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

I’d give a very different answer for ELI10, perhaps talking about how awesome it is that there’s so much of the world we don’t really understand.

But for a five-year-old, I’d simply say it’s your body’s way of saying that what you are doing is hard.