"Accelerate evenly through the ball"

[5263]

Here is another forehand study that I've come across. It suggests that peak racquet head velocity occurs at impact whereas peak wrist velocity and the max shoulder horizontal velocity occurs about 40 ms prior to impact for an elite player.
.

this seems right to me

 

[SystemicAnomaly]

I do NOT want to be a pest but the picture is diffiicult to read
i.e it is very hard to see which solid line represnts what

It's figure 3 from either of the 2 links in that post. You should be as to see the details if you increase the font size or magnification in the full document.
.

 

[SystemicAnomaly]

SA,
Applied Anatomy and Biomechanics in Sport-2nd Edition

Domo arigato. I can take a limited peek at the contents with Amazon or Google Books. Which pages (or sections) do you suggest?

http://www.amazon.com/Applied-Anatomy-Biomechanics-Sport-Bloomfield/dp/0867933054

Two points by Knudson
1.Interpolated smoothing is good according to Knudson
2.With interpolated smoothing the peak of velocity is ON THE CONTACT

I picked up on that first point but the 2nd one puzzles me. It seems that Knudson came to pretty much the same conclusion that Plagenhoef did. Didn't Plagenhoef say that the peak racquet velocity at (or immediately prior to) contact?

Perhaps the errors in toly's recent diagrams reflected the data smoothing errors that Knudson speaks of.

this seems right to me

It seems that we have been seeing some conflicting data in this thread. Perhaps some of it is due to data smoothing errors or perhaps not. Nonetheless, I believe that the double pendulum model, trebuchet model and the triple pendulum model are all useful for providing us with some insight into what is happening with a tennis serve or forehand.

Even if these models are not completely accurate, they still provide us with some useful information/insight as you mentioned before (several pages ago). Yes, they are only part of a larger, more complex sequence of events. I'll have more to say about the models in another post.
.

 

[julian]

Separate date for pull and push forehands?

Domo arigato. I can take a limited peek at the contents with Amazon or Google Books. Which pages (or sections) do you suggest?

http://www.amazon.com/Applied-Anatomy-Biomechanics-Sport-Bloomfield/dp/0867933054




I picked up on that first point but the 2nd one puzzles me. It seems that Knudson came to pretty much the same conclusion that Plagenhoef did. Didn't Plagenhoef say that the peak racquet velocity at (or immediately prior to) contact?

Perhaps the errors in toly's recent diagrams reflected the data smoothing errors that Knudson speaks of.




It seems that we have been seeing some conflicting data in this thread. Perhaps some of it is due to data smoothing errors or perhaps not. Nonetheless, I believe that the double pendulum model, trebuchet model and the triple pendulum model are all useful for providing us with some insight into what is happening with a tennis serve or forehand.

Even if these models are not completely accurate, they still provide us with some useful information/insight as you mentioned before (several pages ago). Yes, they are only part of a larger, more complex sequence of events. I'll have more to say about the models in another post.
.

SA,
Nos morituri te salutamus.

1.Separate data for pull and push forehands would be very useful
I have tried to indicate that separation of data would improve the understanding of the role of wrist
see your quote from one of posts above:
"It suggests that peak racquet head velocity occurs at impact whereas peak wrist velocity and the max shoulder horizontal velocity occurs about 40 ms prior to impact for an elite player."ides
Does it mean that the speed of the wrist is somehow "synchronized" with the speed of
the tip of the racket (i.e one peak coincides with ANOTHER peak)?

2.Problems with one camera
Please see
http://tt.tennis-warehouse.com/showthread.php?t=384050&page=293 Post #5860
I understand that articles we discussed have more than one camera
so we are dealing with a bit better scenario.
It is a BIT marginal issue RIGHT NOW.

3.You did NOT to response to my post #193
I understand that my question was NOT well explained-
is it the case?

Your quote
"Nonetheless, I believe that the double pendulum model, trebuchet model and the triple pendulum model are all useful for providing us with some insight into what is happening with a tennis serve or forehand."
My opinion is that it is correct if we agree what is the expression for the energy of the system.

