Dear Djordje
Rookie
Who can translate?
Kinetic Chain - What do we know on the serve?
- Thread starter Chas Tennis
- Start date
Chas Tennis
G.O.A.T.
This is Sharapova serve video http://youtu.be/yV_Dy7xqrc8
I can see ISR now, but probably around 90° forearm pronation also???
Frame #1. This looks about the most external shoulder rotation or maximum internal shoulder rotation pre-stretch. Shoulder looks up according the Ellenbecker video but I'm not familiar with this camera angle.
Frame #2. I believe that ISR has just started. I made a mark on the elbow shadows for reference of the ISR angle. Not very good tracking as the elbow shadows in the video are not so distinct. Shoulder looks up according to the Ellenbecker video, bad camera angle.
Frame #3. Best guess as to impact frame. I watched the mark move frame by frame and that's best guess as to where it would be. A marker on the arm takes care of this spot for tracking ISR angle. Also, the more definition - with shadows from muscle, vein,etc. - the better chance of tracking ISR angle without a marker. It does not look like much ISR between the two frames. Accuracy is not good. Estimate ISR angle rotated roughly 35° between the two frames with the red marks. (To do this, download the Youtube video with DownloadHelper and view it frame by frame with Quicktime or Kinovea, both free. Recommend that everyone who views high speed videos on Youtube learn how to download them. )
(Suggest that you don't read this unless you intend to dig into video analysis, there are some missing details -
Method of estimating the ISR rotation angle - Estimated the rotation angle by measuring the distance from the red mark to each side of the arm, 10 mm and 6 mm for the frame #2 red mark. After the arm rotated in frame #3, it measures 5 and 11 mm. Took a cardboard cylinder with a mark on it and placed it on a protractor. Viewed it so it looked like Frame #2. Then rotated the cylinder so that it looked like frame #3.)
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Cheetah
Hall of Fame
I'm not trying to discourage the use of the suresh fh gif because it's awesome and hilarious...
but.. in suresh's defense I have to say that the ball that was coming to him would have been slightly difficult to handle for someone of his skill level. It has good spin and is on the heavy side for the amount of pace it had. There is considerable sidespin on it as well as you can clearly see it is curving away from him after the bounce. It's also has some kick on it and it's still rising when he makes contact from a few feet behind the baseline.
So, ignoring all of his other shots and technique, that one in particular was essentially a reaction shot as you can see he has to change his swing mid stroke and quickly jut his arm out to the side of his body to make contact as it curves away and kicks up a bit. The resulting ball his hit also was not bad. He hit it back deep with topspin and well in so it could have turned out worse.
Ok, with that said, carry on with the gif usage.
but.. in suresh's defense I have to say that the ball that was coming to him would have been slightly difficult to handle for someone of his skill level. It has good spin and is on the heavy side for the amount of pace it had. There is considerable sidespin on it as well as you can clearly see it is curving away from him after the bounce. It's also has some kick on it and it's still rising when he makes contact from a few feet behind the baseline.
So, ignoring all of his other shots and technique, that one in particular was essentially a reaction shot as you can see he has to change his swing mid stroke and quickly jut his arm out to the side of his body to make contact as it curves away and kicks up a bit. The resulting ball his hit also was not bad. He hit it back deep with topspin and well in so it could have turned out worse.
Ok, with that said, carry on with the gif usage.
SystemicAnomaly
Bionic Poster
Don't know that it's ever been shown that Maria developed shoulder problems specifically because of her serve mechanics. However, the converse is undoubtedly true -- she's had service problems since 2007/2008 because of her shoulder problem (injury). Prior to that her serve was considered one of the best in the WTA.
Sharapova is hardly the only top pro to have developed shoulder problems from tennis. Roddick, Sampras, Rafter, Nadal and others have experienced overuse issues of the shoulder. Not sure that anyone has recovered from shoulder injuries as serious as Maria's and been able to get back to the top. I believe that she had 2 rotator cuff tears as well as bursitis of the shoulder. It has been suggested that the shoulder problems of Nadal, Sampras and Sharapova have more (or as much) to do with the prolific use of the reverse forehand than the serve.
http://www.kinohi.org/tennis-shoulder-injuries
What are your specific issues with Sharapova's serve mechanics? Altho' her toss is very high (too high for my tastes), there is more right with Maria's serve than wrong with it. She provides a great example of a consistent serve ritual, a pronounced archer's bow, left arm extension (after the ball release), trophy position, leg drive and right leg kick (on the follow-thru).
http://www.top-tennis-training.org/wp-content/uploads/2012/12/sharapova-serve.jpg
Because of her height, her long lean musculature and significant leg drive, Maria's serve action gives the impression that she is employing a non-trivial amount of effort. She also appears to be a bit off-balance. However this off-balance is usually controlled and she does resolves it with her follow-thru and recovery more often than not.
http://www.optimumtennis.net/maria-sharapova-serve.htm
http://www.pptandfitness.com/shoulder-bursitis-ends-maria-sharapova-us-open-bid/
http://www.postandcourier.com/article/20120621/PC20/120629817
arche3
Banned
The ball was hit right to his fh. He didn't even need to take a step. At his skill level any ball that goes over the net is a difficult shot to deal with. lol. So bad. He needs more YouTube tennis lessons. Ha ha. Hundreds of hours watching YouTube lessons and dissing real life coaches and we see the result. 2.5 tennis after years of play.
