Leg drive myth?

sureshs

Bionic Poster
#51
Timely article in tennisplayer.net latest issue:

@JohnYandell

Synchronizing the Legs Dr. Brian Gordon

How does the leg drive contribute to racket head speed on the serve? Indirectly but critically. The key is synchronizing the push of the legs with the entry of the racket into the backswing. Dr. Brian Gordon believes this is the most critical element in developing high performance serving. Find out how perfect timing with the legs maximizes the effect of the arm rotations in the upward swing.
 
#52
Timely article in tennisplayer.net latest issue:

@JohnYandell

Synchronizing the Legs Dr. Brian Gordon

How does the leg drive contribute to racket head speed on the serve? Indirectly but critically. The key is synchronizing the push of the legs with the entry of the racket into the backswing. Dr. Brian Gordon believes this is the most critical element in developing high performance serving. Find out how perfect timing with the legs maximizes the effect of the arm rotations in the upward swing.
Do you have the link?
 
#53
Look at the elbow shadows only and before impact you will see a twitch-like internal shoulder rotation (ISR) that rotates the entire arm. The ISR joint motion involves the upper arm bone rotating like a top at the shoulder joint. Keep replaying the video until you see ISR (lasts 25 milliseconds in real time). That's ISR and its timing leading to impact.

"For instance, in the power serve, pronation is primarily responsible for racquet orientation, ..............."
"
Right....so how is that 25 milliseconds leading into contact not the same as "in the last instance" or "at the last moments"???

I've never bought into the various studies about which segment generates how much power....they don't often agree and don't explain what they are measuring in a meaningful way Imo. Try hitting a big power serve without pronation and see how that works out.....
 
#54
Right....so how is that 25 milliseconds leading into contact not the same as "in the last instance" or "at the last moments"???

I've never bought into the various studies about which segment generates how much power....they don't often agree and don't explain what they are measuring in a meaningful way Imo. Try hitting a big power serve without pronation and see how that works out.....
The last 25 milliseconds conveys information for athletic motions but "at the last instance" or "at the last moments" does not convey accurate or unambiguous information. Also, what is occurring is identified as ISR, acceleration but nothing special in the last X milliseconds. For using 'last', I can't tell if that is during the last 5 milliseconds, the last 100 milliseconds or the last 1/2 second. Why not use the correct time and let the readers decide how they want to handle it?
https://www.youtube.com/watch?v=IMgQWotcPYE

Sometimes the words "at the last moments" or "in the last instance" will convey that there is something special and different. What is different? It looks as if most motion toward the ball from the Big L to impact is a simple acceleration and rotation from ISR. What is 'last' second, or instant, or moment?

Please post links to a few of the disagreeing publications on measurements.

The research is not on power. The research is on the contributions from each joint to forward racket head speed vs time at any instant of time, like impact. Measurements are made by 3D multi-camera motion capture systems. In principle, the speed measurements could be very accurate. One inaccuracy in the measurement is that motion capture systems measure the locations of retro-reflective balls that are attached to the body - to the skin. But the skin moves around relative to the joints and bones inside. That is one of the bigger errors in measuring the forward racket head speed contributed by each joint. That is not too bad because the racket motion itself shows dominant joint contributions, like ISR, but I don't want to try to prove it. The early research publications discussed errors. I have not seen more recent error discussions, maybe you have something new? Also, the end result, the racket movement itself is proof of the significance of ISR even if there are some inaccuracies in the measurements. I have also pointed out that the shadows at the elbow - which are an indication of bone movement and joint motions - are good enough to indicate ISR is very significant. But I would not want to attempt to measure ISR speed using the changing elbow shadows (but it might be possible?).
 
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#57
Why not use the correct time and let the readers decide how they want to handle it?

Sometimes the words "at the last moments" or "in the last instance" will convey that there is something special and different. What is different? It looks as if most motion toward the ball from the Big L to impact is a simple acceleration and rotation from ISR. What is 'last' second, or instant, or moment?
we will just agree to disagree on this one..There is NO correct millisecond time and things change as the serve improves. What you call the "correct time" is you just quoting someone else on something you (or almost anyone else for that matter) can't measure or confirm. You are just regurgitating what you found in a book that will vary with different servers. These books are full of errors and represent best scientific approach to capture and measure things that in most cases, these guys don't fully grasp. If you think it's just simple acceleration, I suspect you will never really get what goes into the biggest serves. Imo what you are getting from your references is more of an intro into serving but you treat it like a trump card. Nothing looks different in that serve as much because it wasn't a big serve with full ISR. I doubt it got close to 120 and was likely less than 115.

