Leg drive myth?

#1
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?
 
#2
The leg drive isn't a myth but it is a little overrated. The legs maybe add 10-15 mph to a high level serve which is important but the same player who hits 130 could hit 110+ barely using his legs.

The legs mostly help to increase the stretch in the shoulder and chest.

Watch sjeng schalken. He didn't have a big serve but he maybe bent his legs 10 degrees and still he could serve like 120 mph (still a weakness of him of course as he is really tall and only had like an average serve)
 

Dragy

Professional
#3
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?
First of all, elbow bending has nothing to do with a proper racquet drop, although it may happen to some minor degree in some players' motions. All the drop thing, which is actually upper arm external rotation, aka external shoulder rotation (ESR) has a purpose of stretching muscles powering internal shoulder rotation, biggest of which are pec and lat. It's performed by utilizing racquet and forearm inertia to "try staying in place" while moving shoulder and upper arm around the spine as axis and upward. One can achieve decent racquet drop and associated racquet acceleration with torso rotation and shoulder-over-shoulder motion only, but well-timed leg drive adds up to the shoulder and upper arm lift and to stretch stage of the stretch-shorten cycle. Well-timed is key here, as "volleyball-style" jump actually hurts the move. Tell you as one suffering...
 
#4
First of all, elbow bending has nothing to do with a proper racquet drop, although it may happen to some minor degree in some players' motions. All the drop thing, which is actually upper arm external rotation, aka external shoulder rotation (ESR) has a purpose of stretching muscles powering internal shoulder rotation, biggest of which are pec and lat. It's performed by utilizing racquet and forearm inertia to "try staying in place" while moving shoulder and upper arm around the spine as axis and upward. One can achieve decent racquet drop and associated racquet acceleration with torso rotation and shoulder-over-shoulder motion only, but well-timed leg drive adds up to the shoulder and upper arm lift and to stretch stage of the stretch-shorten cycle. Well-timed is key here, as "volleyball-style" jump actually hurts the move. Tell you as one suffering...
I understand the inertia momentum, but if I do not force the racket to drop a bit, then how it can go down because of inertia, while its starting (standing) point is the throphy position?
 
#5
I think I still don't understand how and why the racket would/should drop back if I can hit a fast serve without dropping it. I mean, it doesn't feel natural to me, or I am missing something.
 

Dragy

Professional
#6
I understand the inertia momentum, but if I do not force the racket to drop a bit, then how it can go down because of inertia, while its starting (standing) point is the throphy position?
With your shoulder low and rotated back, the instance you start uncoiling your forearm and racquet lags behind, elbow comes from under the racquet, then leg drive and shoulder-over-shoulder rotation lift your shoulder and upper arm and elbow, while forearm, hand and racquet now lag not just behind but below as well. You can model this as some point on the forearm is pinned it the air while shoulder, upper arm and elbow go around the spine and up, and hand holding racquet goes down.
 

Dragy

Professional
#7
I think I still don't understand how and why the racket would/should drop back if I can hit a fast serve without dropping it. I mean, it doesn't feel natural to me, or I am missing something.
If you consider your whole arm with racquet as a unit body (which it is until elbow begins straightening) and find the center of mass of that body, it never goes down but moderately up during the racquet drop phase. And it rotates, flips upside down, so now the elbow looks up and racquet head looks down.
It may be key to get this so that you don't deliberately drop anything but just swing and let things happen.
 
#8
With your shoulder low and rotated back, the instance you start uncoiling your forearm and racquet lags behind, elbow comes from under the racquet, then leg drive and shoulder-over-shoulder rotation lift your shoulder and upper arm and elbow, while forearm, hand and racquet now lag not just behind but below as well. You can model this as some point on the forearm is pinned it the air while shoulder, upper arm and elbow go around the spine and up, and hand holding racquet goes down.
Thanks. I will try to understand and visualize what you described here. Right now it sounds abit confusing.
 
