There’s nothing like an annoying, sharp side stitch to zap your energy and suck the fun out of your run. You might find comfort in knowing you’re not suffering alone: Seventy percent of runners report experiencing exercise-related transient abdominal pain (ETAP)—a.k.a. side stitches—while training, reports a new review in the journal Sports Medicine.

Despite how common side stitches are, though, there has never been definitive proof for why they occur. So we asked experts to weigh in on the possible reasons why ETAP happens—and how you can stop it in its tracks.


You might be able to blame your diaphragm—a dome-shaped muscle that expands and contracts with each breath—for the ache in your side, says Jordan Metzl, M.D., and author of The Athlete’s Book of Home Remedies.

If you’re new to running or you’ve suddenly increased your training, you can tax your diaphragm just like any other muscle, he says. This can cause a spasm in the respiratory muscle that translates into a stinging cramp in your abdomen.

How to fix it: The first thing you should do while still running is to raise the arm that’s on the same side as the cramp and place your hand on the back of your head, says Dr. Metzl. This stretches your diaphragm in an attempt to stop those firing muscle contractions from slowing you down. If you need a deeper stretch, stop running and bend your torso in the opposite direction of the pain. Hold this position for 30 to 60 seconds.


Your body needs more oxygen to fuel your muscles when you tire during a run. But when you’re gassed, you’ll find yourself taking shorter and shallower breaths, says Jeff Gaudette, head coach and owner of

Keep huffing and puffing with short breaths over several miles, and this can piss off an already overworked diaphragm and its surrounding ligaments—hitting you with a nasty stitch to signal you need to slow down and get more air.

How to fix it: Try switching up you’re breathing pattern so you take in more air over the long haul. It can be tricky at first, says Gaudette, but you can extend your deep inhalation by taking a full belly-breath to a count of three and blowing out through pursed lips for a count of two. Keep repeating that pattern when trying to run through oncoming pain.


Running with a water balloon in your stomach is a bad idea, yet plenty of guys overhydrate before a workout or race, says Nancy Clark, R.D., a Boston-based sports nutritionist and author ofNancy Clark’s Sports Nutrition Guidebook.

“The weight of a full stomach tugs on the ligaments that hold the stomach in place, causing the cramp,” she says. The same goes with eating too much food before a run, especially those full of fiber or protein that take longer to digest.

Previous studies have found that drinking too much of anyfluid right before a bout of running increased side stitches for most runners tested.  But ETAP was worse if study participants had a sugar-sweetened beverage like a fruit juice before the run. While it wasn’t as severe, sports drinks caused slightly more side cramping than water.

How to fix it: Avoid drinking a lot of fluid two hours prior to a run or a race, says Clark. If you feel thirsty before a run, limit yourself a half-cup of water or sports drink. It also helps to write down what you ate and drank prior to your run so you can spot patterns that might cause attacks, Clark says.


Runners who had more forward slouching postures were more likely to get side stitches, reported a study in The Journal of Science and Medicine in Sport. The reason stitches become more severe as you slouch may be because you put more strain on the peritoneum, a membrane that lines the abdominal cavity.

How to fix it: As you run out of gas, you’re more likely to lean forward from the waist, says Gaudette. In order breathe deep from your diaphragm, you need to correct your posture and run tall.

Cue yourself to run tall by swinging both arms  straight behind you—like you’re pushing a wall behind you—and holding for a few seconds. You’ll feel your chest muscles instantly open up. You could also visualize that there’s a piece of string tied to your head and somebody in front of you is pulling up on it.