What is the reason for all the movement when we really need to go pee? Is it a subconscious reaction to distract the mind from a full bladder, or does sloshing the pee around in your bladder make it somehow better? I would assume not, since that probably increases the physical urge that you need to go pee, but why then do we dance and hop…
My ‘theory’:
Your sphincter and other pelvic floor muscles functionally work together to hold your pee in.
You actually have two sphincters, the external one is skeletal muscle and is controlled voluntarily/directly by you most of the time, the internal one is smooth muscle, that you generally cannot consciously control, its on autopilot.
When you really need to hold your pee in, your sphincters get more active, and start to get tired.
The muscle groups near them, they basically try to do load balancing, by shifting you around into other configurations that make it easier for the specific muscles to be able to hold your urethra shut.
Thats why you find yourself, or may be directing yourself, (EDIT: or a kind of confusing combination of both), to reorient/reconfigure your pelvic muscles, to basically ‘help’ your sphincters be able to hold on a bit longer, by finding a mechanically less demanding pose for them to assume, that still keeps the gates closed.
Think of how if you’re carrying something heavy for a while, you’ll tend to try and shift to a different way / configuration of carrying the thing, that uses different muscle groups in different ways, if a particular muscle group is just way too exhausted.
Combine that with a built in biological / genetic understanding that you are vulnerable to attack when urinating/defecating, and you get a subconscious element or autonomic element of the nervous system that switches into this behavior mode, to prevent you from letting loose untill you are somewhere safe to do so.