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What Happens to Your Stomach When You Ride

From digesting cookies to sometimes tossing cookies, your belly is really busy when you're on the bike

by selene yeager
cyclist riding
tony pedula

Your leg muscles might function as your cycling powerhouse, but that balloon-like organ in your core is what makes it possible to keep them going. Being tuned in to the goings-on of your stomach while riding will not only make you a smarter eater on the bike, but it'll also keep you protected against ride-ending bummers like gastric distress.

Here is what your gut goes through on a ride, from when you saddle up to when sprint home.

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Blood Gets Scarce

blood flowing to heart

We’ve all heard of “fight or flight”—that adrenaline-boosted state we enter when faced with a stressful challenge. The flipside of that is “rest and digest,” because your body isn’t really equipped to do everything at once.

When you start exercising, blood flows away from your gastrointestinal tract and into your muscles and lungs. The harder you ride, the less blood there is available for digestion—research shows that when you’re out hammering at your max, blood flow to your gut plummets by 80 percent.

That's why going super hard for too long can leave you hurling your cookies: Your stomach doesn’t have enough blood and oxygen to digest what’s in there... so it gets rid of it. That’s also why you want to give yourself time—at least an hour, preferably longer—to digest a meal before you go out for a hard ride.

RELATED: Tips to Keep Your Stomach Happy on Every Ride

Digestive Muscles Relax

stomach acid reflux

During normal digestion, the food you chew and swallow is moved along your digestive tract by rhythmic contractions called peristalsis in a biological process called gastric motility. As your digestive muscles are called off duty during exercise, this system can go a little haywire, leaving you with decreased motility and setting the stage for reflux—where your stomach acid starts coming up the wrong way and giving you heartburn.

RELATED: 7 Weird Things That Happen to Your Body When You Ride

A survey of more than 600 endurance athletes found that 67 percent of cyclists—more than runners and triathletes—suffered acid reflux.

“Cyclists may be even more susceptible because of their hunched over position on the bike,” says Leslie Bonci, MPH, RD, sports nutritionist at Pittsburgh based company Active Eating Advice and author of the American Dietetic Association Guide to Better Digestion.

If this problem plagues you, eat smaller amounts more frequently while on long rides and consider taking an antacid, such as Tums, prophylactically before you roll out.

You Stomach Dehydrates

dry dehydrate

Here’s another reason to stay properly hydrated. Dehydration not only exacerbates GI distress symptoms, but also your body will draw water from your digestive tract when there’s not enough to go around—leaving you with more problems, like constipation. Aim to drink a bottle of hydrating fluid like a sports drink each hour you’re out riding.

RELATED: What Happens to Your Lungs When You Ride

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You Spring a Leak

leaky gut

Your gut is lined with a thin mucosal barrier that works as a two-way gatekeeper, allowing you to absorb nutrients while preventing germs from inside the gut to enter your bloodstream. Strenuous exercise, particularly in the heat, can make this barrier more permeable, leading to a condition known as leaky gut.

Keeping your gut healthy with probiotic-rich foods like yogurt, kefir, and fermented foods can help. Also, avoid non-steroidal anti-inflammatory drugs like ibuprofen, which studies show can damage your gut.

RELATED: How Riding the Tour de France Changes Cyclists' Bodies

Your Stomach Adapts

steel stomach

Research shows that people who aren’t accustomed to eating and drinking during exercise have twice the risk of developing GI symptoms. You can—and should—train your gut just as you train your other muscles, says Bonci.

“[Your digestive system] can acclimate to activity and become better able to tolerate fluid, carbohydrate, even protein and fat for longer-duration activity with less discomfort,” she says. As a bonus, you’ll be able to deliver more much-needed nutrients to your working muscles.

RELATED: How to Eat Light on Your Bike

Gut Flora Bloom

gut blora bloom

A study of athletes published in the journal Gut recently reported that athletes have a higher diversity of gut microorganisms than their sedentary peers. Animal studies show that exercise has a favorable impact on your gut flora, which can help prevent diseases as well as improve your overall digestive health.

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Your Stomach Gets Healthier

happy healthy stomach digestive system

Though your gut may not always agree with you when you’re out there pushing it to its limits, it will generally be happier with you for riding regularly.

RELATED: 5 Reasons You Should Be Riding Every Day

Regular aerobic exercise like cycling has been found to help prevent colon cancer and protect against other digestive diseases and conditions such as diverticular disease and constipation.

Headshot of selene yeager
selene yeager
“The Fit Chick”
Selene Yeager is a top-selling professional health and fitness writer who lives what she writes as a NASM certified personal trainer, USA Cycling certified coach, Pn1 certified nutrition coach, pro licensed off road racer, and All-American Ironman triathlete.
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