Modelling strokes after professional players

No, your hitting arm. Your elbow joint would face the sky if you weren't arming the ball, but yours faces the net.

J
I see. But I think this might be different from stroke to stroke. I checked my other videos and sometimes the elbow joint is facing the net and sometimes it doesn't. Same with Fed I suppose:


I think to copy simons strokes by themselves o any pros for that matter isnt a good idea unless you like / hve the ability to copy the rest of their game. Simon for example is basically a pusher with quick strokes and good aim. Most over 40 players shouldnt copy this style unless theyre also marathon runners etc.
I agree. His strokes are made to be consistent with good accuracy and his whole game is built around that.
Sorry, I don't buy that at all. I will explain.

When you do stretch your arm for the SA FH, you neither try to really stretch it uncomfortably nor keep it consciously bent. In other words, it is just a feel. You feel your arm is fully extent and not bent any degree. However, in reality it's neither physically straight or noticeably bent.

Want proof? Consider the master, the epitome of the SA-- Mr. Federer:


Is he aware that his arm aren't straight with this shot?




Very straight, eh?



A little bendy, no?




Bendy or straight? Your choice. I go with comfortably extended.




So, likewise, the so called bent FH has the same logic. The same feel. The play extends and hit the ball, his arm happens to be physically bent, but he couldn't tell that precisely.
I agree. You hit with a "comfortably extended" arm because for thsi kind of stroke mechanics it feels natural to do so to accelerate the racket. You don't do it to have a consistent length lever, but rather this is the consequence of hitting like this.

@Fliiix on your strokes vs racquet dilemma have you looked into Nishikoris racquet? He's got a great 2hbh i believe its quite light his racquet
I'we tried something similair and it was good for the backhand, but the problem is that my forehnad and and serve mechanics don't like the kind of balance tha tkei uses, just under even balance I believe.

I actually meditated on this whole idea and came to the conclusion we should consider various phases of swing. When initially speeding up the racquet after the backswing, there's not much centrifugal force yet, but momentum of inertia is there in the "resting" arm and racquet. It's easier to propel the racquet closer to the body (with shorter radius), which makes for arm collapsing and tucking into torso when a huge takeback is followed by high acceleration right from the start of forward swing. We see lots of players increasing the bend in their arms on the initial stage of forward swing. The ones who get their arms lower and closer to the body at the end of the backswing (Nadal) or early through the forward swing, before major rotaional acceleration (U-shape swing), don't suffer from the effect. So here is where my confusion regarding withstanding the unbending comes from))
Now when arm is already moving fast in a circular motion centrifugal force is built up and acting to unbend the arm, as you said. There are some swings where arm is straightening towards contact (some my swings). This may be harmful for RHS hindering the recently discussed on the forums "parametric acceleration", hindering racquet had release and natural rotation from under the handle to over the handle. So bent-arm forehanders better resist that straightening. This also explains all the pull-accross and use-your-biceps talks - if you accelerate your arm with bent posture you don't want it to straighten into contact.

All above are thoughts and speculations rather than confident ideas.

I actually have ~3g under the buttcap to get to 8pts HL. Also re-measured SW with iPhone app to be 328. Last time I checked 20.8 MGR/I was pretty close to "magical 21" (yes I remember you don't share the single magical number approach). So I'm not way off from what you suggested for Fed FH in your video. I guess you suggest throwing ~5g at the balance point?

Also I have some thoughts that I think you may be interested in with the way you approach all this stuff. They are used to refer to racquet balance as major spec to get similar feel swinging racquets with different mass. Ok, let's even say balance and MGR/I, as extremely polarized vs extremely depolarized setups will likely swing and feel different despite same mass and balance point. But let's take into consideration racquet doesn't act by itself - we grip it. Therefore when playing tennis we must consider at least racquet mass+hand mass (if we call wrist a loose hinge point), because hand is always on the handle, and despite some move allowed and not dead grip, its mass is always contributing to the swing and to ball collision.

