Kinetic Chain - What do we know on the serve?

[SystemicAnomaly]

Thanks for sharing. Why does his wrist look cocked in the first two pics?

Can anyone point me to a thread that discusses the changes Fed has made to his serve while on the tour and why. For example, wrt his stance - his feet are much more farther apart now.

http://www.dailymotion.com/video/xg6b23_roger-federer-serve-in-slow-motion_sport

In this video, RF employs a milder wrist flexion prior to his trophy phase. Roddick and others would also use this flexion action -- letting the racket head lag a bit for the movement to the trophy. This action produces something of a whip effect. This action can unnecessarily complicate the serve motion for some players. For many, it might be best to simplify or employ only a moderate wrist flexion prior to the trophy phase.

Not sure when or why RF changed his stance. The pro will often tinker with their mechanics for one reason or another. Sometimes it is more of an evolution. Don't recall a thread on this wrt to RF. However, I have mentioned a few times about changes Novak has made to his serve. Others have talked about stance changes for ARod.

 

[Chas Tennis]

Raonic puts a lot of flexion into his wrist to start but simply gets to a more normal wrist angle by the trophy position.
https://vimeo.com/63688133

Sampras also, less wrist.
https://www.youtube.com/watch?v=7BIs-YnjkXc

I have also seen servers take all but one or two fingers off the racket handle just going to the trophy position.

Karlovic does both the wrist angle and fingers off the racket going to the trophy position.
https://vimeo.com/27528522

Sampras loose fingers.

These wrist and finger motions, way before impact, may be just a personal feature or possibly a reminder to have a loose wrist or grip. ? Some function in the motion?

Maybe we should all have bent wrists and loose fingers at this part of in the motion. ?

 

[gambitt]

smh. This is the reason why I recommend getting a coach and not listening to internet advice. This little piece of gem will result in a post in the Health & Fitness forum asking why my shoulder hurts, and lemmings in this forum parroting the advice telling you to "arm the ball".

In case you couldn't tell, i was being sarcastic. I do NOT recommend arming the ball. Sheesh.

Sheesh all you like. Taylor Dent knows more than you. I'll listen to him.

 

[SystemicAnomaly]

Yes legs provide a platform, otherwise you'd be sat on the floor. This thread is about serve speed, not control. The power comes from the upper body.

Taylor Dent has a good serve tutorial on youtube. He says it's mostly shoulder and arm. People like to say "it's all in the legs" for some reason. Look at Fernando Gonzalez - it's all coming from his upper body.

https://www.youtube.com/watch?v=34A9Zp10BKE

Is this the Dent serve "tutorial" you are referencing? If not, please point us to the proper youtube video. Here, Dent does NOT discount other important of the legs, core, etc -- he does not indicate that the other elements of the kinetic chain are not important. He is not making the claim that you attribute to him -- that it's mostly the shoulder and arm.

This video is about using the shoulder and the arm as a whip to generate RHS. That is all this video is about. It is not meant to be a statement about the complete kinetic chain for the serve. If this is the video, you are misinterpreting Dent's view.

 

[SystemicAnomaly]

This guy says that 62% of his speed comes from the arm.

https://www.youtube.com/watch?v=pRyJM7hvF3Q

I believe that I can hit a 40-60 mph forehand using primarily my shoulder/arm -- without a knee bend and very little hip, core or torso rotation. Does this mean I should hit most of my FHs this way? Will my shoulder and arm hold up after hitting this way for an hour or two? How about after hitting this way for a number of years?

Using a full kinetic chain for the FH is more efficient and puts less demand on the shoulder/arm. The shoulders and arm are not expected to generate almost all of the power. Instead, they generate some of it. With an efficient kinetic chain, they also transfer a good chunk of the power accumulated from the previous links of the chain. This puts less demand on the shoulder/arm for power production. They are used more for controlling this swing path of the racket instead of generating all of the power.

Same thing goes for the serve. Sure I can hit big serves w/o a leg drive and with very little rotation of my hips. Does this mean that the contribution of these other elements is not significant? "This guy" makes an incorrect assumption -- it is a fallacy. Just because he can hit an 80+ mph serve w/o leg drive and very little hip rotation, does this really mean that the arm & shoulder contribute more than 60% of the RHS (or the speed of the ball) for a full-motion serve?

