Racquet snaps the wrist on serve...

[julian1]

Another article by Rod Cross

Interesting article by Rod Cross...

http://www.racquetsportsindustry.com...the_serve.html


This is why we must aim high when hitting the serve and why the elbow remains high after impact on good serves...

http://twu.tennis-warehouse.com/learning_center/doublependulum.php

To be exact it is really a paper describing a recently published article in American Journal of Physics by Rod Cross
It has Paragraph 8 devoted to forehand

[tennis_chiro]

Whole new meaning

http://twu.tennis-warehouse.com/lear...lependulum.php
To be exact it is really a paper by someone else describing a recently published article in American Journal of Physics by Rod Cross
It has Paragraph 8 devoted to forehand

Thanks, Julian. That was really great. I've now done my mental gymnastics for the whole day, maybe even the whole week.

Wow. Talk about paralysis by analysis. I'm not even going to consider linking to the American Jounal of Physics article. I probably need to read that a couple of times to really digest it, but there are a few things that this article validates on a more applicable level.

(I like to think my students walk away from my lessons thinking, "Wow, that was interesting. Don really knows what he is talking about!". This is great information for me, but I already have a reputation for being too technical. If I integrate too much of this overtly into my lesson presentation, as true as I believe it must be, students may be really fascinated during my presentation, but as they don't get to "reread" that presentation, they will probably walk away saying, "What the hell was that about?!")

So:
1. Trying to hit your serve "harder" when you are serving really well will probably make the ball go slower, if not totally destroying your rhythm and effectiveness. Hit it "faster", not harder, by releasing more completely.

2. On the groundstrokes, use the wrist as a "passive hinge" controlling the ball, but not snapping through it as you try to keep the strings on the ball as long as possible.

3. In the same vein as the passive hinge, try to swing the racket head, not your arm or your hand. This means the wrist maintains its position and slight wrist cock as you swing forward to the ball on the forehand.

4. On the other hand, this validates Phil's effort to emulate the Federer wrist extension/flexion flick at the beginning of his forehand forward swing.

I do think we missed a whole lot of stuff here about internal rotation and the optimum angle of the racket shaft to the forearm to create effective power from internal rotation (you don't get much if the upper arm, forearm and racket shaft form a straight line...which they do in the frying-pan-grip-serve used by rank beginners). I wish we could get a comment from Rod about where that fits into the picture. Probably, I just need to do a little more reading in "The Physics and Technology of Tennis" (Is it in there, Julian?)

Well, that's good for a start on Sunday morning. Curious to hear what the rest of you think.

don

[julian1]

Two pictures to analyze

Thanks, Julian. That was really great. I've now done my mental gymnastics for the whole day, maybe even the whole week.

Wow. Talk about paralysis by analysis. I'm not even going to consider linking to the American Jounal of Physics article. I probably need to read that a couple of times to really digest it, but there are a few things that this article validates on a more applicable level.

(I like to think my students walk away from my lessons thinking, "Wow, that was interesting. Don really knows what he is talking about!". This is great information for me, but I already have a reputation for being too technical. If I integrate too much of this overtly into my lesson presentation, as true as I believe it must be, students may be really fascinated during my presentation, but as they don't get to "reread" that presentation, they will probably walk away saying, "What the hell was that about?!")

So:
1. Trying to hit your serve "harder" when you are serving really well will probably make the ball go slower, if not totally destroying your rhythm and effectiveness. Hit it "faster", not harder, by releasing more completely.

2. On the groundstrokes, use the wrist as a "passive hinge" controlling the ball, but not snapping through it as you try to keep the strings on the ball as long as possible.

3. In the same vein as the passive hinge, try to swing the racket head, not your arm or your hand. This means the wrist maintains its position and slight wrist cock as you swing forward to the ball on the forehand.

4. On the other hand, this validates Phil's effort to emulate the Federer wrist extension/flexion flick at the beginning of his forehand forward swing.

