"wrapping" the ball.

[zeio]

On the "wrapping" itself, what often gets missed is that it only happens during contact (or very close to contact) and continues during the followthrough. There's a couple of Ma Long slowmos that illustrates the sudden shaking of the racket from the pronation/supination during contact. From the majority of the backswing, it should be mainly trying to hit the ball square on to ensure max accuracy (the more tangential the contact is the more error prone the stroke is) and this is where the "convex" stroke comes in. It is only once you're just about to hit the ball that it transitions from a "convex" to a "concave" stroke - this is why I also don't like trying to distinguish it using these terms and a lot of ppl get confused (I used to be quite confused myself too) - make solid contact then brush is a lot simpler as an instruction and produces the same results.

Table tennis is a very complex sport with complex interactions and sometimes trying to simplify it using overly simple equations like what brokenball always tries to do are bound to fail. It's like trying to explain quantum mechanics using Newtonian laws - the theory simply breaks down.

Was going to supplement NextLevel's post in the European Games thread, but keeping it here for future reference.

Images of the path of the racket tip for the FH and BH mid-far distance loop from the studies from mainland China.
FH
https://i.imgur.com/KkgPY1k.png
FH and BH
https://i.imgur.com/cOPuJIa.png

Also, for those who haven't had a chance, check out the path and racket angle of the FH counterhit by Singaporean expert (pro teams and clubs) and novice players (1 hour of playtime per week, w/o formal training) in a study (2017) from Singapore.
http://mytabletennis.net/forum/foru...ID=1111185&title=looping-racket-angle#1111185

 

[zeio]

This right here is a great example of how posting video of yourself can really help add context to a discussion.

I'm not saying that every good player has opinions that I agree with (about technique/coaching/equipment etc).

But when you have a low level player who has never hit a very good topspin (I don't say that to be cruel, but the video evidence I have seen would indicate that the OP can not truly understand what is required to hit a good topspin), trying to argue with a player who can very clearly hit consistent, excellent top spins......

You see how ridiculous this all sounds.

In normal circumstances, I'd think it was fine for *any* player to question a technique or an opinion, and I would hope that the higher level player could explain what they mean - This benefits everyone.

Given the history of the OP, and the personal nature of the thread, I'd just ignore it completely.

Sigh, I've tried my best on Confucius' teachings.

https://ctext.org/analects/yan-yuan/zh?en=on

顏淵:
子貢問友。子曰：「忠告而善道之，不可則止，無自辱焉。」
Yan Yuan:
Zi Gong asked about friendship. The Master said, "Faithfully admonish your friend, and skillfully lead him on. If you find him impracticable, stop. Do not disgrace yourself."

 

[blahness]

It's funny how brokenball still insists on his hypothesis even against the mountain of scientific papers and video evidence directly contradicting his position. I don't know any engineer worth their salt who does this (not in my profession at least).

 

[brokenball]

It's funny how brokenball still insists on his hypothesis even against the mountain of scientific papers and video evidence directly contradicting his position. I don't know any engineer worth their salt who does this (not in my profession at least).

What papers? None have been posted yet. That is what I was asking for in the first place when I asked for proof. So far none has been submitted. Only a lot of opinions.

 

[latej]

Sometimes players realize a little too late and then compensate during the stroke - bigger bat angle change.

 

[turbozed]

What papers? None have been posted yet. That is what I was asking for in the first place when I asked for proof. So far none has been submitted. Only a lot of opinions.

Zeio posted a paper specifically demonstrating that pro players are doing things that you say are suboptimal. These include accelerating the racket past the contact point and pronating the forearm shortly before contact.

Are you suggesting that pro players are performing strokes suboptimally and would achieve better ball quality if they listened to you instead?

 

[latej]

I admire your good will @turbozed ;-)

 

[zeio]

Nothing new. Anything not in agreement with hardheaded engineer is labeled as opinions. This thread was never started with the intention of holding an open and fair discussion from the get-go. Hardheaded engineer has no interest in that shit. Never did, never do, and never will. It's all about binary reasoning - right or wrong, while practically all the arguments that have been presented are based on assumptions without substantiation (not with maths but actual play).

As stated before, the crux of the matter is interpretation. On top of that, applying physics in a purely scholarly fashion without any regards to biomechanics that players must deal with in actual practice is appalling.

 

[Dominikk85]

I think technically you can't change the racket angle while the ball is in contact because contact duration is just a few thousands of a second.

However sometimes the bat does have the tendency to get more open as you swing so for some it might help to have a feel of the bat closing above the top of the ball as you swing even though it doesn't really happen.