Lukhas
Legend
Personally, I will have an issue with a player that is reported to be the tallest on his/her tour and cannot simply put the ball on the other side consistently. No matter what issues she has with her shoulders: Rafter also had shoulder issues and surgeries and there wasn't as an huge shift in pure serving performance for him than there was for Sharapova.
I don't ask Sharapova to suddenly serve as good as before: she prefers to let her groundstrokes to do the talking anyway. But as long as she cannot serve simply consistently, and by this I really mean simply put the ball on the opposite box, I always will have an issue (personally) with her serve. No matter how much she holds serve as I believe she's expected to against most of the tour regardless because of her superiority over most players. She literally isn't in any top 10 serving statistics (in consistency and percentage, not in absolute value) this year despite being Would Number #2... although her return stats are much more remarkable.
http://www.wtatennis.com/SEWTATour-Archive/Rankings_Stats/match_stats_2014.pdf
Just play percentage if your serve is weak or if you cannot bring the goods consistently. Errani has the best serve percentage of the tour this year, and she's far from serving like Henin.
EDIT: Then about her mechanics... I believe she exaggerates her leg drive and archer's bow too much instead of having better upper body posture. More chest pointing upwards, more upper body coil. I think she then compensate with her shoulder to get her power because I think that the lack of coil doesn't allow her leg's power to properly go into her serve. I think she isn't using her body the best she can, and that's part of the reason why she injured her shoulder or cannot serve anywhere near as well as before with her damaged shoulder. On which case I simply would agree with Pat Dougherty: too much legs distracting from what you could achieve with better upper body mechanics.
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SystemicAnomaly
Bionic Poster
Rafter and Sharapova. Apples and Oranges. Different shoulder anatomy. Different shoulder injuries. Maria's, in part, due to her prolific use of the reverse FH. Rafter's toss not as high as Sharapova's. Really can't compare the two. Rafter's injuries shortened his career. Sharapova's injuries in 2007/08 were considered severe enough to end her career. She considered this possibility according to interviews with her.
Absurd statement to say "no matter what issues she has... ". How could you possibly know all the details? She had one of the dominant serves prior to injury. Despite surgery, changes in mechanics and racket changes it took her quite a while to find her serve again. It's better than it was a few years ago but has still not equalled what she had before.
SystemicAnomaly
Bionic Poster
^ Note that I have had 2 significant shoulder injuries as well. Not only has it affected the serve, it has affected my ability to hit high contacts on groundstrokes. Difficulty getting the racket around quickly for FH volleys. Needed to change mechanics to compensate for limitations. Even learned to hit a right-handed serve. However, the left shoulder injuries affected the toss with that arm. Unless you've have the same anatomy and the same injuries, you can't possibly know what it is like -- what the limitations might be and what compensations must be made.
"No matter what issues... "??? As I said, an absurd statement.
"No matter what issues... "??? As I said, an absurd statement.
Ash_Smith
Legend
Fact or speculation on your part?
Lukhas
Legend
I need the exact specifics, since you seem to be so knowledgeable about the subject.
And yet I still think that when you're the tallest player on your tour, not being able to push the damn ball in the opposite service box regularly enough is an issue no matter what issue she has. Rafter could despite what according to you was a career-ending injury. Sharapova can't. Errani has a worst serve than Sharapove and she can. And as I already wrote, it's not like Sharapova's game is based around her serve either.
I doubt she or her coach cares honestly. Especially not my opinion: she fired Connors for much less. EDIT: A coach in tennis is someone that carters to your interests and goals. It's not like in football/soccer where if you don't like it, you're not playing. Much more personal in tennis. I don't think Maria cares that much anymore; at least not at this stage of her career.
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SystemicAnomaly
Bionic Poster
Don't know if it is a certainty but it seems to be a distinct possibility from several sources that I've read (book and articles). Check out my first link in post #207.
Most of the reverse FHs that Maria hits appear to be a late contact variety -- not much uncoiling into the shot. With Nadal's reverse finishes, some are late contact (with little body rotation) while others appears to use more of a full-body kinetic chain. I would think that the Sharapova variety would take its toll after a while since she has done it so often.
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Chas Tennis
G.O.A.T.
FYI
Here is a 2006 reference on tennis shoulder injuries that uses the kinetic chain for analysis. One of the authors is W. Kibler, the same author, I believe, that came up with the kinetic chain graph that is in the OP, Reply #1.
Shoulder injuries in tennis players
H van der Hoeven and W B Kibler
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577490/
I believe that the Marshall & Elliott references of 1995 and 2000, reply #78, point out an inconsistency - a 'missing link' - in treating the serve with the kinetic chain concept.
--------------
Second reference applying the kinetic chain to the serve.
Kinetic chain abnormalities in the athletic shoulder.
Aaron Sciascia, Charles Thigpen, Surena Namdari and Keith Baldwin
http://www.researchgate.net/publica..._chain_abnormalities_in_the_athletic_shoulder
I don't follow this kinetic chain treatment completely because of the 'missing link' above.
Here is a 2006 reference on tennis shoulder injuries that uses the kinetic chain for analysis. One of the authors is W. Kibler, the same author, I believe, that came up with the kinetic chain graph that is in the OP, Reply #1.
