Originally Posted by BevelDevil
Do you currently pronate on the take back (face your palm downwards)? I found this, and the timing of it, to be the trickiest part of the Federer stroke.
Instead, I like Del Potro as a model because he doesn't pronate on the takeback. It's a lot simpler and easy to learn, though I don't think it generates the same power or topspin.
Pronation at the end of the take back, just before the forward swing is the exact movement you WANT to be doing -- it's what splits both types of forehand transition moves into the efficient and inefficient kinds. If you want to generate more spin and swing faster while retaining a much higher level of control, you need to swing forward with your arm set into a prone position.
That movement (pronation) allows you to tap into a stretch-shortening cycle in the muscles responsible for the internal rotation of the shoulder... in short, your arm moves faster around your body if you get that. Every player who doesn't meet this standard will suffer consistency issues when trying to retain control at high power levels -- and that's scientifically established.
Del Potro is an example of player who doesn't fit the bill, although he's more in a third kind of transition movement apparently. But note that even players who use a double bent structure will reach this position. Others will supinate before swinging forward. You must meet the ball with a slightly closed face and your arm will inexorably supinate as you move it forward... if you already begin the movement, you'll have troubles reaching a consistent contact and you might as well not be able to exploit a second stretch-shortening cycle, this time in your forearm pronators, which is responsible for added spin at contact. The point here is that both of these little tweaks can be added to the forehand of any player, even amateur, so long as he has a fundamentally sound basis; if everything's there with the foot stance, the arms and body posture, you only need to add little twitches to make it go from good to great.