I do think we missed a whole lot of stuff here about internal rotation and the optimum angle of the racket shaft to the forearm to create effective power from internal rotation (you don't get much if the upper arm, forearm and racket shaft form a straight line...which they do in the frying-pan-grip-serve used by rank beginners). I wish we could get a comment from Rod about where that fits into the picture. Probably, I just need to do a little more reading in "The Physics and Technology of Tennis" (Is it in there, Julian?)

Well, that's good for a start on Sunday morning. Curious to hear what the rest of you think.

don

I would suggest two analyze 2 pictures/graphs:
Fig 3b
Fig 10
Don,
please let me know what do you think about these pictures/graphs

[tennis_chiro]

Not as simple as it seems

I would suggest two analyze 2 pictures/graphs:
Fig 3b
Fig 10
Don,
please let me know what do you think about these pictures/graphs

At first glance, it is pretty obvious: the arm comes to an almost complete stop as the racket head approaches impact. I say obvious for the serve because I can explain that the measurements are in the x/y plane and don't account for the internal rotation aspect of the swing at that moment. We know wrist flexion and ulnar deviation are not enough to account for the racket head speed at that moment, but they are contributors as well. But figure 10 is for the forehand and that is a kind of a "scratch my head" realization because there is not that much at the wrist at this point except some radial deviation to generate topspin...so that is a little more surprising.

When I first started the Clark Graebner Tennis Academy in Grand Central Station 40 years ago (6/7/71!), I had the classes start with teaching grips and contact points on the first lessons (750 students in classes of 8 with 8 ball machines on two 55' courts); second lesson we focused on the follow through (no wraps back then). I don't think I knew how right I was to put the emphasis there. I've always felt it was really important to get the student to feel the contact point out in front of them at the appropriate spot. I think we've had discussions on this forum, led primarily by Geoff, about the importance of "defending the contact point". Rod Cross's article just points up even more how important that attitude is.

I still have a little question in that while this measures angular velocity, the question is in what plain is that taking place. If it is in a plain parallel to the upward movement of the racket towards the ball, we could calculate by its' angle how much the arm is moving upward at contact (which I believe would not be zero). If it is measured in the horizontal plane, then there is no accounting for the upward movement of the arm and that is a little disingenuous, because the arm is really still moving pretty fast. It may be true from a physics point of view that the upward movement in the z plane should not contribute to linear velocity in the x and y planes, but let's let the data show that.

don

[julian1]

A paper for you

Don,
please check your E-mail

[llll]

Okay, Bottle, I went through the Cross article once more. Try this

You can't create the actions Cross is talking about with specific deliberate actions. (I think.) However, you can perform drills that include intrinsically the motions and actions that must be included in the total service motion to accomplish the effects Cross is talking about in the article.

You will not generate those 150 lb. forces deliberately, but if you generate enough racket head speed and simply hold on to the racket (!), you are by definition exerting the necessary centripetal force to balance the centrifugal force the momentum of the racket head has created. If your wrist is relaxed while controlling the racket head, the racket face will direct a force perpendicular to this centrifugal force which powers the ball forward.

So there are a few steps to this drill.

First, you have to understand what my "Figure 8 drill" is. I think you are familiar with this but other members of the forum might not be. Just pretend you are making continuous swings standing in an alleyway extending to the target and there are 30 foot high glass walls on this approximately 2 foot wide alley. Here's a clip of the figure 8 drill.

http://www.youtube.com/watch?v=gaS-qtQWym4&NR=1

Unfortunately, I didn't have audio (I thought I did) when I made this recording. I need to update it and put some more videos up, but haven't done it yet. You could use this in conjunction with the positions demonstrated by Kerry Mitchell in his first service article

http://www.tennisplayer.net/members/teaching_systems/kerry_mitchell/the_lesson_process_serve_part_1/

