Exactly Why You Get a Stomach Ache After a Workout

When GI problems pop up mid-workout, things can get messy in a hurry.

Why Some Workouts Make You Feel Like Throwing Up
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If you spend enough time running, biking, or hiking in the great outdoors, you learn to get comfortable with bodily functions not discussed in polite conversation. But no matter how seasoned you may be, coming to terms with a queasy stomach (often, an upset stomach after workouts) isn't easy. Those who've dashed for the Porta-Potty or thought they were going to get sick during CrossFit know just the feeling.

If it's any consolation, you're not alone. According to a study in Current Sports Medicine Reports, up to 70 percent of athletes deal with GI problems. Other experts put the number even higher. "About 95 percent of my clients experience some GI problem over the course of their career," says Krista Austin, Ph.D., a coach and founder of Performance and Nutrition Coaching in Colorado Springs, Colorado. The most frequent symptoms read like a Pepto-Bismol jingle: nausea, heartburn, indigestion, and diarrhea.

Who Is More Likely to Suffer From Stomach Aches After Exercise?

According to gastroenterologist and professor of medicine at Harvard Medical School, J. Thomas LaMont, M.D., woman may be more likely than men to suffer from post-exercise stomach aches. "Out of the 25,000 patients we see each year, 60 percent are women, and they outnumber men in diagnoses of functional GI disorders, like irritable bowel syndrome," says Dr. LaMont. "Exercise, especially running, tends to bring out symptoms." And though gastrointestinal distress isn't usually a health threat, these embarrassing symptoms can prevent sufferers from getting help and discourage them from exercising altogether.

So, if you find yourself wondering why your stomach hurts after working out, here's what you need to know: When you begin your workout, the muscles you're relying on most (e.g. your quads during a run) compete with your internal organs for blood. Your organs need blood for digestion; your muscles need it for strength as you exercise. (ICYMI, here's the real difference between muscle strength and muscle endurance.) Because the energy demands of your quads are greater, your organs lose out and your body directs a majority of its blood flow to your legs. In turn, the gastrointestinal system is left with fewer resources with which to digest the food and water you've taken in before or during your workout.

This is why, even just 20 minutes in, you may start feeling nauseous during your workout. "Some people can exercise comfortably after wolfing down a meal 15 minutes before a workout. Others can't eat anything within two hours or they'll feel bloated and sluggish," says Bob Murray, Ph.D., founder of Sports Science Insights, a consulting group that specializes in exercise science and sports nutrition in Fox River Grove, Illinois.

Possible Causes — and Solutions — for Stomach Aches During and After Workouts

Take a look at some of the things that are commonly thought to increase your chance of nausea and ways you can avoid this awful feeling in the future.

Anti-Inflammatory Medication

Although it's always important to take the recommended dosage of any medication, pay close attention to your intake of anti-inflammatory medicines; excessive amounts of NSAIDs, like ibuprofen or naproxen can cause nausea, says Daphne Scott, M.D., a primary care sports medicine physician at the Hospital for Special Surgery in New York City. So while it may be tempting to muffle your knee pain with OTC anti-inflammatories to get you through that tough workout, one too many can leave you feeling sick.

What to do: Never take more than recommended on the box or prescribed by your doctor. And if taking an anti-inflammatory, do so post-workout instead. You can also try eating one of these 15 anti-inflammatory foods to tame inflammation naturally.

Exercise Intensity

Surprisingly, exercise-induced nausea can happen at any speed and at any intensity. Dr. Scott says that high-intensity exercise can increase your chance of nausea during workouts due to the sheer fact that the harder you work, the more you ask of your body; however, nausea can occur at any intensity level. "This is thought to be partly due to conditioning level," she says, but emotions and anxiety play a large role too. "If you're stressed or excited about a competition, or if you're trying a new gym or new exercise routine, the nervous excitement could cause you to be nauseous during or lead to an upset stomach after workouts."

What to do: At the gym? Reduce your speed or resistance until the feeling subsides — usually fairly quickly after you slow down or stop moving, says Dr. Scott. In class? Dr. Scott recommends simply taking a step back, slowing down, and rejoining the group once you feel better. Stop internally competing with yourself; if you get sick, no one wins.

