Originally Posted by Povl Carstensen
Is this a universal truth?
If you pull the racket in, and it in turn is in physical contact with the ball at impact, do you think it will pull the ball further in towards you or send it out at 80 mph? You can try it by leaving a ball on the court, touching it anyway you want with the racket at any angle you like, and pulling the racket. See if the ball comes in towards you or goes out speeding in the other direction.
The Federer forehand consists of a tucking in of the arm (inwards pull) as part of the rotation before contact, followed by an extension towards the target at contact, eventually coming inwards again across the body after contact, the last phase being mostly due to the accumulated inertia and not a conscious action.