Why You Get a Side Stitch When You Run

You are three miles into a run, feeling strong, when a sharp ache grabs you just under your ribs on the right side. Every step makes it worse. You slow to a walk, press your side, and wonder what you did wrong.

You did nothing wrong. You got a side stitch, the most common complaint among new runners and one that even experienced athletes still get. It is painful, annoying, and almost always harmless. And once you understand what causes it, you can usually stop one in its tracks and keep it from coming back.

What a side stitch actually is

Doctors call it exercise-related transient abdominal pain, or ETAP. That long name describes it well: pain in the abdomen, triggered by exercise, that passes on its own.

The leading explanation points to the diaphragm, the dome-shaped muscle under your ribs that powers your breathing. When you run, your diaphragm works hard, moving up and down with every breath. At the same time, your liver (on the right side, which is why stitches usually strike there) bounces with each foot strike. The ligaments holding the liver tug on the diaphragm, irritating it, and your brain reads that irritation as a sharp pain under the ribs.

A second factor is blood flow. During hard exercise, your body diverts blood away from the gut and toward your working muscles. That shift can irritate the lining of the abdomen, especially if your stomach is still busy digesting a meal. This is also why stitches are far more common in running than in cycling or swimming: the up-and-down jolting of running is uniquely rough on the organs in your belly.

Stitches are especially common in beginners. Studies of runners have found that most new runners experience them, while seasoned runners get them far less often. Stronger core muscles, better breathing patterns, and a body that has adapted to the bouncing all help. If you are training for your first 5K, or gearing up for a Thanksgiving Turkey Trot, a stitch is practically a rite of passage, not a sign that running is not for you.

Why it happens to you

A stitch rarely has a single cause. Usually a few of these stack up on the same run:

• Eating too much, too soon. A big meal, a sugary sports drink, or a large glass of juice in the hour or two before a run leaves your stomach full and sloshing. High-sugar drinks are the worst offenders because they sit in the stomach longer than water.
• Starting too fast. Sprinting out of the gate before your breathing settles into a rhythm strains the diaphragm before it has warmed up.
• Shallow, rapid breathing. Panting with short, shallow breaths keeps the diaphragm in constant tension. Runners who breathe in a steady rhythm tend to get fewer stitches.
• Weak core muscles. Your core stabilizes your torso with every stride. When it tires, your organs bounce more, and the tug on the diaphragm increases.
• Being new to running. Your body simply has not adapted yet to the impact and the breathing demands. This improves quickly with consistent training.

How to stop a stitch mid-run

When one hits, do not try to push through it at full speed. Try these, in order:

1. Slow down, but keep moving. Dropping to a brisk walk usually eases a stitch within a minute or two. Stopping dead can actually make it linger, because your breathing stays ragged.

2. Press and massage the sore spot. Press your fingers firmly into the painful area while you breathe out slowly. The pressure gives your brain a competing signal and often dulls the pain fast.

3. Change your breathing pattern. Try this classic trick: exhale when your LEFT foot hits the ground instead of your right. Since most stitches are on the right side, this shifts the jolt away from the liver and reduces the tug on the diaphragm. It feels awkward at first, but many runners swear by it.

4. Stretch the right side. Raise your right arm overhead and lean gently to the left while walking. This stretches the diaphragm and the tissue around the liver. Hold it for 20 to 30 seconds, breathing slowly.

5. Slow your breathing on purpose. Breathe in for three steps, out for two. A slower, deeper rhythm relaxes the diaphragm instead of keeping it clenched.

Most stitches fade within two to five minutes once you slow down. If yours does not, walk until it passes.

How to prevent the next one

Prevention is mostly about timing and warmups:

• Eat smart before you run. Finish a full meal two to three hours before a run. If you need a snack closer to go time, keep it small and simple, like a banana or a slice of toast, at least 30 to 60 minutes beforehand. Skip sugary drinks and juice right before running; plain water is your best bet.
• Warm up gradually. Start with five minutes of easy walking or slow jogging before you pick up the pace. Your breathing and your gut both need time to adjust.
• Strengthen your core. Planks, dead bugs, and side planks two or three times a week stabilize your torso and reduce the bounce that triggers stitches. You do not need a six-pack; you need a core that does not quit at mile two.
• Build mileage slowly. The classic 10 percent rule still works: do not increase your weekly running distance by more than about 10 percent. Your diaphragm and core adapt alongside your legs.
• Practice rhythmic breathing. During easy runs, practice breathing in for three foot strikes and out for two. It becomes automatic with time, and it is one of the most reliable stitch preventers there is.

When a side stitch is not just a stitch

A true stitch is sharp but short-lived, sits under the ribs, and fades when you slow down. See a doctor promptly if your pain:

• Lasts longer than 30 minutes after you stop exercising
• Spreads to your shoulder, arm, jaw, or back
• Comes with dizziness, shortness of breath, nausea, or sweating
• Happens even when you are not exercising
• Is in the lower right abdomen and gets worse over hours (this can signal appendicitis, not a stitch)

Chest pain during exercise should always be checked, especially if you are over 40, have high blood pressure or high cholesterol, or have a family history of heart disease. When in doubt, get it checked. A stitch is common; a heart problem is not something to guess about.

The bottom line

A side stitch is your diaphragm complaining about the bounce, the breathing, and the breakfast all at once. Slow down, press the spot, switch your exhale to the left foot, and stretch the right side. Then fix the setup for next time: eat earlier, warm up slower, and strengthen your core.

Most runners find stitches fade away as fitness improves. Keep showing up, and the pain that once stopped you at mile three will become a story you tell at the finish line.