Now, we get to the specifics of generating your increased racket head speed.
We start with internal rotation.
Stand facing the net with your upper arm next to your body and your forearm perpendicular with the racket shaft actually parallel to the baseline, the palm up, racket face horizontal and off to the right of your body. (for righties. Are you a lefty, Bottle? I mean left handed.) You can even rest your right elbow in your left hand.
Without taking the elbow out of your left hand, rotate your forearm to the left so the racket face moves 180 degrees to where it is face down, palm down, but the face again horizontal, but on the opposite side of your body.
Swing it back to the start.
Now go back and forth as quick as you can without moving your right elbow out of your left hand.
Optionally, you can go one stage further with this particular step by swinging the racket so far to the left that the face goes past horizontal and the shaft even begins to point down as it goes more than 180 degrees. At this point, you would be adding a little pronation and your elbow would pull out of your left hand.
In any case, do this back and forth as fast as you can. Feel the internal rotation and how the racket head goes past the wrist.

Now you try to take this feeling into doing the aforementioned Figure 8's. Try to "whistle" the racket at its highest point in the swing, just at or after contact. Next try it actually hitting the ball.

Want more?

Stand with a slightly open stance at about 45 degrees to the baseline (because this is an abbreviated motion and you won't have the benefit of a full swing to turn the hips and shoulders forward from the normal starting position).

Position yourself so the shoulders are actually parallel to the baseline (or even perpendicular to the intended path of the ball).
First put the racket face up to the contact point. (Remember the racket is not straight up. For a righty, the forearm and the racket shaft form a 10 to 20 degree angle at contact. Just guessing on those numbers. Check with John and Brian's data.)
From the contact point, while leaving the elbow exactly where it is pull the racket head back down as you externally rotate as you reverse the internal rotation that took the racket up to the ball.
Now, while leaving the elbow where it is, swing the racket head up to the contact point and past to the "Sampras racket head down" point. Now swing the racket back and forth along this path. It's kind of like what we were doing in our first exercise here, but a little different.

Note: it is important that at the starting point of this motion the butt of the racket is pointed like a flashlight at the ball and also in the direction of the target. Most people have to be corrected from a position where they have the shaft of the racket pointed too far to the right and they are unable to generate sufficient force in this swing in the direction of the target to get the ball over the net.

Once you get a little feel for it, starting from that point with the elbow up in front of you, toss and "tap" the ball over the net. Range of motion and a "clean" contact is the goal here, not speed.

When you feel you can do that a little bit, try to incorporate the feeling into the figure 8 drill. See if you can get a little more "whistle". But don't worry too much about speed in the actual hit just yet. "Hard" is your enemy right now. "Relaxed" is your friend.

Now we go to the next step. Maintaining the same stance position you had in the last drill (about 45 degrees open), go to the "trophy" position. Now see if you can toss the ball (always transfer your weight forward as you toss the ball; you don't get to use your normal backswing, but you can still have a little rhythm with a rock or just a back to front shift as you toss the ball) and then do the last drill from "trophy" position and still finish with the right elbow up and the "Sampras racket head down" ending…literally. Of course, that means you can't swing too fast; but you can still propel the ball a little faster than we did in the initial version of this drill.

Now if you can feel this, you can try and put that feeling into the Figure 8 and go for even more "whistle".

Bottle, all this is pretty removed from what Rod Cross was pointing out. But one key to doing this drill is that the wrist must be in control, that it is it must have the racket handle snug in the hand and against the heel of the hand; at the same time, the wrist must be completely relaxed and just acting as a hinge to allow this full range of motion. Certainly, there will be some wrist flexion and ulnar deviation involved as you move the racket head up to the ball, but the true primary forces are going to be coming from other elements.

And finally, if you can put all this together and feel a little more racket head speed and get the "whistle" to happen at the right time (up through impact and just beyond), you will be forced to exert significant centripetal forces to overcome the momentum and forces of the racket as it swings up to the ball; thereby you will have to do what Rod Cross is describing in his article. But I don't think you will be able to accomplish that if you try to "exert centripetal force on the handle of the racket with a vector at the heel of your hand counter to the vector exerted at the first knuckle and the fingers". Not going to happen!

