I used to do that as a kid. I’d put my legs behind my head and hop around on my arms.
Then somewhere around 12 years old, after a body lengthening growth spurt, my hips seems to lose that amazing flexibility and I got stuck.
“Mom? MOM!?” “MOOOOOOOMMMM!?!?!?”
Last time I did that, although I’d still cross my legs and hop around on my arms and walk on my knees for a few years after that.
I’m always been “just slightly taller” than standard American ergonomics, so I’d end up with legs falling asleep after sitting on some toilet seats.
Nothing like trying to stand up and just having to ‘stoop’ there for MINUTES… waiting… waiting… waiting for the legs to wake up. Sometimes I’d try to force it but I’d always be afraid that “oh no the pins and needles are going to be so painful!” but of course the fear is worse than the reality… slightly.
Cross-legged on floor does it to me everytime. I have a mental clock. I can sit for a maximum of 10 minutes on the floor and no more. It’s annoying because I like sitting on floors but the body is *weird* and does what it do.