#9
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?
I find as slowly going through trophy, I let gravity act above hand with loose wrist, the racquet head "falls" and wrist/ forearm supinates with a type of esr of shoulder (elbow moving up and "in")
 
#10
The leg drive isn't a myth but it is a little overrated. The legs maybe add 10-15 mph to a high level serve which is important but the same player who hits 130 could hit 110+ barely using his legs.

The legs mostly help to increase the stretch in the shoulder and chest.

Watch sjeng schalken. He didn't have a big serve but he maybe bent his legs 10 degrees and still he could serve like 120 mph (still a weakness of him of course as he is really tall and only had like an average serve)
yes, maybe a bit overrated as a power producer, but then again, who doesn't want that 15mph? Also as you mention, the legs are downright critical for improving not only the height of the contact point, but also the angle and direction for the contact to create the best spin and trajectory that can control big power on serve. Then there is the aspect of shifting a power source...because the legs may not add more than 20% to the output, but they can take on some of the fomer load from the shoulder and arm, which is shifting a power source to a much stronger and safer power source.
 
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#11
The leg drive isn't a myth but it is a little overrated. The legs maybe add 10-15 mph to a high level serve which is important but the same player who hits 130 could hit 110+ barely using his legs.

The legs mostly help to increase the stretch in the shoulder and chest.

Watch sjeng schalken. He didn't have a big serve but he maybe bent his legs 10 degrees and still he could serve like 120 mph (still a weakness of him of course as he is really tall and only had like an average serve)
amazing that he was able to serve 120 with that motion... hardly any leg drive, hardly any hip snap (like wawrinka)
 
#14
Before 1961 the rules of tennis required that one foot remain on the ground until, I believe, the ball was impacted. That requirement was ended around 1961 by a new rule that allowed both feet to leave the ground. Jumping was then added to the serving technique.

Gerald Paterson in 1919 is shown hitting a high level serve with internal shoulder rotation (ISR) and one foot on the ground. Gerald was famous for his top serve and was called the 'human catapult'.

How the serve worked using internal shoulder rotation was described by badminton researchers using high speed imaging in the 1970s (I wish I had known then!). But this description was not widely accepted in tennis. In 1995 clear high speed imaging involving 3D motion capture system (multi cameras, high speed film) confirmed the important part played by internal shoulder rotation. (the upper arm bone spins like a top at the the shoulder joint). See serve publications by B. Elliott and Marshall in 1995 and 2000.

Researchers established that leg thrust adds to the high level serve. In addition, researchers named several other motions that produced the same main effect of stretching shoulder muscles. That serve knowledge was established before the reference book Biomechanics of Advanced Tennis was published in 2003.

Good luck finding anyone at your tennis club that knows what ISR is or how it contributes to the serve. Some may speak of 'pronation' a different joint motion, weaker and not significant for racket head speed that happens to turn the hand. Leading to impact, ISR lasts about 30 milliseconds so it is not visible by eye. People don't see it in videos unless they know what to look for.

This post is a very strong argument for the significance of leg thrust. 10-15 MPH added speed is likely to often be the difference of the returner reaching the ball or not, or of controlling the return. Leg thrust also adds to impact height.
The leg drive isn't a myth but it is a little overrated. The legs maybe add 10-15 mph to a high level serve which is important but the same player who hits 130 could hit 110+ barely using his legs.

The legs mostly help to increase the stretch in the shoulder and chest.

Watch sjeng schalken. He didn't have a big serve but he maybe bent his legs 10 degrees and still he could serve like 120 mph (still a weakness of him of course as he is really tall and only had like an average serve)
Mixing advice for what high level servers are doing and what recreation player can or should do is an uncertain topic, to be determined. But high level serves have been well studied, described and clear high speed videos are available. But for lessor stroke techniques there is nearly nothing. Leaving out leg drive may be workable. ?

