What's happening when I get a stitch?
The stitch is one of the most familiar afflictions of exercise. It’s mentioned in the works of Pliny the Elder (who recommended “the urine of a she-goat, injected into the ears” in certain cases) and Shakespeare. But it has been virtually ignored by modern sports scientists, as Australian researched Darren Morton noted in a recent British journal of sports Medicine review. Morton describes the pain as ‘sharp or stabbing when severe, and cramping, aching, or pulling when less intense. Until a series of studies was conducted over the past decade, no one even knew what the stitch (or side-cramp, or “exercise-induced transient abdominal pain”) was, let alone what was causing it. Was it a cramp or spasm of the abdominal or respiratory muscles? Constricted blood supply to the diaphragm? Too much jostling of the ligaments supporting the internal organs?
Morton and his colleagues have carefully ruled out these popular theories one by one. By feeding volunteers carbonated, high-sugar soft drinks and then putting them on a treadmill, they’ve learned how to provoke stitches with reasonable reliability. They used electrodes to monitor abdominal muscle activity during stitches and found no change, ruling out abdominal muscle spasm. They analyzed breathing parameters during stitches and again found no change, ruling out respiratory muscle spasm. The wide variety of stitch locations, including low in the abdomen, rules out the diaphragm. And the occurrence of stitches during non-jolting activities like swimming argues against the ligament theory.
So what’s left? There’s still no definitive answer, but new studies have offered some revealing hints. Doctors have sometimes seen patients with stitch-like pain caused by brain lesions or by compressed nerves in a certain part of the thoracic (upper-back) spine. Morton and his team found that they could induce a stitch by pressing on this area of the spine, suggesting that there’s a neural component. And in a 2010 study, they found a link between the degree of spine curvature in 159 volunteers and their susceptibility to stitches. The greater the kyphosis (curvature of the upper back) and lordosis (curvature of the lower back), the more severe the pain of the stitch.
The actual pain, the researchers argue, is best explained as irritation of something called the parietal peritoneum,” the outer layer of the membrane that lines the abdominal cavity. Friction between layers of the peritoneum could be caused by a full stomach pressing from to the inside or the constrained shape of a rib cage with excess spine curvature. Notably, the nerves of the peritoneum are connected through the same region of the thoracic spine that can trigger stitches – and other peritoneal nerves are linked to the shoulder, where some people experience stitch pain.
This suggests that, if you’re prone to stitches, you should avoid filling up your stomach with food or water right before exercising. It also suggests that postural exercises to limit spine curvature could be helpful. Since other studies have found that consuming high-sugar beverages before exercise makes stitches more likely, it makes sense to avoid them and to experiment with what other foods may be triggers for you. Finally, the clearest correlation they’ve found is with age; the younger you are, the more likely you are to get a stitch. So if all else fails, time may cure you.