So no, I'm not quoting a bunch of measurements that people can't use, but instead, sharing more of an understanding of how the serve works and how it's done, along with how I've helped, developed and improved several 130+ servers. Never have I had a college or pro player ask me... was it 15 or 25 milliseconds where he was supposed to do something, but it does help them when I share that certain actions are delayed until the last moment where they can be properly completed. A player doesn't develop timing because you quoted a number. Imo this is much like if one guy said the girl had wavy, think hair and you came along saying that means nothing....she 431,121 hairs on her head with an avg bend of 7 degrees. People have a much better idea what thick hair is than what 431,121 hairs means, never mind that 427 hairs fell out in the mean time.

You keep referencing the Big L. Can you explain what you think the Big L represents to you?
 
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#58
If you are 6feet tall (and more), you dont need gravity for the serve. Players who has/had serve as a weapon are/were 6f and more ... Sampras, Becker, Lendl, Federer, Raonic, Isner, Karlovic ...
 
#59
Timely article in tennisplayer.net latest issue:

@JohnYandell

Synchronizing the Legs Dr. Brian Gordon

How does the leg drive contribute to racket head speed on the serve? Indirectly but critically. The key is synchronizing the push of the legs with the entry of the racket into the backswing. Dr. Brian Gordon believes this is the most critical element in developing high performance serving. Find out how perfect timing with the legs maximizes the effect of the arm rotations in the upward swing.
Bold part is something I shared many times on TP.net back in 2004 or earlier.
 
#60
............................
You keep referencing the Big L. Can you explain what you think the Big L represents to you?
http://www.hi-techtennis.com/serve/flash/nalbandian_l.mp4

For the serve, the Big L is an an upside down "L" formed by the racket and the near straight arm. It's a checkpoint. Play the above video to see it.
1) This is about the time that ISR starts.
2) The arm has just become near straight.
3) It is also about the time that the 'edge on' racket checkpoint appears. (The majority of active tennis players have the racket face facing the sky= not a high level serve. )
4) The racket is about straight back.

Look at high speed videos for the details and variations.

Webpage on the Big L.
http://www.hi-techtennis.com/serve/nalbandian_l.php

Webpage on Waiter's Tray Error
http://www.hi-techtennis.com/serve/big_l_student.php
 
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#61
If you are 6feet tall (and more), you dont need gravity for the serve. Players who has/had serve as a weapon are/were 6f and more ... Sampras, Becker, Lendl, Federer, Raonic, Isner, Karlovic ...
For under 6 ft, don't need gravity either, just need gaseous molecules so the spin causes a higher pressure above the ball and lower pressure below the ball causing the ball to dip. Airplane wing
 
#62
http://www.hi-techtennis.com/serve/flash/nalbandian_l.mp4

For the serve, the Big L is an an upside down "L" formed by the racket and the near straight arm. It's a checkpoint. Play the above video to see it.
1) This is about the time that ISR starts.
2) The arm has just become near straight.
3) It is also about the time that the 'edge on' racket checkpoint appears. (The majority of active tennis players have the racket face facing the sky= not a high level serve. )
4) The racket is about straight back.
Thanks for the description, but Imo all this pretty obvious and very basic. What I'm trying to get at is why you feel it is an important checkpoint. This sort of reminds me of the straight arm vs double bend nomenclature, where we can see something, but there is little significance to it. What is the significance of this L? While you will see this L with high level servers, you will also see it in all but the worst avg servers as well. I don't see where it's much of a checkpoint. ISR starts well before this, right as you come out of the serving slot, and even begins the big surge coming out of the serving U, just before this L. The racket is on edge there, but it but better be on edge well before this for good serves. The biggest key with this Imo, is that the racket starts to come OFF edge with pronation at the L.... and that the L is that last part where the serve will still be on edge; so I think you are seeing this a bit in reverse if you say it's where the racket first comes on edge. If the majority of active players have the RFace to the sky as you claim, it's because they came off the edge too early, not because they didn't find the edge at the L point. Anyway, sounds like you are suggesting they could waiter's tray in the trophy position, then just catch the edge later at the "L", but we know that won't work.

