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Old 02-05-2013, 07:49 AM   #7
Chas Tennis
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Join Date: Feb 2011
Location: Baltimore, MD
Posts: 4,119

Originally Posted by jakeytennis View Post
how do the pros get topspin when they pronate on serves?

im trying to learn to pronate, but i can't imagine how to get topspin.seems like pronating just helps you hit a super fast flat serve.

where exactly during the serving motion is the strings brushing up on the ball, before the pronation?

this video says it's harder to get spin with the pronating finish than the "dirty diaper" finish

i have the "dirty diaper" finish

i would experiment and practice on my own, but it's winter and the nearest indoor courts are over an hour a way.
I have the same conceptual problem and still am trying to sort it out.

Believe that this is a kick serve. For single frame click play-pause as fast as possible.

Somewhere just before 0:08, when Stosur has her arm straight and up, she forcefully and rapidly uses internal shoulder rotation (or upper arm rotation) best seen by the elbow bones rotating. ISR occurs as the racket goes from about 90 to the straight arm and with the racket 'edge on' toward the ball to an angle called β at impact (shown in the thumbnail).

See ISR and β on all the other Vimeo serves showing the view from behind the server. β is the racket angle at impact shown on all thumbnails.

Leading up to β at impact the racket must be at an angle (~90 to β) to the arm to develop racket head speed from the straight arm rotation provided by ISR. Notice at impact that the strings are still going up for topspin even though she is near the top of her swing path.

In the later part of her follow through you see strong pronation that is necessary because the arm and racket are rotating and translating so fast that pronation is necessary to reduce stress stopping the motion and avoid injury.

This sequence of motions is complex and I have never seen it described in its entirely by words. I believe that you need words and high speed video together.

To video this rapid motion and the racket and ball at impact requires high speed video and a fast shutter speed.

Term Usage -
Internal Shoulder Rotation and Pronation. The term 'pronation' is widely used for tennis discussions in a way that is not definable:
1) by searching on the internet
2) by tennis instructors
3) by any forum readers

The discussions loosely describe - internal shoulder rotation (upper arm rotation) plus pronation (forearm rotation) - mistakenly as 'pronation'. This usage muddles understanding of the serve and stops dead anyone who attempts to look up the tennis usage 'pronation' on the internet. Try it.

Last edited by Chas Tennis; 02-05-2013 at 08:18 AM.
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