Interactive Forum: Extension

[EricMatuszewski]

Great work lukman and Jeff!

You guys love talking tennis technique.

I think you guys are mistaking shoulder extension with flexion, I was trying to get you all on the same page with the earlier post, but I didn't think you picked up on it. It's a very common mistake in movement description your not alone in making. Lukman, you can check this out with an Anatomy book, I'm sure you've got one somewhere.

Shoulder flexion raises the elbow and hand to the front (anteriorly in the sagittal plane), Extension takes the elbow and pulls it back (posteriorly in the sagittal plane).

Sorry to be so picky sounding, I think you guys are doing great work and I just want people to be able to understand what your trying to say.

Can someone comment on what effect shoulder flexion (what I think you were calling extension) has on the shot.

For instance,

Is it a force producer?, does it determine spin level?, does it control height of the ball?

Also, when during the stoke is the shoulder flexion value important?
During contact or at maximum (after contact)?

What about the "reverse" finish (continuing flexion over the head).

What does it do to the ball?

[stroke]

Following up on Eric's thought/questions, I believe, when John did his series on the Nadal forehand, he determined that Rafael got no significant spin differences whether he finished with his forehand reverse sytle(over his head like he most often seems to) or the over to his right side/hip finish.

[crosscourt]

Aren't the differences in Federer's swing in the pics in post 44 caused by the different height of the ball and therefore -- on the baeline --different shot trajectories?

[lukman41985]

Eric, thanks for your correction. I've gone back and edited my post. Don't apologize--we should all strive for absolute precision in our discussion. With regard to your questions:

1.)It is my belief than shoulder flexion (with limited elbow flexion) provides a stable source of velocity and spin. It is definitely a force producer. It produces spin by aiding in the low-to-high motion, although spin can be increased via in-the-socket shoulder rotation, arm rotation, and elbow flexion. Whether or not it controls the height (I think you meant trajectory) of the ball--that is unclear. The relationship between ball velocity, spin, and racquet path is still not well understood and John has said as much.

2.)Shoulder flexion is important, in the world of tennis physics, in the few miliseconds that correspond to contact. However, studying stroke positions in which the shoulder is at maximum flexion, even though this occurs far after the ball has left the racquet, aids in understanding the important role this movement plays in the forehand stroke. Remember, positions are part of the stroke continuum. This is why Jeff's article this month is so fantastic.

3.)It is my opinion that the reverse finish is characterized by a relatively limited use of shoulder flexion and a realtively ample use of elbow flexion. The motion tends to increase the spin on the ball, and if the shoulder is relatively stable (doesn't move "up"), it seems to increase spin without increasing the trajectory of the ball. My judgement of course is completely anecdotal and the relationship between these factors must be more complex. But here are some clips. I think you'll see the passive role of the shoulder and the active role of the elbow...
Nadal:

Sampras:

Sharapova:

Davenport:

[lukman41985]

Aren't the differences in Federer's swing in the pics in post 44 caused by the different height of the ball and therefore -- on the baeline --different shot trajectories?

Perhaps--all speculation. But determining why there are, as you say, "differences in Federer's swing", is a venture separate from determining whether or not there are differences. The latter question is what we are concerned with in this discussion.

[crosscourt]

"But determining why there are, as you say, "differences in Federer's swing", is a venture separate from determining whether or not there are differences."

Well, maybe. But it may depend on what you think of as a difference and what you think of as being an adaptation to meet the requirements of a particular shot.

But don't others here think that they manufacture their swings differently depending on the height of the ball, their position on the court, the amount of spin required and so on. And don't you sometimes hit the ball better than others, just execute to a higher standard? And is it only me who is conscious of what I have always just thought of as hving better body rotation in to and then through the ball on some shots than others -- depending on where the ball is and therefore on the plane of my shot?

And of course not all these videos show the players hitting the ball as well as they might have liked.

[lukman41985]

I'm not sure I follow what you're saying and what it has to do with what's being discussed in this thread. We're not talking about which technique is the best or whatever...

[jr2044]

straight arm versus double bend, and the shoulder

Jeffrey, appreciate your contribution. I've been intrigued by the straighter arms of Nadal, who is totally straight as he comes forward, and Federer who is straighter than others, but whose arm length seems to vary with the shot. The theory which I am exploring has to do with the length of the lever. What I think I see with all who are sound on their forehand is a lever length that is stable as they come into and shortly after contact with ball. As I study more film this seems to hold true. Nadal and Federer seem to have a longer lever from hand through racket as they come finto the ball, and one that stays stable in length until after contact, although Federer's lever length may vary from shot to shot. Club players change the length of lever before, during, and/or after contact. Nadal and Federer do consistently have the single bend of the layed back wrist. So my theory is that one needs the bend at the wrist and a stable lever length on the forehand.
I also,believe that the longer lever produces a different action in the shoulder,
which moves the base of the arm up and forward toward the chin. It seems to involve external rotation of the upper arm but I think it's more than that, given the flexible nature of the shoulder joint. When this occurs I think the shoulder is loaded in a way that it isn't when the the double bend occurs, and adds to the spring and racket speed without giving up the all important stability.
Jody Rush