So I'd suggest that if there is a significance worth pointing out on the L, it's that the server should still be on edge at that late stage....not just getting there. And while the L may rule out some things you could have done wrong, it doesn't confirm you will do things right. I guess I answered my own question here in that it is a checkpoint to make sure you didn't leave the edge too soon. If someone sees other strong points to this L, then please share because we all want to learn. Until then, I'd suggest that the Upside down "U" of the launch is a far more important key checkpoint for spotting a strong serve.
 
#65
Did you word it the same way?
good point...I read that as "a critical aspect" and not "the most critical element" as he words it. Looking back at it that way, I'd have to respectfully disagree and say it isn't "the most critical element".
Thanks
 
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#66
one tennis scientist said, "To conclude, I'm reminded of something I learned in a computer science seminar: "Data do not imply their own explanation." The ability to measure and calculate millions of numbers will not further the understanding of tennis strokes. Biomechanics alone is not the holy grail of sport understanding, and there are some issues the current methods of biomechanics can't address. "
 
#67
@brc7
Late to the party here (disclaimer: not read all the replies)...

Leg drive is not a myth. Sure, ESR is possible w/o leg drive. However, max/optimal ESR is much more easily achieved with a properly-timed leg drive. Note that primary benefit of leg drive for added ESR is a greater stretch of the internal (shoulder) rotators. The release of this stretch occurs during the upward swing -- during the ISR/pronation phase. The importance of leg drive on an elite/advanced serve, or for a high intermediate serve for that matter, has been promoted by serve experts: Rick Macci, Brian Gordon, Bruce Elliot, Pat Dougherty, Rod Cross (physicist), John Yandell, Miguel Crespo and numerous others.




https://pdfs.semanticscholar.org/e301/c5ee8131d325fda7a8f41240ed19c938459e.pdf
.
 
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#68
one tennis scientist said, "To conclude, I'm reminded of something I learned in a computer science seminar: "Data do not imply their own explanation." The ability to measure and calculate millions of numbers will not further the understanding of tennis strokes. Biomechanics alone is not the holy grail of sport understanding, and there are some issues the current methods of biomechanics can't address. "
Here is the original article that has your quote from about 2002. This article was written about 16 years ago and one year before the reference Biomechanics of Advanced Tennis, B. Elliott et al was published, still in the early days of tennis serve research. I think a lot has changed since those early days of tennis research measurements using 3D motion capture film systems.

Quantum Tennis: The Serve and Tennis Science
https://tennisone.tennisplayer.net/content/issue/gordon/Science/science.htm

In fact, Brian Gordon now has an advanced 3D motion capture system (I believe it is a 500 fps multi-camera system) and analyses tennis strokes with measurements much like the first tennis serve researchers did.

In research, you should be very aware of what the most prominent and recognized researchers have done in the past and also the prominent researchers of the current time. Be aware and be skeptical.
 
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#69
Here is the original article that has your quote from about 2002. This article was written about 16 years ago and one year before the reference Biomechanics of Advanced Tennis, B. Elliott et al was published, still in the early days of tennis serve research. I think a lot has changed since those early days of tennis research measurements using 3D motion capture film systems.

Quantum Tennis: The Serve and Tennis Science
https://tennisone.tennisplayer.net/content/issue/gordon/Science/science.htm

In fact, Brian Gordon now has an advanced 3D motion capture system (I believe it is a 500 fps multi-camera system) and analyses tennis strokes with measurements much like the first tennis serve researchers did.

In research, you should be very aware of what the most prominent and recognized researchers have done in the past and also the prominent researchers of the current time. Be aware and be skeptical.
Exactly, and a lot will change again as they learn to measure better.
 
#70
When you have a question always search and include the word "pictures" or "images" at the end.

Google: racket drop pictures



There are excellent videos on measuring joint motions. Search: external shoulder rotation measure Youtube

Look at the upper arm - it has rotated back and down near the end of its range of motion for external shoulder rotation (ESR) = that the internal shoulder rotation muscles (ISR) are stretched very much.

