Why Your Side Hurts When You Run And How To Stop It?

That sharp, stabbing pain in your side — usually just below the ribs — has a name: side stitch, or exercise-related transient abdominal pain. It is one of the most common complaints among runners, and it is not a sign that something is wrong with your organs. For most people, the pain comes from irritation of the peritoneum, the thin membrane that lines the abdominal cavity, often triggered by the up-and-down motion of running while the stomach and its supporting ligaments are stretched and jostled. The good news: it usually responds quickly to simple changes in breathing, posture, and what you eat before you run.

What Actually Causes a Side Stitch When Running?

The leading explanation involves the peritoneum. This membrane has two layers — one lining the abdominal wall and one covering the organs — and running causes them to rub against each other. That friction is thought to produce the sharp, localized pain.

Several factors make that friction more likely:

• A full stomach. Eating or drinking too close to a run stretches the ligaments that support your stomach and intestines. Those stretched ligaments tug on the peritoneum with every stride.
• Shallow, rapid breathing. When you breathe from your chest instead of your diaphragm, the muscles that support your abdominal organs get less of the stabilizing support they need.
• Poor posture. A hunched upper body compresses the torso and reduces the space your diaphragm has to work.
• Running downhill or on hard surfaces. More vertical bounce means more jostling of everything inside your abdomen.
• Weak core and trunk muscles. The muscles that hold your torso steady also help hold your internal organs in place.

There is also a less common but distinct pain that comes from the shoulder tip. It is called referred pain, and it happens when blood or fluid irritates the diaphragm. That pain travels along the phrenic nerve, which shares nerve roots with the shoulder. This is different from a typical side stitch and warrants a medical evaluation.

Why Does the Pain Usually Show Up on the Right Side?

Most side stitches occur on the right side, just below the rib cage. The anatomy explains why. Your liver sits on the right side of your abdomen, directly under the diaphragm. It is the heaviest internal organ, and it is suspended by ligaments that can stretch and pull during running. That extra weight and the ligament attachments on the right side make the peritoneum there more vulnerable to irritation.

Left-side stitches happen too, but they are less common. If your pain is consistently on the left, it is still most likely a stitch, but persistent left-sided pain that does not go away with rest deserves a doctor’s attention.

Is It a Stitch or Something More Serious?

A side stitch has a predictable pattern. It comes on during activity. It is sharp and localized. It eases when you slow down, change your breathing, or press on the area. It goes away completely within minutes to hours after you stop.

Some pain is not a stitch. Seek medical evaluation if you notice any of these:

• Pain that continues at rest or lasts more than a few hours after you stop running
• Pain that radiates to your shoulder, neck, or groin
• Pain accompanied by nausea, vomiting, fever, or changes in bowel habits
• Pain that gets worse over days or weeks rather than better
• Pain that is severe enough to stop you from standing up straight

These signs could point to conditions that have nothing to do with exercise, including gallbladder problems, kidney stones, or appendicitis. A side stitch does not cause fever or vomiting. If you have those symptoms, see a doctor.

How Do You Stop a Side Stitch While Running?

You can usually stop the pain without ending your run. The techniques below are widely used by runners and coaches, and while formal clinical trials are limited, they are based on the mechanical explanation of what causes the stitch.

Try these in order:

• Slow down. Drop to a walk or a very slow jog. The reduced bouncing lessens the friction on the peritoneum.
• Change your breathing pattern. Breathe deeply into your belly rather than your chest. Inhale for three steps, exhale for two, or whatever rhythm feels natural. The key is to use your diaphragm.
• Press on the painful area. Place your hand just below the rib cage on the side that hurts and push inward while you breathe out. This supports the abdominal wall and may reduce the stretch on the peritoneum.
• Bend forward slightly. A slight forward lean can take tension off the ligaments that attach to the diaphragm.
• Stretch the affected side. Raise the arm on the painful side over your head and lean gently to the opposite side. Hold for a few seconds.

If the pain does not ease with these steps, stop running for the day. Pushing through a stitch rarely works and can make it worse.

How Can You Prevent Side Stitches Before They Start?

Prevention focuses on the same mechanical factors that cause the stitch. The most reliable strategy is to adjust what and when you eat before running.

Wait at least two to three hours after a full meal before you run. If you need something closer to your run, choose a small, low-fat, low-fiber snack — a banana or a slice of plain toast, for example — about 30 to 60 minutes beforehand. Large amounts of fruit juice, high-fat foods, and high-fiber foods are common triggers because they sit in the stomach longer and stretch it more.

Other prevention strategies:

• Strengthen your core. Planks, dead bugs, and bird dogs build the muscles that stabilize your trunk. A stronger core means less jostling of your internal organs with each step.
• Practice diaphragmatic breathing. Lie on your back with one hand on your belly and one on your chest. Breathe so only the hand on your belly rises. Do this for a few minutes daily until it becomes automatic during running.
• Warm up properly. Start with a brisk walk or easy jog for five to ten minutes before you pick up the pace. Cold, sudden exertion is more likely to trigger a stitch.
• Check your posture. Keep your shoulders back and your torso tall. Avoid hunching forward, especially when you get tired.
• Hydrate early, not right before. Drink water throughout the day rather than gulping a large amount in the 15 minutes before you run.

Do Side Stitches Mean Something Is Wrong With Your Training?

Not usually. Side stitches are more common in newer runners because their bodies have not yet adapted to the repetitive motion and their breathing patterns are less efficient. As fitness improves and core strength develops, stitches tend to become less frequent.

They are also more common in children and adolescents than in adults. This is likely because their diaphragms and abdominal muscles are still developing and their breathing patterns are less coordinated during exertion.

If you are an experienced runner who suddenly starts getting stitches on every run — especially if they are severe or do not respond to the usual fixes — that is worth mentioning to a doctor. A change in a familiar pattern is always worth checking.

What About Stitches in Swimming or Cycling?

Side stitches are most common in running because of the vertical bouncing. But they can happen in any sport that involves repetitive torso movement. Swimmers sometimes get them, particularly during flutter kick sets. Cyclists can get them when they are hunched over the handlebars for long periods.

The same principles apply. Breathe deeply into your belly, adjust your posture, and press on the painful area. In swimming, slowing your kick and focusing on exhaling fully underwater often helps. In cycling, sitting up taller and taking a few deep breaths can ease the pain.

When Should You See a Doctor About Side Pain During Exercise?

See a doctor if the pain does not follow the typical stitch pattern. A stitch comes on during activity, eases with rest, and disappears. Pain that does not fit that description needs a medical evaluation.

Also see a doctor if you have a history of gallbladder disease, kidney problems, or abdominal surgery. In those cases, exercise-related side pain could have a different cause.

And if you are over 50 and experiencing new chest or upper abdominal pain during exertion, get evaluated promptly. Heart-related pain can sometimes feel like it is coming from the abdomen or side. That possibility should be ruled out before you assume it is a stitch.