What make a slider bad for your arm? from what i know about how to throw it you use less supination than with a curve and cock your wrist a bit and the throw a fastball so what makes it hard on your arm?

well there is some debate that it is as bad for your arm as people say, but the general consensus is that it isn’t the best for your arm. I think the thing about the curve ball is that I believe many people that throw curves don’t totally extend their arm and thus doesn’t put as much strain on the ucl. Some people would argue that when a curve is thrown correctly that after release one actually pronates his arm. I know I’ll catch flack from that statement but so be it. You can’t just straight up karate chop because that WOULD blow out your arm. As for the slider, it is thrown with the same arm speed and action as a fastball but you supinate as opposed to prontate and that puts a lot of extra stress on the ucl. I believe, for the most part, that the injury history of people that throw sliders as opposed to curves speaks for itself.