Good luck with it, Bottle. And Phil, you might try this too. And Ed, did you get this down?

good night,
don

im sorry but i get lost in your description
could you post a youtube video???
pretty please
larry

[tennis_chiro]

A little much

im sorry but i get lost in your description
could you post a youtube video???
pretty please
larry

Yeah, that is a lot to follow without a video. I'll try to get something up and give a link to it by the end of the week.

don

[llll]

Yeah, that is a lot to follow without a video. I'll try to get something up and give a link to it by the end of the week.

don

THANK YOU DON

[bottle]

~

Great, but what's the matter with the Don videos which are already up?

[julian1]

Plane

Don,
your quote below.
Do you talk about forehand or serve ?
If forehand a following quote from a paper by Rod of American Journal of Physics would apply:
"A forehand in tennis is often struck with topspin by swinging the racket upward as well as forward.We will ignore vertical motion of the racket and assume that forearm and the racket swing in a horizontal plane"
----> your quote
I still have a little question in that while this measures angular velocity, the question is in what plain is that taking place. If it is in a plain parallel to the upward movement of the racket towards the ball, we could calculate by its' angle how much the arm is moving upward at contact (which I believe would not be zero). If it is measured in the horizontal plane, then there is no accounting for the upward movement of the arm and that is a little disingenuous, because the arm is really still moving pretty fast. It may be true from a physics point of view that the upward movement in the z plane should not contribute to linear velocity in the x and y planes, but let's let the data show that.

[tennis_chiro]

Distinction

Don,
your quote below.
Do you talk about forehand or serve ?
If forehand a following quote from a paper by Rod of American Journal of Physics would apply:
"A forehand in tennis is often struck with topspin by swinging the racket upward as well as forward.We will ignore vertical motion of the racket and assume that forearm and the racket swing in a horizontal plane"
----> your quote
I still have a little question in that while this measures angular velocity, the question is in what plain is that taking place. If it is in a plain parallel to the upward movement of the racket towards the ball, we could calculate by its' angle how much the arm is moving upward at contact (which I believe would not be zero). If it is measured in the horizontal plane, then there is no accounting for the upward movement of the arm and that is a little disingenuous, because the arm is really still moving pretty fast. It may be true from a physics point of view that the upward movement in the z plane should not contribute to linear velocity in the x and y planes, but let's let the data show that.

Cross made a distinction in parts of his paper about the forehand and the serve. In the part I was referring to in what you exerted, Cross was talking about the forehand and that was what I was referring to as well. My concern was with the vertical velocity in the wiper.

don

[julian1]

Vertical velocity is zero

Cross made a distinction in parts of his paper about the forehand and the serve. In the part I was referring to in what you exerted, Cross was talking about the forehand and that was what I was referring to as well. My concern was with the vertical velocity in the wiper.

don

1.he assumes no topspin for forehand.
2.he assumes no u shape of forehand

He may try to do some generalizations of his paper.
I believe that an easiest one is to assume three segments of an arm as
opposite of two.
I do NOT think that generalizing from two dimensions to three dimensions
is a piece of cake but I was wrong too many times before.
Probably a case of an arm locked at a right angle with a racket
is THE EASIEST ONE for three dimensions..
However I do NOT think "a right angle" above is a very realistic assumptions.
I do NOT know what is done in three dimensions for golf and baseball.

PS An interesting subject to talk is a fact that he has two different models
of forehand.
I will try to discuss it soon
PS there was an attempt to talk about his paper at Tennis Warehouse
but a discussion got diverged to unrelated topics.
Some comments posted there are incorrect

http://tt.tennis-warehouse.com/showthread.php?t=384083

[llll]

Great, but what's the matter with the Don videos which are already up?

he goes into another discussion which a video would clear uo.
at least for dense people like me that are highly motivated

[tennis_chiro]

I hope this helps

im sorry but i get lost in your description
could you post a youtube video???
pretty please
larry

Notes on Complete Snap Sequence

I couldn't get youtube to release my 7 minute video from processing (maybe by the time I wake up in the morning), so I broke it into 4 mpeg4 parts (which is their preferred format it seems.)

