Originally Posted by SystemicAnomaly
Interesting observation. Rafa's torso pretty much ends up facing the net at the completion of his rodeo finish. In contrast, this video shows one of his more conventional finishes on a high ball that goes across his chest. In this case, we see that his torso does slow down at contact but still continues to rotate after contact (more than 60 degrees).
Yes, I think that we can definitively say that on most forehands the torso rotation slows prior to contact but doesn't stop, especially for the more conventional finishes used by most players. The rest of the rotation is due to momentum and safely decelerating the racket, arm, and torso rotation.
I still have a suspicion that the ball can be hit hardest when the deceleration of the torso turn is rapid, as when serving. I recall reading an article by a back/core muscle researcher named McGill(?) who asserted that top professional athletes have the ability to stiffen the core rapidly during complex actions and thereby causing other parts of the body to greatly accelerate, as when throwing or swinging a tennis racket or bat.
The Rafa rodeo finish is intriguing but not something that I'd start beginners hitting. The other guy who seems to use a similar technique to crack deceptively fast fhs is Dolgopolov, but I think Dolgopolov relies on his leg muscles more than Rafa for producing topspin.