The answer is in the question, because contact is not one moment in time, and the racket plane is not the same as the string local deformation plane.
Hitting Up on Serves
- Thread starter Topspin Shot
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The answer is in the question, because contact is not one moment in time, and the racket plane is not the same as the string local deformation plane.
Chas Tennis
G.O.A.T.
Any evidence?
1) no the racquet does not not point up at impact - high speed videos could show this if we had someone to do the work. Not presented in this thread as discussed in earlier replies.
2) no the path of the strings is not upward at impact - High speed videos show the path of the strings is upward for the kick serve. They move laterally, up and forward during contact. [lateral means to the side of the forward racket motion]
For the flat and slice serves, these have topspin also so there is probably a lateral upward component to the path but that would have to consider ball drop as a source of the topspin. On the videos I've looked at, my impression is mostly that there is an upward path for slice and flat but it would have to be studied. I have seen slice serves where the highest point of the racket is higher a frame after impact (240 fps) and other slice serves where it is the same height. . It is very difficult to describe what the racket is doing with words. High speed videos with small motion blur are the best way to understand and communicate the motions.
High speed videos have not been presented or are easy to find to support your conclusion in #2.
As far as I can tell there is not a single high speed video showing someone releasing their racket in a simulated service motion. I'd expect the centrifugal force from the swing to throw the racket upward and the centrifugal force from internal shoulder rotation to make it go to the left for a right hand server. The racket would fly at an angle up and to the left. For a Waiter's Tray technique with no ISR I would expect the racket to only go up. Some people advocate throwing the racket, why don't we have a single video of this motion.
There are videos that show that the ball can be thrown in a way that simulates the internal shoulder serve but most are not high speed so the upper arm ISR is impossible to see for nearly all viewers. The video in #100 above could be very good if it were in slow motion, with small motion blur so that people could see what happens. Why show a rapid 3D motion where all that is caught is one or two frames of a complex 3D motion. And then try to fill in the gaps of what is not shown with undefined words that can be interpreted in many ways by viewers?
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Um.....what? You're hopeless I'm afraid.
I have no idea why you think the racquet could go to the left (it wouldn't) but you do see that the racquet will go up - so what else is there to discuss? The serve is an upward throw, you're hitting up so the racquet will go up if released at contact. And no, that doesn't mean that the racquet face is pointing up, it's vertical or close.
To answer your question, someone would have to have the control to release a racket at the precision of below a millisecond, at any time from the initial contact and spanning the dwell time. And what hits the ball is the strings, not the racket. See the posts on asymmetric string deflection. That is why your question is misleading. You just want a simple answer which supports your opinion.
It is simple. The contact point corresponds exactly to the release of the racquet in a "racquet throw" at a certain angle. Determining the angle to release the racquet (to contact the ball) is why you practice thousands of serves by yourself on the court.
Maybe this will help - perform your normal serve, toss the ball, swing up to contact but at contact truly release the racquet; the racquet will contact the ball. This is not hard to do and if you can't do it then you're serve is completely messed up and if your racquet does not go up then you got some serious work to do.
You win, man.
Chas Tennis
G.O.A.T.
If you held your arm up and only did rapid internal shoulder rotation and let go of the racket when the stings were facing forward -
What direction do you think that the racket would fly off in?
Depends when you let go - it would fly in a straight line so you could make it go any direction you wish. If you're letting it go at contact with the ball then it will go in that direction - wherever the ball is. That's one of the keys to the serve - when to let go or when to make contact. You toss the ball and throw the racquet at it - the timing is worked out for you because you have a target, and the target has to be up. Most poor servers let the ball play them, they follow the ball with their racquet, adjusting. That is wrong - the ball is in the air, you see it as stationary, and you hit it.
Chas Tennis
G.O.A.T.
Do you understand the joint motion of internal shoulder rotation or ISR?
Yes, shoulder rotates such that the hand, if outstretched, will rotate counter clockwise if looking at it from that person's vantage point. Do you understand that if a child is flung off a rapidly moving merry-go-round, the child will fly in a straight line?
Power Player
Bionic Poster
I stand by Sureshs.
LakeSnake
Professional
Evidence?
As far as I know, all pro servers have been taught via coaching cues, not video. Thus, the best way to communicate and understand the motions is via these cues.
Raul_SJ
G.O.A.T.
Taking the racket plane as the reference, I think there is agreement that the racket plane at initial contact is always tilted upwards on topspin serves. During the 5 millisecond dwell time, the racket plane may cross the vertical, but it is tilted upwards at initial contact.
So the only question is what happens on the flat serves. It may be similar to topspin serves, but with less of an upward tilt at initial contact.
If you're going to throw in the kick serve - what's the point in having a discussion? This is about flat serves.
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Chas Tennis
G.O.A.T.
Looks like you are correct and I'm wrong and did not see what I expected. I guess the physics principle is that the center of mass of the racket travels in a straight line with constant velocity after the restraining forces of the hand are removed and the angular momentum (rotation) around the center of mass remains constant. Nice demo.