The majority of active tennis players use a Waiter's Tray technique with little ISR. WT is more than 70% at my club. So first the technique that you are using has to be determined with video. Advice for a high level serve has an unknown effect on a Waiter Tray technique or an unknown technique, you are on your own. Google: Waiter's Tray Error. The Pat Dougherty video Hammer that Serve deals with the common Waiters Tray serve but does not use that name. He also refers to the high level serve as the Advanced Serve. Listen carefully.

For the high level serve some servers place the arm at Trophy Position or pause there and others rotate the arm and racket up using external shoulder rotation. Rotating the arm up to TP probably requires more timing. I'd say the stronger servers rotate the forearm and racket up, but that should be researched.

Also, the high level serve should be performed with the upper arm at the proper angle to the shoulder joint so that the risk of shoulder impingement risk is minimized. See upper arm angle to shoulder throughout service motion in ATP servers. The Ellenbecker video "Rotator Cuff Injury" has an excellent description of this issue.

The Tennis Serve Nuthouse.......
 
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#15
The majority of active tennis players use a Waiter's Tray technique with little ISR. WT is more than 70% at my club. So first the technique that you are using has to be determined with video. Advice for a high level serve has an unknown effect on a Waiter Tray technique or an unknown technique, you are on your own. The Pat Dougherty video Hammer that Serve deals with the common Waiters Tray serve but does not use that name. He also refers to the high level serve as the Advanced Serve.

The Tennis Serve Nuthouse.......
Maybe worth mentioning as well, is that many who avoid WT and come on edge, still don't ISR/pronate, but instead carve/supinate.
Chas, did I get that right that carving with the opposite turn of pronation is supination?
 
#16
I find the leg drive is essential to get spin on the ball. If I'm not moving up into the ball I hit too flat and sail balls long on all types of serves. If I drive up to the ball it adds more topspin which also allows me to swing more freely into the ball as I know it will spin into the service box.

But that's just me.
 
#17
I find the leg drive is essential to get spin on the ball. If I'm not moving up into the ball I hit too flat and sail balls long on all types of serves. If I drive up to the ball it adds more topspin which also allows me to swing more freely into the ball as I know it will spin into the service box.

But that's just me.
Nope, not just you. This is an important key that many can use!
 
#18
In the racket drop the wrist angle is very large. The wrist is second only to ISR as the joint used for racket head speed.

Look at a high speed video and time the racket drop and accelerations from various body parts. Once the feet leave the ground and the legs are straight the acceleration from the legs is zero or low.

Reference for joint contributions (%) to racket head speed at impact.
Biomechanics and Tennis. Elliott
 
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#20
Maybe worth mentioning as well, is that many who avoid WT and come on edge, still don't ISR/pronate, but instead carve/supinate.
Chas, did I get that right that carving with the opposite turn of pronation is supination?
Some do ISR/pronate but never have the necessary changing angle between the rotating forearm and racket, the racket head speed never develops from ISR. The racket head faces the ball for impact from ISR and or pronation but the racket has not picked up enough speed from the ISR. Or.....the ISR is late just before impact. I believe that this error involves the incorrect thought to 'go at the ball edge-on and at the last second pronate the racket'. This statement pops up quite a bit in threads.

Carve is undefined and I have not seen a high speed video of carving. You can go at the ball and supinate, sort of, around the ball or impact with a racket face angle so that the side of the ball is impacted, but there is not much ISR before impact. I don't recall many videos of that type from the forum posters. If I see 5-10 posters with some pattern I have may some chance of remembering it as a new unknown technique.

I do a trick serve that I've mentioned before where I (RH server) go across the ball from the right to the left for spin but the pace is low. Often it works for an error because the reverse spin makes the ball bounce differently (side spin is reversed). That trick serve has a little ISR and or pronation and I don't know about the rest of it. 2 or 3 times a match only and my regular indoor block time friends never caught on.
 
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atp2015

Hall of Fame
#21
I find the leg drive is essential to get spin on the ball. If I'm not moving up into the ball I hit too flat and sail balls long on all types of serves. If I drive up to the ball it adds more topspin which also allows me to swing more freely into the ball as I know it will spin into the service box.

