system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When we fall and land hard on our backs, why is it we can't breathe for a few seconds after? What happens that causes that?

I just remembered when I was a kid and I did this. The landing was hard and the panic that sets in when you realizes you can't breathe. Oof.
gpt
The diaphragm is a big muscle underneath your lungs that helps you breathe. When you get hit really hard on the back/chest/tummy where the diaphragm attaches, then it'll spasm (i.e. not move for a few seconds).

It's like if you get punched in the arm and then you don't want to move your arm because it hurts. Similar thing going on here.

Fun fact: skirt steak in cows is the same muscle as the diaphragm in you!