That’s interesting. I don’t actually know. An orgasm triggers contractions, that’s one of the physical signs used to test for orgasms. But tightening up as you edge, that’s not something I’ve come across.
Seems pretty awesome though. The thought of you sitting on top of a guy, squeezing his cock tighter and tighter as you edge, well, sounds damn hot to me. It might mean you don’t want to edge BEFORE sex though, as being super tight can make it uncomfortable for you both.
Might be fun with a vibe or some jiggle balls in you too!