I do not believe that this is the case. While I can generate a considerable amount of RHS with primarily my shoulder/arm, as wheelchair servers do, this does not mean that this is what I am doing when I employ leg drive and other elements of a full-motion serve. With a full kinetic chain, I am sharing or redistributing the production of the power to other links. The arm is no longer responsible for generating most of the speed. A full-motion serve is more efficient and puts less demands on the shoulder and arm than "this guy" would have us believe.
.

 

[Chas Tennis]

I believe that I can hit a 40-60 mph forehand using primarily my shoulder/arm -- without a knee bend and very little hip, core or torso rotation. Does this mean I should hit most of my FHs this way? Will my shoulder and arm hold up after hitting this way for an hour or two? How about after hitting this way for a number of years?

Using a full kinetic chain for the FH is more efficient and puts less demand on the shoulder/arm. The shoulders and arm are not expected to generate almost all of the power. Instead, they generate some of it. With an efficient kinetic chain, they also transfer a good chunk of the power accumulated from the previous links of the chain. This puts less demand on the shoulder/arm for power production. They are used more for controlling this swing path of the racket instead of generating all of the power.

Same thing goes for the serve. Sure I can hit big serves w/o a leg drive and with very little rotation of my hips. Does this mean that the contribution of these other elements is not significant? "This guy" makes an incorrect assumption -- it is a fallacy. Just because he can hit an 80+ mph serve w/o leg drive and very little hip rotation, does this really mean that the arm & shoulder contribute more than 60% of the RHS (or the speed of the ball) for a full-motion serve?

I do not believe that this is the case. While I can generate a considerable amount of RHS with primarily my shoulder/arm, as wheelchair servers do, this does not mean that this is what I am doing when I employ leg drive and other elements of a full-motion serve. With a full kinetic chain, I am sharing or redistributing the production of the power to other links. The arm is no longer responsible for generating most of the speed. A full-motion serve is more efficient and puts less demands on the shoulder and arm than "this guy" would have us believe.
.

I am not an expert in applying the kinetic chain concept. (Biomechanics researchers kindly jump in on this anonymous forum!) My interpretation of applying the kinetic chain concept would be that the legs get the hips moving and perhaps stretched also. Next, hips get the trunk moving involving also the stretch shortening cycle, etc. These parts of the chain consecutively follow the legs.

But for the serve the main function of the legs, in my opinion, is that they directly stretch the internal shoulder rotator muscles. Several links of the kinetic chain, no matter how you view it, have been skipped. In this view, the ISR muscles act as a distant - in terms of the kinetic chain - energy storage spring.

I believe that the Elliott and Marshall references in reply #78, referring to the "missing link" for the serve, involved this issue.

In other words, the kinetic chain concept involves more speeding up the next link, likely with stretching. But what is going on in the serve involves directly stretching several links ahead. Viewing the serve as a kinetic chain of sequential body parts and motions, one after the other like a chain, may miss this.

For the serve, I'm not trying to think in terms of the kinetic chain anymore unless I can understand how to apply it.

 

[toly]

Where is kinetic chain here? Federer is just arming the ball!!! :???:

See also video http://youtu.be/MA3AXIlmwPQ

 

[LeeD]

Photo don't show Fed at full backswing.
Fed is moving forward thru the shot.
In the pics shown, there is upper body rotation looking at the shoulder alignment.

 

[Chas Tennis]

Where is kinetic chain here? Federer is just arming the ball!!! :???:

See also video http://youtu.be/MA3AXIlmwPQ

This is a view by the USTA on the kinetic chain for the one hand backhand. http://www.usta.com/Improve-Your-Game/Sport-Science/114390_Technique_The_Kinetic_Chain/

"Example—One-handed backhands tend typically involve five kinematic links that the player has to coordinate (Groppel, 1992). In most cases the one-handed backhand is based on a sequential summing of the motions of the legs, trunk, arm, forearm, and wrist/hand. Two-handed backhands during early learning use fewer body segments, so many young players find this stroke easier to coordinate. In the modern two-handed stroke a similar number of segments are rotated as for the on-handed stroke."

