I like this lesson a lot because it is a great example of a swing problem that has no explainable cause. Dan is a very tall guy, but he is athletic and perfectly capable of making a nice, full swing, when there is no ball in front of him. When his brain knows that he is going to hit the ball his right wrist bends back, his right arm jams up, and his left arm squashes low against his chest, which means that his backswing is not going much past left arm parallel.