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The great China vs Euro loop myth
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Baal View Drop Down
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    Posted: 10/24/2012 at 3:59pm
My favorite players have always included WLQ (straight) and Gatien (extreme chicken wing).  I really focus more on how well these guys move in a more global sense, since that is by far the most important thing.  Among Chinese, WLQ and KLH played very differently, but they were both so graceful and fluid on their feet.  Awesome is an over-used word, but that is how I always regarded their footwork. (And for me, everything about WLQ in his prime). Samsonov is not blindingly fast, far from it (!), but he is always so amazingly relaxed that he nearly always plays a very solid shot in perfect balance.  I have always felt that people would be better off if they practiced mostly hitting loops and counters while having to constantly move to get to the ball, rather than how they move their arm.  If you're in the right place, the arm pretty much takes care of itself.  I noticed in China that's how they trained people.  Multiballs to exhaustion, and then their movements become economical and efficient.
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Originally posted by Baal Baal wrote:

  Also, as the body rotates, a movement of the elbow properly timed adds extra speed/spin to the ball.  If your arm is already fully extended, you can maybe get that extra zip from the shoulder, but those muscles are not as capable of fine controlled movement as the ones that control the elbow joint (and rotator cuff injuries are no fun). It is harder to time.  That of course is pure physiology.  Likelihood of badly hit ball increases.
  A good example of this tendency for bad misses due to mis-timing is Chen Qi, who has possibly the most extended arm swing of any player.  He can really spray some balls when he's off. Having said that, I personally prefer watching straight-arm loopers.
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Also his bat starts closer to his body. His body rotation/swing makes his arm go outward and stretch horizontal.
With enough swing of the upperbody the arm can be completely relaxed and allready have a proper trajektory for the bat because this also lifts the arm.
Something similar happens with old fashioned swing mills with seats hanging on longer wires. As the swingmill starts the seats go to a further radial distance and gain height with the rope more horizontal. Keeping the feet on the floor when the swingmill starts helps to increase the height and radius distance and accelleration at highest / furthest point is much higher.

For tabletennis bending the elbow would interfere with this because it brings the bat closer to the body.

Something I haven,t seen mentioned is the abillity of muscles to take over energy from other muscles and even gravity.

Muscles have a spring quality for this. For instance jumping as high as possible from stand it,s better result to start straight up, then go down and up. The action where the knees and hips bend tensons the muscles with energy from gravity. With some timing the muscles own energy adds to this with a much higher jump as result.

A swift body rotation/swing tensions the shoulder muscles for the longer arm in a similar way. The long arm is much more explosive from that.

Part of the swing action is even hidden. When the arm is relaxed the arm and bat move outward and gain height also. The energy for the swing finds an easy way out to the arm and bat. The  increase for moment of inertia counteracts the muscle action with almost no visible body swing as result. But when Ma long would do the same action except keep his play arm tight to his body  he would rotate as if he drank too much alcohol and be balanced.




Edited by mercuur - 10/24/2012 at 2:19pm

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Originally posted by V-Griper V-Griper wrote:

ML-
Ma Long's fh is somewhat unique and is, imho, a significant advancement in fh technique. I may off course be wrong, but I think the key to his fh, as well as his bh, is the use of his left arm. My ,hypothesis is that it acts as a counter weight when he pulls it in. The accelerated mass of his left arm applies a torque to the upper torso which then is directly applied to the right arm. Bending his left arm at the elbow condenses the mass. It's like firing a trebuchet.
...
Among other benefits this allows him to keep his arm relatively straight but not sacrifice as much swing speed/acceleration.

V-Griper, I didn't notice this until you pointed it out.  It does appear like Ma Long's left arm's action
adds more momentum to his forehand stroke.  As with finely tuned athletes, dancers, capoeira artists, 
martial artists and the like, some people have a highly developed body awareness/kinesthetic sense that
employ almost sub-conciously to the ends of their sport or art.  It is a joy to watch someone execute
with such fluid power and grace.
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I think when one does training with multiball or a robot set in sequence, one realize pretty quickly there is optimal and less than optimal ways of getting a good quality ball over the net.