In the video, the legs get the entire body (center of mass) moving forward. It appears that Federer is off the ground before impact. Then viewing from above, his pelvis appears to rotate counter-clockwise as the line between his shoulders rotates clockwise - these motions are in opposite directions because of conservation of momentum for somebody not in contact with the ground. Since he is off the ground maybe that is a pure trunk twist. The upper body turn that the two shoulders show and LeeD identified, moves the uppers arm. I don't see how to apply the kinetic chain to the pelvis going one way and the line between the shoulders the other way.

Probably if he were in contact with the ground the kinetic chain could be applied. Similar to the view by Groppel above. ?

 

[LeeD]

What do we know on the serve?
About the only thing that counts is how fast the player can make the rackethead come thru it's swing, the faster, the harder the serve.
Everything else is open to debate.

 

[julian]

Completely not true

What do we know on the serve?
About the only thing that counts is how fast the player can make the rackethead come thru it's swing, the faster, the harder the serve.
Everything else is open to debate.

Other important numbers are:
A projection angle
How high is a contact point on a toss
I wish you would read your posts before posting them.
Julian W.Mielniczuk
USPTA pro

 

[wannabe good]

This is a view by the USTA on the kinetic chain for the one hand backhand. http://www.usta.com/Improve-Your-Game/Sport-Science/114390_Technique_The_Kinetic_Chain/

"Example—One-handed backhands tend typically involve five kinematic links that the player has to coordinate (Groppel, 1992). In most cases the one-handed backhand is based on a sequential summing of the motions of the legs, trunk, arm, forearm, and wrist/hand. Two-handed backhands during early learning use fewer body segments, so many young players find this stroke easier to coordinate. In the modern two-handed stroke a similar number of segments are rotated as for the on-handed stroke."

In the video, the legs get the entire body (center of mass) moving forward. It appears that Federer is off the ground before impact. Then viewing from above, his pelvis appears to rotate counter-clockwise as the line between his shoulders rotates clockwise - these motions are in opposite directions because of conservation of momentum for somebody not in contact with the ground. Since he is off the ground maybe that is a pure trunk twist. The upper body turn that the two shoulders show and LeeD identified, moves the uppers arm. I don't see how to apply the kinetic chain to the pelvis going one way and the line between the shoulders the other way.

Probably if he were in contact with the ground the kinetic chain could be applied. Similar to the view by Groppel above. ?

He appears to be hitting a "scissor " backhand. Federer's best forehands, the most violent ones, and the ones that most often appear in tribute videos are scissor forehands - where hips rotate in the opposite direction from shoulders. I don't know how to analyse these shots in terms of kinetic chain, but I wouldn't describe what he is doing here as arming the ball. Quite the opposite.

 

[Chas Tennis]

He appears to be hitting a "scissor " backhand. Federer's best forehands, the most violent ones, and the ones that most often appear in tribute videos are scissor forehands - where hips rotate in the opposite direction from shoulders. ...................

Interesting. See if his feet are off the ground the next time you see a 'scissors forehand' video.

 

[Greg G]

^ Fed is hitting a return of serve, isn't he? Abbreviated takeback/shoulder turn, open stance push off from the left leg. But I still see the use of the kinetic chain there, albeit much abbreviated. Definitely not arming the ball.

 

[SystemicAnomaly]

Photo don't show Fed at full backswing.
Fed is moving forward thru the shot.
In the pics shown, there is upper body rotation looking at the shoulder alignment.

Yes, this. On most, if not all, of his backhands Federer coils up his so that the back of his right shoulder can be seen by his opponent. In fact, from the opponent's position, the back of both shoulders can be seen. At contact, the opponent no longer sees RF's back. After contact, RF's chest can be seen by the opponent. This is a clear indication that both coiling and uncoiling of the torso occurs. Granted, it is not as much body rotation as we see on his FH or 2-handed BHs hit by other players. However, it is still there.

