You can really see the push/lift of the entire arm and shoulder from contact on in this video. Notice as well how Andy's shoulders rotate through contact, aiding the push, and driving the right side of his body through the ball.
Pause the video on contact and you will see how Andy's racket is angled below his hand. This is standard technique with the modern forehand and helps create the "leveraged lift" of the ball. Pause on contact and go through the next three frames - notice how much lift of the arm is occuring here. Also notice how the strings of Andy's racket continue to face the net. The tip of the racket holds back to create maximum connection between the arm, racket, and ball.
In the follow through notice how Andy's chin is touching his right shoulder. His right shoulder has really rotated over (windshield wiper) as an after effect of the extreme lift of the ball.
Also take a look at the great pulling motion Andy uses to deliver the arm and racket to the ball. From behind his hip, the butt cap of the racket leads the way as the arm and racket get pulled and lifted to contact. To read more about how to pull /lift the arm and racket to contact, click here