To eat on the go, endurance athletes need to train their stomachs

Among the lesser-known skills that ex-track star Mike Woods has picked up in his five years as a professional cyclist is the ability to scarf down an arborio rice cake loaded with sugar, coconut oil and cream cheese in the middle of the peloton, ideally before a sudden breakaway makes it too hard to eat and breathe at the same time.

"Going from running to cycling, there was a big learning curve in all aspects of the sport, and diet was certainly one of them," says Woods, a 30-year-old Ottawa native who turned to cycling in 2011 after a series of stress fractures derailed his running career.

On the track, Woods was a middle-distance specialist: his 3:57 mile from 2005 still stands as a Canadian junior record. But as a cyclist with top pro team Cannondale-Drapac, he's often competing for several hours at a time; his road race at last summer's Rio Olympics took more than six hours. That means refuelling on the go is crucial to his success – even though, as many would-be marathoners and cyclists discover, eating and hard exercise don't always mix well.

By some estimates, 30 to 50 per cent of endurance athletes regularly experience gastrointestinal problems, such as bloating, nausea, and diarrhea. One solution, according to a review published last month in the journal Sports Medicine, is "training the gut." Just as your muscles and heart, your digestive system can adapt and respond to repeated challenges, so that you can eat and run with fewer problems.

The idea that the gut is adaptable has long been recognized anecdotally, says Asker Jeukendrup, the author of the review, who is currently a visiting professor at Loughborough University in Britain and the head of mysportscience.com. That's how, for example, competitive eaters can eat 70 hot dogs in 10 minutes: by progressively stretching their stomachs through techniques such as drinking large volumes of fluid.

Jeukendrup has worked with athletes, including retired marathon great Haile Gebrselassie, driving alongside him during training runs in the mountains of Ethiopia and handing him bottles of concentrated carbohydrate solution, in an attempt to improve his ability to absorb carbohydrate on the run.

When Gebrselassie set his first marathon world record, in 2007, he was able to stomach far more fluid and carbohydrate than during his earlier attempts at the distance. Over the course of just over two hours, he downed two litres of sports drink and water, as well as six gels.

Training the gut focuses on two key goals, Jeukendrup explains. First, to reduce bloating and fullness, you want to ensure that food and fluid exits your stomach quickly. Training immediately after a meal, or while ingesting deliberately high volumes of fluid, will help speed stomach emptying. It will also likely reduce your perception of how full you feel, even if there's still fluid in your stomach.

Second, once the food and fluid have passed from the stomach to the small intestine, you want to speed its absorption into your bloodstream, where it can be quickly delivered to fuel-starved muscles. There are two key types of transporter that move carbohydrate across the intestinal wall; by training while consuming carbohydrate, you'll increase the number of these transporters in the intestine, as well as their efficiency.

In practice, one of the best ways to train your gut is to simulate your race plan in training. Start by figuring out how much fuel you're aiming for; for races longer than two hours, a goal of about 60 grams of carbohydrate per hour is ideal but challenging for most people. Then figure out how much you can tolerate in training – and gradually, over the course of weeks, push the limits of what you find comfortable and tolerable.

Ultimately, Jeukendrup notes, digestive challenges vary greatly between individuals. You may struggle to reach 60 grams an hour, but if gut training increases your limits from 20 to 40, that's still a significant gain. You can also experiment with different forms of fuel: while cyclists tend to favour a mix of solid and liquid food, most runners have trouble with solids due to the up-and-down jostling of the running motion.

For Woods, eating plain yogurt every morning and taking a sport supplement from Sound Probiotics has helped with digestion. And for the last two days before a race, he follows a low-residue "five-year-old's diet" with no vegetables, red meat, or other high-fibre foods, in order to reduce bloating.

During races, in addition to rice cakes, he'll receive a mid-race feedbag with a banana, an OTE sports bar, and perhaps a waffle filled with Nutella or speculoos. And he carries gels with him, which are easier to swallow when the pace is hard.

All that has taken a while to master. But then again, a CT scan after the Olympics revealed that Woods had raced on an undiagnosed fracture in his left femur, the consequence of a mass wipeout in the Tour of Poland earlier that summer. So compared to the intricacies of peloton etiquette and bike handling, maybe learning to eat Nutella waffles on a bike isn't such a tough job after all.

Alex Hutchinson's latest book is Which Comes First, Cardio or Weights? Follow him on Twitter @sweatscience