In toly's video, upon close inspection, it can be see that the torso uncoils. The back shoulder starts to come around somewhat prior to contact -- this is an indication of uncoiling. He then flings his left hand/arm back. This action helps to stop the uncoiling of the torso so that a near-complete transfer to the right shoulder/arm occurs.

If we take a look at RF's front (right) shoulder, we see that it moves even more than his left shoulder. Further indication of the uncoiling of the torso. It also indicates that the chest is expanded (shoulder blades are squeezed together). This pectoral/back action is another link in the kinetic chain that toly appears to overlook. While most of this action appears to happen after contact, it actually starts prior to contact. The actions we see after contact are a result of action prior to contact. RF is not arming the ball.

 

[toly]

Federer body rotation is negligible compare to right forearm flexion and wrist ulnar deviation. The left arm is doing nothing significant. BTW, the grip is semiwestern.:shock:

 

[oble]

Federer body rotation is negligible compare to right forearm flexion and wrist ulnar deviation. The left arm is doing nothing significant. BTW, the grip is semiwestern.:shock:

Again, it's what Greg G said: abbreviated motions because it's a return of serve. Also he has plenty of forward motion initiated from his split step-forward hop scissor kick from the open stance which contributes to the power generated by the kinetic chain. Left arm has always been for balancing for the 1hbh.

Just because there's no major coiling/uncoiling doesn't mean there is zero kinetic chain/pure arming. Your example is just not a good example of showing what Fed does on his regular 1hbh. Also if Fed has been arming his bh return of serve all these years, his arm would have fallen off from returning 140~150+ MPH serves.

Btw, grip looks more like a weak-ish eastern.

 

[Greg G]

Also toly, his shoulders aren't moving because even in a regular ground stroke, that's where they're supposed to stop. The energy has already passed on to the arm at that point. Since it's a return of serve, the power source is more linear. Which is probably why you see it as all arm. While I see it as perfect

 

[toly]

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

 

[Greg G]

^ that's a second serve! he had a lot of time to take a huge backswing. Plus he is way back in the court.

Almagro also has a more 'modern' technique with the shoulders opening up a lot more. Not an apples to apples comparison with the fed video. Just my opinion.

 

[toly]

Once again Federer arming backhand

See also video http://youtu.be/m8MU5sftY64

 

[dominikk1985]

a one handed BH will always have less trunk Rotation that a two hander (or FH, serve, overhead).

 

[Greg G]

Toly, you are cherry picking these videos to make your point. That's almost a half volley on the run. So yes, when he is under pressure that way, fed will arm it. What's your point?

 

[Chas Tennis]

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

What is a 'scissors' stroke?

Almagro's back foot must still be in contact with the ground when his shoulders accelerate. The foot looks as if it is in contact based on the knee flexion and body rise. In that case, all body parts and particularly his shoulders can be rotated in one direction from ground forces.

For Federer, both feet are off the ground when he turns his upper body. Then, in order to accelerate the upper body to rotate in one direction, some other parts of his body must be accelerated to rotate in the opposite direction. This is necessary from conservation of momentum for the whole body - no external forces, no change in momentum.

 

[toly]

Toly, you are cherry picking these videos to make your point. That's almost a half volley on the run. So yes, when he is under pressure that way, fed will arm it. What's your point?

I think kinetic chain is overrated too much and everyone should learn “arming the ball” technique.

 

[toly]

What is a 'scissors' stroke?

Player is airborne with split legs. Typically it is like one jump from open stance into closed stance.

Almagro's back foot must still be in contact with the ground when his shoulders accelerate. The foot looks as if it is in contact based on the knee flexion and body rise. In that case, all body parts and particularly his shoulders can be rotated in one direction from ground forces.

For Federer, both feet are off the ground when he turns his upper body. Then, in order to accelerate the upper body to rotate in one direction, some other parts of his body must be accelerated to rotate in the opposite direction. This is necessary from conservation of momentum for the whole body - no external forces, no change in momentum.

When Federer uses the arming ball technique his right arm actively generates acceleration (force) in clockwise direction, consequently, according to conservation of momentum, his upper body must slow down clockwise rotation.

This is Kvitova usual scissor kick forehand and she applies the arming the ball, that’s why around contact her upper body has no clockwise rotation.

