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Old 12-04-2012, 01:43 PM   #103
toly
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Quote:
Originally Posted by sureshs View Post
That is why I said it is almost impossible to keep the wrist laid back and pronate the forearm. The wrist will rollover by itself.
Sorry, but I think your statement is incorrect.

Letís analyze Federer straight arm forehand. FH with bend elbow is more difficult for explanation.

When Federer rotates the arm around shoulder, he creates centrifugal force which has normal component to the racquet string plane. This force normal component (motion dependent torque) automatically rotates the racquet about the wrist in counterclockwise direction, see Rod Cross article http://www.racquetsportsindustry.com...the_serve.html.

This normal component is function of angle (ϕ) between axes of arm and racquet. If ϕ=0, this component is zero.

On other hand, Federer usually applies arm pronation. This is also angular rotation, which also creates its own centrifugal force and motion dependent torque. Rod Cross completely ignored this fact. Moreover, this motion dependent torque pushes the hand to rotate the racquet about the wrist in clockwise direction, opposite to the torque created by arm rotation.

If the wrist is passive, pronation torque always prevails and the racquet string bed would be vertical after impact!!!

If active wrist ulnar deviation creates torque which is bigger than pronation dependent torque, then the racquet string bed will be horizontal!!!

So, Monfils is definitely hits the ball with strong active ulnar deviation, but Fish hits with passive wrist. Thatís why there are so big differences in their follow through.
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