But that's just me.
Agree completely.
Leg drive, even if a tiny bit, adds one important element to the serve technique - promotes hitting up rather than down or flat. That's a good enough reason to at least attempt a bit of leg drive - tremendous for overall tension free swing and proper serve form.

After learning to add the leg drive, I feel as if I'm using my legs to push the racket up rather using my arm or shoulder.
 
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#22
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Leg drive, even if a tiny bit, adds one important element to the serve technique - promotes hitting up rather than down or flat. That's a good enough reason to at least attempt a bit of leg drive - tremendous for overall tension free swing and proper serve form.

After learning to add the leg drive, I feel as if I'm using my legs to push the racket up rather using my arm or shoulder.
Nearly all high level serves are hit down, that is they have a projection angle that is down relative to the horizontal.

Projection angle scale runs +1 to -8 degrees. 0 degrees is horizontal. Also shown is the height of impact.


https://tt.tennis-warehouse.com/index.php?threads/timing-on-serve.551466/#post-9904983

 
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atp2015

Hall of Fame
#24
Nearly all high level serves are hit down, that is they have a projection angle that is down relative to the horizontal
The ball's trajectory is down after the impact, but the swing path is up until the point of contact or very close to the point of contact. Because the racket face is closed, the ball starts travelling down even though the swing path is up.
Since we can only control the swing path in terms of hitting mechanics, I think the phrase "hitting up" makes sense. If not swinging fast enough, opening the racket face will help the ball over the net.
 
#25
Carve is undefined and I have not seen a high speed video of carving.
Interesting you don't see this more, because I see this as the #1 mistake better rec players make that blocks them from more power. It is also why we see so much talk and tips to pronate, since most players tend to start out by trying to carve for slice spin. Salzy even teaches carving as a way to really hit that super wide serve with lower power. I realize that the nubies tend to pancake, but as players level up going for slice spin, carving is the next thing.
 
#26
Or.....the ISR is late just before impact. I believe that this error involves the incorrect thought to 'go at the ball edge-on and at the last second pronate the racket'. This statement pops up quite a bit in threads.
Interesting. I think the error is more with your take on "on edge" and how you seem to understand "at the last instant" , although I'd be interested in how you believe you express these situations better. From over a decade of experience and working with some the biggest servers, I can attest to how both of these cues work extremely well while Imo, are very accurate.

On the serve, you have to go on edge or pancake....your choice. "At the last second means" to begin the action at the last moment where you can complete it successfully. The later you can do it, the more power and spin you will create, with some upper parameters of course. The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact.
 
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#27
Interesting. I think the error is more with your take on "on edge" and how you seem to understand "at the last second" , although I'd be interested in how you believe you express these situations better. From over a decade of experience and working with some the biggest servers, I can attest to how both of these cues work extremely well while Imo, are very accurate.

On the serve, you have to go on edge or pancake....your choice. "At the last second means" to begin the action at the last moment where you can complete it successfully. The later you can do it, the more power and spin you will create, with some upper parameters of course. The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact.
Here is how to express it better.

Toly composite picture from my high speed video.

From the first red arrow to the one on top represents 4 high speed video frames.

"Edge-on" to the ball is the one frame at the lower red arrow. The edge of the racket aligns with the ball only for an instant. That is roughly where ISR starts.

The racket goes up in a smooth and continuous motion with one of the joint motions being ISR to bring the near straight arm & racket to face the ball.

Now pick the frame between the lower red arrow and the upper red arrow that represents "At the last second" as you use it. Or any other frames. Also, describe the motion of what happens 'at the last second' and identify it in this picture by counting racket positions from a red arrow.

".......The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact." I don't agree. Look up this information in serve publications of B. Elliott & Marshall around 2000 and 1995. The picture above or high speed videos show ISR also.
 
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#28
Here is how to express it better.

