Sometimes, the only thing standing between you and a new PB is that pesky mid-race toilet break. And even if it’s not a full-on sprint to the bathroom, maybe the cold-sweat-inducing cramps that come with it are enough to keep you from a strong finish.

We chatted with top gastroenterologists for eight strategies for making it through your next race without these abysmal experiences happening to you. (No nappies required.)

1/ Add food and bathroom columns to your running log

“We are all different in how we react to specific foods,” says gastroenterologist Hardeep Singh. “The best thing to do is to track what foods you eat and how that correlates with your bowel movements in the weeks leading up to a race.”

This can help you identify foods that may cause you to run for the bushes during those training runs. Common triggers include lactose, sugar substitutes, wheat, gluten, soy, caffeine and eggs, Singh says.

2/ Improve your running form

It takes the average runner 1,000-plus strides to cover a single 0.5km. That equals a whole lot of intestinal jostling, literally shaking the crap right out of you, says Singh.

An easy way to decrease the trauma to your innards – and also improve your running economy – is to minimise your vertical oscillation, or how much your body bounces up and down with each stride.

On your next run, imagine that a ceiling is 2.5cm above your head; try not to hit it. Also, incorporating eccentric leg exercises into your strength-training routine – simply slow the “down” portion of exercises like squats or lunges – can help you to naturally minimise bounce. That’s because eccentric exercises strengthen your muscles while they lengthen – exactly what happens in your hips and calves every time your foot strikes the ground. So, when you increase your eccentric strength, you reduce how much your body drops (and bounces back up) with each foot strike.

3/ Taper your fat and fibre intake

One to two days before your race, reducing your intake of both nutrients can help to make sure that you don’t 1) have any more food than absolutely necessary hanging around in your GI tract when you cross the start line and 2) beeline anything you consume during the race all of the way through your intestines before you cross the finish line, says John Pandolfino, chief of gastroenterology and hepatology at a U.S hospital.

That’s because dietary fat slows digestion and is hard to break down in the gut. And, since blood flow is diverted from the gut and toward the muscles during exercise like running, you don’t want to make any midrace digestion more difficult than it needs to be. What’s more, while fibre is good during training to keep your bathroom habits regular, when combined with prerace jitters and race-length workouts, it can contribute to diarrhoea.

In the days immediately before your race, cut out any rich or fatty foods – such as creamy sauces, fried foods and potentially whole fat dairy – and switch from complex to simple carbs (yay for white bread!). Absolutely no cruciferous vegetables like broccoli and cauliflower the day before your run if it often brings trouble, he says.

4/ Tweak your caffeine routine

Many runners have a love-hate relationship with caffeine. While the fatigue-fighting compound can definitely improve exercise performance (why many running gels actually contain caffeine), it can also send your bowels into high gear, says Pandolfino.

FYI: a single pouch of GU Energy Gel contains up to 40 mg of caffeine, versus an 240ml cup of coffee, which contains 95 mg. Consumed every 30 to 60 minutes throughout a race like a half or full marathon, that adds up to a lot of caffeine.

Still, while the amount of caffeine each stomach can tolerate is unique, the gels might be a little easier on your stomach than pre-race shots of espresso. That’s because research also shows that various compounds in coffee (other than caffeine) increase the body’s levels of gastrin and cholecystokinin, two hormones that speed up how fast things move through the gut. Any coffee is usually best consumed at least an hour before start time, he says. That way, you have a good chance of completely emptying your system before you even set foot on pavement.

5/ Get your nerves in check

Butterflies in your stomach aren’t as pretty as they sound. “The brain and gut are directly wired to each other, and any stressor can contribute to a change in bowel habits,” says Singh. The best way to keep pre-race jitters from going straight to your gut is to eliminate any anxiety that you don’t find motivating or energising. After all, while a certain amount of adrenaline can be helpful during a race, too much can make you feel like (and go for a) Number 2.

Everything from taking slow, deep breaths to laying out everything you need on race morning the night (or even two) before can help eliminate excessive stress. (Check out more tips for pre-race stress relief.)

6/ Schedule a pre-race toilet trip

“If you can get on a regular schedule, ideally you should try to time it so that you have a good healthy bowel movement a few hours prior to race time,” Singh says. That way, you’ll have the least amount of food in your system during the race. Running causes your body to divert blood from your GI tract to your muscles, which, if you have much of anything in your system, can contribute to diarrhoea.

7/ Slow down your fuelling

“In general, eating and drinking slowly during a race is helpful at preventing gastrointestinal distress,” Singh says. Sipping and nibbling slowly allows your gut to absorb nutrients efficiently with as little work as possible and minimises any stomach grumbling. What’s more, quick eating or gulping generally involves swallowing some air, which can lead to gas, cramps and, eventually, a bathroom break.

That said, it’s important to avoid under-fuelling. When you reduce how much you eat or drink during every fuelling session, make sure that you increase feeding frequency proportionally.

8/ Consider a prophylactic

“For some people, taking an over-the-counter anti-diarrhoeal medication before a big race isn’t a bad idea,” says Pandolfino, noting that any pills should be part of a last-ditch effort when nothing else seems to work.

Still, you shouldn’t try them out for the first time the morning of your marathon, either. Try taking your preferred anti-diarrhoeal treatment (start with a half or quarter dose) immediately before a long training run and tweak how much you take and when from there to determine what works best for you, he says. While, ideally, you shouldn’t need to go during the race, you should be “regular” both before and after your race.

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