So I went out and took some videos of myself releasing the racquet into the ball and I have a confession. It is very difficult if not impossible to time it such that the racquet goes up and the ball goes down. Turns out the point of impact is exactly between the point where the racquet hits its highest point and the point where it starts to descend rapidly. Still, I am throwing up but when I let the racquet go while still swing up, the ball would fly up too. It's a upward throw where you hold on to the racquet and it contacts the ball right as it starts to turn over and go down. The videos are pretty funny.
Thanks - I was a little off on my opining about throwing the racquet at the ball as you'll see above.
Yeah the contact is close to the apex as the racket is turning around. That is why the first serve is so difficult and the pro percentages are so low. If you really hit up, the ball fill fly up. If you really hit down, most likely it will go into the net. You need to hit up such that the contact is very close to the apex during the dwell time, and the falling ball causes a local string deformation pointing downwards. It is amazing that people are able to serve at all. It shows how wonderful the human brain is to be able to do it without conscious effort. As the swing speed increases, the more difficult it gets.
Yeah but it's still an upward throwing motion on all serves. The timing is the key but it's not like you're missing into the ground or into the backcourt, it's not that tricky.
Tight Lines
Professional
Slightly off topic, but I think it deserves a mention here. IMO, the most important factor in a serve is the toss. If you get the toss at the correct spot (correct height and location), I am pretty sure that you will get it in the service box more than 90% of the time. Whenever I have trouble serving, ball going into the net or going long, 9 times out of 10, it's my toss. When I get nervous in a match, I tend to toss lower and that screws up my rhythm.
Try standing against a vertical post of a tennis court fence and toss to a spot with a racket in your hand. You will be amazed how much variation there is in the location and height. How many people practice tossing? I'd bet not that many.
Harry
Up ward throwing motion for sure, then the racket head passes the shoulder before impact, just inside the court.
Gravity helps on slow flat serves.
Some spin helps on fast serves, but not underspin.
Most players have contact points well above 9'6" off the ground.
How upwards we need to hit depends on our contact point and how hard we actually serve.
Gravity helps on slow flat serves.
Some spin helps on fast serves, but not underspin.
Most players have contact points well above 9'6" off the ground.
How upwards we need to hit depends on our contact point and how hard we actually serve.
Chas Tennis
G.O.A.T.
Back to throwing the racket as a drill for learning the serve:
If you asked me to throw a racket I believe that I would throw it like a Tomahawk.
Here is a slow motion of a Tomahawk throw.
Another Tomahawk throw-
I'd say that they are not throwing with a motion that is similar to a high level serve, an internal shoulder rotation serve. They seem to be throwing with a technique similar to a Waiter's Tray technique!
Does anyone have a video of the racket throwing as a drill or practice technique for the serve?
Is there ISR or not?
Should there be for racket throwing to have value as a drill?
If you asked me to throw a racket I believe that I would throw it like a Tomahawk.
Here is a slow motion of a Tomahawk throw.
Another Tomahawk throw-
I'd say that they are not throwing with a motion that is similar to a high level serve, an internal shoulder rotation serve. They seem to be throwing with a technique similar to a Waiter's Tray technique!
Does anyone have a video of the racket throwing as a drill or practice technique for the serve?
Is there ISR or not?
Should there be for racket throwing to have value as a drill?
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Chas Tennis
G.O.A.T.
duplicate post
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Chas Tennis
G.O.A.T.
If the principle above is correct and the racket's center of mass travels in a straight line after the hand lets go and before wind resistance and gravity change the racket's trajectory, there are some interesting implications. (The center of mass for my racket - by balancing on my finger - is close to where the head's lower frame is on the racket's centerline.)
Toly pictures of Fuzzy Yellow Balls overhead videos showing the path of the racket's center of mass from above. The forward and side motion show well and you have to estimate the upward component.
The pictures show the racket paths from above for the three types of high level serves. With the overhead camera view, the forward and side to side motions are shown well but the racket is coming up also toward the camera and that direction does not show well, keep that 3D racket path in mind. Track the center of mass. Then
To throw the racket up - using the real high level serve's racket path as shown in the pictures - you have to release it while the center of mass is rising. Track the center of mass to see the direction that it should go on release.
1) For the slice or flat serves at the time of impact, if you release the racket rear impact when it is going mostly in the direction that the ball is traveling it should go mostly forward - and not much up or down - there should be much smaller up or down velocity depending on the exact millisecond timing when it was released and also maybe some side velocity to the right for the slice. How could you release it at around the time of impact and have it go considerably up?
2) For the kick serve the racket's center of mass has an upward velocity for a some milliseconds after impact so you probably could release it around the time of impact and it would continue with a considerable upward component.
At this point, I don't understand how to throw the racket up using the racket path for an internal shoulder rotation serve.
For a Waiter's Tray serve, the Tomahawk throw would probably allow upward release before the point of impact position of the racket. See reply # 128.
