Stomach squeezed in extremely tight
When I was a boy, my older teenage cousin always held me on her lap with her hands kept pulled back into my stomach a good inch to two inches deep. We never talked about it, we just did it all the time, so I have no idea how or why this practice got started.
My cousin often held me this way openly in front of our family, and it was secretly affecting me in ways nobody (including probably her) ever recognized. I sometimes worried someone might get horrified if they noticed the peculiar way she was holding my stomach in. But nobody ever thought anything of it, in fact they usually paid no attention even when she was holding my stomach in two inches deep right out in front of everyone.
This led to me asking my babysitter, a big brawny farmgirl, to hold me on her lap with her hands sunk back into my stomach "just as tight as you can." I think she found this a simple way to keep me entertained, and also to keep me conveniently immobilized and out of mischief. So whenever she came over to babysit she would hold my stomach all the way back in, excruciatingly white-hot ULTRA-tight, while we watched TV. I would sit there silent and still, locked on her lap and unable to go anywhere even if I tried.
I cannot possibly exaggerate just how freaking tight this huge farmgirl always held my stomach in... just about as absolutely tight as was physically possible. I don't think it could have gotten any tighter. And I loved it! Though I know I would have died if anyone else had ever seen the strange way she held me.