As per this link (https://www.quora.com/How-much-does-a-human-hand-weigh) hand mass is ~0,58% of body mass - which is huge 430g for me personally, more than the whole racquet! If we add this mass to racquet customization tool @2" we get the "actual" balance point at the top of the handle (6.5"). And it's the location to add mass to keep "actual" balance and increase "actual" MGR/I.

Of course it's not that straight and easy as it is for just racquet - already mentioned non-dead grip, and at the flip side - non-loose wrist and forearm being part of a unit (though not rigid one) for many shots. But taking the described circumstances into consideration I don't by the idea that ~320g and ~350g racquets will swing similarly if having same balance point and MGR/I.

Another interesting conclusion is for the backhand side: having extra ~400g on the handle for 2HBH favors less HL balance than for 1HBH. It's a "known fact" reasoned by "more strength from 2 hands", but it's also actual for most flippy 2HBHs like Nishikori's - just extra mass on the handle allows for faster recoil of the high-SW, less HL balanced racquets.
Actually extending/straightening into the contact can accelerate the racket head, if the angular speed of the swing stays the same, which usually does (if you don't decelerate the swing for some reason) because of the angular (centrifugal) momentum that is building throught the swing will carry it and if you increase the lenght of the lever, the actual peripheral speed will increase. The thing is if your arm stays bend during the whole swing, the momentum you are transferring to the racket is decreasing as the racket builds up the speed and your arm/muscles has to struggle less to move it with the same speed. But if you extend the arm, you force your self to apply more momentum on the racket to keep it accelerating and as the end result you will transfer more energy to the the actual racket during the swing. Now this is the first time I thought of it this way, I know it's confusing, but I think I'we finally found a solid argument for the SA Forehand. I have to polish the theory and explain with some sketches for you all.

As for the racket, you should try that. Maybe not at the balance point, but a bit higher. I had great success with the mass on the bottom of the hoop with the DR, or 9'o clock.

Yeah all this is correct, but impossible to take in to account, at least with the tools availabe to us today. Maybe one day we'll be able to scan our body, put the racket in the hand and simulate the swing to determine the optimal specs. Until then all we can do is start with more empirical approach, by finding the ball park of the ideal spces, and than fine tune it with a couple grams here and there by experimenting. If we took the arm etc in to account all we would do is change the "ball park" of the optimal MGR/I to let's say around 30 from presumed 21.

What do you mean by flippy backhands? hah

lol. I just ran across him in some review I was doing on FH's. I think TTW needs to do a Ernie challenge to see who can demonstrate the best crane position forehand.




We should start accepting video entries of members imitating him =)
 

J011yroger

Talk Tennis Guru
I see. But I think this might be different from stroke to stroke. I checked my other videos and sometimes the elbow joint is facing the net and sometimes it doesn't. Same with Fed I suppose:



I agree. His strokes are made to be consistent with good accuracy and his whole game is built around that.

I agree. You hit with a "comfortably extended" arm because for thsi kind of stroke mechanics it feels natural to do so to accelerate the racket. You don't do it to have a consistent length lever, but rather this is the consequence of hitting like this.


I'we tried something similair and it was good for the backhand, but the problem is that my forehnad and and serve mechanics don't like the kind of balance tha tkei uses, just under even balance I believe.



Actually extending/straightening into the contact can accelerate the racket head, if the angular speed of the swing stays the same, which usually does (if you don't decelerate the swing for some reason) because of the angular (centrifugal) momentum that is building throught the swing will carry it and if you increase the lenght of the lever, the actual peripheral speed will increase. The thing is if your arm stays bend during the whole swing, the momentum you are transferring to the racket is decreasing as the racket builds up the speed and your arm/muscles has to struggle less to move it with the same speed. But if you extend the arm, you force your self to apply more momentum on the racket to keep it accelerating and as the end result you will transfer more energy to the the actual racket during the swing. Now this is the first time I thought of it this way, I know it's confusing, but I think I'we finally found a solid argument for the SA Forehand. I have to polish the theory and explain with some sketches for you all.

As for the racket, you should try that. Maybe not at the balance point, but a bit higher. I had great success with the mass on the bottom of the hoop with the DR, or 9'o clock.