Shoulder injuries in tennis players
H van der Hoeven and W B Kibler
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577490/
I believe that the Marshall & Elliott references of 1995 and 2000, reply #78, point out an inconsistency - a 'missing link' - in treating the serve with the kinetic chain concept.
--------------
Second reference applying the kinetic chain to the serve.
Kinetic chain abnormalities in the athletic shoulder.
Aaron Sciascia, Charles Thigpen, Surena Namdari and Keith Baldwin
http://www.researchgate.net/publica..._chain_abnormalities_in_the_athletic_shoulder
I don't follow this kinetic chain treatment completely because of the 'missing link' above.
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MasturB
Legend
What gets me isn't the swing, but more so the lack of any follow through whatsoever. That follow through stop is how the 3.0 ladies hit the ball on a clay bounce here, and how those players who never picked up a racket and run on the court and punch everything look.
Cheetah
Hall of Fame
agreed. i wasn't trying to imply it was a good swing or anything. obviously it's not.
sundaypunch
Hall of Fame
One of the funniest things I have read here this year.
SystemicAnomaly
Bionic Poster
I am not privy to Maria's medical records or her training regimen. What I know of her shoulder issues/condition, I've picked up from reading a variety of sources. I do not pretend to know everything she's had to go thru. I am sure that you are quite capable of using Google to confirm or refute the details I've already provided.
I seriously doubt that Maria does not care. Her results indicate otherwise. It appears to me that she has put considerable effort into improving her footwork and her serving woes. She's done a great job of mastering clay and getting herself back up to #2. Do not know the specifics of the situation with the Connors -- perhaps he said something or maybe it just wasn't a good fit.
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SystemicAnomaly
Bionic Poster
Thanks for the links. It appears that, even with decent serve mechanics, an overuse injury of the shoulder is not uncommon. (Couple those overhead stresses with other shoulder stress, such as the reverse FH).
(The throwing) motion is unnatural and highly dynamic, often exceeding the physiological limits of the joint. Owing to overload of various anatomical structures, the shoulder is susceptible to injury.
The shoulder is the most mobile joint in the human body. Its anatomical design provides stability allowing a wide range of motion in all directions. This leads to a fragile equilibrium between stability and mobility, particularly in the tennis player, who is trying to generate as much energy as possible for the serving motion. In sports science literature, this is referred to as the “thrower's dilemma”.
Lukhas
Legend
Sorry for not being specific. When I wrote "cares", I believe at her serve "not being the ultimost priority". Her serve isn't the best part of her game, it would be natural (to me) that she'd be satisfied as long as she wins while keeping the pain or injury potential relatively low in comparison. That IMO is her goal. Especially since only one player beats her consistently. I don't see her like Nadal in 2010 before the USO take a specific course and several days of training to improve her serve for example. I believe she concentrates on her strengths, that I already mentioned (at least the RoS and return games in general).
0d1n
Hall of Fame
Where is kinetic chain here? Federer is just arming the ball!!! ???:
See also video http://youtu.be/MA3AXIlmwPQ
This is Almagro scissor kick backhand serve return and he uses a lot of upper body rotation, so we can see real kinetic chain.
See corresponding video http://youtu.be/aDyzOGO9ML4
There are clear differences between the two situations. Court position, intent and direction of the ball.
Federer is hitting an inside out backhand from way inside the court, Almagro is hitting cross court backhand from way out of the court.
Federer needs to limit body rotation so that his direction is the one he wants. He also doesn't need to generate a lot of power since he's taking the ball very early and simple correct contact will give him all the power he needs.
Almagro needs to generate a lot of power from that position, and his ball is going in a totally different place.
There are some cases where one needs to "block" or limit the follow through in order to achieve a certain purpose, but only a fool would extrapolate this into something like "one doesn't ever need a complete follow through...look at player X hitting".
MasturB
Legend
The federer image is not entirely accurate.
What you don't see is the scissor kick Federer does before he swings. So in a way he's hitting it inside out but you use open stance on the return because it gets your body momentum going in balance.
There is body rotation, but not the rotation you're thinking.
Chas Tennis
G.O.A.T.
This is one of the more informative reports on the serve. a later report on the 'kinetic chain's' "missing link" -
"Long-axis rotation: the missing link in proximal-to-distal segmental sequencing." R N Marshall, B C Elliott
http://www.researchgate.net/publica...nk_in_proximal-to-distal_segmental_sequencing
A well presented graph showing contributions to the forward racket head speed for various joint motions. See internal shoulder rotation and pronation. See figures 1 and 2.
"Long-axis rotation: the missing link in proximal-to-distal segmental sequencing." R N Marshall, B C Elliott
http://www.researchgate.net/publica...nk_in_proximal-to-distal_segmental_sequencing
A well presented graph showing contributions to the forward racket head speed for various joint motions. See internal shoulder rotation and pronation. See figures 1 and 2.
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Perhaps leg drive is not a great term, it implies pushing straight down into the ground, when really what the body is doing is screwing on top of the ground, and the feet pushing against the ground provides resistance so the body can unscrew against it. Same feeling on the forehand, which is why eg. Federer hardly moves his head up and down much even when he is drilling the ball.
Chas Tennis, thanks for email. This is my answer.
Let’s analyze Sharapova serve.
