To all of you who had shoulder pain as a result of this movement, I urge you to consider correcting your posture. I've found that if I shove my back and ass right up against the back rest/top of the seat, and clip in with the seat belt, it puts me into a position that causes my shoulders absolutely no pain what so ever. In fact, my delts felt more annihilated with slightly less weight, so as long as I was in the position just described. Needless to say, I can now safely use this movement with no concern of injury.