Now look at the forearm-to-racket angle. Is it about 90 degrees? Look at it earlier at Trophy Position, what is the forearm to racket angle there? Much more than 90 d. ? (corrected to "more")

At racket drop the arm has been rotated to near the end of ESR. (But the back bend, often called 'chest up', is helping that too, thoracic extension). Also, the racket has been shifted farther down because the wrist is very extended and radially deviated.

You should Google the joint motions with the word 'pictures' to see joint motions.

A kinesiology text saves a lot of time learning the defined joints, muscles and the named joint motions. Manual of Structural Kinesiology, Thompson and Flloyd, 14th or 15th edition recommended. Should be less that $15 used.

Drop vs. Rotation.
 
#71
Timely article in tennisplayer.net latest issue:

@JohnYandell

Synchronizing the Legs Dr. Brian Gordon

How does the leg drive contribute to racket head speed on the serve? Indirectly but critically. The key is synchronizing the push of the legs with the entry of the racket into the backswing. Dr. Brian Gordon believes this is the most critical element in developing high performance serving. Find out how perfect timing with the legs maximizes the effect of the arm rotations in the upward swing.
This is why for some players a slight hesitation is used, to help synchronize the limbs just before leg drive.
 
#73
If you are 6feet tall (and more), you dont need gravity for the serve. Players who has/had serve as a weapon are/were 6f and more ... Sampras, Becker, Lendl, Federer, Raonic, Isner, Karlovic ...
> 6' tall = service weapon, also has to do with longer lever arm, not just gravity/no gravity.

Baseball pitchers with fastball as a weapon also tend do be > 6', which has nothing to do with gravity. Classic example is Randy Johnson, look at his lever arm at 6'10"...
 
#74
Until then, I'd suggest that the Upside down "U" of the launch is a far more important key checkpoint for spotting a strong serve.
@5263 - do you have a good image which you feel illustrates the optimal "upside down U"?

Are you talking about something like the 5th and 6th still shots from this Roddick serve progression?

 
#78
This position is the most important key to having a truly big serve. The other stuff is either getting you to it or making use of what can be generated from hitting this position.
I can feel my timing with leg drive "loading" this position as I drop out of "trophy". Prior to this many times jumped later, still need to get elbow higher
 
#79
@IowaGuy @5263
That a deep U . Gotta work on that, that will definitely take me to the next level
If you have outstanding shoulder flexibility and don't have tight internal rotators, that deep inverted U is certainly something to strive for. But not all are so blessed or capable of this. A few decades back, I had a fairly decent drop. However in the early 90s, I damaged my rotators because of flawed volleyball spiking technique. After some time I found that my internal rotators became tight and/or my external rotation became rather limited. However, I found that even tho' my racket drop (deep U) potential was no longer as great as it once was, as long as I stretched my internal rotators as much as possible with my more limited racket drop, I could still generate a pretty decent SSC reflex action and pretty good power/RHS.

This past week, while working on alleviating pain in my "good" (non-dominant) shoulder, my physical therapist brought up this very subject. He indicated that baseball pitchers and tennis servers who have tight internal rotators or do not have exceptional ROM for their ESR, can still generate a good amount of power (or hand speed) as long as they are getting a good stretch (and subsequent release) of the internal rotators.

Bottom line: The deep inverted U is a worthwhile goal if your shoulder is capable of it. But not all are. A decent leg drive with a good stretch of the internal rotators can still generate near-optimal results even if your shoulder flexibility is somewhat limited.
.
 
#80
@IowaGuy @5263


If you have outstanding shoulder flexibility and don't have tight internal rotators, that deep inverted U is certainly something to strive for. But not all are so blessed or capable of this. A few decades back, I had a fairly decent drop. However in the early 90s, I damaged my rotators because of flawed volleyball spiking technique. After some time I found that my internal rotators became tight and/or my external rotation became rather limited. However, I found that even tho' my racket drop (deep U) potential was no longer as great as it once was, as long as I stretched my internal rotators as much as possible with my more limited racket drop, I could still generate a pretty decent SSC reflex action and pretty good power/RHS.

