Side Stitch When Running: Why It Happens and What Helps
Asier G. Morato
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8
min read
Cover image generated with AI — © Chubby Studio S.L.
KEY TAKEAWAY
A side stitch is a sharp pain under the ribs that about 70% of runners get in a given year. The best evidence points to irritation of the lining of the abdominal wall, not an oxygen-starved diaphragm. Avoid big meals and sugary drinks in the two hours before a run, and if one hits, slow down until it eases. Pain that persists after you stop is not a stitch.
A side stitch is a sharp, well-localized pain just under the edge of your ribs that comes on while you run and fades within minutes of stopping. Its formal name is exercise-related transient abdominal pain. Around 70% of runners get one in a given year, and the best-supported explanation is irritation of the lining of the abdominal wall, not a diaphragm starved of oxygen.
That matters, because most stitch advice is built on the diaphragm story. What has evidence behind it is duller: how much you eat and drink before you run, and what you drink. Here is what the research says, and when a pain in your side is not a stitch at all.
What does a side stitch feel like?
A stitch sits in one spot, most often at the side of the mid-abdomen along the lower edge of the ribs. It feels sharp or stabbing when it is bad, and aching, pulling or cramping when it is mild. It can appear on either side, and it eases quickly once you slow down or stop.
The best numbers come from the Sydney City to Surf, a 14 km community run where researchers questioned 848 finishers. 27% had a stitch during the event, runners far more often than walkers (30% against 16%), and 42% of them said it hurt their performance. The right side was reported about twice as often as the left. Some people also feel pain at the tip of the shoulder on the same side, a useful clue about the cause.
What causes a side stitch when running?
Nobody has proven it yet, but several popular explanations have been ruled out. The strongest candidate is irritation of the parietal peritoneum, the membrane lining the abdominal wall and the underside of the diaphragm, as your organs move with every stride.
The diaphragm theory says your breathing muscle cramps because it runs short of blood. When Morton and Callister had runners do a full breathing test in the middle of a stitch, their inspiratory capacity was essentially unchanged, and the authors concluded the diaphragm is not directly involved. Stitches are also common on horseback, where breathing demand is low, and muscle electrical activity at the painful spot is not elevated, so it is not a cramp either. In other words, the most repeated explanation, a diaphragm starved of oxygen, is the one the evidence has knocked down hardest.
The peritoneum explanation fits almost everything else. Irritating that lining produces sharp, localized pain that worsens with movement, the part under the diaphragm refers pain to the shoulder tip, and the pain fades fast once the movement stops. The 2015 review by Morton and Callister in Sports Medicine calls it the best fit so far, while being clear that more work is needed.
Why do new runners seem to get stitches more often?
Partly age, partly the sport, partly conditioning. 77% of active people under 20 reported a stitch in the past year, against 40% of those over 40, and running provoked them around ten times more often than cycling.
Fitness helps, but only so much. Better-conditioned people reported stitches less often, though not less severely, and well-trained athletes still get them. So the hopeful and honest version is that stitches tend to show up less as running becomes routine, but no amount of training makes you immune. The easy running that builds an aerobic base is the same running that makes the sport familiar to your body, which is one more reason easy sessions deserve most of your week.
One thing a stitch is not is proof that you started too fast or skipped your warm-up. At the City to Surf, stitches were unrelated to finishing time, and they appeared in equal numbers in the first, middle and final third of the course.
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What should you eat and drink before a run to avoid a stitch?
Avoid large amounts of food and drink in the two hours before you run, closer to three or four if you are prone to stitches. Sip small amounts during the run rather than gulping, and skip very sugary, concentrated drinks like fruit juice. This is the prevention advice with the most evidence behind it.
At the City to Surf, runners who ate a large amount relative to body weight one to two hours before the start were more likely to get a stitch. The size of the meal mattered, not whether it was carbohydrate, fat or protein. About half of the people with a stitch said it started shortly after a drink station.
