Cable preacher curls demand three things: sit tall on the bench, pull your wrists back at the top to fully stretch the forearm, and move slowly. Fast reps in that stretched position tear biceps.
This guy doesn't tear his bicep. I hate watching this shit. Oh, he hit himself in the face. This exercise is the cable preacher curl. I'm sitting up nice and tall, which makes it a hell of a lot harder. I can get into that full stretch position on a preacher bench is to pull the wrists back. See at the top, not here with my wrists, I'm pulling them back. I'm allowing the forearm flexors to stretch completely, but you want to do it under conditions of control. And certainly you don't want to do this fast because you can tear a bicep very, very easily in this position.
