I tore mine a couple years ago. Put your arm at a 90 degree angle. Move your hand in a left to right circular motion(like you are supinating at the top of a concentration curl). Now watch your bicep, if it moves when you twist your hand, it more than likely is not torn. If it does not move at all, you tore it. If the bicep has already moved up the arm a bit, its a good chance you tore it.