1) Sometimes both your feet don't leave the ground, but not always.
2) Tossing arm brought down to side 9 times & 4 times it goes behind you. Also, limp. Might relate to how you are moving your trunk forward. ?
The service motion for pros has the tossing arm always tuck in front
, often across the body, with some intent. See pro videos linked below.
3) The racket-forearm angle at/near impact seems to have a reasonable angle to it. But check more serves as it might be varying.
4) Shoulder angle at impact did not look bad, but always check yourself
. Search for the Ellenbecker video on shoulder orientation to use while serving to minimize the risk of impingement. Your angles did not look bad from what I could see _ but watch the Ellenbecker video.
5) Approaching contact your elbow is not straight as early as the pro serves. Watch how straight the pros's elbows are. The arm goes up, gets about straight, the racket-forearm angle is at about 90°. Then the arm rotates as the racket forearm angle decreases to say 30°, (varies) at impact. The final approach to the ball takes only 20 milliseconds for pro serves, see Raonic serve below, so you have to be on automatic and not expect to think through this extremely rapid motion. (Considering the shoulder joint ISR & wrist joint motions, the racket head sort of 'spirals up
' to impact. But lasting only about 1/4 second as played back at 30 fps from the 240 fps recordings
, it can be hard to see. See 420 fps Raonic video.)
Raonic serve spiral up.
See the other pro videos
(To do stop-action single-frame on Vimeo press the play-pause control as fast as possible.)
There is nothing forced - don't put the arm up, try to force a turn, etc. It should flow on its own as a final result. But check your serves against high level serves.
Get a clear understanding of what internal shoulder rotation
is. It is clearly shown in most of my Vimeo pro videos. Watch carefully for the very fast arm axial rotation as indicated by the bone shadows of the elbow. Also the stretch shortening cycle
where stretched muscles are used for rapid joint motions.
To video your serve better:
1) Your view point behind the server was good. Move the camera closer, the higher the better. Frame to get the complete foot to racket plus a little more but consider the distortions from the wide angle lens......
2) Shoot videos in direct sunlight (a sharp shadow will be cast). With more light the automatic exposure control of your camera will pick a fast shutter speed and you will get much less motion blur.
3) You might wear a sleeve-less shirt to show how your upper arm rotates, or put a piece of tape at your elbow as a marker
4) Take some videos from the side. Probably perpendicular to the ball's trajectory might be better than along the baseline.
What camera did you use?