What is a “stitch” in your side when running? And why do they seem to happen to a specific side more frequently?

Question

Title — when I’m running I pretty regularly get a stitch in my right side, I assume it’s something like a muscle spasm that may be on a side I’m overcompensating on or something, but what exactly are they?

In: Biology

Answer 1

So – we don’t know.
At one point we thought it was due to buildup of lactic acid during exercise. But this was disproven.