Caroline Wozniacki Photos: Picture Gallery of Strokes

The kinetic chain that produces a powerful serve starts with a strong upward thrust from the legs, which depends upon a good knee bend, as Caroline Wozniacki demonstrates in this photo. By reaching after the tossed ball with her left arm, Caroline helps to ensure that she lets go of the ball fairly high and thus closer to her point of contact, which makes her toss more reliable. Caroline's shoulders are turned so that her back partly faces the net. As her upper body uncoils to strike the ball, it will contribute to her power.