What Makes Your Side Hurt While Running?

Almost everyone who runs has experienced that pain in the side known a runner's stitch. Like a case of the hiccups, it can come on without warning and resolves itself sooner or later.

There's no consensus about what causes Runner's Stitch. (Image: Staras/iStock/Getty Images)

Perhaps compensating for their inability to agree on its cause -- let alone its cure --researchers have at least given the stitch a long and fancy name: exercise-related transient abdominal pain, or ETAP for short. Knowing more about ETAPS may or may not help you avoid it, but it will at least give you something else to talk about.

ETAP Facts

About 20 percent of runners in any given running event will experience ETAP, according to the September, 2014 journal, Sports Medicine, which also notes that 70 percent of runners will experience it at least once in the course of a year.

ETAP is most likely to be brought on by activities that require repetitive torso movement with the torso in an extended position, such as running and horseback riding. The pain can range from mild to severe. When intense, it's usually a stabbing or sharp pain. Milder cases may involve aching, cramping or pulling sensations.

ETAP is more common for younger people than adults but is unrelated gender or body type. ETAP does seem to become less frequent with improved conditioning, so if you've just started up running, it may get better. Another scenario suggests ETAP is referred pain stemming from the shoulder tip by the phrenic nerve, which also serves the diaphragm.

ETAP typically manifests on the right side of the body around the middle third of the abdomomen, just to the side of the navel.

Improving core strength is one strategy for avoiding side pain when running. (Image: hedgehog94/iStock/Getty Images)

Possible Causes

There's no consensus about what causes ETAP but there's no shortage of theories either. One is restricted blood flow to the diaphragm, causing it to go into spasm. Another is stress on the network of ligaments that support the abdominal organs.

Yet another possible cause is compression of the celiac artery and one more theory for the road is aggravated spinal nerves. Or just maybe you've irritated your peritoneium, the membrane that lines your abdominal cavity.


There's no single strategy for fighting ETAP and probably the best thing you can do is see what works for you. The first order of business is to avoid heavy meals and excessive beverage consumption 2 to 3 hours before running.

Improving posture, particularly in the middle back region may help, as may strengthening your core muscles. Some people find that wearing a a broad, supportive belt staves off the stitch. If ETAP occurs anyway, you may also try massaging the area, slowing your pace, or pausing your run until it passes.

You should also avoid hypertonic drinks with more than 6 to 8 percent of their calories from carbs because they can slow down your digestion, according to the American Council on Exercise. Same goes for bulky snacks with high fiber content.

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