Sometime you are too close and the paddle is right up against you body as you torque your upper body quickly to get the paddle over the ball.  Sometime you are too far away and your arm is completely straight at the elbow, requiring a snap of the wrist to generate enough topspin to land.

In a game, it is even more erratic.  But it is good to know the ideal for those easy balls that come your way every now and then for the text book pretty kill...Why else do we practice? If not to look good sometimes...lol.


Edited by power7 - 10/07/2012 at 9:05pm
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With a straighter arm, I find it easier to adjust the blade angle relative to my swing angle.

And about this forever unending debate/discussion, just understand what needs to happen and find YOUR way to try to make it happen, be it straight arm, bent arm, or double bent arm. Yes, TT as well as human physiology obey the principle of physics, but ultimately it's YOU who decides what works for you. Realize your limitations and stick with what you CAN do rather than chasing after THE ideal or perfect swing on paper and on the table.
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Originally posted by Baal Baal wrote:

Originally posted by pnachtwey pnachtwey wrote:


I don't need a model to tell me that mass that is rotating farther way from the center of rotation will have more inertia than mass that is rotating closer to the center of rotation.   If you twist your whole body the center of rotation becomes the COG, or close to it, of the body but the radius is larger and that increases the rotational inertia.  Also one must include the rotating the body.

The question all you have failed to ask is what is the optimal radius of rotation of the paddle?  The inertia goes up with the radius of the mass squared.   The velocity of the paddle goes up with the radius of rotation.



This is of course all correct, but those same rotational forces are also tending to cause the player to lose his/her balance -- in the worst case falling over -- so there is an optimum distance from the paddle and body and different players find their optimum at different degrees of elbow extension (ascertainable by simple observation).  Remember, good players expect the ball is coming back and they will need to hit another good shot.  Also, as the body rotates, a movement of the elbow properly timed adds extra speed/spin to the ball.  If your arm is already fully extended, you can maybe get that extra zip from the shoulder, but those muscles are not as capable of fine controlled movement as the ones that control the elbow joint (and rotator cuff injuries are no fun). It is harder to time.  That of course is pure physiology.  Likelihood of badly hit ball increases.
So go one step furth and talk about the difference between professional level players and amateurs.  Professionals use their training to develop strength and balance, hence it makes sense for them to seek more power with a straighter arm.  Amateurs, by comparison, suffer those problems that you mentioned: balance, fine motor control, and so on.  So if people are going to argue the merits of these two type of FH loops, they should distinguish according to the level of players they are discussing. 
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Originally posted by king_pong king_pong wrote:

Originally posted by Baal Baal wrote:

Originally posted by hallur hallur wrote:

 
The guy in the blue? That is the biggest understatement I've ever heard...


Yes.  It is a very dark blue.
 
LOLClap That was good! LOL
lol.... 

Anyway I'm starting to dislike labels like this, because it has many racial connotations. I find that most people become agitated when race is involved, and it ends up derailing the thread. Why not just call it a straight-arm loop and a bent-arm loop? That'll help to make the discussion much more objective, than calling Euro, Chinese, Hungarian, American loops.... there's no Swiss stroke in tennis nor is there any Indonesian/Malaysian/Chinese stroke in badminton...
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Originally posted by Baal Baal wrote:

Originally posted by hallur hallur wrote:

 
The guy in the blue? That is the biggest understatement I've ever heard...


Yes.  It is a very dark blue.
 
LOLClap That was good! LOL
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Originally posted by pnachtwey pnachtwey wrote:


I don't need a model to tell me that mass that is rotating farther way from the center of rotation will have more inertia than mass that is rotating closer to the center of rotation.   If you twist your whole body the center of rotation becomes the COG, or close to it, of the body but the radius is larger and that increases the rotational inertia.  Also one must include the rotating the body.

The question all you have failed to ask is what is the optimal radius of rotation of the paddle?  The inertia goes up with the radius of the mass squared.   The velocity of the paddle goes up with the radius of rotation.