In frame 1 the front of the forearm is parallel to bicep, thus forearm pronation is in neutral position. Then Sharapova uses 90° supination and in frame 2 the front of the forearm is perpendicular to the bicep. After that she starts forearm pronation and at contact, frame 3, front of the forearm is parallel to bicep again. So, during the forward swing she applies forearm pronation around 90°!
According to fig. 2 of Elliott data the server managed just 4° of pronation. This is absolutely unbelievable!
In fig. 2 pronation creates angular speed 15 rad/sec and internal shoulder rotation (ISR) 30 rad/sec, so if the arm is straight the linear speed of the pronation must be just two times slower than ISR linear speed. But according to table 1 of the article they are 1.6 m/sec and 16.8 m/sec respectively and that is practically impossible.
There are also a lot of more very suspicious data. :shock::evil:
Let’s analyze Sharapova serve.
In frame 1 the front of the forearm is parallel to bicep, thus forearm pronation is in neutral position. Then Sharapova uses 90° supination and in frame 2 the front of the forearm is perpendicular to the bicep. After that she starts forearm pronation and at contact, frame 3, front of the forearm is parallel to bicep again. So, during the forward swing she applies forearm pronation around 90°!
According to fig. 2 of Elliott data the server managed just 4° of pronation. This is absolutely unbelievable!
In fig. 2 pronation creates angular speed 15 rad/sec and internal shoulder rotation (ISR) 30 rad/sec, so if the arm is straight the linear speed of the pronation must be just two times slower than ISR linear speed. But according to table 1 of the article they are 1.6 m/sec and 16.8 m/sec respectively and that is practically impossible.
There are also a lot of more very suspicious data. :shock::evil:
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Chas Tennis
G.O.A.T.
Where is "2°" located?
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Chas Tennis
G.O.A.T.
.........................................
In frame 1 the front of the forearm is parallel to bicep, thus forearm pronation is in neutral position. ...................................
................................................................................................
"the front of the forearm is parallel to bicep" I'm not sure of these reference points or how you are estimating.
Measurement of pronation. (my sound for this video is very low)
https://www.youtube.com/watch?v=PLE1uAWCrVU
I view the marker in her hand as similar to the tennis racket. In the first frame of the Sharapova serve, the tennis racket is pointing backward (it appears considerably shorter) so the pronation angle would not be neutral (0°), 45° supination?
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Before impact pronation has positive angular speed (see fig. 2) from – 0.01 sec to 0.0. Max pronation angular speed = 15 rad/sec and average speed around 7 rad/sec. Thus angular path is 7 rad/sec * 0.01 sec = 7*(180/π) degree/sec*0.01 sec = 4°.
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Chas Tennis
G.O.A.T.
Here is explanation.
In the first picture on the left, the marker is in the same plane as the upper arm and that's neutral pronation, we agree. Now picture replacing the marker with the tennis racket.
Sharapova's racket does not appear to be in the same plane with the upper arm - neutral pronation. To me it appears to be supinated by a large angle, in other words, pointing toward the camera.
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Chas Tennis
G.O.A.T.
I guess that Picture 1 would be some supination. Sharapova's first frame would be considerably more supination. If the racket were in the plane of the upper arm the pronation would be neutral. Pronation and supination can be demonstrated with the racket in your hand.
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1. Yes, there are some forearm supinations. Does it prove that Elliott’s article is correct?
2. I’m not talking about humerus, but about unique biceps plane. Here is picture from above, bicep looks like ellipse.
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Chas Tennis
G.O.A.T.
You have pointed out an inconsistency here or something that we both don't understand yet.
Here is some information on the reference:
Long-axis rotation: the missing link in proximal-to-distal segmental sequencing
1) History. A 2000 publication on the serve which is closely related to a similar 1995 publication. Represents important early publications that establish the importance of internal shoulder rotation for the serve. Both publications point out and discuss in detail that there is a problem with the 'kinetic chain' concept regarding the strong rotations late in the motion leading to impact. The graphical presentation, of the individual joint motions vs time relative to impact, is a very logical and clear way to present the complex joint motions of the serve. Everybody interested in the serve should spend some time to see the joint sequencing and times involved. Pictures are added to show the server's position in the service motion for the times on the graphs. (Compare to common text descriptions of the serve.)
2) The 1995 & 1996 servers. The measurements were made in 1995 and 1996 using 11 male tennis players that were said to have strong serves by coaches who were familiar with their serves. The data in the graphs are averages from all the players.
3) Serving Techniques. The techniques of these servers of almost 20 years ago may differ from high level ATP servers of today. ? This research itself probably has resulted in changes in high level serving technique from 1995 to 2014. Speculating - one issue that may differ in these 1995 & 1996 serves is the amount of wrist flexion or snap. Maybe these servers (college players?) had more wrist flexion than current ATP servers. ? A well known 2006 paper with data on the wrist motion seems to hedge and lump "Hand, Flexion,(palm/ulnar)" motion together. ? We should recognize that these were early ground-breaking results and that the experiments could be improved. Limitations of the experiments are mentioned in the 1995 and 2000 papers.
3) High Speed Camera 3D Measurements. The high speed imaging consisted of 3 cameras filming at 200 fps, or 5 milliseconds between frames. The time between frames of 5 milliseconds, less than an ideal sampling rate, should be kept in mind when considering presented data 5 and 10 milliseconds before impact. A single camera gives 2D information and cannot fully show position in 3D space. The multi-camera data was handled to provide 3D positions for certain joint reference points on the body that had reflective markers. (These 3D techniques are now called 'motion capture'.)