 

[NextLevel]

I think technically you can't change the racket angle while the ball is in contact because contact duration is just a few thousands of a second.

However sometimes the bat does have the tendency to get more open as you swing so for some it might help to have a feel of the bat closing above the top of the ball as you swing even though it doesn't really happen.

I had already written my last post but since I know your motives are pure and you probably are reading things late and may be confused about the main point, let me state it again in different terms.

Don't let anyone fool you that the issue is fundamentally about changing racket angle during the brief contact period or any such stuff, especially if you focus is on how to play better.

There are many ways to swing at the ball, just about all of them involve swing/stroke paths that require racket angle changes given the biomechanics of the human body. Changing these swing paths affects the ball quality, especially if you think if these swing paths as where you start the racket (end of backswing), where you contact the ball (contact point), and when you finish the racket (end of follow through). When you perform these swings, you may or may not feel like you are changing the angle through the swing but you are, but that is besides the point for improving your table tennis. The key is that do these swing paths when changed produce tangibly different effects on the ball despite the brief contact time?

In my experience playing and coaching, the answer is clearly yes. Of course there are many important things to consider in building a swing including risk of missing the ball contact, proper use of the body etc. There are better and worse ways to create a swing path. But if you think that the contact time is too short for the awing path to make a significant and sometimes even massive difference in whether the ball lands safely or goes long, or bounces high or stays low, you just need to experiment more with your swings.

All of this knowledge is implicitly built into standard table tennis training. Some of it you learn intuitively as you read spin better and adjust to it better. If you watch high level table tennis, you see it expressed all the time.

So the feeling you think is useless is a real feeling and it makes a difference to your stroke path. Pitchford has the same feeling. many good players will tell you they have the same feeling. You can decide whether you think the feeling doesn't matter. But don't let it be because you played better with the feeling but some idiot engineer convinced you that the ball contact time was too short for it to matter.

 

[zeio]

Ok, there are 2 major categories of counterarguments here:
1. Contact duration is simply too short for any meaningful change of angle to have a noticeable/significant effect on the shots, not to mention the issue of reaction time and the increased likelihood of hitting the racket edge;
2. Shots hit while accelerating through the contact means maximum velocity was not achieved.

Give 1 and 2 a deep thought for a minute.

Ignore the rights and wrongs and just consider the following logic, if the whatever minuscule change of angle during the whatever minuscule contact duration cannot lead to an increase in shot quality, then it follows that the whatever minuscule difference between contact velocity and maximum velocity should also not result in an increase in shot quality.

See the problem? 1 and 2 above cannot be true at the same time. For "if p then q" to be true, contact velocity and maximum velocity should also be considered negligible, which is the conclusion in the Polish study.

Negligible or not, and convinced or not, even recreational players with no formal training are found to "wrap" around the ball in FH counterhits in the Singaporean study.

http://mytabletennis.net/forum/foru...ID=1111185&title=looping-racket-angle#1111185

Experts had more pronation (DEps) during the backswing and part of forward swing. The wrist of experts had more flexion (DWfe) and ulnar deviation (DWru) compared to the novices.

...

For example, the experts represented larger range of racket movement, faster racket centre velocity, smaller racket plane angle against horizontal plane, different posture in the majority of the joints while not including elbow flexion angle, and joint angle velocity in trunk, shoulder internal rotation, elbow, and wrist radial flexion etc.

And lastly, out of 6 tries, MLin and WH achieved maximum velocity right upon impact 1 time (16.67%) and 2 times (33.33%), respectively. LSW, OTOH, consistently achieved maximum velocity after impact.

https://www.tabletennisdaily.com/fo...against-underspin-technique.24739/post-335791

MLin achieves maximum velocity 5ms before impact 4 times, right upon impact 1 time, 10ms after impact 1 time. WH achieves maximum velocity 5ms before impact 2 times, right upon impact 2 times, 10ms after impact 2 times.

https://www.tabletennisdaily.com/fo...against-underspin-technique.24739/post-336602

Last, there's another paper from 2017 by former CNT player Chang Chenchen where she finds LSW consistently "accelerates through the ball" when BH looping against both topspin and backspin, only reaching maximum velocity after impact.

 

[brokenball]

Zeio posted a paper specifically demonstrating that pro players are doing things that you say are suboptimal.

Not about "wrapping" the ball. It was one of his distractions.

These include accelerating the racket past the contact point and pronating the forearm shortly before contact.

