system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why is it so incredibly difficult to hold in a bowel movement?

I mean people, no matter how strong they are, have the hardest time holding it in if they really really need to use the restroom.  Also, it's not like you are holding in a pounds worth or gallons worth.
gpt
The anus is an involuntary scphincter. When you try to hold in your poops you are controlling muscles around the anus but not the anus itself. Once there is enough internal pressure the anus will relax and there is nothing you can do about it.