Maybe we are pushing the early 200 fps camera data too far for conclusions? It would be nice to see the experiments repeated for a current ATP high level serve and faster instrumentation............
Toly pointed out that pronation reached a high rotation rate at impact but that pronation's listed contribution to racket head speed also at impact seems much too low, inconsistent. I don't see the explanation but would like to point out some interesting and possibly relevant details in Figures 1 & 2.
See Figure 2 in
http://www.researchgate.net/publica...nk_in_proximal-to-distal_segmental_sequencing
Figure 2 shows the angular rotation rates of specific joints. The time scale is on the heavy dark line in the center. The grey vertical lines that look like graph lines are not, those lines just connect the pictures to approximate times on the graph.
The points plotted appear to correspond to the frames of the camera at 200 fps, 5 milliseconds apart.
The angular rotation rates can be interpreted to indicate things about the muscle forces in play. But just because rotation rates accelerate does not mean that the muscles of that joint supplied forces.
[A radian or rad = 57.3°]
1) At impact the rotation rates: internal shoulder rotation- 27 rad/sec, pronation- 16 rad/sec. Pronation rises from 0 rad/sec to 16 rad/sec in the 12 milliseconds before impact. The final ISR begins about 95 milliseconds before impact.
2) Recall that impact itself, ball-string contact, lasts 3-5 milliseconds. Capturing a frame every 5 milliseconds is not ideal for accurate measurement of 'impact' time 0 and other times. An error analysis is needed to determine the uncertainty for timing.
3) Now look at the internal shoulder rotation near -0.100 sec, a tenth of a second before impact, the rotation rate is 0 rad/sec, is just starting. Look at the pronation and ISR together. My interpretation is that when ISR increases, pronation decreases. The ISR muscles are much more powerful than the pronation muscles. Observe how as the ISR rotation rate increases to its peak, the pronation rate decreases. But pronation rate increases may stop near the end of the range of motion of pronation, around -0.025 sec. ? When the IRS peaks and starts to decline the pronation again increases, see about 12 milliseconds before impact. One possibility - Maybe the pronation muscles were pre-stretched by the forceful ISR and those muscle forces cause the pronation angular rotation rate to increase, the pre-stretched muscles shortened to cause this late pronation. A second possibility - maybe when the ISR is slowing down after the peak, the inertial of the racket and arm causes the pronation to increase, then, even if there is accelerated joint rotation, there would be little muscle force supplied by the pronator muscles.
4) In performing a serve, how consistent is the timing of the peak of ISR rotation rate relative to impact? What is the variation for an individual server? When do faults occur because ISR peaks too early or too late? For first serves, 30% are faults. Those would be interesting measurements.
5) Now look at the elbow extension. Elbow extension continues past impact. Doesn't that indicate that the elbow was bent at impact for some of the servers?
Toly said above "...so if the arm is straight....". That's important because if the elbow is not straight ISR will produce more racket head speed than pronation for the same angular rotation rate (as in Fig 2). Could an elbow angle account for the large difference in the table that Toly pointed out?
6) Now look at wrist flexion. WR is 17 rad/sec at impact and high before and after impact. I don't think that I see much wrist flexion around impact in current high level serves. ? I don't understand why there is such a large difference unless the earlier players were using much more wrist flexion. ?
7).................
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5263
G.O.A.T.
The problem or the key? If the best wheelies are around 110, we should look at the best ATP serves in the 160 range by Groth and others, which gives about 50% more speed. Could indicate the legs are providing power and a bigger window of success.
Chas and toly, interesting comments but you simply cannot use 2D images to estimate angles.
Although golf-related, you may find this interesting. http://www.clubmakerscalculator.com/golfbiomechanics/3d-golf-swing-analysis-of-pga-tour-pros/
Although golf-related, you may find this interesting. http://www.clubmakerscalculator.com/golfbiomechanics/3d-golf-swing-analysis-of-pga-tour-pros/
Chas Tennis
G.O.A.T.
I don't see your conclusion.
I have mostly considered in detail the final 30 milliseconds of racket motion toward the ball for the various joint motions. Elliott's work is the clearest that I have found for these measurements, resulting in the well-known table of individual joint motion contributions to forward racket head speed - at the time of impact. ISR was the largest contributor. Elliott has plots of joint velocities throughout much of the service motion but I have not spent time on the pronation and supination during those earlier times. You might take the rates for pronation in his plot and see if the pronation equals your estimate - "There is around 90° forearm pronation before impact."
Maybe we are arguing over different things, over different time ranges, you, the pronation angle for the last 300 milliseconds including with the elbow bent and me, the pronation motion for the last 30 milliseconds with the elbow nearly straight?
I am unable to see pronation with any certainty on serves. I trust that the Elliott work took the proper approach. I'm not familiar with more recent research that may cost $40 per paper to see (unless you are in college and your library has a subscription).
Here are the markers that Elliott and Marshall used to see the pronation and distinguish it from internal shoulder rotation.
There is a marker to indicate
1) the shoulder,
2) one to indicate the elbow,
3) two to indicate the end of the forearm, and
4) two to indicate the hand on the other side of the wrist joint.