This past week, while working on alleviating pain in my "good" (non-dominant) shoulder, my physical therapist brought up this very subject. He indicated that baseball pitchers and tennis servers who have tight internal rotators or do not have exceptional ROM for their ESR, can still generate a good amount of power (or hand speed) as long as they are getting a good stretch (and subsequent release) of the internal rotators.

Bottom line: The deep inverted U is a worthwhile goal if your shoulder is capable of it. But not all are. A decent leg drive with a good stretch of the internal rotators can still generate near-optimal results even if your shoulder flexibility is somewhat limited.
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I separated my shoulder in a mountain biking incident around 1990, its all good to go has more movement pretty deep esr but I've started stretching more and am trying to understand define the my correct process so I can see the issues and improve on it. Jo11yroger pointed out my drop was after my jump so I think I've repaired that, next i'm thinking getting my elbow up and maybe working on that "upper chest fold back" you see Rodick doing in the pic above. That might be a bridge too far unless I can get my legs,lower back to a vastly better supportive level. Lotta good tips on technique coming from a lot of posters here. Poaster "childs" of ttw instruction
 
#81
yes, frame 6 is excellent
The 'racket drop' is a checkpoint. You have a checkpoint for the 'inverted U'. Are there differences between the 'inverted U' and the 'racket drop'?

dominikk1985 has posted on 'thoracic extension', the bending of the upper back in frames 5 & 6 of Roddick's serve. Adds to 'chest up' body position.

What do you look for in the 'inverted U'?
 
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#82
This position is the most important key to having a truly big serve. The other stuff is either getting you to it or making use of what can be generated from hitting this position.
And you believe that leg drive is an important part of getting to the "inverted U"?

Laver has some form of the "inverted U" even though sometimes his right foot never leaves the ground. He seems to have much less leg drive than any "modern" player. Thoughts?

 
#83
And you believe that leg drive is an important part of getting to the "inverted U"?

Laver has some form of the "inverted U" even though sometimes his right foot never leaves the ground. He seems to have much less leg drive than any "modern" player. Thoughts?

He might not be leaving the ground but he has the kinetic chain going just like the modern players, he coils his body and bends legs and uses stretch shortening cycle to "drill" into the ground and then the "explosion" or main power that activates the whole motion comes from pushing into the ground and then transfering that energy chain from chain up through the body into the arm.
 
#84
He might not be leaving the ground but he has the kinetic chain going just like the modern players, he coils his body and bends legs and uses stretch shortening cycle to "drill" into the ground and then the "explosion" or main power that activates the whole motion comes from pushing into the ground and then transfering that energy chain from chain up through the body into the arm.
OK, agree that Laver uses kinetic chain on his serve, but this thread is about the "myth" of leg drive.

i.e. what is the importance of leg drive to having a big serve?

Of all the ATP pros I can think of, Laver has what seems like the least amount of leg drive (as evidenced by not even leaving the ground). He is obviously using his legs, but arguably not as much as big servers such as Sampras, Fed, Roddick, etc who explode a foot or more off the ground when serving.

User5273 says that leg drive is crucial for getting into the "inverted U" - yet Laver seems to get into his version of the inverted U just fine.

Roddick would be on the other end of the spectrum - I can't think of another ATP pro that has more leg drive than Roddick.

Do you think Laver has the same amount of leg drive as Roddick?



 
#85
OK, agree that Laver uses kinetic chain on his serve, but this thread is about the "myth" of leg drive.

i.e. what is the importance of leg drive to having a big serve?

Of all the ATP pros I can think of, Laver has what seems like the least amount of leg drive (as evidenced by not even leaving the ground). He is obviously using his legs, but arguably not as much as big servers such as Sampras, Fed, Roddick, etc who explode a foot or more off the ground when serving.

User5273 says that leg drive is crucial for getting into the "inverted U" - yet Laver seems to get into his version of the inverted U just fine.

Roddick would be on the other end of the spectrum - I can't think of another ATP pro that has more leg drive than Roddick.

Do you think Laver has the same amount of leg drive as Roddick?



I recently talked to some coach about this issue, just general talk in a coffee bar.
He said leg drive is extremely important, but its not that important in pure top end speed, you can serve very big serves without a huge leg drive, but with leg drive you get a tiny bit more mph but MUCH MORE importantly you put less strain on the upper body/arm.
Without a strong leg drive your arm will get tired faster and by the end of set 2 or 3 your serve will drop down alot, but with a strong leg drive the upper motion is much more effortless and you can sustain it for long periods of time.
 
