What’s going on when I push my belly out?

Ask Science is a joy, it’s a place you can go and ask scientists anything and get well written answers with sources. It’s part of reddit which is generally a cesspit but Ask Science is carefully curated with throwaway comments, jokes and unsourced answers deleted. I like the way this simple answer quickly develops into a more complicated question about how breathing works.

Link: What’s going on when I push my belly out?