Why do you get a stitch when running, and how do you get rid of one?

The stitch is one of running's great mysteries: a sharp, stabbing pain just under the ribs that appears out of nowhere, makes you run like a wounded crab, then disappears as if nothing happened. It is very common, it is very annoying, and the good news is that for most people it is harmless and passes.

What a stitch actually is

The formal name is a mouthful: exercise-related transient abdominal pain. It usually shows up as a sharp, localised pain at the side of the abdomen, just below the ribcage.

According to the summary of the research on Wikipedia, it affects people at every level, from schoolchildren to elite athletes, and it is more common in younger people. It turns up most in activities with a lot of jolting or twisting of the upper body, which is why runners, swimmers and horse riders all know it well. Surveys have found that around two thirds of runners get at least one in a year.

What causes it (honestly: we're not sure)

Several explanations have done the rounds over the years, and some have not survived contact with evidence:

• Not enough oxygen to the diaphragm. This one used to be popular, but stitches also happen in activities like horse riding where breathing demand is modest, and imaging during a stitch has shown the diaphragm moving normally.
• Organs tugging on ligaments. This struggles to explain why swimmers get stitches too, since there is little downward jolting in the water.
• Irritation of the abdominal lining. This is currently the favoured idea among the researchers who have studied stitches most closely. The lining of the abdomen is sensitive, and friction or pressure on it would explain the sharp, localised pain and why a full stomach seems to make things worse.

The honest summary: the cause is not settled. What is clearer is when stitches tend to happen.

When stitches are more likely

The research summarised above links stitches with eating a meal or drinking a lot, particularly sugary drinks, shortly before exercise. In practice, runners who get frequent stitches often find it helps to:

• leave a gap between a big meal and a run;
• sip during a run rather than gulping a lot at once;
• start gently and build into the pace, rather than sprinting out of the door. Our guide to the first ten minutes of a run is a good habit for many reasons, and this is one of them.

None of this is a promise. Some people get a stitch on an empty stomach on a perfect morning, simply because the universe enjoys a joke.

How to get rid of one mid-run

Because nobody is sure of the cause, the tricks runners use are practical rather than scientific. The ones most people swear by:

1. Slow down or walk. This alone often makes it fade.
2. Breathe deeply and slowly. Long exhales help you relax your trunk.
3. Press into it. Push your fingers firmly into the painful spot while you walk or jog, and hold.
4. Bend forward slightly. Some people find leaning forward, or stretching the arm on the painful side up and over, eases the pain.
5. Change your breathing rhythm. If you always breathe out on the same foot, try switching.

Give it a minute or two of walking and pressure before starting again gently. Most stitches go as suddenly as they arrived.

When it isn't a stitch

A stitch comes on during exercise and goes away with rest. Pain that continues after you stop, pain at rest, chest pain, or pain with other symptoms such as feeling unwell is a different matter: stop and get it checked by a doctor rather than diagnosing it as a stitch.