Toly composite picture from my high speed video.

From the first red arrow to the one on top represents 4 high speed video frames.

"Edge-on" to the ball is the one frame at the lower red arrow. The edge of the racket aligns with the ball only for an instant. That is roughly where ISR starts.

The racket goes up in a smooth and continuous motion with one of the joint motions being ISR to bring the near straight arm & racket to face the ball.

Now pick the frame between the lower red arrow and the upper red arrow that represents "At the last second" as you use it. Or any other frames. Also, describe the motion of what happens 'at the last second' and identify it in this picture by counting racket positions from a red arrow.

".......The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact." I don't agree. Look up this information in serve publications of B. Elliott & Marshall around 2000 and 1995. The picture above or high speed videos show ISR also.
This is mostly just a different perception of what is going on. I'd say the racket is clearly edge on almost the whole path upwards up until the frame before the last arrow and well before your first arrow. Otherwise you end up with a waiters tray approach going up instead of leading with the edge on the way up as he does here. You seem to be attempting to make some impossible reference to the racket head being perfectly horizontal to the swing path or something, but 'edge on' or 'leading with the edge' are both very common ways to address when the frame edge is leading the path as we see above. Even where you claim with the arrow as being edge on is not likely that perfect moment you seem to cite and even if it were, that would be useless in instruction or even vid study except as an estimate.... I don't think I said at the last second, as it is far less than a second before impact where the racket starts a strong move with pronation. (I looked back and as you said, I had mistakenly typed 'second' so I corrected it given how hard this seems to be to understand)

You also keep bringing up ISR as though somehow you think I tried to deny ISR?? What are you referencing on that? I've been a big advocate of ISR and learning to use it with throwing a football for over 15 yrs now, so this is way old news to keep harping on. I think I was the 1st one on TT to discuss how the ISR was the precursor and driver of pronation, back when most everyone was just harping on pronation without the input of the shoulder action. What are you seeking to correct about ISR in your posts?
 
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#29
@5263

What does this mean? Misworded?

".......The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact."
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I use the term "edge on" to the ball because it is a useful checkpoint for the high level serve. The position to use this checkpoint is the Big L. The picture in post #27 shows the racket about 'edge-on" to the ball at the lower red arrow.

The edge-on checkpoint is on the far right. Nalbandian's upper arm - between his shoulder joint and elbow - will spin like a top, that is, do ISR. I have often shown this when I used the term edge-on to define my usage.

http://www.hi-techtennis.com/serve/big_l_student.php

Almost always when a racket is traveling toward the ball, even often at impact for the serve, one edge will be ahead of the other. Therefore saying 'leading with the edge' does not say much.

In the late 80's, I must have heard about pronation (before ISR was understood) and was experimenting by swinging at the ball and at the last second, about 6-10" before impact rotating the racket face using forearm pronation. So I see how the word descriptions can be misleading from first hand experience. After 35 years of following oversimplified word instructions and descriptions of the serve, I'd like to junk the word descriptions of motions and replace them with high speed videos plus words.

I have looked at a lot of poster's serves. Some literally rotate the racket face a very short distance before impact, much like I did in the 80s, but using ISR or ISR & pronation or pronation. Other posters, especially for the slice or kick serves, lead with one edge, fixed angle, and go at the ball to impact with it; there is little ISR. I believe some of them have been misled by simple but ambiguous word descriptions. Now I advise everybody to use high speed videos as their most accurate information, plus some words to point out what is in the videos.

Many posts are arguments about what undefined terms like edge on mean to two different people. Basically describing a complex 3D athletic motion with poorly defined words is unworkable and can mislead people.
 
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#31
Doesn't ISR (maybe it is ESR) happen after the trophy position? That's where the confusion starts for me, does the drop really happen, or does ISR make it look like the racket drops? (except the intertia momentum)
 
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#32
@5263

What does this mean? Misworded?

