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Old 03-04-2013, 06:51 AM   #14
Fuji's Avatar
Join Date: Aug 2010
Location: Canada, Eh?
Posts: 6,378

Originally Posted by Chas Tennis View Post

This is a slice serve as indicated by:
1) the racket motion- mostly across the back of the ball
2) the label of the ball can be seen spinning in mostly a horizontal direction. (better seen in my copy than on Vimeo)
3) the ball has the characteristic slice trajectory curve and bounce for a right handed server.

The rapid internal shoulder rotation can be seen by looking at the rotation (axial) of the bones of the elbow.

I'm not able to see pronation before impact in this high speed video. However, I'm sure some pronation occurs on all serves before impact, possibly completed prior to the ISR. The server has a watch on; it's useful as a marker for total arm rotation at the wrist. When the arm is straight the total arm rotation is -

Total Arm Rotation Rate (at wrist) = ISR + Pronation.

If the rotation rate at the wrist is different than the ISR rate then that is pronation (or supination). In my opinion, the total rotation rate leading to impact might be due just to ISR. Needs better high speed videos with markers to measure.

I'm sure you can slice serve by carving on the outside of the ball, as Fuji describes, but this video is more of a rapid brush across the ball, exact angle not clear.

(The best stop-action single-frame can be done on Vimeo by pressing the play-pause button as fast as possible. I can't view Vimeo videos on my Samsung Galaxy S2 smartphone.)
Haha, it's hard to describe how in my mind I slice. The way I learned to slice off a serve was something like "peel the apple" by carving/brushing along the side of the ball.

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