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You can't release at impact and have it go up - I thought I admitted that. At impact it will go straight ahead, maybe a little down. For flat serve.
Those tomahawk guys are not throwing like you'd throw a ball in the air.
Most of the ISR comes after impact - it's just the deceleration phase of a regular throw, the shoulder unwinding after being rotated from the torque of the throw.
compare the two
Those tomahawk guys are not throwing like you'd throw a ball in the air.
Most of the ISR comes after impact - it's just the deceleration phase of a regular throw, the shoulder unwinding after being rotated from the torque of the throw.
compare the two
Chas Tennis
G.O.A.T.
The Tomahawk is a better comparison for throwing the racket.
For the baseball pitch, the powered part of ISR accelerates the arm and ball to speed before ball release. The forearm is at a changing angle (elbow extension) to the rotating upper arm to get hand velocity from ISR.
For the tennis serve, the powered part of ISR accelerates the arm and racket to speed before ball impact. The racket is at a changing angle to the forearm (wrist motion) in order to get racket head speed from the upper arm rotation from ISR.
For both the baseball pitch and serve, there is a considerable amount of ISR and pronation in the decelerating phase of the follow through, but it is more just for slowing down and has no effect on ball speed. But there is considerable angular ISR change after release or impact.
Girl throwing ball and serving. ISR rotates the upper arm (humerus, between the shoulder and elbow).
http://tt.tennis-warehouse.com/inde...in-my-front-garden.481498/page-3#post-8061362
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How much ISR contributes to racquet head speed is irrelevant because it is completely involuntary and comes at the release (of ball) of a proper throwing motion. There is almost zero control component on the serve, the arm is simply flung like a rope at the ball. As I said, the ISR is simply an unwinding of ESR (brought on by the force of body's pull of the hand/ball/racquet). I have ISR on my serve (from video) yet I do nothing but throw my racquet at the ball. If you want ISR, you have to be able to throw in such a way that the elbow lags behind the body (racquet drop).
Chas Tennis
G.O.A.T.
There is a stretch shorten cycle involving ESR and ISR. The details of ESR and ISR can be seen in high speed videos. I don't understand how ISR works regarding nerve signals and muscles but somehow timing on millisecond time scales can be trained, perhaps trial and error once the proper motion is there.
At Wimbledon, I just heard one stat for a small sample of serves in one match (maybe Federer vs someone?) - 30+ percent of serve bounces were within 9" of one of the side lines. That stat indicates amazing timing accuracy of ISR since the racket head rotates around a vertical axis at perhaps 3° per millisecond at impact and timing errors cause the ball to go to the sides.
One principle that was mentioned in the Biomechanics of Advanced Tennis (2003) is that nerve signals might be given for ISR to start while the ISR muscles are still being stretched by ESR. ? I believe that this is called 'active' stretch. In more recent research, the details involve Titin and how it might be controlled, a subject that is not well understood.
I think that we are very aware of EMG Signals and our effort levels, as in slowly curling a heavy dumbbell. But the awareness of feelings during rapid stretch shorten cycles lasting 20-30 milliseconds are not as obvious. ? But the forces from pre-stretched muscles play a big part in athletics regardless of the feelings or awareness - a very interesting subject.
At Wimbledon, I just heard one stat for a small sample of serves in one match (maybe Federer vs someone?) - 30+ percent of serve bounces were within 9" of one of the side lines. That stat indicates amazing timing accuracy of ISR since the racket head rotates around a vertical axis at perhaps 3° per millisecond at impact and timing errors cause the ball to go to the sides.
One principle that was mentioned in the Biomechanics of Advanced Tennis (2003) is that nerve signals might be given for ISR to start while the ISR muscles are still being stretched by ESR. ? I believe that this is called 'active' stretch. In more recent research, the details involve Titin and how it might be controlled, a subject that is not well understood.
I think that we are very aware of EMG Signals and our effort levels, as in slowly curling a heavy dumbbell. But the awareness of feelings during rapid stretch shorten cycles lasting 20-30 milliseconds are not as obvious. ? But the forces from pre-stretched muscles play a big part in athletics regardless of the feelings or awareness - a very interesting subject.
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Yes, it is a stretch shortening thing - and that means that it is involuntary and cannot be timed. If someone is not getting ISR/ESR - it is a problem with a poor throwing motion. People call it waiter tray or push serve etc. - it's a lack of a throwing motion.
onehandbh
G.O.A.T.
For the TL;DR people on TTW:
Tomas does not recommend flinging a child from a rapidly-moving merry-go-round in order to understand how hitting a serve feels like.
Shroud
Talk Tennis Guru
Man. That was one of the funnest things as a kid…
johnmccabe
Hall of Fame
a very common phemomena in research. Some young students identified a gap in literature with their new findings. Then realize some Russian papers from 30 years ago already covered it nicely. There is also a meme that I could forward. Why posting photos is such a pain in the butt here?
