In my first two articles on the professional forehand, I discussed why I think the "double bend" structure leads to such blistering pace on professional forehands. Now let's see the role of this underlying structure in the windshield wiper action that is common in pro tennis. In my opinion this wiper action is widely misunderstood and often executely incorrectly by players who believe they are copying the pros.
When the pros make contact with the ball, you see a wonderful double bend, where the shoulder and hand are solidly behind the racket on contact. The ball compresses not only into the strings, but (indirectly at least) into the supporting hand and shoulder. There is another interesting aspect to the double bend on contact here. This is where we can see the relationship between the windshield wiper and the double bend.