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Old 12-04-2012, 02:15 PM   #104
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Originally Posted by toly View Post
Sorry, but I think your statement is incorrect.

Let’s 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

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. That’s why there are so big differences in their follow through.
Toly, you should join Tennisplayer and read Brian Gordon's articles on the forehand...I think you would enjoy is biomechanical perspective...Btw, if i understand you correctly, you are essentially correct with your observation.

Active wrist usage is a requirement to counter the rotational force created as the racquet rotates around the hand....Much of wrist movement is for proper racquet face orientation and for directional/shot line purposes.

Last edited by chico9166 : 12-04-2012 at 02:38 PM.