#86
And you believe that leg drive is an important part of getting to the "inverted U"?

Laver has some form of the "inverted U" even though sometimes his right foot never leaves the ground. He seems to have much less leg drive than any "modern" player. Thoughts?

The serve rule for the feet was changed about 1961. Before 1961 one foot had to stay on the ground. 1961 was during Laver's prominent years of tennis that continued from 1964 to 1970 as #1. Other outstanding servers like Pancho Gonzales also learned to serve with one foot on the ground before the rule change.

Adding the jump and optimizing its effect may not have occurred quickly after the 1961 rule change.

This subject is discussed in the Pat Dougherty video.

Laver is not a good example without knowing about his technique, serve quality, coming to net, etc. .

This article discusses the history of the jump in the tennis serve. See end of the article, starting at the 1961 rule change.
https://www.nytimes.com/2011/08/29/sports/tennis/the-genteel-origins-of-tennis-and-the-serve.html

Gerald Paterson, in a 1919 video, has a strong modern looking serve for the upper body but with one foot on the ground.
 
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#87
Is the back drop during the serve really about leg drive? I am not so sure, because when I do basic serve drills to get used to the timing (no jump, not too much rotation etc. Just working on the swing), I feel like I do it more relaxed (not feeling forced or being in an unnatural position which is how serve feels to me), a drop happens on its own. It is the same with the over head shots. I do not do the leg drive but the racket can drop back (even if not too deep). So, do you wait at the trophy position and really let the body rotation, leg drive etc do the back drop, or before that you slightly begin to move the racket lower bending your arm from your elbow?
The leg drive initiates the back drop, in that it needs to begin before the backdrop in order to achieve the maximum effect.

You can do a leg drive at the beginning, middle , or at the end of the back drop if you want, the question is, when is it optimal?

Watch this Rick Macci video from 5:05 onwards:


If you were asked to throw a ball as far as you can - you will naturally initiate the leg drive before your arm drops behind your head without even thinking about it.

Give it a try right now - pretend to throw a ball and see when your leg drive starts in relation to your arm drop behind your head.
 
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#89
The leg drive initiates the back drop, in that it needs to begin before the backdrop in order to achieve the maximum effect.

You can do a leg drive at the beginning, middle , or at the end of the back drop if you want, the question is, when is it optimal?

Watch this Rick Macci video from 5:05 onwards:


If you were asked to throw a ball as far as you can - you will naturally initiate the leg drive before your arm drops behind your head without even thinking about it.

Give it a try right now - pretend to throw a ball and see when your leg drive starts in relation to your arm drop behind your head.
Some time ago I looked for the racket drop and its timing relative to the leg thrust. I was assuming that it started when the forearm and racket were up and maybe slightly back. I looked at a few serves and saw that was not true. The leg thrust sometimes started as the racket was still rotating up but still below its peak at Trophy Position. Some servers also pause at Trophy Position or start backward forearm motion from there, a very different timing situation.

Some possibilities for timing the jump with the forearm & racket position seen in videos are -

1) The timing was not as effective as it could be. ?
2) The timing was effective considering that there may be other body motions occurring at the same time as the leg thrust occurs and the timing is overall effective for the average forearm & racket orientations for all motions. The motions are the leg thrust, shoulder-over-shoulder, trunk twist and others as described in the Biomechanics of Advanced Tennis, 2003, Elliott, Reid and Crespo. Anyone interested in the serve should be familiar with this book, it still provides a framework for analyzing the serve.
3) Different players are using different timing for a variety of reasons. I recall that for one serve Isner thrust his legs while his forearm and racket were still tilted forward. I saw a Raonic serve where the forearm and racket were about vertical when leg thrust started. Is that the optimal timing for legs? For all other motions?

Understanding what is being done and why requires more research, or some serious TT readers, for each type serve, each body type, look at 8 servers,........... The time leg thrust starts and the position of the forearm & racket are easy to see in high speed videos.