4.I am interested in the sections(written by Elliot) of the book
http://www.amazon.com/Applied-Anatomy-Biomechanics-Sport-Bloomfield/dp/0867933054#reader_0867933054
I am interested in the newest edition -the price is around $300 (sic)
The full link from Human Kinetics is
http://www.humankinetics.com/produc...atomy-and-Biomechanics-in-Sport-Image-Bank-2E
Please note the phrase "Sport Image Bank" in the title
My quote above was NOT complete,I apologize
5.Your quote
"Didn't Plagenhoef say that the peak racquet velocity at (or immediately prior to) contact? "
I have problems finding this quote

6.About Johannes Landlinger
http://www.itfcoachesconference.com/2011/?q=user/87

7.I will check for new papers and quotations of authors of
http://www.jssm.org/vol9/n4/15/v9n4-15pdf.pdf

8.A quotation about The B.E.S.T
Neuromuscular Training – The B.E.S.T. system generally replaces range of motion with muscle performance optimization. Full benefit of this transformation requires specific training of the bodies’ neuromuscular system. Training sessions utilize innovative techniques designed to improve the performance of this system through specially developed exercises. The exercises specifically target the force that muscles can produce at HIGH SPEED while using the exact motion patterns of the B.E.S.T. system stroke techniques.
One may consider to put a separate thread-I have to think about it

 

[5263]

Separate date for pull and push forehands would be very useful

I think the pull/push thing is very interesting.
I also think it relates to Suresh's theory about holding the racket tightly
causing TE.
Do others agree that to push will force a tighter grip in the process?

 

[julian]

Speed of the arm

http://www.itftennis.com/shared/medialibrary/pdf/original/IO_17033_original.PDF

 

[julian]

SA,I expanded my post #204

I expanded my post #204

 

[bhupaes]

I think the pull/push thing is very interesting.
I also think it relates to Suresh's theory about holding the racket tightly
causing TE.
Do others agree that to push will force a tighter grip in the process?

5263, in my opinion the push-pull based taxonomy of forehands is very ill defined and contributes nothing towards understanding the stroke.

Almost everyone in pro tennis - ATP and WTA - uses the kinetic chain very effectively, and no one really pushes in the sense that they rotate the body and the arm as a unit, as far as I can tell (although some videos that appear to be examples of so called "push" forehands require really careful examination). Someone hitting such a "push" forehand, IMO, would be doing something terribly wrong and would need to be corrected asap by their coach.

The only place where the word "pull" seems to make sense is where one pulls the racquet by the handle towards the ball with the head lagging the handle. This is more of a visualization than an actual realization, since the racquet can only be moved by the hand operating on the handle for any kind of forehand... so trying to define the "push" version would be really convoluted.

So I say, let's drop this push-pull classification of forehands once and for all!

 

[5263]

5263, in my opinion the push-pull based taxonomy of forehands is very ill defined and contributes nothing towards understanding the stroke.

Almost everyone in pro tennis - ATP and WTA - uses the kinetic chain very effectively, and no one really pushes in the sense that they rotate the body and the arm as a unit, as far as I can tell (although some videos that appear to be examples of so called "push" forehands require really careful examination). Someone hitting such a "push" forehand, IMO, would be doing something terribly wrong and would need to be corrected asap by their coach.

The only place where the word "pull" seems to make sense is where one pulls the racquet by the handle towards the ball with the head lagging the handle. This is more of a visualization than an actual realization, since the racquet can only be moved by the hand operating on the handle for any kind of forehand... so trying to define the "push" version would be really convoluted.

So I say, let's drop this push-pull classification of forehands once and for all!

You may understand it better than me. I'm no expert on it by any means, but
I think Murray somtimes uses a push aspect to his Fh and often to his Bh.
I think the push aspect in the ladies Bhs is almost the norm.

 

[Funbun]

You may understand it better than me. I'm no expert on it by any means, but
I think Murray somtimes uses a push aspect to his Fh and often to his Bh.
I think the push aspect in the ladies Bhs is almost the norm.

Please excuse my minutia but...

Are you talking about current Murray form? (2011-now)
If you take a look at his recent practice videos, you'll notice that he takes the racquet back, then brings it forward like a whip. His wrist is loose enough so that you can see he pulls the racquet forward from the "pat-the-dog" position, when his racquet, arm, and hand is aligned parallel to the ground on takeback.

But honestly, discussing push/pull is useless in terms of tennis, because there are many mechanics in the forehand that can be considered push (body rotation towards the ball) or pull (dragging your racquet into the ball). If anything, the forehand should be considered both a push and pull mechanism.