 

[boramiNYC]

I think kinetic chain is overrated too much and everyone should learn ?arming the ball? technique.

Hey toly,

Mastery of the control of the kinetic chain includes being able to limit parts of the chain depending on the situation. (even when doing this there's specific patterns) When a pro goes for a easy kill shot right in front of the net he won't set his feet and use the jump scissor fh. He'll most likely set the feet securely and use a pretty compact stroke holding the rest of the chain firmly in secure position. This secure positioning of each joint shows full mastery of the kinetic chain. And when the situation arises where a full use of the chain is needed he'll do so.

This ability to securely hold the non-moving joints is the bases for good posture.

 

[wannabe good]

What is a 'scissors' stroke?

Almagro's back foot must still be in contact with the ground when his shoulders accelerate. The foot looks as if it is in contact based on the knee flexion and body rise. In that case, all body parts and particularly his shoulders can be rotated in one direction from ground forces.

For Federer, both feet are off the ground when he turns his upper body. Then, in order to accelerate the upper body to rotate in one direction, some other parts of his body must be accelerated to rotate in the opposite direction. This is necessary from conservation of momentum for the whole body - no external forces, no change in momentum.

I am more and more of the opinion that this push back of the right hip during the right-handed forehand is an essential part of the open-stance forehand. When right knee extends it pushes back the hip, and allows the shoulders and arm to spring forward in the whip-like motion.

 

[Chas Tennis]

Player is airborne with split legs. Typically it is like one jump from open stance into closed stance.

Almagro is unlikely to be doing a scissors backhand because it appears that his foot is in contact with the ground. Use videos that show no ground contact if you want to say that the player is airborne.

When Federer uses the arming ball technique his right arm actively generates acceleration (force) in clockwise direction, consequently, according to conservation of momentum, his upper body must slow down clockwise rotation.

Not sure about forces but you can see the velocity of his upper body by the shoulders turning. That motion has to be compensated by an opposite motion since he is airborne. I believe that his trunk is twisting and that the shoulders turn one way and the pelvis & other lower parts turn the other way. I believe that the video shows that. It may be more complicated because of the forward running, did the last ground - foot contact speed something up? . Where are those great overhead camera views......

This is Kvitova usual scissor kick forehand and she applies the arming the ball, that’s why around contact her upper body has no clockwise rotation.

Again, it is hard to know if Kivitova is airborne - in the scissors position - and has no foot touching the ground when she is running and performing a motion. Find videos that show both feet off the ground to analyze 'scissors' effect. If you have a foot on the ground you can 'arm' the ball with any force that you are capable of. The body muscles lock the body isometrically and the shoulder and pec muscles work. (Maybe also the shoulder and or pec muscles were pre-stretched a short time earlier for more racket head speed.)

 

[toly]

Kvitova running (scissor kick) forehand winner

See also video http://youtu.be/x3W4sNRIOP8

 

[Topspin Shot]

I think kinetic chain is overrated too much and everyone should learn “arming the ball” technique.

 

[nabrug]

I think kinetic chain is overrated too much and everyone should learn “arming the ball” technique.

https://www.youtube.com/watch?v=Ic719x-94c4 at 11:06

 

[Chas Tennis]

Kvitova running (scissor kick) forehand winner

See also video http://youtu.be/x3W4sNRIOP8

Poor quality video for this. I don't understand what processing may have been done.

Here are the individual frames starting before your video clip. When the foot does not have motion blur it is on the ground or not moving fast.

Frame #1 - Left foot is on the ground just before last letter. Right foot is moving slowly not too much motion blurred. Shoulder are turned back and racket is visible.
Frame #2 - Left foot on the ground, right leg coming up, racket visible probably not moving very fast because motion blur is not too bad.
Frame #3 - Left foot on ground or just left ground. ? Right leg too motion blurred to see. This is the first frame of your video above. Racket barely visible. Correction - I believe that the shoulders have begun to turn and that we are seeing her right arm has moved to the left of her upper body.

Analysis all 6 frames - It appears likely that the left foot is on the court (see foot near the right-most white letter on the court) when the shoulders start rotating. I don't see that as a scissors stroke as you defined it.

