Side Stitches: Causes and How to Fix Them Mid-Run

A sharp, cramping pain under your ribs — usually on the right side, sometimes the left — that shows up ten or fifteen minutes into a run and makes every breath a little unpleasant: almost every runner meets a side stitch sooner or later, and almost every runner's first reaction is to wonder if something is seriously wrong. In the vast majority of cases, nothing is. This is exercise-related transient abdominal pain, commonly just called a "stitch," and it's one of the most common minor complaints in running — uncomfortable, sometimes bad enough to slow you to a walk, but not dangerous, and it almost always fades within minutes once you address it. This article covers what's actually thought to cause it, what to do about it mid-run, how to head it off before it starts, and — importantly — how to tell the difference between an ordinary stitch and pain that needs a doctor's attention instead of a running tip.

What a side stitch actually is

Here's the honest answer: nobody has fully nailed down the exact mechanism, and you should be suspicious of any source that states one cause as settled fact. What exists instead is a handful of leading hypotheses, each with some supporting evidence, and they're probably not mutually exclusive — different stitches in different runners may have different dominant causes.

The hypothesis with the most traction points to the diaphragm and the ligaments that anchor your internal organs to it. Your liver (on the right) and other organs hang from ligaments attached to the underside of the diaphragm, and the diaphragm itself is working hard with every breath while your torso absorbs the repeated jolt of footstrike. The idea is that this combination — a working diaphragm, a bouncing torso, and organs pulling on their attachment ligaments with every stride — creates a kind of repetitive strain on those ligaments, which reads as a sharp, localized pain. This would explain a few things that are otherwise hard to account for: why stitches are so often on the right side (the liver is bigger and heavier than the structures on the left), why they tend to show up with rhythmic, bouncy sports like running rather than steadier efforts like cycling, and why exhaling on the same foot every time — meaning the same side absorbs the downward jolt during every exhale — seems to make it worse for some runners.

A second, related idea is that the diaphragm itself is simply working harder than it's used to and cramping the way any overworked muscle can, especially if breathing is shallow or irregular rather than deep and rhythmic — the diaphragm doesn't get a full, efficient range of motion, has to work harder to move the same amount of air, and fatigues faster as a result.

A third hypothesis centers on food and drink in the stomach. Running with a full stomach, especially after a meal high in fat, protein, or sugar, or after gulping a large volume of fluid right before heading out, is consistently associated with a higher stitch rate in surveys of runners. The proposed mechanism is that a fuller stomach and the digestive process pull more blood and attention to the gut, tug more heavily on the same supporting ligaments described above, or simply add extra weight and movement to an already bouncing abdomen. This one has decent circumstantial support — cut the pre-run meal timing and volume, and stitch frequency tends to drop for a lot of runners — even without a fully confirmed biological pathway.

Poor posture and shallow breathing come up too, more as a contributing factor than a standalone cause: running hunched forward compresses the torso and can shallow out your breathing, and shallow breathing means the diaphragm is working in quick, incomplete cycles rather than long, full ones — plausibly compounding whichever of the mechanisms above is doing the real work. Being new to running, unfit, or pushing an unfamiliar pace also correlates with more stitches, which fits loosely with several of these hypotheses at once.

The honest summary: something about the mechanical stress of running — on the diaphragm, on the ligaments anchoring your organs, made worse by a full stomach or shallow breathing — is almost certainly involved. Which piece matters most, and whether it's the same piece for every runner, isn't settled. Treat the causes below as "things that plausibly help, and mostly do in practice," not as a diagnosis of exactly what went wrong in your body.

In-the-moment fixes

When a stitch hits mid-run, a few things reliably help, and you can layer them together.

Change your exhale timing. If the ligament-strain hypothesis is right, exhaling on the same foot every single stride — which most runners do without noticing — means that foot's footstrike always lands during the moment your diaphorm and organs are most jostled. Deliberately switching which foot you exhale on, or exhaling every third step instead of every second so the pattern doesn't lock to one side, is one of the simplest things to try and costs you nothing.

Push into the spot with your fingers. Pressing firmly on the painful area with your fingers or the heel of your hand while you keep moving takes some of the mechanical bounce out of that patch of tissue and provides real, if temporary, relief for a lot of runners. Some people find bending forward slightly at the same time helps further.

Slow down, and if that's not enough, walk. This is the fix that works regardless of which hypothesis is correct, because it addresses the common thread across all of them: mechanical stress. Dropping your pace immediately reduces the bounce, the breathing demand, and the overall load, and a stitch that doesn't ease within a minute of slowing usually does ease within a minute or two of walking. There's no shame in walking through a stitch — every experienced runner has done it, and pushing hard through sharp pain rarely shortens the episode.