Drinks are not all equal. In a trial of 40 runners prone to stitches, reconstituted orange juice, at 10.4% carbohydrate and highly concentrated, provoked more stitches and more bloating than flavored water, a standard sports drink or nothing at all, and there was no difference between the water and the sports drink. The gut may also get used to fluid with practice, a good reason to rehearse race-morning eating on a long run, the way you would before a big-city marathon with a long wait at the start.
How do you get rid of a side stitch while running?
Slow down, and if that is not enough, walk or stop. A stitch usually settles within a few minutes once the jolting stops. Pressing into the painful spot and breathing slowly and deeply while you walk are reasonable to try, but the evidence for any specific trick is weak.
When roughly 600 people with stitches were asked what brought relief, the most common answers were deep breathing (40%), pushing on the painful area (31%), stretching it (22%) and bending forward (18%). None has been properly tested, and stretching and bending forward pull in opposite directions. Pushing in may work by holding the organs still, like the wide belt that helped in one small study. The review's own conclusion is blunt: the only remedy with consistent support is to stop the movement that caused the stitch. A planned walk break is a perfectly respectable way to do that.
Does breathing or foot strike cause stitches?
Probably not in the way you have heard. The advice to exhale as your left foot lands, so the liver is not jolted on the out-breath, has never been tested in a trial and rests on ideas the newer research has weakened. In a small 1999 trial described in the review, making runners land harder had no effect on the pain. It is harmless to try, just do not expect much, and being out of breath in your first weeks of running is a separate thing entirely.
Is it okay to run through a side stitch?
Yes, if it is a genuine stitch and the pain is tolerable: it is uncomfortable but benign. In a survey across six sports, 76% of people with stitches had to ease off when one hit and 12% had to stop altogether, so stopping is not a failure either.
A stitch also says nothing about whether you are running too much. Pain that sits in a shin, a knee or an Achilles and comes back run after run is a different category, and it is usually a load problem rather than bad luck.
When is side pain not a stitch?
A stitch comes on during movement, stays in one spot and eases within minutes of stopping. Pain that stays after you stop, or keeps getting worse, is not behaving like a stitch and deserves a doctor's attention, not another run.
Stop and get medical help urgently for chest pain or pressure, pain spreading to the arm, jaw or back, breathlessness out of proportion to the effort, dizziness or fainting. See a doctor if side pain comes with fever, vomiting or blood, or if severe stitches hit the same spot on almost every run. The review describes case reports where a recurring stitch had another cause, from abdominal adhesions to irritated nerves near the lower ribs. That is a job for a clinician.
Can your watch tell you anything about a stitch?
Not directly. No sensor on your wrist detects a stitch, and it leaves no trace in your heart rate beyond the dip where you slowed down. The data can still show a pattern: if stitches keep arriving on runs that start soon after a meal, you have your answer.
FitWoody is an iOS app for iPhone, iPad and Apple Watch that turns what your watch records into a clear read on how your body is doing. It does not detect stitches. It scores each run by what the session cost you internally, tracks your training load against your own baseline, lets you set heart rate zones from your own numbers, and builds recovery baselines from HRV, resting heart rate and sleep. Flyover replays an outdoor run along its route with heart rate and speed, so the spot where you slowed down is easy to find. An Apple Watch is required, and it informs rather than diagnoses.
Next run: eat at least two hours before, sip rather than gulp, and if a stitch arrives anyway, slow down, press into it and carry on when it lets go. Showing up, in any form, counts.
Frequently asked questions
How long does a side stitch last?
A genuine side stitch usually eases within a few minutes of slowing down or stopping, because the pain fades quickly once the jolting movement ends. If the pain stays after you stop, or keeps getting worse, it is not behaving like a stitch and should be checked by a doctor.
Is a side stitch on the right side more serious?
No. In a study of 848 finishers of a 14 km run, right-sided stitches were reported about twice as often as left-sided ones. The side alone is not a warning sign. Pain that persists after stopping, or comes with fever, vomiting, chest pain or unusual breathlessness, is.
Does drinking water cause a side stitch?
Large volumes of any drink before or during a run can provoke a stitch, but water is not the worst offender. In a trial of 40 stitch-prone runners, concentrated orange juice caused more stitches than water or a standard sports drink, which did not differ from each other. Sip small amounts rather than gulping.