In looking at the videos keep in mind that movements start with forces and accelerate to higher velocities. Forces can be strong before velocity changes becomes apparent.

We need better videos for this issue. It might be difficult on running shots - what is the time that a foot is on the ground compared to the time that no feet are on the ground for running?

I believe that there is an interesting difference for strokes with no ground forces. Probably research has been done.

 

[Chas Tennis]

Frame #4 - Left foot leaving ground still near last court letter. Toe down? Right foot seems slow from motion blur.? Shoulders have turned. Racket arm around. Racket too motion-blurred to see.
Frame #5 - Left foot still near court letter. Toe down? Right leg and foot motion blurred.
Frame#6 -After impact. Left foot definitely off ground, look at calf. Right leg and foot very blurred.

 

[gambitt]

https://www.youtube.com/watch?v=34A9Zp10BKE

Is this the Dent serve "tutorial" you are referencing? If not, please point us to the proper youtube video. Here, Dent does NOT discount other important of the legs, core, etc -- he does not indicate that the other elements of the kinetic chain are not important. He is not making the claim that you attribute to him -- that it's mostly the shoulder and arm.

This video is about using the shoulder and the arm as a whip to generate RHS. That is all this video is about. It is not meant to be a statement about the complete kinetic chain for the serve. If this is the video, you are misinterpreting Dent's view.

https://www.youtube.com/watch?feature=player_detailpage&v=C6QPIgcEtqI#t=210

No one ever discounts the core or the legs, but Dent says there are a whole load of other things that are more important (ball toss, RHS, whippy arm). And he's right.

Happy to help.

 

[SystemicAnomaly]

I think kinetic chain is overrated too much and everyone should learn “arming the ball” technique.

You're losing it, toly. You are not doing students of tennis any favors posting this stuff here and on Youtube. Even tho' the hip and torso rotations are quite a bit less for the 1-handed BH of Federer and many others, does not mean that it is trivial or insignificant.

This nonsense does a disservice to those learning tennis. Stick to physics and leave the biomechanics to the experts in the field.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/

 

[SystemicAnomaly]

... People like to say "it's all in the legs" for some reason...

Who says this? Don't know credible source who has made this claim.

... No one ever discounts the core or the legs...

It appeared that you were doing just this a a previous post or two.

https://www.youtube.com/watch?feature=player_detailpage&v=C6QPIgcEtqI#t=210

... Dent says there are a whole load of other things that are more important (ball toss, RHS, whippy arm). And he's right.

Dent shows us 2 versions of the serve -- one that employs a jump and another w/o a jump. However, he is still employing a leg drive in the 2nd version. The first version looks similar to other modern serves of the past few decades. The 2nd version looks very much like the serve of Rod Laver, Pancho Gonzales and others of their era -- they developed their serve mechanics at a time when jumping was not allowed. However, they still used leg drive on their serve.

Dent does say that "the legs are an important factor...". This is not in dispute. Of course, the legs alone are not going to generate all the power (or RHS) on the serve. GRF, leg drive, and body rotations are part of an efficient kinetic chain for the serve. If we start the kinetic chain with these lower links, it make it easier on the shoulder and the arm. It makes it easier to load up the shoulder (stretching certain muscle group) which make it easier to employ that "loose, whippy" arm action.
.

 

[toly]

You're losing it, toly. You are not doing students of tennis any favors posting this stuff here and on Youtube. Even tho' the hip and torso rotations are quite a bit less for the 1-handed BH of Federer and many others, does not mean that it is trivial or insignificant.

This nonsense does a disservice to those learning tennis. Stick to physics and leave the biomechanics to the experts in the field.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2577481/

This is particular questions for you. Why does Almagro upper body rotation slow down around contact? What is good about it?

Here is video http://youtu.be/94SGGfY7Qxg

 

[LeeD]

How do you crack a whip?
You start your hand fast, then SLOW IT DOWN to get the whipping action.

 

[oble]

This is particular questions for you. Why does Almagro upper body rotation slow down around contact? What is good about it?

