Originally Posted by dominikk1985
trunk rotation slows down and arm accelerates. you don't want to spin through contact. many people now think that modern strokes are just relaxing the arm and then spin the body like crazy but this is not true. guys like fed have a great INDEPENDENT arm action. it's a multi stage rocket, first fires the rotation and then the arm as the rotation stops.
also get rid of the thought that the arm gets whipped through passively. the arm is accelerated by active contraction of the arm, shoulder and pec muscles. but this contraction must not be initiated too early or the kinetic chain is ruined. the muscles fire sequentially from the ground up. every ounce of muscle is used in a high level stroke but it has to be coordinated in the right sequence.
For the most part, this is an excellent perspective on the FH stroke -- it further clarifies what I was saying in posts #3 and #7. However, I must take exception to the parts that I've bolded
above. The torso/body might very well slow down prior to contact, but it does not stop rotating until well after contact. Once the "arm" stage of the rocket fires, the body continues to rotate for the FH (or a 2-handed BH). However, much of the later rotation of the torso/body is because of the momentum of the racket, racket arm and racket shoulder. Because the back shoulder continues to come around for the contact and follow-thru, the torso/body are pulled around with it.
OTOH, the torso often does stop rotating for the 1-handed BH of elite players. Since the back shoulder/arm is not attached to the racket, the back shoulder does not need to come around and, therefore, the torso can stop completely well before contact. This represents a more complete kinetic chain transfer than the FH mechanics.