[crosscourt]

The point that I am trying to make is that of course there are differences in Federer's swing from shot to shot. These differences will be caused by any number of things -- mostly intended, some unintended. Federer hits with a "longer" arm and more shoulder turn when the ball is higher or when he is trying to hit a winner. He hits with a shorter arm when he is defending/rallying and trying to get more work on the ball. Compare the two shots in post 39 -- one is clearly an attempt to win the point, the other is a rally shot. He produces them differently.

Height is key. Look at the picture of Djokovic in post 11 that you like so much. Where is the ball that he is hitting? Up high where he can drive the ball without having to get it up and down.

And Federer is no different from me, and maybe from you for all I know. When the ball is up and I want to drive it straight or down, I can let my arm get "longer" and straighter and rotate my body and arm in more or less one plane. But if the ball is lower and I am having to hit a higher trajectory ball that is going to land deep my arm and body are going to be in different planes and I can't get that same long flowing forehand.

If I am behind the baseline I hit with more of a double bend. My objective is to hit the ball with more spin, higher and deep. I want to give myself time to recover and to make sure that my opponent doesn't have the chance to step into the court. So I want a lot of action on the ball over a long range with a higher loop. I put more of a double bend in my arm and let my back and shoulders do the work. My arm just connects the racket to my back and shoulders, which supply the power. The best thing that my arm can do is act as a neutral link between the source of the power and the racket. A double bend does this besyt. Andy Murray does this very well.

In court, if the ball is up, I want to drive it away and through the court. Here I hit with my arm straighter because the plane of body and arm are less difficult. Lengthening the lever gives me more power.

[jeffreycounts]

Jeffrey, appreciate your contribution. I've been intrigued by the straighter arms of Nadal, who is totally straight as he comes forward, and Federer who is straighter than others, but whose arm length seems to vary with the shot. The theory which I am exploring has to do with the length of the lever. What I think I see with all who are sound on their forehand is a lever length that is stable as they come into and shortly after contact with ball. As I study more film this seems to hold true. Nadal and Federer seem to have a longer lever from hand through racket as they come finto the ball, and one that stays stable in length until after contact, although Federer's lever length may vary from shot to shot. Club players change the length of lever before, during, and/or after contact. Nadal and Federer do consistently have the single bend of the layed back wrist. So my theory is that one needs the bend at the wrist and a stable lever length on the forehand.
I also,believe that the longer lever produces a different action in the shoulder,
which moves the base of the arm up and forward toward the chin. It seems to involve external rotation of the upper arm but I think it's more than that, given the flexible nature of the shoulder joint. When this occurs I think the shoulder is loaded in a way that it isn't when the the double bend occurs, and adds to the spring and racket speed without giving up the all important stability.
Jody Rush

I am very much in agreement. I think the idea of a lever on the forehand makes perfect sense to me. It first hit me when I read Bungalow Bill's article on the one hander and he described it as a lever. Then looking at forehands, I thought the same dynamic was occuring. You have a straight or bent structure which maintains its integrity and lifts upward. Sounds like a lever to me! And I agree completely that club players break that lever down (if they ever establish it).

And I agree as well about the shoulder working differently on the two types of forehands. The shoulder is the base of support for both levers, but I agree that there seems to be a difference in how it is fully used.

Good stuff!

Jeff

[jeffreycounts]

[QUOTE=crosscourt]But don't others here think that they manufacture their swings differently depending on the height of the ball, their position on the court, the amount of spin required and so on. And don't you sometimes hit the ball better than others, just execute to a higher standard? And is it only me who is conscious of what I have always just thought of as hving better body rotation in to and then through the ball on some shots than others -- depending on where the ball is and therefore on the plane of my shot?
QUOTE]

Absolutely!

[lukman41985]

crosscourt,
We're not in disagreement and I really like you're last post. I just didn't understand where you were coming from until that last post, which again, was really good. Thanks for the explanation.

[crosscourt]

Sorry, I didn't mean to sound cross.

[veena]

Could you guys clarify something for me? I mostly understand the discussion up to this point, except for the anatomy stuff which I will look into later. I agree with cross's point in the last post about the aggressiveness/type of ball. However, I was wondering how much of an impact that two finishes would have because from what I can tell regardless of the finish fed hits the ball in about the same spot (in front of him) and the just the finish is different. Could it have to do with the angle of approach?

[gzhpcu]

IMHO, Federer is very talented, and is not a robot, so he has a great variation in his forehand, and might have two different finishes even when the angle of approach is identical in both cases.