Markers #1 & #2 indicate ISR.
Markers #2 & #3 indicate pronation.
They viewed these markers with 3 separate high speed cameras, at 200 fps. 200 fps captures a frame every 5 milliseconds. The last 20 milliseconds of the serve are very fast and have significant angular changes in 5 milliseconds. 200 fps is a little slow. The positions of the markers were measured for each camera and a computer program was used to determine 3D positions. Seems reasonable to me.
I could get some rough 2D measurements of ISR and pronation when the arm is nearly straight - if the servers were wearing markers. Since they aren't and I have to look for bone shadows at the elbow and usually nothing as a marker for the wrist, the accuracy for measuring pronation or even seeing it is not good, very marginal, if at all.... But I can see the elbow bones rotate well enough to know that ISR is very rapid over a large angle. It appears consistent with Elliott's data to me. This is all during the last 30 milliseconds leading to impact. I'm not trying to estimate pronation earlier when the elbow is bent, just when the arm is nearly straight and the big pre-stretched muscles are about to contribute with ISR.
Once that I was able to see the ISR in this video, by looking at the shadows around the elbow - just 1/4 second as played back at 30 fps - I first understood how fast ISR is.
https://vimeo.com/27528701
I don't think that anyone has yet replied that they can see the ISR in that video. Anybody?
Can we separate the ISR and pronation of this video?
There is a wrist watch that can be used as a marker. If the wrist watch turns the same rate as the elbow bones, it is all ISR. If it turns faster then there is some pronation added to the ISR. The pronation may occur as the ISR slows down, in which case, possibly little force may be produced by the pronation muscles shortening. Or it might be the 100 MPH racket causing the pronation. Obviously, servers with markers and multi-cameras systems, as used in Elliott's research, would be nice.
Elliott's research looks good to me. Do you want to pitch in for one of those 3D motion capture systems to make your point?
I have mostly considered in detail the final 30 milliseconds of racket motion toward the ball for the various joint motions. Elliott's work is the clearest that I have found for these measurements, resulting in the well-known table of individual joint motion contributions to forward racket head speed - at the time of impact. ISR was the largest contributor. Elliott has plots of joint velocities throughout much of the service motion but I have not spent time on the pronation and supination during those earlier times. You might take the rates for pronation in his plot and see if the pronation equals your estimate - "There is around 90° forearm pronation before impact."
Maybe we are arguing over different things, over different time ranges, you, the pronation angle for the last 300 milliseconds including with the elbow bent and me, the pronation motion for the last 30 milliseconds with the elbow nearly straight?
I am unable to see pronation with any certainty on serves. I trust that the Elliott work took the proper approach. I'm not familiar with more recent research that may cost $40 per paper to see (unless you are in college and your library has a subscription).
Here are the markers that Elliott and Marshall used to see the pronation and distinguish it from internal shoulder rotation.
There is a marker to indicate
1) the shoulder,
2) one to indicate the elbow,
3) two to indicate the end of the forearm, and
4) two to indicate the hand on the other side of the wrist joint.
Markers #1 & #2 indicate ISR.
Markers #2 & #3 indicate pronation.
They viewed these markers with 3 separate high speed cameras, at 200 fps. 200 fps captures a frame every 5 milliseconds. The last 20 milliseconds of the serve are very fast and have significant angular changes in 5 milliseconds. 200 fps is a little slow. The positions of the markers were measured for each camera and a computer program was used to determine 3D positions. Seems reasonable to me.
I could get some rough 2D measurements of ISR and pronation when the arm is nearly straight - if the servers were wearing markers. Since they aren't and I have to look for bone shadows at the elbow and usually nothing as a marker for the wrist, the accuracy for measuring pronation or even seeing it is not good, very marginal, if at all.... But I can see the elbow bones rotate well enough to know that ISR is very rapid over a large angle. It appears consistent with Elliott's data to me. This is all during the last 30 milliseconds leading to impact. I'm not trying to estimate pronation earlier when the elbow is bent, just when the arm is nearly straight and the big pre-stretched muscles are about to contribute with ISR.
Once that I was able to see the ISR in this video, by looking at the shadows around the elbow - just 1/4 second as played back at 30 fps - I first understood how fast ISR is.
https://vimeo.com/27528701
I don't think that anyone has yet replied that they can see the ISR in that video. Anybody?
Can we separate the ISR and pronation of this video?
There is a wrist watch that can be used as a marker. If the wrist watch turns the same rate as the elbow bones, it is all ISR. If it turns faster then there is some pronation added to the ISR. The pronation may occur as the ISR slows down, in which case, possibly little force may be produced by the pronation muscles shortening. Or it might be the 100 MPH racket causing the pronation. Obviously, servers with markers and multi-cameras systems, as used in Elliott's research, would be nice.
Elliott's research looks good to me. Do you want to pitch in for one of those 3D motion capture systems to make your point?
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Chas Tennis
G.O.A.T.
Here is a recent paper on the Kinetic Chain and the tennis serve by Ben Kibler, a prominent researcher that has employed the KC concept for many years.
http://www.aspetar.com/journal/viewarticle.aspx?id=6#.Vxm5rUc1r4w
http://www.aspetar.com/journal/viewarticle.aspx?id=6#.Vxm5rUc1r4w
Chas Tennis
G.O.A.T.
