Why you get a stitch and what to do when it comes

It’s called exercise-related transient abdominal pain, and it’s extremely hard to avoid entirely: around 69% of runners say they’ve had it in the past year. In any given race, roughly one in five participants will feel it.

What it actually is

For decades it was said to be the diaphragm running short of blood. The explanation that best fits what we observe today is a different one: irritation of the parietal peritoneum, the membrane lining the inside of the abdominal wall.

That explains things the diaphragm theory didn’t: that it also hurts in the shoulder, that it shows up in non-impact sports like swimming — where it’s actually even more common, at 75% — and that drinking very concentrated drinks sets it off.

What to do once you have it

Let’s be honest here: the only thing fully proven is that stopping works. The rest are the manoeuvres people who get it say give them relief, collected in the research but without trials to prove it. Even so, they’re free and they do no harm:

• Deep, full breathing. It’s what most people use: four in ten.
• Pressing the sore area with your hand.
• Bending forward while tightening your stomach.
• Stretching the sore side by raising the arm on that side.

How to get it less often

• Don’t eat much in the 2 or 3 hours before you head out.
• Avoid very sugary or concentrated drinks right before. In the studies they’re among the biggest triggers there are.
• Don’t drink a lot of water in one go before starting either.
• Working the core and improving upper-back posture seems to help in the medium term.