 

[toly]

There are the charts from, Chapter 7, Biomechanics of Tennis Strokes, by Duane Knudson and Bruce Elliot
http://books.google.com/books?id=ZL...v=onepage&q=Knudson & Bahamonde, 2001&f=false

Again, the wrist/handle doesn’t slow down before impact.

So, there are too much very contradictory "scientific" data about handle speed before impact.

IMO, my charts are the best!!!???

 

[toly]

So I say, let's drop this push-pull classification of forehands once and for all!

But honestly, discussing push/pull is useless in terms of tennis, because there are many mechanics in the forehand that can be considered push (body rotation towards the ball) or pull (dragging your racquet into the ball). If anything, the forehand should be considered both a push and pull mechanism.

You are absolutely right!!!

 

[julian]

A little piece of advice

There is the chart from, Chapter 7, Biomechanics of Tennis Strokes, by Duane Knudson and Bruce Elliot
http://books.google.com/books?id=ZL...v=onepage&q=Knudson & Bahamonde, 2001&f=false

Again, the wrist/handle doesn’t slow down before impact.

So, there are too much very contradictory "scientific" data about handle speed before impact.

IMO, my charts are the best!!!???

Spend ten minutes comparing what you wrote above with post #198.
Next talk to SystemicAnomaly
Please define the phrase "my charts" to him as well.
You may consider reading the bottom part of your post $#190 again

 

[toly]

Spend ten minutes comparing what you wrote above with post #198.
Next talk to SystemicAnomaly
Please define the phrase "my charts" to him as well.
You may consider reading the bottom part of your post $#190 again

I don’t see any contradiction among my posts in this thread. If you found something, just tell me. I’ll really appreciate that.

 

[5263]

Please excuse my minutia but...

Are you talking about current Murray form? (2011-now)
If you take a look at his recent practice videos, you'll notice that he takes the racquet back, then brings it forward like a whip. His wrist is loose enough so that you can see he pulls the racquet forward from the "pat-the-dog" position, when his racquet, arm, and hand is aligned parallel to the ground on takeback.

I agree he has improved, and have posted about it as well,
but if you watch his matches, you will see him revert back from to time in matches.

 

[bhupaes]

IMO, my charts are the best!!!???

Toly, that is absolutely true - have no doubts about it!

 

[SystemicAnomaly]

SA,
I was trying to write down an expression for energy for
the discussion in this thread
I did NOT go very far.Let me summarize couple of points
1.The energy will be the sum of three expressions
the sum of kinetic energies(linear movement)
the potential energy
the sum of rotational energies

2.The equation (A7) of the Rod Cross's paper should help with formulating the expression for THE SUM of ROTATIONAL ENERGIES
Let me quote this equation for cpmpleteness

C1 − C2 + Fx1h1 cos + Fy1h1 sin + Fx2L1 − h1cos
+ Fy2L1 − h1sin = Icm,1
d1
dt

where Icm,1 is the moment of inertia of the forearm about an
axis through G1.

3.The potential energy would obviously depend on g.
g shows up one line above Equation (A2a)

4.Is it true that the energy is constant here?
Would it be true if both C1 and C2 are BOTH equal zero.



If you can push this subject by a bit I really would appreciate it
regards,
Julian

Sorry, I had only briefly scanned this post when I first saw it. I missed the fact that you had specifically addressed it to me. Not sure that I am up to the task on this right now. I would need to review quite a bit on it. My math is rather rusty -- it's actually been nearly 40 years since my calculus and physics college classes . My memory is pretty shaky as well these days -- I'd have to review the Cross paper again -- I do not even recall what C1 and C2 are.

Perhaps toly might be better suited to take this on.

 

[julian]

For SA

Sorry, I had only briefly scanned this post when I first saw it. I missed the fact that you had specifically addressed it to me. Not sure that I am up to the task on this right now. I would need to review quite a bit on it. My math is rather rusty -- it's actually been nearly 40 years since my calculus and physics college classes . My memory is pretty shaky as well these days -- I'd have to review the Cross paper again -- I do not even recall what C1 and C2 are.

Perhaps toly might be better suited to take this on.

