A sharp pain under the ribs, usually on the right, minutes into a run: a side stitch catches almost every runner at some point. The good news is that in most cases the cause isn’t your fitness – it’s your breathing while you run.

Why side stitches come from your breathing

A side stitch (medically, “Exercise-Related Transient Abdominal Pain”, or ETAP) most likely comes from tension on the ligaments that anchor your diaphragm, triggered when breathing and stride rhythm fall out of sync. Shallow, high chest breathing forces the diaphragm into quick, uneven movements. Combined with the up-and-down impact of running, that’s exactly the irritation that shows up as a stitch.

Runners who breathe deeper into the belly instead take real pressure off the diaphragm and noticeably reduce that pull. It’s also why side stitches show up more after unfamiliar effort, after eating, or under stress – all three push you toward shallow breathing.

3 breathing techniques that stop side stitches

• Asymmetric breathing (3:2 pattern). Inhale over three footstrikes, exhale over two. Alternating which side you exhale on spreads the load across both sides of the diaphragm, and it’s the best-studied technique for reducing ETAP.
• Breathe deeper into the belly. Rest a hand on your stomach while running and aim to feel it rise, rather than lifting your shoulders. That takes the urgency out of the diaphragm’s movement.
• When a stitch hits: exhale longer. Ease your pace slightly and exhale slowly and fully, lips gently pursed. This relaxes the diaphragm directly, and the stitch usually eases within a few breaths.

One thing you can do today

On your next run, practise the 3:2 pattern for the first ten minutes, even before any stitch appears. That builds the habit before you need it under pressure. If you have persistent or severe abdominal or chest pain, especially pain unrelated to breathing, get it checked by a doctor.

If you want the fuller picture on nose versus mouth breathing while running, see our guide Breathing Technique for Running: Nose or Mouth?. And if you generally run out of breath faster than training partners with similar fitness, your CO2 tolerance is worth a look as a possible cause.

Frequently asked questions

Why do I always get a side stitch on the same side?

Usually because you always exhale on the same side, overloading one half of the diaphragm. The asymmetric 3:2 pattern alternates your exhale side automatically and helps prevent exactly this.

Does it help to avoid eating before a run?

Yes – a full stomach shortly before running raises the risk. Leaving two to three hours after your last larger meal noticeably reduces side stitches for most runners.

Is a side stitch a sign of poor fitness?

No. Even highly trained runners get side stitches, often exactly during pace changes or unfamiliar efforts. It’s primarily a breathing-technique issue, not an endurance one.

How long before the 3:2 pattern becomes automatic?

Most runners notice a difference after one to two weeks of deliberate practice. Counting the pattern in your head at first helps until the rhythm sets in on its own.

If you want to know where your breathing efficiency currently stands, our BOLT test is a good place to start. For a personal read on your situation, you can also book a free intro call.

Atemstark App
Want to practise the 3:2 pattern and other running-specific breathing techniques with guided audio? The App’s Foundations Programme walks you step by step through the core breathing techniques for endurance sport. Start the Foundations Programme – CHF 39

More running and breathing guides are on the breathing blog.