There’s a reason porta potty lines rope around the block at running events: Most runners want to empty out their system before going out and running miles upon miles.

It’s a valid concern—not being able to go to the bathroom before a race means you may get hit with the urge mid-run, and in turn, cramps and gas or a need to pause mid-race and make a bathroom pit stop.

“The vertical movement of running causes things to move through the colon, so not going to the bathroom before a long run or race may increase the chances of feeling something you don't want to feel while you run,” says Jason Karp, PhD, a running coach and the owner of Run-Fit.

Fear not: We polled the experts on exactly what to do to get your bowels moving first thing (plus what not to do).

Do drink coffee

Hollis Lotharius, a coach at Mile High Run Club in New York City, swears by a cup of Joe to help prompt a bathroom run.

“I am one who likes to run ‘light,’” she says. “I have found that a strong cup of coffee is the best way to dump, pun intended, extra weight prior to stepping out the door.”

And it works, says Roshini Rajapaksa, MD, Health’s contributing medical editor and a gastroenterologist at NYU Langone Medical Center. “Caffeine is what we call a cathartic,” she explains. “It stimulates the colon to contract and works as a laxative for many people.”

For the non-coffee drinkers, Lotharius has tried and tested a healthy (and yummy) alternative that works for her. “Combine 1 to 2 tablespoons of coconut oil, 1 teaspoon of honey, juice from one fresh lemon, and some grated raw ginger in a mug of hot water,” she says.

Do give yourself plenty of time

“The problem is typically more about not having the time to go before the race start—because of long lines at the porta potties or getting to the race late—rather than not being able to go,” says Karp.

Unfortunately there’s no exact science to how long your body needs before being “ready” to have a bowel movement, Dr. Raj says. “But waking up extra early allows you to have enough time for the crucial steps of eating, having coffee, et cetera.”

Lotharius agrees: “I set my alarm clock an hour early,” she says. “I honestly believe that the one hour less of sleep is far better than the alternative.”

Do eat breakfast

Most people feel an urge to go to the bathroom after eating something, Dr. Raj says. “There is something cause the gastrocolic reflex,” she explains. “When you eat and the food moves into your stomach, there’s a reflex that stimulates your colon to contract a bit.”

The reflex may be more pronounced for some people than others, she adds, but having a bite first thing in the morning is a promising way to get things moving.

RELATED: The 20 Best Foods to Eat for Breakfast

Don’t park it on the toilet

It may be tempting to coax your body into going by sitting on the John for a while. But kicking back with a newspaper and waiting it out can end up doing more harm than good, Dr. Raj warns.

“First of all, if you’re sitting for a long time, that suggests that you’re not going naturally and you may be straining or pushing for a lot of that time,” she says. “Also, sitting in that position puts pressure on the veins within the anal area, which is what causes hemorrhoids.”

Instead, move about, eat breakfast, have your coffee and wait for the urge to set in. Then sit down for just a few minutes so that the bowel movement comes on its own.

Do fill up on fiber

Upping the fiber in your diet can help keep you regular and prevent constipation, Dr. Raj says (a smart move whether you’ve got a race looming or not).

Insoluble fiber is the matter in foods that doesn’t get broken down by the gut and absorbed by the bloodstream. It adds bulk to stool in the digestive system, which helps keep it passing through smoothly and frequently.

Increase your fiber intake far in advance of your race so that your body has time to get used to a higher intake if you normally don’t get enough (adults should aim to get between 21 and 38 grams of fiber per day, per the U.S. National Library of Medicine). Try adding one serving a week; eating lots of fiber in a short period of time can cause your GI tract to protest in the form of gas or cramping, issues you don’t want to deal with during a race.

Find insoluble fiber in whole grains, nuts, fruits, and vegetables. Prunes are particularly rich in fiber, with roughly 1 gram per prune. A heads up: Prunes also contain fructans and sorbitol, which are fermentable sugars that can have a laxative effect, so you’ll want to see how your body reacts at a time other than right before a race.

RELATED: 20 Best Foods for Fiber

Don’t try a laxative

…even if the label says something promising, like “gentle overnight relief.”

“Laxatives can end up having a painful effect, or they may work so strongly that you’re going for several hours or even the whole next day as opposed to the one, or maybe two, bowel movements that you were hoping for,” Dr. Raj says. “Especially if your body has never seen it before, it may have a super-strong reaction.”

The same goes for smooth-move teas, Dr. Raj adds, which can cause uncomfortable cramping or abdominal pain for some people.  

Do warm up

“Typically the more active you are, the more regular you’ll be,” Dr. Raj says. “And physical activity tends to bring more activity to the colon as well.”

That doesn’t necessarily mean doing 20 jumping jacks in your living room will suddenly spur the need to go number-two, she says. But stretching out, doing a dynamic warm up, and getting your body up and moving may be worth a shot.

RELATED: 6 Dynamic Stretches That Prep You for Any Workout

Don’t stress about it

Constipation can sometimes stem from stress and anxiety, Dr. Raj warns. “So sitting there worrying about whether or not you’ll be able to clear your system while the clock is ticking can definitely block you from going,” Dr. Raj says. Focus on getting your head in the game for your run, maybe try some deep breathing exercises, to take your mind off of your GI concerns.

And if your corral is creeping toward the start line and your poop is still a no show? That doesn’t mean your run is doomed. “I don’t really know why physiologically it would be such a big problem to not have emptied your bowels before a race,” Dr. Raj says. “It’s sort of like giving birth; women are always freaking out that they’re going to need to have a bowel movement midway through. But it rarely happens, even though people are so paranoid about it.”

Karp says the bummer is when you do get a strong urge to go in the middle of a race. “Having that feeling affects you physically and psychologically,” he says, be it in the form of cramps that you need to walk off or as extra stress on your mind about whether you’ll be able to finish without needing to stop for the bathroom.

But if you’ve got to go, you’ve got to go—and tacking on an extra minute to your time is better than having an accident or running in discomfort the whole way. “Don’t overthink it,” Dr. Raj says.

Do practice in advance

Curious about sipping prune juice the night before? Planning to add extra beans and spinach to your dinner plate to wake up and “go”? Take any poop-related tricks for a trial run (literally) weeks in advance, Dr. Raj suggests. You don’t want any surprises about how your body reacts to these changes on race day.

The bottom line: “Give yourself some peaceful time in the morning, and start any new poop-related habits far in advance so that your body has time to adjust and get in sync,” she says.