Try a deep, controlled exhale through pursed lips. Instead of shallow, quick breaths, take a few breaths where you consciously push the exhale out longer and fuller than normal. If shallow breathing and diaphragm fatigue are contributing, a handful of deliberately deep breaths can reset the pattern.

Stretch the side that hurts. Raising the arm on the painful side overhead and leaning gently away from that side, for a few strides or during a brief walk break, stretches the muscles and connective tissue along that flank and eases the cramping sensation for some runners.

Most stitches resolve with some combination of these within a few minutes. If a stitch is severe enough that none of this helps and you have to stop entirely, that's worth remembering for next time — it's a strong signal to look hard at the prevention section below, particularly what and when you ate beforehand.

Prevention: cutting the odds before you start

None of the following guarantees a stitch-free run — stitches happen to well-prepared runners too — but each one measurably shifts the odds, based on what plenty of runners report and what fits the leading hypotheses.

Mind your meal timing. Give a full meal two to three hours to clear before you run, and if you need something closer to run time, keep it small, low in fat, low in fiber, and easy to digest — a banana or a slice of toast sits far better than a big plate of pasta an hour before you head out. The same logic applies to fluid: sip steadily in the hour before a run rather than chugging a large volume right before you start, since a stomach sloshing with a big gulp of water is itself a plausible stitch trigger.

Warm up properly instead of starting fast. Jumping straight into race pace or a hard effort from a cold start seems to raise stitch risk, plausibly because your breathing hasn't settled into an efficient rhythm yet and your diaphragm is being asked to work hard before it's warmed up. A gradual warm-up — a few minutes of easy jogging or walking before you pick up the pace — gives your breathing time to find a steady, deep rhythm before the real demand hits.

Build core strength over time. A stronger, more stable core supports better running posture and may reduce the amount of bounce and torque your torso absorbs with every stride, which several of the hypotheses above point to as a contributing factor. You don't need a dedicated ab routine to see benefits — general core work like planks, dead bugs, or bird-dogs, done a couple of times a week, is enough for most recreational runners.

Practice deep, rhythmic breathing on easy runs. Since shallow breathing shows up in more than one hypothesis as a contributing factor, using easy runs to practice long, full breaths — in through the nose or mouth, all the way down into your belly rather than just your upper chest — builds a habit that tends to carry over into harder efforts, where stitches are more likely to strike. The pace calculator is a useful way to find what an easy, conversational pace actually looks like in minutes per mile or kilometer, so you're not accidentally running "easy" runs hard enough to shallow your breathing without realizing it.

Notice your own pattern. Some runners get stitches almost exclusively after a specific food, at a specific pace, or on a specific side. If you track a few episodes — what you ate, how long before the run, what pace you were holding — a personal pattern often becomes obvious faster than any general advice can predict, because the mix of contributing factors seems to vary from runner to runner.

When repeated pain isn't a stitch — see a doctor

Everything above describes an ordinary side stitch: sharp but not severe, closely tied to running, and gone within minutes once you slow down, change your breathing, or press on it. That pattern is genuinely common and, in the overwhelming majority of cases, harmless. But a handful of warning signs mean the pain in your side or chest isn't a stitch, and pushing through it or trying the tips above instead of getting it checked is the wrong move. See a doctor — and stop running, don't try to work through it — if you notice any of the following:

• Pain that doesn't ease off once you stop running and rest, or that keeps building rather than fading.
• Pain that spreads to your shoulder, arm, neck, or jaw rather than staying localized under your ribs.
• Any chest pain, as opposed to pain clearly in your abdomen or side.
• Shortness of breath that feels out of proportion to how hard you're actually working, especially alongside chest or upper-body pain.
• Fever alongside abdominal pain, which can point to an infection or inflammation rather than a running-related cramp.

These symptoms can indicate something other than a stitch — a cardiac issue, a gallbladder problem, or another condition that has nothing to do with your training and everything to do with needing prompt medical evaluation. This article is not a substitute for that evaluation, and none of the in-the-moment fixes above are the right response to pain that fits the list above. A stitch is a nuisance you can run through and forget about by the next mile. Anything that looks like the list above is not that, and deserves a doctor's judgment, not a running article's.

Getting started

Most side stitches are a minor, well-understood annoyance, not a medical event: slow down, change your exhale pattern, press into the spot, and it almost always passes within a few minutes. If they keep showing up, look first at meal timing, warm-up pace, and breathing depth before assuming anything more serious is going on — those three changes resolve the problem for most runners who get stitches regularly. And if what you're feeling doesn't match the ordinary pattern — pain that lingers, spreads, or comes with chest pain, disproportionate breathlessness, or fever — that's not a stitch to run through. That's a reason to stop and see a doctor.