A side stitch—also known as a side ache or a cramp—is an intense stabbing pain in your side that occurs during exercise. Sometimes the pain goes away during your workout, and sometimes it sticks around until you stop exercising altogether.

Whatever the case, side stitches are frustrating. But what causes side stitches, and is here a way to prevent them? Here’s what to know.

What Causes a Side Stitch?

About 70 percent of runners experience at least one instance of exercise-related transient abdominal pain (ETAP) each year. The condition seems to be most common in runners, although bikers, swimmers, and other exercise lovers also report incidences of it.

As common as side stitches are, scientists still aren’t sure exactly what causes them. Some believe it has to do with the overuse of the diaphragm muscle, which is crucial to the breathing process and is therefore heavily relied upon by runners. Repeatedly hitting one’s feet against the ground while the diaphragm is fully expanded may cause the muscle to spasm and cramp.

Other scientists believe the condition may be caused when organs start to bounce around during intense exercise. However, this theory doesn’t hold much weight though, because bikers and swimmers often maintain good posture and still get side stitches.

More theories as to what causes side stitches include having an increased curvature of the spine, drinking sugary beverages before exercising, skipping warmups before exercising, and employing improper breathing techniques.

But the most likely explanation points to the lining of the abdominal and pelvic cavity known as the peritoneum. This membrane helps to support all the organs in the body. Normally, fluid between the separate layers ensures that they don’t rub against each other. But after a person eats a large meal, the layers expand and press against each other. And, when the body is dehydrated, less fluid is available between the layers.

Ultimately, both of these factors may contribute to the layers rubbing against each other, which causes the sharp pain associated with a side stitch. Many athletes also report shoulder pain during a side stitch, which fits in with this theory because when the abdominal lining is irritated, pain may be localized in other parts of the body.

How Do You Treat Side Stitches?

The easiest way to treat a side stitch is to stop exercising until it passes.

The pain usually subsides within minutes after the body relaxes. However, if you must keep exercising (if you’re in a competition, for example), breathe deeply and exhale slowly. Regulating your breathing can help relax the body and thus may limit uncomfortable rubbing.

How Do You Prevent Side Stitches?

Don’t eat for at least two or three hours before working out, although you may need to extend this time if you still experience problems within this timeframe. Avoid high-fiber and high-fat foods before exercising. Don’t drink sugary beverages either before or during your workout. Take note of what you eat and drink before running or biking and use that information to make adjustments until you find something that works for you.

Increasing core muscle strength may also help reduce the frequency of side stitches and improve your posture as well. If you’ve tried everything but are still experiencing side stitches often, visit a doctor to see if you have an underlying condition that’s contributing to the pain.

If you’ve been experiencing side stitches, they’re a fairly common occurrence among those who work out regularly. However, if you believe your side stitches are worsening or might be caused by an underlying condition, it’s best to speak to your physician.