SA,
switching gears a bit
post #204 was rewritten especially for you.
Please note the first line if you know Latin.
Every minor point from you would be appreciated
If I am too cryptic please let me know.
The most interesting topic is the role of the wrist plus possible definitions/features of the kinetic chain
Some comparison of Stossur vs Gulbis vs Kohlschreiber should come from me as well
Running google on "double pendulum normal modes" gives some interesting aspects as well
Getting ready for Brian Gordon is important as well.

Regards,
Julian

 

[SystemicAnomaly]

SA,
Nos morituri te salutamus.

1.Separate data for pull and push forehands would be very useful
...

I did not fully recognize this Latin phrase at first glance.
The form that I recall is: Morituri te salutant

I have never been completely comfortable with the push and pull Fh concepts. The distinctions have always seemed somewhat arbitrary to me (as others have also indicated above). To my mind, a true push Fh would be the forehand loop used in table tennis:

http://www.youtube.com/watch?v=okYH-3oPzYE&t=17s

I do not really see anything like this in (court) tennis. Some forehand may emphasize more of a pull aspect than others. But I do not recall any pro forehands that I would classify as push. Perhaps you could provide a specific example of a push Fh.

It would be interesting to see differences in the timing & velocity data of the various links in the kinetic chain for a classic OTS forehand compared to an aggressive WW modern forehand.

I will get to some of your other points later when I have a bit more time.
.

 

[julian]

More wrist movement

I did not fully recognize this Latin phrase at first glance.
The form that I recall is: Morituri te salutant

I have never been completely comfortable with the push and pull Fh concepts. The distinctions have always seemed somewhat arbitrary as others have indicated above. To my mind, a true push Fh would be the forehand loop used in table tennis:

http://www.youtube.com/watch?v=okYH-3oPzYE&t=17s

I do not really see anything like this in (court) tennis. Some forehand may emphasize more of a pull aspect than others. But I do not recall any pro forehands that I would classify as push. Perhaps you could provide a specific example of a push Fh.

It would be interesting to see differences in the timing & velocity data of the various links in the kinetic chain for a classic OTS forehand compared to an aggressive WW modern forehand.

I will get to some of your other points alter when I have a bit more time.

Let say that pull requires MORE wrist movement
Let say that Stossur is an example
You may look/search youtube
I do NOT have an access to youtube but Stossur should be there
Bing or google should provide some links,IMHO

 

[julian]

"those who are about to die salute you,"

I did not fully recognize this Latin phrase at first glance.
The form that I recall is: Morituri te salutant

I have never been completely comfortable with the push and pull Fh concepts. The distinctions have always seemed somewhat arbitrary to me (as others have also indicated above). To my mind, a true push Fh would be the forehand loop used in table tennis:

http://www.youtube.com/watch?v=okYH-3oPzYE&t=17s

I do not really see anything like this in (court) tennis. Some forehand may emphasize more of a pull aspect than others. But I do not recall any pro forehands that I would classify as push. Perhaps you could provide a specific example of a push Fh.

It would be interesting to see differences in the timing & velocity data of the various links in the kinetic chain for a classic OTS forehand compared to an aggressive WW modern forehand.

I will get to some of your other points later when I have a bit more time.
.

"those who are about to die salute you,"
Make a guess why I did use the greeting above

 

[5263]

Let say that pull requires MORE wrist movement
Let say that Stossur is an example
I do NOT have an access to youtube but Stossur should be there

Are you sure the pull requires more wrist?
Just movement or work?

 

[julian]

One more crash

Are you sure the pull requires more wrist?
Just movement or work?

I want to discuss a forehand with A LAID BACK WRIST.
I do NOT care about names
My Gaelic is NOT good.

 

[julian]

want to discuss a forehand with A LAID BACK WRIST.

I did not fully recognize this Latin phrase at first glance.
The form that I recall is: Morituri te salutant

I have never been completely comfortable with the push and pull Fh concepts. The distinctions have always seemed somewhat arbitrary to me (as others have also indicated above). To my mind, a true push Fh would be the forehand loop used in table tennis:

http://www.youtube.com/watch?v=okYH-3oPzYE&t=17s

I do not really see anything like this in (court) tennis. Some forehand may emphasize more of a pull aspect than others. But I do not recall any pro forehands that I would classify as push. Perhaps you could provide a specific example of a push Fh.

