i've done it for reps, but i wish i didn't, at least not in the flat back, no idea where my shoulders were, way i did it.
no real reason either, was never a powerlifter. apart from thinking that it was some sort of pre-requisite to join the big boys club or something. in short - ego.
i'm sure the experienced lifters can finish the story here, but yeah, i banged my shoulder stabilizers up real good. of course it didn't help that i was boxing at the time, even doing that wrong - belting the heavy bag as hard as i could with poor technique.
basically did everything i could to destroy the shoulder joints. my young body got away with it...for a while.
anyway, i have since learnt to respect this movement. actually, i don't even do it now. i do parallel dips with weights and that does the job
anyway, just wanted to share mainly because i think it's such a stupid movement to just do.
if you are going to do them learn how to do them powerlifting style - lock the shoulders in, arch the back, bring bar down to sternum in absolutely PERFECT form. pleeeeeeeeeeeeeeease don't let the shoulders rotate too much during the lift. go see dave tate or louie simmons from westside. they'll set u straight. if you don't want to compete just do partials.
if i save just 1 shoulder out there in iron land by writing this, just one and i'll die happy.