Yeah all this is correct, but impossible to take in to account, at least with the tools availabe to us today. Maybe one day we'll be able to scan our body, put the racket in the hand and simulate the swing to determine the optimal specs. Until then all we can do is start with more empirical approach, by finding the ball park of the ideal spces, and than fine tune it with a couple grams here and there by experimenting. If we took the arm etc in to account all we would do is change the "ball park" of the optimal MGR/I to let's say around 30 from presumed 21.

What do you mean by flippy backhands? hah



We should start accepting video entries of members imitating him =)
No. The picture you posted is at contact, mine is in the lag phase.

J
 
I also made part 2 of the RF FH modelling. I was shot a while back. Now I have actually started to understand what and how to do with the left arm. I have to extend it more to the "side of the court" and not so much in front of me pointing to the net. I'we been doing this the last week and I really like the feel, and I can hit more spin. I guess I'll leave this update for next time, when I feel comfortable enough and start filming again. But for now an update.

 
I also made part 2 of the RF FH modelling. I was shot a while back. Now I have actually started to understand what and how to do with the left arm. I have to extend it more to the "side of the court" and not so much in front of me pointing to the net. I'we been doing this the last week and I really like the feel, and I can hit more spin. I guess I'll leave this update for next time, when I feel comfortable enough and start filming again. But for now an update.

I really like the camera angle you used at 4:45. Makes it much easier to watch your progress.

How high and how far back was the camera? Was it mounted on the fence?
 

J011yroger

Talk Tennis Guru
Let me just make sure I understand your thought process, a 4 gram difference in brands of leather grip is important and matters to your stroke, but your arm facing the wrong direction is irrelevant?

J
 

Dragy

Hall of Fame
Actually extending/straightening into the contact can accelerate the racket head, if the angular speed of the swing stays the same, which usually does (if you don't decelerate the swing for some reason) because of the angular (centrifugal) momentum that is building throught the swing will carry it and if you increase the lenght of the lever, the actual peripheral speed will increase. The thing is if your arm stays bend during the whole swing, the momentum you are transferring to the racket is decreasing as the racket builds up the speed and your arm/muscles has to struggle less to move it with the same speed. But if you extend the arm, you force your self to apply more momentum on the racket to keep it accelerating and as the end result you will transfer more energy to the the actual racket during the swing. Now this is the first time I thought of it this way, I know it's confusing, but I think I'we finally found a solid argument for the SA Forehand. I have to polish the theory and explain with some sketches for you all.
I'll try one more time.

By this mooment torso rotation acceleration has finished. It's only going to slow down further on. Now almost nothing powers arm further rotation, it's moving inertially. With no power there's no effect from increasimg the radius. So if he straightens his arm after torso rotation has started to decelerate he'll get no gains. In the meantime, arm pivoting aroud shoulder joint creats "accross" acceleration which is believed to be important to speed up the racquet head with racquet flipping back from the deep lag. Straightening the arm will delay and/or erode this acceleration (aka parametric acceleration) which will likely hurt the RHS.

If a player manages to get his arm straight before the phase shown on Djokovic picture, he will be able to capitalize on the increased "lever length" around the major acceleration phase. However the difference will be more evident compared to more bent armers than Nole is.
As for the racket, you should try that. Maybe not at the balance point, but a bit higher. I had great success with the mass on the bottom of the hoop with the DR, or 9'o clock.
Actually I couldn't help putting 11g to the bottom of the V of my sticks, right before a meetup with a new partner I never played before... Messed my timing quite a bit, overly-muted stringbed didn't help as well... But as I stick with it's becoming good. Cannot say if it really improved my game, but I've been looking for an excuse to add something to my sticks for so long, couldn't miss a chance.
Meanwhile, your suggestion to put smth to 9 o'clock makes no sence to me. I dunno what kind of success you've got with your DR and how it's related, but bumping mass, SW and moving balance to less HL together makes a significant change to the stick, in my opinion. Putting in some mass to buff MgR/I while slighly lowering the balance point should be much easier to adopt.
What do you mean by flippy backhands? hah

I mean this letting the racquet drop and lag and catch up into the shot, contrary to some shots with rigid arm-racquet structure.
 