It would be interesting to see differences in the timing & velocity data of the various links in the kinetic chain for a classic OTS forehand compared to an aggressive WW modern forehand.

I will get to some of your other points later when I have a bit more time.
.

want to discuss a forehand with A LAID BACK WRIST.
I do NOT care about names

 

[SystemicAnomaly]

Just took a quick look at the Stosur Fh. It has not changed my mind about classifying FHs as push and pull. She has a sequential overlapping kinetic chain. The racket head lags quite a bit at the start of her forward swing and suddenly accelerates forward before contact. While I might agree to call the ping ping forehand loop as a push FH, I've still not seen any pro FHs in tennis that I would classify as such.

http://www.youtube.com/watch?v=E_mNZGq8TfE

 

[OTMPut]

Actually momentum is conserved for both type of collisions. It is kinetic energy that is not conserved for inelastic collisions. Some heat (energy) is lost due to compression.

Momentum is conserved only in a closed system i.e. no external forces acting on the system. Sum of forces acting on the system F(j) = Rate of change of the total momentum of the system dP/dt.

Here what is the system under discussion- racquet and ball? Or hand, wrist, racquet & ball? or the whole kinetic chain?

 

[julian]

I apologize for busting into the conversation

Momentum is conserved only in a closed system i.e. no external forces acting on the system. Sum of forces acting on the system F(j) = Rate of change of the total momentum of the system dP/dt.

Here what is the system under discussion- racquet and ball? Or hand, wrist, racquet & ball? or the whole kinetic chain?

We have two cases:
everything without ball before the contact
with ball after the contact
Gravity is taken into account for one of papers (Cross)
So there is an external force
No slowing down by air,etc,etc

 

[SystemicAnomaly]

want to discuss a forehand with A LAID BACK WRIST.
I do NOT care about names

It's not the names that bother me. It's the concept and classification (or taxonomy as bhupaes puts it). Perhaps it's a matter of degree rather than 2 distinct types. Blake and Agassi have quite a bit less wrist extension than Federer (or Stosur). Is this what you are talking about?

http://www.youtube.com/watch?v=EaUH9Bevnew

http://www.youtube.com/watch?v=lXWks8yvRJQ
.

 

[5263]

Just took a quick look at the Stosur Fh. It has not changed my mind about classifying FHs as push and pull. She has a sequential overlapping kinetic chain. The racket head lags quite a bit at the start of her forward swing and suddenly accelerates forward before contact. While I might agree to call the ping ping forehand loop as a push FH, I've still not seen any pro FHs in tennis that I would classify as such.

http://www.youtube.com/watch?v=E_mNZGq8TfE

Still well back at contact

 

[SystemicAnomaly]

^ Yes, but she still manages to accelerate/whip the racket head forward to contact. Still seeing more pull behavior than push.

 

[Funbun]

^ Yes, but she still manages to accelerate/whip the racket head forward to contact. Still seeing more pull behavior than push.

Agreed here. When looking SOLELY at the arm and racquet, it is obviously a "pull".

julian, please disregard the wrist on the takeback. Pros have their own styles of laying back the wrist when they do; Murray likes to keep it way down, not laid back at all. Sam Stosur and Federer like to keep it up a bit. In the end, it doesn't matter.

However, when they all bring the racquet forward, their wrist is laid back as a result of bringing the racquet forward, pulling it into the ball.

http://www.youtube.com/watch?v=e3Ce65Adz4k

Check 0:16 or 0:22, and we see that you don't have to lay back your wrist on takeback. However, his forward swing is just the same as any other pro on tour.

Btw, I have no clue what you guys are talking about. I'm just saying crap. If anything, I just agree with SA, as usual, though.

 

[OTMPut]

Fig. 3 (see full document link below)
​

Here is another forehand study that I've come across. It suggests that peak racquet head velocity occurs at impact whereas peak wrist velocity and the max shoulder horizontal velocity occurs about 40 ms prior to impact for an elite player.

http://bmsi.ru/doc/171d89e9-5c89-4105-b0d1-ac41b5537502

http://www.jssm.org/vol9/n4/15/v9n4-15pdf.pdf
.
.

I think the the time lag is simply the pendulum motion in action at wrist. In other words, it accounts for pronation.
You can also see this effect from the fact that it is the vertical component that peaks at the impact (properly timed topspin stroke) and the azi*****l(z) component peaks after the impact.