For example of more motions than just leg thrust, it appears that Roddick's leg thrust, shoulder-over-shoulder and trunk twist overlap in time. See frames #3-6. All three and other motions may be important for the racket drop, chest up and "inverted U" shown in frames 5 & 6. The racket drop is a widely known checkpoint. The chest up has been mentioned and needs more usage to be a known checkpoint. The "inverted U" from 5263 is new to me, is it a checkpoint used by others?
 
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#90
> 6' tall = service weapon, also has to do with longer lever arm, not just gravity/no gravity.

Baseball pitchers with fastball as a weapon also tend do be > 6', which has nothing to do with gravity. Classic example is Randy Johnson, look at his lever arm at 6'10"...
No gravity meaning no rotation (upper pressure on the ball)
 
#91
Some time ago I looked for the racket drop and its timing relative to the leg thrust. I was assuming that it started when the forearm and racket were up and maybe slightly back. I looked at a few serves and saw that was not true. The leg thrust sometimes started as the racket was still rotating up but still below its peak at Trophy Position. Some servers also pause at Trophy Position or start backward forearm motion from there, a very different timing situation.

Some possibilities for timing the jump with the forearm & racket position seen in videos are -

1) The timing was not as effective as it could be. ?
2) The timing was effective considering that there may be other body motions occurring at the same time as the leg thrust occurs and the timing is overall effective for the average forearm & racket orientations for all motions. The motions are the leg thrust, shoulder-over-shoulder, trunk twist and others as described in the Biomechanics of Advanced Tennis, 2003, Elliott, Reid and Crespo. Anyone interested in the serve should be familiar with this book, it still provides a framework for analyzing the serve.
3) Different players are using different timing for a variety of reasons. I recall that for one serve Isner thrust his legs while his forearm and racket were still tilted forward. I saw a Raonic serve where the forearm and racket were about vertical when leg thrust started. Is that the optimal timing for legs? For all other motions?

Understanding what is being done and why requires more research, or some serious TT readers, for each type serve, each body type, look at 8 servers,........... The time leg thrust starts and the position of the forearm & racket are easy to see in high speed videos.

For example of more motions than just leg thrust, it appears that Roddick's leg thrust, shoulder-over-shoulder and trunk twist overlap in time. See frames #3-6. All three and other motions may be important for the racket drop, chest up and "inverted U" shown in frames 5 & 6. The racket drop is a widely known checkpoint. The chest up has been mentioned and needs more usage to be a known checkpoint. The "inverted U" from 5263 is new to me, is it a checkpoint used by others?
I think id just simplify it and say the leg drive creates momentum. Your racket drop and swing creates momentum.

You need to time the 2 together so that when you add the 2 together, or perhaps to a certain extent pass momentum on from one to another, it creates the highest combined momentum possible by the time you hit the ball. Any mis timing between the 2 will cause a loss of power.

Is there a specific checkpoint that the leg drive must happen? Well if everyones serve is different, with a different ball toss, and everyones timing is different then the answer is no, there cant be.

Its just a rough guide that the leg drive has to occur near the beginning of the serve motion (assuming the racket drop is roughly the start of your swing taking place) in order to pass the maximum momentum onto the arm.
 
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#92
I think id just simplify it and say the leg drive creates momentum. Your racket drop and swing creates momentum.

You need to time the 2 together so that when you add the 2 together, or perhaps to a certain extent pass momentum on from one to another, it creates the highest combined momentum possible by the time you hit the ball. Any mis timing between the 2 will cause a loss of power.

Is there a specific checkpoint that the leg drive must happen? Well if everyones serve is different, with a different ball toss, and everyones timing is different then the answer is no, there cant be.

Its just a rough guide that the leg drive has to occur near the beginning of the serve motion (assuming the racket drop is roughly the start of your swing taking place) in order to pass the maximum momentum onto the arm.
When we analyze tennis strokes and use terms such as "momentum". Nobody knows what momentum is, or its units of measurement, or how it 'transfers'. Add the word kinetic chain and it brings all progress to understanding to a halt. "Power" ditto in spades... Nobody knows what these terms mean in tennis usage. And the early studies of tennis stokes using these words leave out one very, very important phenomena.