If the paddle is still accelerating at impact, it isn't at maximum speed yet. Any acceleration after the impact doesn't' affect the trajectory of the ball and must be countered with extra time or effort in recovery.
Acceleration though the ball can yield extra dwell time but it would be a fraction of a micro second. Accelerating through the ball makes more sense when the ball is moving slowly and the need to hit the ball slow is important.
Do you know how much force there is at impact? It depends a lot on the impact speed.
If you divide the force of impact by the mass of the ball you get the acceleration rate necessary to "hold" or extend dwell time indefinitely but people cannot accelerate at that rate.
If the impact force is 100 N then divide that by 0.0027kg and you get 3777.7g or about 37K m/s. Clearly humans cannot achieve this kind of acceleration.
Accelerating at a fraction of that like 20g may achieve an extra fraction of micro second. Some how TT people think they can feel the difference. BS!
Now if the ball hits the paddle with only 1 N of force ( very little ), one still needs about 370 m/s to hold the ball on the paddle. Since people still can't accelerate anything near that about the dwell time still may be extending by a few micro seconds. I haven't calculated that yet. For catching the ball on the paddle the impact force should be extremely low but this is not typical of normal TT play.

Note, if you do extend the dwell time you lose the spring effect from the rubber and sponge since it returns to normal shape over a longer period of time.
At slow speeds this makes little difference because paddle can hit tangentially fast enough to make up for this lost of spring action.

Are you suggesting that pro players are performing strokes suboptimally and would achieve better ball quality if they listened to you instead?

Yes, but it is a goal and is not achievable by people. Sometime in the future a robot will achieve this if it doesn't shake itself to pieces trying.
The ability to do the math exists now. The mechanics have a long way to go.

Reading the other posts above it look like people don't think is possible hit the ball, then roll the wrist and that "wrapping" the ball really doesn't happen because of the short contact times and accurate timing involved. I have seen no evidence to the contrary.

 

[IB66]

Is there any info on when maximum acceleration of the stroke is achieved?

 

[Zwill]

Just some theoratical questions

Note, if you do extend the dwell time you lose the spring effect from the rubber and sponge since it returns to normal shape over a longer period of time.

But if the contact time is too short the rubber and the sponge won't have time to snap back which might be even a worse-case scenario.

 

[NextLevel]

Yes, but it is a goal and is not achievable by people. Sometime in the future a robot will achieve this if it doesn't shake itself to pieces trying.
The ability to do the math exists now. The mechanics have a long way to go.

Reading the other posts above it look like people don't think is possible hit the ball, then roll the wrist and that "wrapping" the ball really doesn't happen because of the short contact times and accurate timing involved. I have seen no evidence to the contrary.

So we went through this discussion just to get you to admit that your recommendations on how to play a topspin cannot be achieved by human beings? Seriously?

Let's stop the stupidity around wrapping. "Looping" doesnt happen either because the ball doesnt go round and in circles and return to where it started as if it boomeranged. Semanticists sometimes kill brain cells with dumb stuff like this.

The kind of wrapping (shaping, looping) that many have described does exist. The one you have made up in your head probably doesn't but since we don't know what goes on there I won't think about it much longer. And the kind that we have discussed is to use the shape of your stroke in order to affect the path along which you intend to spin the ball. It is precisely the kind of topspin that Tenergy 05 was designed to enable more strongly.

 

[brokenball]

So we went through this discussion just to get you to admit that your recommendations on how to play a topspin cannot be achieved by human beings?

Nextlevel would have people flail and fail just because they aren't perfect.

Seriously?

Yes, seriously! It is goal. People are not calibrated machines so they aren't perfect but they can try obviously come close.
The goal is consistency. Keep the attitude of the paddle as consistent as possible during the time contact can occurs. There is no consistency if the attitude of the paddle is always changing during the time of contact. Simple, yet this forum seems to be "thick as a brick" when it comes to understanding this after how many posts?
I have already shown how far the ball will land from the intended position, if at all, with just 1 millisecond variance from optimal and the paddle is rotating at 2 degree/ms.

Those that think "wrapping" the ball is a good thing can't answer my questions I posted long ago.
Also, those that think they can hit the ball and then rotate the paddle around the ball are nuts. First, the timing would need to be perfect and second, they can't start suddenly start rotating the paddle. There needs to be some angular acceleration time.

 

[NextLevel]

Nextlevel would have people flail and fail just because they aren't perfect.


Yes, seriously! It is goal. People are not calibrated machines so they aren't perfect but they can try obviously come close.
The goal is consistency. Keep the attitude of the paddle as consistent as possible during the time contact can occurs. There is no consistency if the attitude of the paddle is always changing during the time of contact. Simple, yet this forum seems to be "thick as a brick" when it comes to understanding this after how many posts?
I have already shown how far the ball will land from the intended position, if at all, with just 1 millisecond variance from optimal and the paddle is rotating at 2 degree/ms.

