples, and beans. “Both soluble and insoluble fiber help prevent constipation,” says Presicci. “Soluble fiber helps to make your stool softer, larger and easier to pass, and insoluble fiber adds bulk, which helps fecal material move through the gut easier.” Caveat: If you’re not used to eating fiber and suddenly load up, you’ll become more constipated while your body adjusts, so skip this tip.

High-magnesium foods, like nuts, grains, leafy greens, and seeds, also get things moving, as does a magnesium supplement. “I recommend one that is NSF certified for sport or Informed-Choice certified the night before the race. A bonus is that magnesium also helps some people fall asleep, says Jones.

And sleep in itself makes a difference, too, “Rest helps stress hormones stay in balance, which can impact digestive function,” says Jones. Aim for 7-8 hours the whole week before the race.

What to Do If Constipated: How to Do Your Business on Race Day

The morning of, you can’t beat adequate fluid intake, a healthy breakfast, and if it’s your usual habit, a nice big cup of coffee, which has laxative abilities. And reach for an apple. “Apples offer fiber, but they also contain pectin, which is fermented by bacteria in the gut to form short chain fatty acids that bring water into the colon, soften stool and decrease transit time,” says Presicci.

With any luck, you’ll build a log cabin before lacing up those sneakers.