 

[5263]

^ Yes, but she still manages to accelerate/whip the racket head forward to contact. Still seeing more pull behavior than push.

Yes, I was agreeing.
I don't really see the push aspects in how I view it.
She catches up the racket head by pulling across right before contact,
which alters the hand orientation more than any wrist adjustment.
Even so it stays well back.

 

[toly]

About wrist position

There are two extremely different wrist positions.

Nadal bends the wrist back as much as possible. IMO he is going to hit very hard FH.

Petrova’s wrist is in neutral position. It means that her hand/racquet travels around wrist something like 90°. To provide so long angular path with positive acceleration, she has to use the hand/wrist actively.

 

[5263]

There are two extremely different wrist positions.

:

along with 2 very different time frames.
She is at contact.

 

[toly]

along with 2 very different time frames.
She is at contact.

Petrova doesn’t pull the racquet across (orthogonal) to the ball outgoing direction. The racquet velocity is orthogonal to the strings, not to the direction of the outgoing ball. The direction of the racquet velocity coincides with the direction of the outgoing ball. There is no “across aspect” at all.

 

[julian]

Shoulder rotation contribution?

Just took a quick look at the Stosur Fh. It has not changed my mind about classifying FHs as push and pull. She has a sequential overlapping kinetic chain. The racket head lags quite a bit at the start of her forward swing and suddenly accelerates forward before contact. While I might agree to call the ping ping forehand loop as a push FH, I've still not seen any pro FHs in tennis that I would classify as such.

http://www.youtube.com/watch?v=E_mNZGq8TfE

There is a research specifying percentage of possible contributions
from different segments of the body
Would you say that her wrist contributes more than her shoulder?

 

[julian]

Still pictures are much worse than videos here

along with 2 very different time frames.
She is at contact.

Still pictures are much worse than videos here.
It would be better to discuss a video vs a video
BTW-Nadal does NOT know how to play on (blue) clay
so he does not count

 

[julian]

Fig. 3 (see full document link below)
​

Here is another forehand study that I've come across. It suggests that peak racquet head velocity occurs at impact whereas peak wrist velocity and the max shoulder horizontal velocity occurs about 40 ms prior to impact for an elite player.

http://bmsi.ru/doc/171d89e9-5c89-4105-b0d1-ac41b5537502

http://www.jssm.org/vol9/n4/15/v9n4-15pdf.pdf
.
.

The quote from the second paper
"Moreover, the hyper extended wrist, which reached its
peak about 55 milliseconds before impact, should have
put additional stretch on the forearm of all players;"
Can we see/distingush that the peak for wrist is BEFORE the point of impact?
help generate wrist and racquet speed.

 

[bhupaes]

It's not the names that bother me. It's the concept and classification (or taxonomy as bhupaes puts it). Perhaps it's a matter of degree rather than 2 distinct types. Blake and Agassi have quite a bit less wrist extension than Federer (or Stosur). Is this what you are talking about?

http://www.youtube.com/watch?v=EaUH9Bevnew

http://www.youtube.com/watch?v=lXWks8yvRJQ
.

I believe you hit the nail on the head, SA. It is a matter of degree. There are many shades of gray in how the kinetic chain is used by different players, and the "push" forehand is an extreme case that is never used in practice, IMO.

 

[SystemicAnomaly]

There is a research specifying percentage of possible contributions
from different segments of the body
Would you say that her wrist contributes more than her shoulder?

Stosur lays the wrist back during her forward swing but does appear to release it (or does not release it very much) prior to contact. In light of this I would say that the shoulder contributes more in her case. What does the research say? does it also show a significant contribution from forearm pronation on the FH?

The quote from the second paper
"Moreover, the hyper extended wrist, which reached its
peak about 55 milliseconds before impact, should have
put additional stretch on the forearm of all players;"
Can we see/distingush that the peak for wrist is BEFORE the point of impact?
help generate wrist and racquet speed.

Is the wrist achieving its maximum extension or its maximum speed 55 ms before impact? It sounds like the latter (but I not sure). I assume that the additional stretch on the forearm is due to the hyper extension. Or are they saying that the peak wrist velocity is responsible for that additional stretch?