".......The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact."
------------------------------------------------------------------------------------------------------------

Many posts are arguments about what undefined terms like edge on mean to two different people. Basically describing a complex 3D athletic motion with poorly defined words is unworkable and can mislead people.
I'll start with the last part that you mention as "arguments". Like you mention, this is a good example of a poor term for what we should be doing. Imo It should be a process of "discussion & debate" instead of arguing.

I like your idea of adding pics to the words and I often do that as well, but it doesn't clear up what you don't get about using most of the ISR/pronation in the latter stages just before contact. Sure, there is some ISR and even minor pronation early in the path, but nothing like the amount that is pent up to be released in the last moments before contact, where ISR comes on much stronger and provides more drive to the swing and pronation. ISR is what determines if you are "arming' the serve or not. If you start this strong ISR and or Pronation early in the swing up to the ball, that is what causes weaker and slower serves.
 
#33
using most of the ISR/pronation in the latter stages just before contact. Sure, there is some ISR and even minor pronation early in the path, but nothing like the amount that is pent up to be released in the last moments before contact, where ISR comes on much stronger and provides more drive to the swing and pronation. ISR is what determines if you are "arming' the serve or not. If you start this strong ISR and or Pronation early in the swing up to the ball, that is what causes weaker and slower serves.
I like your explanation. Spot on!! I was confused on this exact point years ago. I always hear people tell you to pronate, but nobody mentions that it needs to be "pent up to be released in the last moments before contact". I had to figure that out for myself by trial/error. Which took a long time and was frustrating.
 
#35
Zero leg drive, deep drop.

No, the early guys had to make several compensations due to the rule of keeping one foot on the ground during the serve. They still used well timed leg drive to help with racket drop, but couldn't push so hard they would come off the ground. The better servers of those days were the ones who did this best but still they didn't get the racket drop players can get today. Notice every top server opts to use enough leg drive to get in the air now that it is legal.
 
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#36
Nearly all high level serves are hit down, that is they have a projection angle that is down relative to the horizontal.

Projection angle scale runs +1 to -8 degrees. 0 degrees is horizontal. Also shown is the height of impact.
I'm pretty sure I've read that it is impossible to hit down on a serve and put the ball over the net and into the service box at 130 mph unless you are 7 feet tall. Any ball that can clear the net at that speed will land outside the service box unless there is topspin provided. It is impossible to hit topspin without providing some upward force on the ball.

In your slow motion example the tennis racket has not reached its peak height until after contact indicating it is still ascending at contact. Whether that is from swing mechanics or leg drive I don't care. For my serve I need to add leg drive to get the extra topspin needed to keep the ball in play. For other players they might get enough from just swinging properly. For taller players with long arms, they might indeed be able to "hit down".
 
#38
Nearly all high level serves are hit down, that is they have a projection angle that is down relative to the horizontal.

Projection angle scale runs +1 to -8 degrees. 0 degrees is horizontal. Also shown is the height of impact.
Ok, so what is your point? That players are not serving up as people often say?

When and where were these measurement taken since 8.5 isn't a very high contact point. Also, how far out were the measurement taken to determine trajectory of the serve off the racket?
 
#39
Ok, so what is your point? That players are not serving up as people often say?

When and where were these measurement taken since 8.5 isn't a very high contact point. Also, how far out were the measurement taken to determine trajectory of the serve off the racket?
My point is that 'serving up' is an undefined tennis term. What would we see in a video?

On the other hand, we can measure the projection angle and I believe that it is mostly down for ATP servers from looking at high speed videos where something in the background provides a reference for the horizontal. There are references for profesional of players but just now looking I did not see free ones.

Rod Cross states the kick serve projection angle is down, see quoted post below.

".......Despite the fact that the server swings up at the ball in a kick serve, the ball must be projected downward below the horizontal for a good serve. The serve angle, A, is typically between 2 and 6 degrees below the horizontal. ..."

Servers for the graph were

"This study compared the body, racquet and ball kinematics characterising successful serves and service faults, missed into the net, in two groups of elite junior female players and one professional female tennis player."