Fitness Level

Although it's reasonable to assume exercise-induced nausea can occur if a beginner pushes themselves too hard, too fast, overall the phenomenon is not prejudiced to any skill level. In fact, GI distress is relatively common among endurance athletes such as marathon runners or long-distance cyclists — some of the most "in shape" athletes in the world. One study published in the journal Appetite tested subjects of different genders and conditioning levels, asking them to fast, eat right before, or eat directly after exercise and found that food intake and intensity level affected nausea during workouts, but gender and conditioning level did not. "Training did not decrease exercise-induced nausea," reported the researchers.

What to do: Progress through your fitness level in stages. Don't try an expert-level kickboxing class if you've never tried the technique before. There's no shame in starting from the bottom—only up from there!


During exercise, blood flows away from your gut, towards larger working muscles. Problem is, inadequate hydration affects the volume of blood pumping through your body, which can exacerbate that GI distress and gut immobility — aka that stomach ache after a workout. Dehydration can come on quickly, especially during strenuous outdoor exercise.

What to do: This answer is as straightforward as it gets: drink more water, more often. And not just when you're exercising: "Be aware of your hydration throughout the week."


Perhaps one of the largest players in the workout-nausea game is eating before a workout. Having a large meal and going to boot camp shortly after is a fairly obvious recipe for a stomach ache after workouts. However, Dr. Scott says that skipping meals or not eating a satiating balance of protein and carbs can also play a role. Too full and your stomach won't have enough time to properly digest. Hungry? An empty gurgling stomach will have your water sloshing around in your stomach making waves. It may take some time to learn what's best for your stomach, as it's different for everyone.

What to do: Examine your pre-, during-, and post-workout eating habits. If you typically don't eat for a long time before a workout, try having a small snack 30 minutes to an hour before, says Dr. Scott. Conversely, if you tend to eat a lot before exercise, try to reduce the amount of food and replace it with a smaller amount of healthy fats, carbs, and protein such as nuts or nut butter on a piece of toast, she says.


You're familiar with the positive hormonal changes that occur with exercise (more endorphins! less cortisol!). But Dr. Scott says there are many different theories on how hormones may affect GI symptoms such as nausea during exercise. "One thought is that hormones are released from the brain and lead to a release of catecholamines (hormones released by the adrenal glands), which can then cause a delay in gastric emptying," she says.

What to do: Take a pause if you're feeling nauseous during your workout, then join the game when you're feeling better. You can still embrace these mental health benefits of exercise.

How to Deal With a Stomach Ache After Workouts

The key is to know which side effects are apt to accompany your favorite fitness activity and practice these smart strategies to minimize them.

Stomach Problems for Runners

  • Abdominal cramping
  • Diarrhea
  • Side stitches

All that pavement-pounding jostles the gastrointestinal tract and its contents, triggering lower GI problems. Numerous studies have found that about 50 percent of long-distance runners report problems such as cramping and diarrhea during the event. Side stitches (which vary anywhere from a dull cramp to a sharp stabbing pain in the side of your abdomen) are caused partly by "gravity and the natural movement of running, which strains connective tissues in the abdomen," says Murray.

Fix it fast: To redirect blood to your gut, slow your pace until your heart rate decreases to a comfortable level. For side stitches, change your stride, slow down, or twist your torso gently in the direction opposite your side ache. A true emergency? Find the nearest Porta-Potty or big tree. You won't be the first or the last to do so, trust.

Prevent it:

  • Hydrate. Drink 4-6 ounces of fluid every 15 to 20 minutes during your workout, alternating between water and sports drinks for longer sessions to replenish electrolytes, says Ilana Katz, R.D., a sports nutritionist in Atlanta.
  • Ditch the soda. Cola is sometimes used as pre-race drink thanks to the stimulating effects of its caffeine and sugar. But carbonated air bubbles cause bloating, says Katz.
  • Dodge the fat. Nix fatty meals a full day before a big workout because fat and fiber are digested more slowly than carbs or protein. Also, foods containing lactose (dairy), sorbitol (sugarless gum), and caffeine activate the GI tract. Avoid them starting four hours before your run, says Kevin Burroughs, M.D., a sports medicine doctor in Concord, North Carolina.