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By this mooment torso rotation acceleration has finished. It's only going to slow down further on. Now almost nothing powers arm further rotation, it's moving inertially. With no power there's no effect from increasimg the radius. So if he straightens his arm after torso rotation has started to decelerate he'll get no gains. In the meantime, arm pivoting aroud shoulder joint creats "accross" acceleration which is believed to be important to speed up the racquet head with racquet flipping back from the deep lag. Straightening the arm will delay and/or erode this acceleration (aka parametric acceleration) which will likely hurt the RHS.
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"By this mooment torso rotation acceleration has finished." Maybe? But maybe only less torque from torso muscles? "It's only going to slow down further on. Now almost nothing powers arm further rotation, it's moving inertially." How do you know the shoulder torque does not take over as the torso torque reduces? "With no power there's no effect from increasimg the radius." I would say there is power from torso or shoulder but it is not easy to see in videos. What evidence or reference do you have for these forces? "So if he straightens his arm after torso rotation has started to decelerate he'll get no gains. You assume the shoulder is not supplying torque? In the meantime, arm pivoting aroud shoulder joint creats "accross" acceleration which is believed to be important to speed up the racquet head with racquet flipping back from the deep lag." For torso and shoulder there is an angle between the forearm and racket at impact to consider. Is acceleration "across" at impact? I believe that shoulder forces start before impact and include forward at ball. ? Straightening the arm will delay and/or erode this acceleration (aka parametric acceleration) which will likely hurt the RHS. I don't think we know the torso and shoulder forces at impact or the variety being used. ?

We need more videos like this. Have you looked at Anatoly (forum "Toly") Antipin's great composite videos and pictures?

The following are some of the possibilities:
1) When the torso is strongly accelerating it may be impossible for the shoulder muscles to produce enough torque to move the upper arm faster than the torso is already moving it. ?
2) After the torso torque stops or reduces then the shoulder joint with stretched muscles can move the upper arm forward. The torso could still accelerate at a reduced amount through impact or not.?
3) I do not understand how or if both torso and shoulder may cease active muscle forces and proceed with only passive forces from stretched muscles. Is this what is called 'release'? OR if the torso and shoulder muscles could cease supplying forces altogether then movement would just be from inertia. Is this other what is called 'release'?

Only forces before and to the end of impact matter for the result on the ball.

When the muscles are active or passive or cease supplying shortening forces is a complicated issue that cannot be directly seen in videos and requires research with 3D motion capture systems and body sensors. Is there an accelerometer on the racket head anywhere? Any references?

Golf is detailed and deals with a better controlled situation with the ball still. I have been trying a little to find information on 'release'. Same for baseball pitching? Both golf and baseball seem more advanced in research than tennis.

What are the muscles doing in the milliseconds around impact? What stroke variations are there among players?
 
Last edited:

Dragy

Hall of Fame
"By this mooment torso rotation acceleration has finished." Maybe? But maybe only less torque from torso muscles? "It's only going to slow down further on. Now almost nothing powers arm further rotation, it's moving inertially." How do you know the shoulder torque does not take over as the torso torque reduces? "With no power there's no effect from increasimg the radius." I would say there is power from torso or shoulder but it is not easy to see in videos. What evidence or reference do you have for these forces? "So if he straightens his arm after torso rotation has started to decelerate he'll get no gains. You assume the shoulder is not supplying torque? In the meantime, arm pivoting aroud shoulder joint creats "accross" acceleration which is believed to be important to speed up the racquet head with racquet flipping back from the deep lag." For torso and shoulder there is an angle between the forearm and racket at impact to consider. Is acceleration "across" at impact? I believe that shoulder forces start before impact and include forward at ball. ? Straightening the arm will delay and/or erode this acceleration (aka parametric acceleration) which will likely hurt the RHS. I don't think we know the torso and shoulder forces at impact or the variety being used. ?

