system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do you get really bad cramps before diarrhea?

Also, why is it that sometimes while you're pooing you get sweaty and clammy and the feeling that yep, I'm about to die?
gpt
That's your large intestine muscles contracting to try and move the poop along. This is thought to be controlled (at least somewhat) by stretch receptors in the gut. 

Under normal circumstances a group of muscles contract when stretched by solid poop, the poop moves down the tube, and then that group of muscles relaxes while another contracts. 

When you have liquid diarrhea it doesn't activate (or deactivate) the stretch receptors properly. So your gut muscles contract harder and harder thinking they'll come into contact with solid poop, but they don't. 

The cramps are pain caused by your gut muscles contracting really hard.