 

[julian]

Wrist horizontal velocity

Stosur lays the wrist back during her forward swing but does appear to release it (or does not release it very much) prior to contact. In light of this I would say that the shoulder contributes more in her case. What does the research say? does it also show a significant contribution from forearm pronation on the FH?




Is the wrist achieving its maximum extension or its maximum speed 55 ms before impact? It sounds like the latter (but I not sure). I assume that the additional stretch on the forearm is due to the hyper extension. Or are they saying that the peak wrist velocity is responsible for that additional stretch?

SA,
I would like to address the issue of research you inquired above
1.I would like to go back to
http://www.jssm.org/vol9/n4/15/v9n4-15pdf.pdf

The values are given in Fig 3
The value of 10 m/s for the WRIST HORIZONTAL SPEED looks very HIGH,I would say 2 HIGH
What do you think?
It is very possible that the word HORIZONTAL is crucial here
i.e HORIZONTAL as "quasi opposite" of ANGULAR

2.The speed of shoulder of Fig 3 is much smaller than the horizontal speed of the wrist.

3.To make the story very amusing (or confusing) post #166 provides the peak value of the wrist speed 15 MM/sec
I am NOT even sure whether post #166 is worth talking about because of that

 

[julian]

Stosur

Just took a quick look at the Stosur Fh. It has not changed my mind about classifying FHs as push and pull. She has a sequential overlapping kinetic chain. The racket head lags quite a bit at the start of her forward swing and suddenly accelerates forward before contact. While I might agree to call the ping ping forehand loop as a push FH, I've still not seen any pro FHs in tennis that I would classify as such.

http://www.youtube.com/watch?v=E_mNZGq8TfE

SA,
A side view or even a front view of Stosur would be better

http://www.youtube.com/watch?v=pPLmCqGIotM&feature=related
has the same problem-it is very hard to make any judgements about the wrist motion/speed

The other issue is :
how to measure how active the wrist is?

How to teach the Stosur version of forehand?

 

[toly]

A side view or even a front view of Stosur would be better.

There is front view of Stosur TS FH.

She exploits very actively hand rotation around the wrist, where angular path is approximately 60°. With shoulder inner rotation these motions create horizontal speed of the racquet.

Pronation and elbow flexion create (mostly) vertical racquet speed, topspin.

 

[julian]

Acceleration of wrist

SA,
Your quote
---->
Is the wrist achieving its maximum extension or its maximum speed 55 ms before impact? It sounds like the latter (but I not sure). I assume that the additional stretch on the forearm is due to the hyper extension. Or are they saying that the peak wrist velocity is responsible for that additional stretch?
----->
1.I do NOT know the answer to your question
2.I am trying to bring the notion of stretch-shorten cycle to the picture
I am trying to read
http://billnordt.com/MUSCLEANDJOINTFUNCTION/stretchshorteningresearcharticle.pdf

SA,
please see the quote
"This time delay is similar to electrical stimulation
measurements performed together with optic "ber recordings
of AT force (Komi et al., unpublished observation).
Considering the duration of a simple stretch re#ex
loop of 40 ms, the maximum delay between initial stretch
and subsequent force potentiation would be around
50}55 ms. When referred to running, the "rst contact on
the ground would indicate the point of initial stretch."

3.Please see
http://tt.tennis-warehouse.com/showthread.php?t=424215&page=3
posts #41 and 42.

4.Research Studies-a quote from Wikepedia

The increased performance benefit associated with muscle contractions that take place during SSCs has been the focus of much research in order to determine the true nature of this enhancement. At present, there is some debate as to where and how this performance enhancement takes place. It has been postulated that elastic structures in series with the contractile component can store energy like a spring after being forcibly stretched [1]. Since the length of the tendon increases due to the active stretch phase, if the series elastic component acts as a spring, it would therefore be storing more potential energy. This energy would be released as the tendon shortened. Thus, the recoil of the tendon during the shortening phase of the movement would result in a more efficient movement than one in which no energy had been stored [2]. This research is further supported by Roberts et al.[3].

However, other studies have found that removing portions of these series-elastic components (by way of tendon length reduction) had little effect on muscle performance [4].