Usually serve speed is measured off the racket.

Here is a research publication discussing impact and the 'angle of projection'.
A kinematic comparison of successful and unsuccessful tennis serves across the elite development pathway. David Whiteside, B. Elliott, B. Lay, M. Reid
https://www.researchgate.net/public...s_serves_across_the_elite_development_pathway

Figure 4 sums up some of the information. Projection angle, measured leaving the racket, is the angle between the ball's trajectory and the horizontal. Zero degrees is horizontal. This graph covers from +1° above the horizontal to -8° below the horizontal. It basically says for the serves covered that almost all have downward projection angles and that the faster serves have considerably greater downward projection angles. I don't remember more details about the types of serves for this graph. This is an excellent reference to be aware of.


The Rod Cross TW article on the kick serve has some projection angle discussions here and there in the article. One point that Cross discusses is the very rapid closing rate of the racket face.
http://twu.tennis-warehouse.com/learning_center/kickserve.php

Quote from the above Cross article on the kick serve
".......Despite the fact that the server swings up at the ball in a kick serve, the ball must be projected downward below the horizontal for a good serve. The serve angle, A, is typically between 2 and 6 degrees below the horizontal. ..."

For the second rotation produced by ISR, the rotation rates of the upper arm might reach about 3000°/sec. Then in 4 milliseconds of racket-ball contact the racket might rotate roughly 12° due to ISR.

The rotation rate of the racket from ISR is somewhat faster than the rotation rate closing the racket face. The rotation axis for the ISR is in the upper arm and is roughly vertical. The rotation axes for closing the racket face are roughly horizontal, at wrist, at shoulder, at hips, etc. . We could measure the closing rotation rate of the racket on the 6000 fps video.

If we simplify very complex ball-string interactions to a word - 'downward' - and ask whether the racket face is 'downward' for impact, how do we account for the significant closing of the racket face during ball-string contact? Do we have research such as the Whiteside, Elliott et al work on projection angle for the racket face angle? Is 'downward' defined for the very first initial contact of the ball and strings? If so defined is that 'downward' feature useful for the overall resulting 'projection angle'? Projection angle is an important and well known biomechanical measurement.
Do you have a definition for 'hit up'? And what evidence is used with that definition for drawing conclusions?

If I say "the racket starts around hip height and impacts the ball at 9 feet", what does saying 'hit up on the serve' add?
 
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#41
Doesn't ISR (maybe it is ESR) happen after the trophy position? That's where the confusion starts for me, does the drop really happen, or does ISR make it look like the racket drops? (except the intertia momentum)
The isr happens as you bring the racquet up "on edge".
 

atp2015

Hall of Fame
#42
It is impossible to hit topspin without providing some upward force on the ball.
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Why does the ball need upward force when it is already at around 9ft or more? (Even if player's height is 5 1/2, the ball is going to at 5 1/2 ft + 1 1/2 ft arm length above the head + 2 ft racket length , which is 9ft.
If the serve is at 50 mph or more, the ball needs to come down from that height, otherwise it will sail long. We need to swing up to reach the height of the ball so we can hit it down (at the right downward angle and spin).

If you have a ball on your palm and if you want to spin it to the maximum using the other hand, which part of the ball would to caress for optimal spin and pace?
 
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#43
Do you have a definition for 'hit up'? And what evidence is used with that definition for drawing conclusions?

If I say "the racket starts around hip height and impacts the ball at 9 feet", what does saying 'hit up on the serve' add?
Where did someone say 'hit up'? I can't find that comment. I don't normally say that, but may have in some context. Maybe you can let us know what brought up this topic, as it is different than the OP question of why to launch and different than my normal phrasing, "rise into contact".

As you mention, Cross says players are swinging up into the ball on the kick, so I can see people calling that hit up. While I don't see it as hitting up, there are several ways to support that position.
 