This brief paper explicitly explains the problem the early tennis researchers and others found with the Kinetic Chain concept.
https://ojs.ub.uni-konstanz.de/cpa/article/viewFile/2695/2533
I'd like to find an updated Kinetic Chain explanation that shows how it deals with the stretching of muscles.
The Kinetic Chain seems to recognize the general trend of movement to have body parts speeding up from larger slower parts (core) to smaller faster parts (hand). When mentioned, the Kinetic Chain does describes the speeding up of body parts, that is obvious, but KE does not describe the pre-stretch of muscles. In other words, in movement the body parts vs time have 1) positions, 2) speeds and 3) muscles that are at some degree of stretch.
publication
"CONCLUSION
The proximal-to-distal sequencing of the kinematic chain for selected striking and throwing skills does not hold up under close scrutiny if movements produced by upper limb segments are analysed. While segment endpoints do increase in linear speed (shoulder-elbow-wrist-distal end of phalanges) an analysis of segment movements about all their degrees of freedom shows that internal rotation of the upper arm does not fit the above sequencing format. It is a primary generator of endpoint speed in striking and throwing skills and occurs very late in the movement sequence."
https://ojs.ub.uni-konstanz.de/cpa/article/viewFile/2695/2533
I'd like to find an updated Kinetic Chain explanation that shows how it deals with the stretching of muscles.
The Kinetic Chain seems to recognize the general trend of movement to have body parts speeding up from larger slower parts (core) to smaller faster parts (hand). When mentioned, the Kinetic Chain does describes the speeding up of body parts, that is obvious, but KE does not describe the pre-stretch of muscles. In other words, in movement the body parts vs time have 1) positions, 2) speeds and 3) muscles that are at some degree of stretch.
publication
"CONCLUSION
The proximal-to-distal sequencing of the kinematic chain for selected striking and throwing skills does not hold up under close scrutiny if movements produced by upper limb segments are analysed. While segment endpoints do increase in linear speed (shoulder-elbow-wrist-distal end of phalanges) an analysis of segment movements about all their degrees of freedom shows that internal rotation of the upper arm does not fit the above sequencing format. It is a primary generator of endpoint speed in striking and throwing skills and occurs very late in the movement sequence."
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Chas Tennis
G.O.A.T.
I believe R. N. Marshall's statements, pointing out problems with the Kinetic Chain Concept and the throw, summed up the situation in 2000. Click on and read the full posts including Marshall's publication.
(I had not seen Marshall's publication on throwing until Raul_SJ just posted it.)
How did baseball pitching researchers receive this publication?
(I had not seen Marshall's publication on throwing until Raul_SJ just posted it.)
APPLICATIONS TO THROWING OF RECENT RESEARCH ON PROXIMAL-TO-DISTAL SEQUENCING
R.N. MarshallThe University of Auckland, Auckland, New Zealand
Most assessments of segmental sequencing in throwing, striking or kicking have indicated a proximal-to-distal sequence; until recently, the role of long-axis rotations had not been adequately quantified. Data showing the timing and importance of upper arm internal-external rotation and pronation-supination in throwing and striking have been considered from conventional concepts of proximal-to-distal sequencing. In general, long-axis rotations reached their peak angular speeds late in the skills, although variations are seen as a result of ball size or mass, the magnitude of external forces and use of aracquet. This analysis indicates it is essential to consider longitudinal axis rotations inexplaining the mechanics of throwing and striking movements as well as in developing coaching emphases, strength training schedules, and injury prevention programmes.
KEY WORDS: proximal-to-distal sequencing, kinematics, throwing, racquet sports
INTRODUCTION:
Many sports demand that maximum speed be produced at the end of the distal segment in a kinematic chain. In throwing activities, for example, athletes try to generate a large hand velocity in a particular direction. Sports that use an implement to increase end point speed, such as tennis or squash, require that the racquet head develops maximum speed. The idea that there is a ‘grand plan’ that would explain the multitude of different, yet similar,throwing or striking movements is appealing.
Indeed, research has suggested that throwing,striking and kicking skills all exhibit aspects of proximal-to-distal sequencing. The concept upon which most others appear to have been developed is the ‘summation of speed principle’ (Bunn, 1972). The ‘kinetic link principle’ (Kreighbaum and Barthels, 1985) and Plagenhoef’s (1971) ‘acceleration-deceleration’ concept are really variations on Bunn’s definition.
In essence, the principle states that, to produce the largest possible speed at the end of a linked chain of segments, the motion should start with the more proximal segments and proceed to the more distal segments. The more distal segment begins its motion at the time of the maximum speed of the proximal one, with each succeeding segment generating a larger end point velocity than the proximal segment.
Aspects of proximal-to-distal sequencing have been confirmed,although evaluation of individual segment contributions to hand or racquet speed and the role of long-axis rotations in temporal patterning have received little quantitative consideration.In some activities, such as kicking a ball, neither segmental long axis rotation nor movement out of the primary plane appears to contribute significantly to the speed of the foot. On the other hand, movements such as throwing a ball or a forehand drive in squash are effective only if the skill takes advantage of movement about all the axes of rotation. An essential aspect of these skills is that the potential for rotation about each arm segment’s long axis is exploited so that maximum speed may be generated at the end of the kinematic chain.