Studies on turkeys have, nevertheless, shown that during SSC, a performance enhancement associated with elastic energy storage still takes place but it is thought that the aponeurosis could be a major source of energy storage (Roleveld et al., 1994). The contractile component itself has also been associated with the ability to increase contractile performance through muscle potentiation (Cavagna, 1977) while other studies have found that this ability is quite limited and unable to account for such enhancements (Lensel and Goubel, 1987, Lensel-Corbeil and Goubel, 1990; Ettema and Huijing, 1989).

 

[julian]

Wrist movement again

SA,
http://tt.tennis-warehouse.com/showthread.php?t=410589
http://www.ncbi.nlm.nih.gov/pubmed/21309302
http://www.youtube.com/watch?v=XTMybOrewGQ

 

[SystemicAnomaly]

^^ Whoa, slow down, Julian. I'm having a difficult time keeping with your pace. I'm having a difficult time reading all this stuff with my poor aging eyes. Convergence insufficiency and near vision issues result in eyestrain after reading -- even after a relatively short time.

I still want to go back an answer some previous questions and have some other points related to the trebuchet/double pendulum that I like to bring up. It may be quite a while before I can catch up to this new material.

 

[julian]

I apologize

^^ Whoa, slow down, Julian. I'm having a difficult time keeping with your pace. I'm having a difficult time reading all this stuff with my poor aging eyes. Convergence insufficiency and near vision issues result in eyestrain after reading -- even after a relatively short time.

I still want to go back an answer some previous questions and have some other points related to the trebuchet/double pendulum that I like to bring up. It may be quite a while before I can catch up to this new material.

I am very sorry

 

[Anton]

I find that the arm speed should be kept either constant or slightly accelerated through the stroke.

But the trick is to combine this smooth arm acceleration with the rotation from the hips/shoulders to create massive racket head acceleration.

A relaxed wrist and proper swingweight is needed to make this work well.

Just to clarify, the tension build up is more or less smooth , but the release of this tension creates rapid acceleration for the racket

 

[SystemicAnomaly]

When we speak of hand/wrist speed are we talking about an articulation of the wrist, a rotation of the forearm/hand or simply the forward linear motion of the wrist/hand w/o wrist articulation? It is not always clear in the articles and in the posts here what is meant.

Note that some players will uncock the wrist just before contact on the serve with little or no flexion. Some will incorporate more flexion -- but primarily after contact.

On the forehand, some players will lay back the wrist and will not release it prior to contact. Others will lay it back and will incorporate moderate flexion prior to contact. I don't believe that a forceful snapping of the wrist is common at all.

It is also unclear as to what if meant by the relative contribution of the hand/wrist compared to the shoulder or some other part/kinetic link. Are we including forearm rotation when we speak of the contribution of the hand/wrist? Are we only considering the speed of body part/link? Or are we taking about the momentum or the kinetic energy associated with that part? While the shoulder may not be moving as fast as the hand/wrist, it is moving a larger mass. In turn, the torso and previous links are also moving larger masses. Is this taken into consideration when speaking of relative contributions.

Note also, the the speed/kinetic energy at the hand/wrist is an accumulation and transfer from previous links. I'm not sure that this is always taken into account when speaking of the contribution of the hand/wrist.

...

She exploits very actively hand rotation around the wrist, where angular path is approximately 60°. With shoulder inner rotation these motions create horizontal speed of the racquet.

Pronation and elbow flexion create (mostly) vertical racquet speed, topspin.

Are you saying that Stosur exploits an active forearm pronation in concert with internal rotation of the shoulder? Or do you mean something else by "hand rotation around the wrist"? Not completely clear.

In viewing a number of Stosur forehands, she often employs a considerable amount of wrist extension at the start of her forward swing. It appears that sometimes she releases the extension somewhat while, at other times, it is not released appreciably or at all.

I also noticed this about the horizontal (transverse) adduction of her arm on her FHs. At times it appears that the arm is moving along with the torso (same angular speed) until contact. It release very close to contact or hardly release at all. On other FHs there is a significant release (transverse adduction) prior to contact.

Elbow flexion? Are you talking abut a static flexion of the elbow during the forward swing? I've seen some of her FHs where the elbow flexion seems to be static. At other times, there appears to an active/dynamic flexion of the elbow?

These 2 links will show some (not all) of the variations I've mentioned above:

http://www.youtube.com/watch?v=Hnik-0TurvY

http://www.youtube.com/watch?v=0XmDydksL0c