First part:

http://www.youtube.com/watch?v=BiGmAHOCtCk

About a minute and four seconds in I say, "My elbow is not moving". I should have said as the upper arm rotates, my elbow is inactive in almost the same place, but it is being rotated by the upper arm.

Second part:

http://www.youtube.com/watch?v=zrxmoQ4HhRA

In the "SnapUp" drill, I am pointing out the lack of internal rotation when you use the "frying pan" grip instead of a continental.

Third part:

http://www.youtube.com/watch?v=rzUB5wjEIzQ

In the trophy position drill, it doesn't matter if you take the racket there like Don demonstrates in the video with a full backswing or you take it up in an abbreviated manner like Gonzales, you still have to get to that "trophy" position. If you were doing a continuous motion without a pause your weight would be going forward as you tossed the ball and brought the racket up simultaneously.

Part 4:

http://www.youtube.com/watch?v=2NCiPeTzdw4

But in the "hiccup", we pause to emphasize a good "trophy" position; now since you brought your weight forward as you brought the racket up (probably) we have already used the weight transfer and don't have the rock to hold everything together as we toss the ball. So, we reload the weight while the arm waits in the trophy position and keep it there until you complete the toss, then drop the racket down and hit up. This is an artificial rhythm, but it is a way to break it down and keep a rhythm where the weight transfer/rock is integrated with the toss. This is a necessity. As strange as it looks at first, most students take to this very quickly and serve quite well with the "hiccup" as an intermediate step until they have a little more control and can do parts 1 and 3 (count 1,2,3,4) together, eliminating step 2. They can even do a practice toss and catch in the hiccup to get the feeling of where to hit the ball without actually hitting it. They can toss it and catch it a few times, with the racket waiting in the trophy position and in a metronomic rhythm, until they are ready to go up and hit it. I will tell them to toss and catch repeatedly until I give them the clearance to go ahead and hit the ball without any pause from the toss and catch. Rhythm is the key to consistency. The rock/weight transfer is the lynch pin that holds everything together. It has to be synchronized to the toss or the serve will never be consistent.

And I threw in a few shots of the snap and my serve when I could still hit it at least a little bit so you could see how this is supposed to work.
Part 5:

http://www.youtube.com/watch?v=7Y6Tu5HxU_o

I'll probably have to figure out how to post the actual clip on ImageShack so that it can be accessed framebyframe.

This presentation goes right along with the post I originally put up for Bottle. I hope it helps. It was a whole lot tougher than I thought to put it together and put it up!

don
And below is most of the text of the original post for Bottle!


So there are a few steps to this drill.

First, you have to understand what my "Figure 8 drill" is. I think you are familiar with this but other members of the forum might not be. Just pretend you are making continuous swings standing in an alleyway extending to the target and there are 30 foot high glass walls on this approximately 2 foot wide alley. Here's a clip of the figure 8 drill.

http://www.youtube.com/watch?v=gaS-qtQWym4&NR=1

Unfortunately, I didn't have audio (I thought I did) when I made this recording. I need to update it and put some more videos up, but haven't done it yet. You could use this in conjunction with the positions demonstrated by Kerry Mitchell in his first service article

