Internal Shoulder Rotation on Serve from Overhead Camera, FYB

Chas Tennis

G.O.A.T.
In about 2009, Fuzzy Yellow Balls made some serve videos from a camera placed above the server. The server was Frank Salazar. The flat, slice and kick serves were covered. Toly added some processing and created a composite picture.

These above camera views particularly show:
1) When internal shoulder rotation (ISR) starts.
2) The angular rotation in degrees from the start of ISR to impact.
3) Angles of the hand path, racket path, racket face, all vs time. Unfortunately, enough of the ball's trajectory is not shown for a firm trajectory. The ball appears to be headed to the right.

These ISR observations are important for the performance of the serve. Also, data on the angular rotation before impact is important for performance but in many years I have not found any data. My guess of the current ATP players' range of ISR rotation angle, from start to impact, is roughly from 50-100 degrees. There is not much available data or overhead videos for current 2021 servers. Angular measurements for ISR are very hard to find. These angles can be measured from these FYB videos for Frank Salazar.

Often posters' serve videos show that ISR starts close to impact or even after impact. This flaw indicates more understanding is needed for their serves. The above videos can be viewed and the range of ISR rotation angle measured with a protractor. Some pronation may be present in addition to the ISR.

Unfortunately, the side of the court for the serves, deuce or ad, is not clear and the ball direction has to be guessed from one frame of ball travel. It would be very informative to see some of the current ATP servers in similar camera set-ups.

Slice

Kick

Flat

This Toly composite picture does not cover the start of ISR, so the full angle of ISR rotation - from start to impact - has to be measured from the videos.


An overhead camera set up with Vic Braden working on a forehand set up probably at Gideon Ariel's Coto Research Center, CA. (Braden's association with Coto in story below.) The PVC cube is a reference for calibrating the camera.



There are drones that have high speed video. Safety issue for some drones? - a builder was using a large drone, 5 lbs?, to document progress on houses that he was constructing. When asked if there had every been accidents, he said that when he started using the drone, he once let go of the controls and the drone was programmed to shut down. It fell to the ground.
 
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yossarian

Semi-Pro
How do you apply these findings to a practical approach to the serve? How do you take this information and actually alter serve mechanics to beneficially change them?

To put this as simply as possible for you: if you are a tennis instructor and you observe from video that your student isn't doing this, what do you do to remedy that?
 
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MoxMonkey

Rookie
FWIW, If you search frank salazar in youtube these videos pop up.

From there I slowed the speed down in the settings to 25% and you can really get a good view of the ISR moving the stringbed into impact.

Thanks for posting this, it's quite insightful
 

Chas Tennis

G.O.A.T.
FWIW, If you search frank salazar in youtube these videos pop up.

From there I slowed the speed down in the settings to 25% and you can really get a good view of the ISR moving the stringbed into impact.

Thanks for posting this, it's quite insightful
On Youtube, you can also move single frame by using the period & comma keys.
 

5263

G.O.A.T.
Unfortunately, the side of the court for the serves, deuce or ad, is not clear and the ball direction has to be guessed from one frame of ball travel. It would be very informative to see some of the current ATP servers in similar camera set-ups.
As you mention, not so clear, but pretty sure he is serving to the ad side based on where he looks at the beginning and again after his serve. Also the arm path supports this best guess.
 

Chas Tennis

G.O.A.T.
As you mention, not so clear, but pretty sure he is serving to the ad side based on where he looks at the beginning and again after his serve. Also the arm path supports this best guess.
Only one ball after impact appears. It is headed to the right from the original ball position of the drop. There is no middle court marking on the baseline.
 
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