We need more videos like this. Have you looked at Anatoly (forum "Toly") Antipin's great composite videos and pictures?

The following are some of the possibilities:
1) When the torso is strongly accelerating it may be impossible for the shoulder muscles to produce enough torque to move the upper arm faster than the torso is already moving it. ?
2) After the torso torque stops or reduces then the shoulder joint with stretched muscles can move the upper arm forward. The torso could still accelerate at a reduced amount through impact or not.?
3) I do not understand how or if both torso and shoulder may cease active muscle forces and proceed with only passive forces from stretched muscles. Is this what is called 'release'? OR if the torso and shoulder muscles could cease supplying forces altogether then movement would just be from inertia. Is this other what is called 'release'?

Only forces through the time of impact matter for the result on the ball.

When the muscles are active or passive or cease supplying shortening forces is a complicated issue that cannot be directly seen in videos and requires research with 3D motion capture systems and body sensors. Is there an accelerometer on the racket head anywhere? Any references?

Golf is detailed and deals with a better controlled situation with the ball still. I have been trying a little to find information on 'release'. Same for baseball pitching? Both golf and baseball seem more advanced in research than tennis.

What are the muscles doing in the milliseconds around impact? What stroke variations are there among players?
If you get back to this video:
you notice hand speed peaks by frame 18. So no, even if there's some torque from shoulder muscles to support and guide arm swing into contact, there is no significant power input and no further acceleration. This corresponds with best coaching instructions and descriptions I've heard and this approach works to practically achieve better forehands, as per my anecdotal experience. That's enough actually to develop a good stroke. Any more scientifically presise description with indication of contribution of various muscles and joints requires a study. Some people do some good job: https://www.repository.utl.pt/bitstream/10400.5/9893/1/Tese definitiva.pdf you know. I don't think you'd trigger some further research by talking to rec players on messageboard and calling out good and bad coaching approaches for not being scientifically precise.

Only forces through the time of impact matter for the result on the ball.
This is very narrow approach. Forces responsible for speeding up the racquet early in the swing obviously relate to the forces working through the impact.
 
If you get back to this video:
you notice hand speed peaks by frame 18. So no, even if there's some torque from shoulder muscles to support and guide arm swing into contact, there is no significant power input and no further acceleration. This corresponds with best coaching instructions and descriptions I've heard and this approach works to practically achieve better forehands, as per my anecdotal experience. That's enough actually to develop a good stroke. Any more scientifically presise description with indication of contribution of various muscles and joints requires a study. Some people do some good job: https://www.repository.utl.pt/bitstream/10400.5/9893/1/Tese definitiva.pdf you know. I don't think you'd trigger some further research by talking to rec players on messageboard and calling out good and bad coaching approaches for not being scientifically precise.


This is very narrow approach. Forces responsible for speeding up the racquet early in the swing obviously relate to the forces working through the impact.
I did not agree with Toly that you could measure speeds in a circular stroke with a 2D video. I don't consider those speed graphs. When the object is going away or toward the camera the speed errors have to be very large, toward speed 0, and when the object is moving squarely across or up-down in the frame the errors may be small. But for but all other object travel directions in 3D space, the speed measurements don't look possible to me.

Maybe the speed measurement application was on the TW website. ?

My wording should have been -
Only forces before and to the end of impact matter for the result on the ball.
 

Dragy

Hall of Fame
I did not agree with Toly that you could measure speeds in a circular stroke with a 2D video. I don't consider those speed graphs. When the object is going away or toward the camera the speed errors have to be very large, toward speed 0, and when the object is moving squarely across or up-down in the frame the errors may be small. But for but all other object travel directions in 3D space, the speed measurements don't look possible to me.
Here’s your scientific source showing there’s only brief acceleration for shoulder flexion in a forehand swing. It shows angular, not linear speed.
 
Here’s your scientific source showing there’s only brief acceleration for shoulder flexion in a forehand swing. It shows angular, not linear speed.
The graph needs interpreting. I don't understand how to interpret this graph for acceleration. There is no time information. Would have to read the report. Link?
 

Dragy

Hall of Fame
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