Why do the seemingly scientific terms momentum, kinetic chain and power bring understanding to a halt if the special important other phenomena is not mentioned or considered? will post later

Instead of momentum look for velocity or speed. You then have a clear concept of MPH or meters per second, etc. But speed is hard to measure in 2D videos, because movement requires measurements in 3D.

The leg drive does not occur near the beginning of the service motion. Look at high speed videos to check your timing of things. Don't redefine "racket drop" or "near the beginning of the service motion" or other terms that are widely used. How does momentum pass into the arm and when does it appear? Does it involve the phemonena above?
 
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#93
When we analyze tennis strokes and use terms such as "momentum". Nobody knows what momentum is, or its units of measurement, or how it 'transfers'. Add the word kinetic chain and it brings all progress to understanding to a halt. "Power" ditto in spades... Nobody knows what these terms mean in tennis usage. And the early studies of tennis stokes using these words leave out one very, very important phenomena.

Why do the seemingly scientific terms momentum, kinetic chain and power bring understanding to a halt if the special important other phenomena is not mentioned or considered? will post later

Instead of momentum look for velocity or speed. You then have a clear concept of MPH or meters per second, etc. But speed is hard to measure in 2D videos, because movement requires measurements in 3D.

The leg drive does not occur near the beginning of the service motion. Look at high speed videos to check your timing of things. Don't redefine "racket drop" or "near the beginning of the service motion" or other terms that are widely used. How does momentum pass into the arm and when does it appear? Does it involve the phemonena above?
We do know what momentum is. And its something we can all visualize such as swinging a ball at the end of a chain.

Talking about speed probably doesnt help you because what are you telling people - to hit the ball as fast as you can? How? Isnt that the question were asking. How?

Momentum passes into the arm in the same way it does when you throw a ball. Its the same process.
 
#98
Agree.

What is that process?
Well now its going into physics. But it looks like its to do with force duration.

We use impulse to create momentum, and the longer the period we are able to apply force on something, the more force we are able to exert on the object.

So the baseball thrower when hes pitching is increasing as much as possible the amount of time he has to implant force onto the ball when he throws it.

So perhaps the reason why you want to do your leg drive early is because it means you are exerting force on the racket for a longer period of time.
 
#99
@IowaGuy @5263


If you have outstanding shoulder flexibility and don't have tight internal rotators, that deep inverted U is certainly something to strive for. But not all are so blessed or capable of this. A few decades back, I had a fairly decent drop. However in the early 90s, I damaged my rotators because of flawed volleyball spiking technique. After some time I found that my internal rotators became tight and/or my external rotation became rather limited. However, I found that even tho' my racket drop (deep U) potential was no longer as great as it once was, as long as I stretched my internal rotators as much as possible with my more limited racket drop, I could still generate a pretty decent SSC reflex action and pretty good power/RHS.

This past week, while working on alleviating pain in my "good" (non-dominant) shoulder, my physical therapist brought up this very subject. He indicated that baseball pitchers and tennis servers who have tight internal rotators or do not have exceptional ROM for their ESR, can still generate a good amount of power (or hand speed) as long as they are getting a good stretch (and subsequent release) of the internal rotators.

Bottom line: The deep inverted U is a worthwhile goal if your shoulder is capable of it. But not all are. A decent leg drive with a good stretch of the internal rotators can still generate near-optimal results even if your shoulder flexibility is somewhat limited.
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you make several good and valid points, but just are reading a bit into the inverted U just a bit. Even if your U is not as deep, the U can still be formed and is the relationship between the upper arm, forearm and the racket. Deep is indeed better for consistently bigger serves, but as you say, everyone (including me) is not capable of optimal range here. Imo it is still key to use the U and be aware of what would be optimal as a reference.
 
And you believe that leg drive is an important part of getting to the "inverted U"?

Laver has some form of the "inverted U" even though sometimes his right foot never leaves the ground. He seems to have much less leg drive than any "modern" player. Thoughts?

Great share on that video of Laver!

It is important not to confuse height of launch with leg drive, especially back during Laver's time. Laver has leg drive and you can see his knees straighten and hips rise as the U position is hit. I'm not sure on the timing of this vid or the date of the rule change, but I think Laver played many of his years where he developed his serve under the rules where you couldn't leave the ground. Many of the guys who learned that way, never went on to adjust their form fully to the new rule.
 
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