recently ive been doing heavy deads every week. tonight i pulled 2 sets of 4 of 375lbs. my old man, whos never done any weight training in his life but has a really bad back from doing years of heavy lifting and shoveling etc at work has been trying to tell me i shouldnt do deadlifts because i will pay for it down the line. what do you guys think? my form is very good, I am friends with one of the trainers at the gym and he usually watches to make sure its all good.