#44
Good luck finding anyone at your tennis club that knows what ISR is or how it contributes to the serve. Some may speak of 'pronation' a different joint motion, weaker and not significant for racket head speed that happens to turn the hand. Leading to impact, ISR lasts about 30 milliseconds so it is not visible by eye. People don't see it in videos unless they know what to look for.
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Where is this "leading to impact ,30 milliseconds of ISR" that you claim is not in the last moments before contact? Also, who is your source that pronation is not significant for RHS?
 
#45
Where is this "leading to impact ,30 milliseconds of ISR" that you claim is not in the last moments before contact? Also, who is your source that pronation is not significant for RHS?
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.

To do single frame on Vimeo, click Vimeo, click full screen and hold down the SHIFT KEY and use the ARROW KEYS.

Here is the same video with a magnification box. It also stops to show ISR with labels. It has a countdown millisecond scale to impact and another after impact. Look for "-25 ms" (milliseconds) before impact when ISR is labeled to start. Click Vimeo and full screen.
The time scale should advance 4 or 5 milliseconds each keystroke. (If more, Vimeo may be skipping a frame.)

During this time the wrist joint is also moving the racket very rapidly.

One source for saying pronation is not significant is the review paper
Biomechanics and Tennis, B. Elliott. He states the part played by pronation and shows percentage racket head speed at impact from pronation in Table 2.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/

"For instance, in the power serve, pronation is primarily responsible for racquet orientation, ..............."

Interesting timing details in graphs are available in a Marshall and Elliott publication in 2000.
https://www.researchgate.net/public...nk_in_proximal-to-distal_segmental_sequencing

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Doesn't ISR (maybe it is ESR) happen after the trophy position? That's where the confusion starts for me, does the drop really happen, or does ISR make it look like the racket drops? (except the intertia momentum)
Study these videos and search the definition of internal shoulder rotation. Much of the service motion is for external shoulder rotation (ESR). The ESR is used for the purpose of stretching ISR muscles for ISR in the last 30 milliseconds leading to impact. Search on forum and Google: internal shoulder rotation "Chas Tennis"
 
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#46
@5263

What does this mean? Misworded?

".......The earlier you start ISR/pronation, the less power and spin that will get delivered to the contact."
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I use the term "edge on" to the ball because it is a useful checkpoint for the high level serve. The position to use this checkpoint is the Big L. The picture in post #27 shows the racket about 'edge-on" to the ball at the lower red arrow.

The edge-on checkpoint is on the far right. Nalbandian's upper arm - between his shoulder joint and elbow - will spin like a top, that is, do ISR. I have often shown this when I used the term edge-on to define my usage.

http://www.hi-techtennis.com/serve/big_l_student.php

Almost always when a racket is traveling toward the ball, even often at impact for the serve, one edge will be ahead of the other. Therefore saying 'leading with the edge' does not say much.

In the late 80's, I must have heard about pronation (before ISR was understood) and was experimenting by swinging at the ball and at the last second, about 6-10" before impact rotating the racket face using forearm pronation. So I see how the word descriptions can be misleading from first hand experience. After 35 years of following oversimplified word instructions and descriptions of the serve, I'd like to junk the word descriptions of motions and replace them with high speed videos plus words.

I have looked at a lot of poster's serves. Some literally rotate the racket face a very short distance before impact, much like I did in the 80s, but using ISR or ISR & pronation or pronation. Other posters, especially for the slice or kick serves, lead with one edge, fixed angle, and go at the ball to impact with it; there is little ISR. I believe some of them have been misled by simple but ambiguous word descriptions. Now I advise everybody to use high speed videos as their most accurate information, plus some words to point out what is in the videos.

Many posts are arguments about what undefined terms like edge on mean to two different people. Basically describing a complex 3D athletic motion with poorly defined words is unworkable and can mislead people.
Exactly. Words/terms/explanations etc are hard to understand and visualize.
 
#49
I think what I understand from drop is that it actually is the rotation of the upper arm. Is it right?
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.
 
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