This is of course all correct, but those same rotational forces are also tending to cause the player to lose his/her balance -- in the worst case falling over -- so there is an optimum distance from the paddle and body and different players find their optimum at different degrees of elbow extension (ascertainable by simple observation).  Remember, good players expect the ball is coming back and they will need to hit another good shot.  Also, as the body rotates, a movement of the elbow properly timed adds extra speed/spin to the ball.  If your arm is already fully extended, you can maybe get that extra zip from the shoulder, but those muscles are not as capable of fine controlled movement as the ones that control the elbow joint (and rotator cuff injuries are no fun). It is harder to time.  That of course is pure physiology.  Likelihood of badly hit ball increases.


Edited by Baal - 10/06/2012 at 2:58am
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I don't need a mathematical model to know that the habitual arm position during a forehand loop is different among several different former world champions and other great players, all of whom had incredible forehands.  It can be proved from youtube, and you know, actually watching good players and noticing that they aren't all the same.  This indicates that it is one of the less important things that go into making this particular shot. There are some things they all do. They all get a lot of rotation around their torso, and they all stay in perfect balance after their loops to get ready for the next shot, which is incredibly important in real rallies.  It's not hard to see that Schlager and Ma Long, for example, tend to have their arms pretty straight, Kong is more relaxed at the elbow, and Philou (and also Timo Boll) exemplifies the classic "chicken wing" position.   We can extend it to penholders.  Xiu Xin is usually more extended at the elbow and Wang Hao is generally more relaxed. Also some of these guys are Chinese and some aren't, not that it matters much.   pnacthwey, I was beginning to wonder if you could possibly be an even bigger ........., and you're not disappointing me. 
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[/quote]
So where is your model?   I don't need a model to notice that when a skater starts spinning and brings her arms in that she spins faster.  

Quote &
 yes bring the bat to your tummy and do the fastest loop, this is streamlining ((skater spinning) where table tennis is more like   tossing a discuss and the further away from you the faster your arm is going, The middle of a Ferris wheel is much slower
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Originally posted by Anderni Anderni wrote:

     Perhaps engineers should read up on physiology so they don't think this entire argument hinges (literally) on inertia.

  But your sentiment is understood and appreciated, pnachtwey. ;) Physics is an interesting subject but the laws need to be applied with some thought and consideration of what you're attempting to model. 

So where is your model?   I don't need a model to notice that when a skater starts spinning and brings her arms in that she spins faster.  

Quote My proposition is that you cannot model a TT athlete just by modeling objects in motion - you'd need to model the behavior of every muscle group and joint.
So where is your model?  If you don't have one then don't bother to criticize those that making the best estimates they can without one.  

I don't need a model to tell me that mass that is rotating farther way from the center of rotation will have more inertia than mass that is rotating closer to the center of rotation.   If you twist your whole body the center of rotation becomes the COG, or close to it, of the body but the radius is larger and that increases the rotational inertia.  Also one must include the rotating the body.

The question all you have failed to ask is what is the optimal radius of rotation of the paddle?  The inertia goes up with the radius of the mass squared.   The velocity of the paddle goes up with the radius of rotation.
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The left arm thing is perhaps a page from tennis FH mechanics. In tennis though, the primary functions for the left arm extension is balance and finding the contact zone.
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I think their may some confusion when some people see the the C players use a "bent arm loop"(BAL). The main difference is whether or not the arm remains at relative angle of 90' during the entire stroke cycle. The C players almost always start with a relatively straight arm, around 160' or so, then bend it, or not, as required or chosen for the stroke they want to execute. They can keep the arm straight for more power or snap the elbow closed when pressed for time and/or distance.  Applegren Persson and Waldner all executed this type of forehand to a greater or lesser degree. However Boll, Maze, Samsonov etc... all keep their arms bent throughout the entire stroke.