Greg G had already answered this question many posts ago, which is applicable to all kinetic chain motions:

Also toly, his shoulders aren't moving because even in a regular ground stroke, that's where they're supposed to stop. The energy has already passed on to the arm at that point.

Even on the forehand side, the trunk rotation slows down just before contact to allow the arm to whip forward. LeeD's whip cracking analogy also provides a good explanation.

The amount of energy that needs to be generated through multiple body parts (and thus the extent of kinetic chain used) is obviously dependent on the shot in question:

• Almagro was standing miles behind the baseline to return the serve in your example so he has more time to setup his shot and he also needs to generate more pace on his own.
• Federer was standing well inside the baseline taking the return on the rise so he does not have as much time to fully load all his muscles nor does he need to generate as much pace on his own, but there is still a kinetic chain from his linear forward motion combined with the mild core coiling/uncoiling.
• Kvitova has kinetic chain from the torso rotation (no loading/unloading of the legs as she was doing a running forehand) as she was facing the left when running and starts uncoiling her body for the running forehand when she's between the "I" and "N" of the "BEIJING", whereas you cherry-picked your GIF image to begin from the moment she had already turned her upper body to show that she's "arming" her shot.

Yes there are moments that pros do just arm the ball back, but those are mostly the shots where they barely get to the ball like a chip backhand or squash forehand on full stretch, or blocking a big serve back, or things like half-volleys where the ball has so much energy in it during the split second after it bounces. Most other shots will have some form of kinetic chain in it.

 

[SystemicAnomaly]

This is particular questions for you. Why does Almagro upper body rotation slow down around contact? What is good about it? ...

This has already been answered quite well be several posters. But I'll add yet another perspective. The upper body rotation on a 1-handed BH is slowed (or even stopped) even before contact happens -- as energy (or momentum) is transferred from the upper body to the shoulder and arm. Variations of this is very common for the kinetic chain for strokes in many different sports. As kinetic energy (or momentum or angular momentum) is transferred from one link to the next, the previous link often slows down.

Let's consider an even simpler part of what is happening. If my physics is flawed, I'm sure you'll let me know. For the brief time that the body is uncoiling, we have the mass of the torso (upper body) plus the mass of the arm and racket moving at some velocity. If we suddenly stop the motion of the torso, we now have a smaller moving mass (arm + racket). Isn't momentum (or angular momentum) conserved in this situation? Won't the speed of the arm + racket increase as the larger mass is reduced or stopped?

There could very well be more going on here than my simplification suggests as various muscles are stretched (stored or potential energy?) and then released as energy is transferred from one link to the next?

 

[gambitt]

Who says this? Don't know credible source who has made this claim.

It appeared that you were doing just this a a previous post or two.


Dent shows us 2 versions of the serve -- one that employs a jump and another w/o a jump. However, he is still employing a leg drive in the 2nd version. The first version looks similar to other modern serves of the past few decades. The 2nd version looks very much like the serve of Rod Laver, Pancho Gonzales and others of their era -- they developed their serve mechanics at a time when jumping was not allowed. However, they still used leg drive on their serve.

Dent does say that "the legs are an important factor...". This is not in dispute. Of course, the legs alone are not going to generate all the power (or RHS) on the serve. GRF, leg drive, and body rotations are part of an efficient kinetic chain for the serve. If we start the kinetic chain with these lower links, it make it easier on the shoulder and the arm. It makes it easier to load up the shoulder (stretching certain muscle group) which make it easier to employ that "loose, whippy" arm action.
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OK buddy, you know more than Taylor. You win. Maybe you should be a professional coach or something.

 

[SystemicAnomaly]

^ Really! Is that what you got from my response? I am providing another perspective (from YOUR's) on what Dent is saying and showing us in his videos.


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[gambitt]

If I'm being honest I saw a wall of text with more randomly bolded words so I actually didn't get beyond the first line. I assumed the rest would be more hyper-theoretical diatribe. Was that not the case?

 

[SystemicAnomaly]

If I'm being honest I saw a wall of text with more randomly bolded words so I actually didn't get beyond the first line. I assumed the rest would be more hyper-theoretical diatribe. Was that not the case?