http://www.tennisplayer.net/members/..._serve_part_1/

Now, we get to the specifics of generating your increased racket head speed.
We start with internal rotation.
Stand facing the net with your upper arm next to your body and your forearm perpendicular with the racket shaft actually parallel to the baseline, the palm up, racket face horizontal and off to the right of your body. (for righties. Are you a lefty, Bottle? I mean left handed.) You can even rest your right elbow in your left hand.
Without taking the elbow out of your left hand, rotate your forearm to the left so the racket face moves 180 degrees to where it is face down, palm down, but the face again horizontal, but on the opposite side of your body.
Swing it back to the start.
Now go back and forth as quick as you can without moving your right elbow out of your left hand.
Optionally, you can go one stage further with this particular step by swinging the racket so far to the left that the face goes past horizontal and the shaft even begins to point down as it goes more than 180 degrees. At this point, you would be adding a little pronation and your elbow would pull out of your left hand.
In any case, do this back and forth as fast as you can. Feel the internal rotation and how the racket head goes past the wrist.

Now you try to take this feeling into doing the aforementioned Figure 8's. Try to "whistle" the racket at its highest point in the swing, just at or after contact. Next try it actually hitting the ball.

Want more?

Stand with a slightly open stance at about 45 degrees to the baseline (because this is an abbreviated motion and you won't have the benefit of a full swing to turn the hips and shoulders forward from the normal starting position).

Position yourself so the shoulders are actually parallel to the baseline (or even perpendicular to the intended path of the ball).
First put the racket face up to the contact point. (Remember the racket is not straight up. For a righty, the forearm and the racket shaft form a 10 to 20 degree angle at contact. Just guessing on those numbers. Check with John and Brian's data.)
From the contact point, while leaving the elbow exactly where it is pull the racket head back down as you externally rotate as you reverse the internal rotation that took the racket up to the ball.
Now, while leaving the elbow where it is, swing the racket head up to the contact point and past to the "Sampras racket head down" point. Now swing the racket back and forth along this path. It's kind of like what we were doing in our first exercise here, but a little different.

Note: it is important that at the starting point of this motion the butt of the racket is pointed like a flashlight at the ball and also in the direction of the target. Most people have to be corrected from a position where they have the shaft of the racket pointed too far to the right and they are unable to generate sufficient force in this swing in the direction of the target to get the ball over the net.

Once you get a little feel for it, starting from that point with the elbow up in front of you, toss and "tap" the ball over the net. Range of motion and a "clean" contact is the goal here, not speed.

When you feel you can do that a little bit, try to incorporate the feeling into the figure 8 drill. See if you can get a little more "whistle". But don't worry too much about speed in the actual hit just yet. "Hard" is your enemy right now. "Relaxed" is your friend.

Now we go to the next step. Maintaining the same stance position you had in the last drill (about 45 degrees open), go to the "trophy" position. Now see if you can toss the ball (always transfer your weight forward as you toss the ball; you don't get to use your normal backswing, but you can still have a little rhythm with a rock or just a back to front shift as you toss the ball) and then do the last drill from "trophy" position and still finish with the right elbow up and the "Sampras racket head down" ending…literally. Of course, that means you can't swing too fast; but you can still propel the ball a little faster than we did in the initial version of this drill.

Now if you can feel this, you can try and put that feeling into the Figure 8 and go for even more "whistle".

Bottle, all this is pretty removed from what Rod Cross was pointing out. But one key to doing this drill is that the wrist must be in control, that it is it must have the racket handle snug in the hand and against the heel of the hand; at the same time, the wrist must be completely relaxed and just acting as a hinge to allow this full range of motion. Certainly, there will be some wrist flexion and ulnar deviation involved as you move the racket head up to the ball, but the true primary forces are going to be coming from other elements.

And finally, if you can put all this together and feel a little more racket head speed and get the "whistle" to happen at the right time (up through impact and just beyond), you will be forced to exert significant centripetal forces to overcome the momentum and forces of the racket as it swings up to the ball; thereby you will have to do what Rod Cross is describing in his article. But I don't think you will be able to accomplish that if you try to "exert centripetal force on the handle of the racket with a vector at the heel of your hand counter to the vector exerted at the first knuckle and the fingers". Not going to happen!

[gzhpcu]

Good stuff don... Worthy of an article in tennisplayer...