Originally Posted by bhupaes
I think Serena uses a combination of ISR and biceps, pretty late in the stroke (close to contact), hence one might say it's abrupt. But that doesn't really matter. In answer to your question on how to create a linear stroke, notice how the path of the racquet head is pretty much linear for most of the stroke. It becomes circular close to contact due to her ISR and biceps action. Now ask yourself, if the ideal stroke is totally linear, why should Serena change a good thing (linear motion) into a bad thing (motion in an arc), and so close to contact at that? Could it be because the act of pulling in the racquet increases RHS both forwards and upwards?!
I think Serena and other pros pull the bicep and use internal rotation of the shoulders to whip the head of the racket at contact. It seems a normal part of the modern type stroke. If you watch old era guys with wood rackets they don't really do this. Its like the serve really. In the serve you serve up so the hand will slow down as the racket whips through the serve. The conti grip and pronation on serve allows this. The fh now follows similar principles of the whip applied in a different way.