Stomach Problems for Bikers

  • Acid reflux
  • Indigestion

Up to 67 percent of cycle athletes get acid reflux, compared with about 10 percent of the general population, according to a study in Sports Med. It's common in cyclists because of their forward-leaning riding position, which increases pressure on the abdomen and can direct stomach acid back up the esophagus, says Carol L. Otis, M.D., a sports medicine physician in Portland, Oregon.

Fix it fast: Switch your position so that you sit more upright in the saddle. If possible, take a short break during your ride and walk for a few minutes. Stop eating and drinking until symptoms subside.

Prevent it:

  • Be proactive. Before you hit the road, consider taking an OTC antacid, such as Maalox or Mylanta, especially if you're prone to reflux. "The medicine protects the esophagus with a thin coating, lessening the burn if you have reflux problems while biking," says Dr. Otis.
  • Perfect your posture. Keeping your upper back flat instead of hunching over your handlebars decreases the pressure on your abs, says Dr. Burroughs. And make sure your seat is adjusted for your height: Too high or too low will alter your posture, increasing tension in the abdomen, leading to reflux.
  • Eat less. Energy bars and similar foods make easy snacks while cycling, but some bikers bite off more than their stomachs can comfortably handle. For rides of less than an hour, skip the snacks. More than 60 minutes? Consume 200 to 300 calories of simple carbs, such as sports drinks, gels, and bars, during each hour to help keep muscles fueled.

Stomach Problems for Swimmers

  • Abdominal cramping
  • Belching
  • Bloating
  • Nausea

"Some swimmers hold their breath without exhaling while their faces are underwater. This means that when they turn their heads to breathe, they have to exhale and inhale at the same time, which causes them to gulp and swallow air and water," says Mike Norman, co-founder of Chicago Endurance Sports, who trains swimmers and triathletes. A stomach full of air can lead to bloating; gulping water during saltwater swims can cause abdominal cramping.

Fix it fast: Most cramping and bloating occur during belly-down strokes (breast and freestyle), so flip onto your back and ease the pace until the pain subsides. Also, try treading water for a few minutes to keep your mouth above the surface, suggests Norman.

Prevent it:

  • Breathe better. Proper technique helps you access oxygen with less effort. You can dodge waves — and your competitors — by learning to breathe on both sides. When you turn your head to breathe, try looking under your armpit, not forward, to avoid getting a mouthful of water. Slowly exhale through your mouth when you return your face to the water.
  • Wear a cap. In an open-water swim, choppy, cold waters can cause disorientation and nausea. Using a swim cap or earplugs can help with balance problems.

Stomach Problems for Strength Trainers

  • Acid reflux
  • Indigestion

"Bearing down to lift a weight while holding your breath, which people often do during strength training, increases pressure on the stomach contents and can force acid up into the esophagus," says Dr. Otis. That leads to heartburn and indigestion. In fact, people who lift weights experience more reflux than those who engage in other sports, even cycling, according to research published in the journal Medicine & Science in Sports & Exercise.

Fix it fast: Pop an antacid mid-workout. Drinking water will also help wash acid down.

Prevent it:

  • Focus on form. Practice exhaling as you contract your muscles to lift the weight and inhaling as you release for each rep.
  • Sleep on a slant. Propping your head atop two pillows when you go to bed at night encourages acid to stay in the stomach. (Stick with one pillow if you're prone to back problems.)
  • Eat earlier. For some some people, last night's dinner may appear as tomorrow morning's workout heartburn. Digestion slows during sleep, so it's better to eat dinner four hours or more before bedtime.
  • Avoid trigger foods. Cut back on reflux aggravators, such as chocolate, citrus, coffee, peppermint, and onions.

Try These Natural Stomach Soothers

These herbs might help take the edge off workout-induced tummy upset. You can find them in capsule form at your health food store, but the simplest way to get your daily dose is to drink them in tea.

  • For gas and heartburn: Try chamomile. This pre-bedtime beverage may be a powerful anti-inflammatory. A cup of chamomile tea is used to soothe and calm the entire digestive tract.
  • For nausea: Try ginger. Ginger is believed to settle the stomach by suppressing gastric contractions and aiding digestion.
  • For cramps and diarrhea: Try peppermint. Peppermint has menthol, which may help control muscle spasms that lead to cramps and the urgent need to go to the bathroom.
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