actually i was told its 60% - 70% of ur 1 rep max... wich for me is 80k ish, but i started on 60 the other day, got all 100 reps out. but what ur supposed to do is rep to fail, so if 7 set in u can only get 4 out, just get them...

do this 10 times, eventually once u can do 10 for 10 move up a weight,

keeps ur muscle guessing and worked harder than the time before

u do really need a spotter to o it properly but even at lesser weight is effective