However, an inspection of the literature suggests that there are aspects of throwing and striking activities where aberrations are seen in the traditional proximal-to-distal pattern. Feltner and Dapena (1986), Sakurai et al. (1993) and Woo and Chapman (1994) have all shown incidences in throwing or striking motions where internal rotation velocity of the upper arm reaches a maximum after the peak speeds of the forearm and hand segments. The peak velocity of pronation has also been reported to occur immediately before impact (Woo andChapman, 1994; Sprigings et al., 1994),
suggesting that this rotation also may not conform to traditional explanations of proximal-to-distal sequencing
2228-Article Text-4603-1-10-20081111.pdf
APPLICATIONS TO THROWING OF RECENT RESEARCH ON PROXIMAL-TO-DISTAL SEQUENCING R.N. Marshall The University of Auckland, Auckland, New Zealand Most assessments of segmental sequencing in throwing, striking or kicking have indicated a proximal-to-distal sequence; until recently, the role of...www.docdroid.net
How did baseball pitching researchers receive this publication?
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Chas Tennis
G.O.A.T.
It's Oct 2024, the news to me is that Spinal Engine is a view that the spine and torso coordinate the surrounding body and limbs and time their movements, somehow. So far there are not many details available for tennis. But it looks as if SE could put the Kinetic Chain Concept to rest. Spinal Engine claims significant motions use a fascia connection between the upper body's arm and lower body's legs. I don't see how 'speeding up of body parts' works across the middle of the body, as Spinal Engine Theory does.
KCC does not even have much to say about the Stretch-Shorten-Cycle. I have a second 1972 edition of John Bunn's original book that popularized Kinetic Chain Concept, Scientific Principles of Coaching. I found this book referenced often for the Kinetic Chain Concept. The first edition was published in1955.
I had to throw away a nicely done German tennis book, that was published in the 1990's, because it was worthless due to its serve description that preceded the research publication describing ISR & the serve by Elliott, Marshall and Noeffel in 1995.
Now Spinal Engine is in the air and it's better to look ahead to understand it.
Biomechanics for tennis seems logical with a lot that is true and has been progressing for almost 30 years. Biomechanics evolves as new research appears. Spinal Engine seems the next thing that will appear or has appeared?
KCC does not even have much to say about the Stretch-Shorten-Cycle. I have a second 1972 edition of John Bunn's original book that popularized Kinetic Chain Concept, Scientific Principles of Coaching. I found this book referenced often for the Kinetic Chain Concept. The first edition was published in1955.
I had to throw away a nicely done German tennis book, that was published in the 1990's, because it was worthless due to its serve description that preceded the research publication describing ISR & the serve by Elliott, Marshall and Noeffel in 1995.
Now Spinal Engine is in the air and it's better to look ahead to understand it.
Biomechanics for tennis seems logical with a lot that is true and has been progressing for almost 30 years. Biomechanics evolves as new research appears. Spinal Engine seems the next thing that will appear or has appeared?
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Fintft
G.O.A.T.
Nice but too complicated. To me the kinetic chain on the serve is mainly the 2 pendulums.
Chas Tennis
G.O.A.T.
Where is the Stretch Shorten Cycle (SSC) mentioned in Kinetic Chain Concept? Where is Spinal Engine's fascia connection that connects the right shoulder's humerus to left buttock and the rest of the lower body?
They were not thought of with Kinetic Chain Concept - KCC is more or less words used to impress people that you may know something. But no one can apply it to any tennis strokes for any gain in understanding. Segments speeding up?? Misleading too. I see stretching muscles up at the shoulder when the jump occurs - energy is being put into the shoulder muscles when the legs extend - where is KCC?
Tennis biomechanics has the SSC. And will likely have Spinal Engine soon.
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SunkTheBirdie
New User
My tennis is winding down for the season (getting cold). Hopefully I'll have some time to tackle tennis biomechanics in the offseason.
I am promising myself to spend the majority of my offseason time focusing on fitness, not mechanics mind you.
A big difference between golf and tennis is mechanics plays a much bigger role in non-pro golf as the ball is stationary. Getting to the ball and setting up effectively plays a much bigger role in tennis - and those aren't fundamentally mechanics.
I'm trying to see if there are tennis flaws that correspond to a few golf flaws like: early extension, and over the top.
Over the top in golf is probably starting your tennis swing with your hands/arms not your core. Food for thought.
I am promising myself to spend the majority of my offseason time focusing on fitness, not mechanics mind you.
A big difference between golf and tennis is mechanics plays a much bigger role in non-pro golf as the ball is stationary. Getting to the ball and setting up effectively plays a much bigger role in tennis - and those aren't fundamentally mechanics.
I'm trying to see if there are tennis flaws that correspond to a few golf flaws like: early extension, and over the top.
Over the top in golf is probably starting your tennis swing with your hands/arms not your core. Food for thought.
Chas Tennis
G.O.A.T.
My posts and threads have often focused on a sub-motions, because I studied high speed videos of the strokes. If interested, forum search serve or forehand, etc by Member: Chas Tennis. You'll find high speed videos of sub-motions. Not much is there on leg work. My interest is on the last high speed approach to ball impact and seeing it in high speed video. Videos are completely true, but things can be missed or misinterpreted, even in perfect videos. (That is, assuming the camera is technically adequate without artifacts, like Jello Effect.)
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