"what are "sitouts"?"
It's a wrestling move, also called a hip heist, also called a peek out, etc.
You probably know it, but call it something else.
Here's what I call a sitout:
Both hands on the floor, both feet on the floor. Raise your left hand off the ground, raise your right foot off the ground. All your weight is on your right hand and left leg. Shoot your right foot through so it is now where your left hand was. Your butt is almost on the mat, your left elbow shoots back hard, your head looks up. Immediately return to the original position and repeat on the other side.
If you do these really fast, you get winded really fast. It's also a core movement for grappling, so you are killing two birds with one stone.