Attention deficit? Are you freely admitting that you can't be bothered to consider any perspective other than your own? If you actually read my posts, you would see that I'm not disagreeing with Taylor Dent as much as I am disagreeing with 1 or 2 statements that you made. You made the generalization that people say it's all in the legs". I asked who these "people" are. Didn't see an answer. Dent is not actually saying anything that contradicts most other sources.

 

[toly]

This has already been answered quite well be several posters. But I'll add yet another perspective. The upper body rotation on a 1-handed BH is slowed (or even stopped) even before contact happens -- as energy (or momentum) is transferred from the upper body to the shoulder and arm. Variations of this is very common for the kinetic chain for strokes in many different sports. As kinetic energy (or momentum or angular momentum) is transferred from one link to the next, the previous link often slows down.

Let’s analyze forehand. Assume an upper body is vertical, arm is horizontal and passive. When the right shoulder (pivot) starts drugging passive arm it inevitably should lag backward due to inertia, see picture below.

So, if at some point of upper body rotation the arm is behind player back we can observe the arm forward snap which could increase speed of the arm end/hand. But, everyone wants short backswing (especially you), so pros never move the arm behind their back.

Next is Salazar forehand with legs on the ground.

His arm is always ahead of the pivot and he has to actively use arm muscles to resist unwanted lag. His arm around contact rotates faster than upper body, then he must use even more energetically arm muscles. Thus in case of powerful forehand pro always applies “arming the ball” technique.

 

[Chas Tennis]

When the upper body rotates as indicated by the shoulders, for a forehand, the pec and some other muscles may be stretched. As long as strong forces are still being applied to accelerate body rotation, the pre-stretched muscles attached to the arm may not be strong enough to pull the upper arm away during an accelerating body turn. It's similar to doing bench presses in an accelerating rocket ship, you can't get the bar off your chest until the rocket stops accelerating.

In analyzing videos, we should try to distinguish between acceleration, that may be very forceful, brief, start slowly, and be difficult to see in high speed videos and high speed motions which are easy to see in videos. Acceleration may involve large forces while high speed movement may involve no forces. Objects moving are easy to see in videos, but the important forces aren't.

Pre-stretching of muscles can occur during accelerations. (often called 'lag') After the body is rotating at a constant velocity - no longer accelerating, no forces - the pre-stretched muscles (pec for forehand & others) can then be used to accelerate the arm. Then the arm pulls ahead of the turning shoulders in videos. For the Salazar video, we should also see the frames during the earlier shoulder acceleration.

In the Almagro backhand video (which looks excellent for analysis, complete and clear) he may be controlling his body position as a priority. ? He is off the ground and his shoulders and arm are turning one way and his left arm and leg are turning in the opposite direction. Watch how his left arm and leg move together. Is he controlling his overall body rotation? Does that keep the center of his body from rotating, for controlling the direction of his backhand?

We also have to keep in mind that the range of motion for twisting the spine to 'rotate the shoulders' is limited, the upper body has to slow down and stop within the range of motion. That could be why Almagro stopped his shoulder rotation. ? His shoulder motion not only accelerates the arm and racket but also may have pre-stretched shoulder muscles (delt, others?) which then accelerates the arm and racket for impact after the shoulder turning has stopped.

 

[Topspin Shot]

The only thing worse than overly technical discussion is overly technical discussion filled with mistakes.

 

[toly]

One handed backhand is completely different story because the arm is always behind the pivot and kinetic chain can be much more efficient. From mechanics standpoint one handed backhand could be more powerful than forehand, but our muscles don’t want to work this way.

 

[Chas Tennis]

One handed backhand is completely different story because the arm is always behind the pivot and kinetic chain can be much more efficient. From mechanics standpoint one handed backhand could be more powerful than forehand, but our muscles don’t want to work this way.

I view that as two links of a kinetic chain with unspecified stretching.

Justine Henin 1hbh.
http://tt.tennis-warehouse.com/show...ht=one+hand+backhand+what+accelerates+initial

The first part of that acceleration is an interesting topic.

One hand Backhand - What causes the initial acceleration?
http://tt.tennis-warehouse.com/showthread.php?t=462997

If there were FYB overhead videos of the 1hbh we might learn something.