Those that think "wrapping" the ball is a good thing can't answer my questions I posted long ago.
Also, those that think they can hit the ball and then rotate the paddle around the ball are nuts. First, the timing would need to be perfect and second, they can't start suddenly start rotating the paddle. There needs to be some angular acceleration time.

You obviously havent heard of things like heuristics. The timing doesnt have to be perfect to expose as much surface area as possible to the ball with a relatively open paddle (appropriately angled) while swinging at it and add a turning motion with acceleration at the appropriate moment. But since you are clearly unable to do this, you think it makes no sense. Get a good coach and learn it first. After you have learned it, then you can speak about it as a pedagogical tool. Not as someone manifesting a bad case of Dunning-Kruger syndrome.

 

[brokenball]

You obviously havent heard of things like heuristics. The timing doesnt have to be perfect to expose as much surface area as possible to the ball with a relatively open paddle (appropriately angled) while swinging at it and add a turning motion with acceleration at the appropriate moment.

Show me.

But since you are clearly unable to do this, you think it makes no sense. Get a good coach and learn it first. After you have learned it, then you can speak about it as a pedagogical tool.

I don't try to wrap my paddle around the ball. Changing the attitude of the paddle during the time it makes contact leads to inconsistency. You haven't been able to debunk that.

Not as someone manifesting a bad case of Dunning-Kruger syndrome.

If you can't win with facts make an ad-hominem attack.
WTF have you done beside spread garbage on TT forums? I have a lot of achievements under my belt.
Has anybody wanted your autograph or say meeting you was on their bucket list?
Are you a moderator on an engineering forum,,,,in China? I admit it is more an honorary position since even my posts get screened by the powers that be.
I have just ask if someone can prove if "wrapping" the ball is good. So far no takers that can't be debunked, but a lot of distractions.
Even USDC has stuck his nose into this thread with his ball dribbling video that has nothing to do with "wrapping" TT balls.

 

[NextLevel]

Show me.


I don't try to wrap my paddle around the ball. Changing the attitude of the paddle during the time it makes contact leads to inconsistency. You haven't been able to debunk that.


If you can't win with facts make an ad-hominem attack.
WTF have you done beside spread garbage on TT forums? I have a lot of achievements under my belt.
Has anybody wanted your autograph or say meeting you was on their bucket list?
Are you a moderator on an engineering forum,,,,in China? I admit it is more an honorary position since even my posts get screened by the powers that be.
I have just ask if someone can prove if "wrapping" the ball is good. So far no takers that can't be debunked, but a lot of distractions.
Even USDC has stuck his nose into this thread with his ball dribbling video that has nothing to do with "wrapping" TT balls.

I have shown you that a high level server does it when he does his favorite serve. He mistimed the effect in the video I presented but with the same serve, he has given players as good as Wang Liqin trouble. You are a low level player so what you do doesnt really qualify as evidence here for what high level players do.

Pointing out that you are a low level isn't ad hominem. Otherwise, you would never bring up the idea that you are an expert in engineering and motion sensing and you wouldn't be talking about moderating Chinese forums, all of which have zero bearing on the argument being presented. I am just pointing out, as Feynmann realized when he tried to explain quantum physics to his father, that there are limits to what you can explain when someone doesnt have the prerequisite experiences.

I have explained what is meant by wrapping the ball and why it is good. The follow through is part of the stroke trajectory and the wrapping accentuates the turning effect while completing the stroke trajectory. You haven't shown the ability to understand and explain what you are criticizing. Till now, you still treat vectors as scalars and keep talking about speed being maximized meaning acceleration is no longer possible (which is only true if your focus is in one dimension). The quality of the reasoning is too poor to take it seriously. I can only generously assume it is driven by the fact you have no real experience with high level strokes.

Will let you have the final word, I am truly over this

 

[zeio]

Is there any info on when maximum acceleration of the stroke is achieved?

From the plots for the mid-far distance loop in that study:
Maximum acceleration in the forward direction happens from ~50ms to ~20ms before impact (-50ms to -20ms, 30ms in total), during which ~95% of the maximum velocity is reached;
Maximum acceleration in the upward direction happens from ~20ms before impact to ~5ms after impact (-20ms to +5ms, 25ms in total), during which (-20ms to 0ms) ~91% of the maximum velocity is reached.

Maximum acceleration is consistently higher in the forward direction than in the upward direction.