ML-
Ma Long's fh is somewhat unique and is, imho, a significant advancement in fh technique. I may off course be wrong, but I think the key to his fh, as well as his bh, is the use of his left arm. My ,hypothesis is that it acts as a counter weight when he pulls it in. The accelerated mass of his left arm applies a torque to the upper torso which then is directly applied to the right arm. Bending his left arm at the elbow condenses the mass. It's like firing a trebuchet.

Bent left arm=counter weight

Left shoulder= counter weight attachment to lever arm

Spine of upper back between shoulders= pivot/fulcrum

Right shoulder= attachment to rope

Right arm= rope

Right hand/paddle= sling




Among other benefits this allows him to keep his arm relatively straight but not sacrifice as much swing speed/acceleration.
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Originally posted by hallur hallur wrote:


The guy in the blue? That is the biggest understatement I've ever heard...


Yes.  It is a very dark blue.
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Originally posted by hallur hallur wrote:

Originally posted by Baal Baal wrote:

OK.  Ckeck out the guy in the blue withe the "Chinese loop" -- at least if you look at just his arm.



The guy in the blue? That is the biggest understatement I've ever heard...
 
Pretty good, "that guy in blue".  After he wins though, he acts as if he'd never won anything before, rolling all over on the floor like that. Wink  His "team in blue" seem really thrilled Wink


Edited by king_pong - 10/05/2012 at 2:57pm
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Originally posted by Baal Baal wrote:

OK.  Ckeck out the guy in the blue withe the "Chinese loop" -- at least if you look at just his arm.



The guy in the blue? That is the biggest understatement I've ever heard...
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OK.  Ckeck out the guy in the blue withe the "Chinese loop" -- at least if you look at just his arm.
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I think Baal has already hit the nail on the head... Its irrelevant what is the best way of doing something. What is relevant is the best way for an individual to achieve something. In simple terms what works for one person may not work for another so it is hard (and seriously naive) to assume any that x ball must always be hit with y stroke.
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Originally posted by Anderni Anderni wrote:

Originally posted by power7 power7 wrote:

As others have mention most of Wang Zeng Yi are drives over the top.  He does do brush loop under the table with a straight arm against underspin.


Also he is a penholder.  They can generate more spin from their wrist motion that shakehand holders cannot, so sometimes their looping swing is not as big as shakehand holders.

Usually not a good idea to compare Asian penholder's swing mechanics to Euro shakehand swing mechanics.  It's really apples and oranges.

I haven't been discussing spin. The post that I replied to (and then you replied to me) said " The same person will always have more power if he opens the arm in the elbow," which is what I've been trying to dispute. 

This is a very simple question, no need to complicate it by talking about Euro shakehanders or generating spin. ;)

Talking about muscle group utilization, how does keeping the arm straight allow your TT muscles to generate more power?  



Think baseball.  Fastest pitch come from those that can extend their arms the farthest in a controlled manner.  All just water filled levers.

You keep talking about "power."  What do you mean exactly?  In Newtonian physics terms?  Relativity?

When people extend their arms out they are usually exerting the most force to have the highest paddle speed (players observe themselves to be powerful).  But from the balls point of the view the paddle is moving twice as fast as the player thinks they are hitting the ball at (balls observe players to be twice as powerful).  From the wrist point of view the paddle is barely moving at all (the wrist thinks the player is a wimp).

You're making the false assumption that the people exert the same effort for all FH swings.  There is no conservation of angular momentum.  No one is going to spin on their toes with the paddle in their mouth to generate the fastest paddle speed to hit the TT ball.
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Originally posted by Anton Chigurh Anton Chigurh wrote:

[QUOTE=Anderni]

There is some important truth embedded in this humor that will be overlooked by some of the less talented and inflexible physicists. Fortunately, I have had the pleasure to know many highly talented physicists (and mathematicians) who are very aware of the limitations of their discipline and who are humble and responsible with its application. Smile

Hehe, well said. I see lots of evidence for the Dunning-Kruger effect from the less talented physicists on this forum. The more talented physicists and mathematicians that I know are well aware of their own limitations as well as the current limitations of their field.
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Originally posted by Anderni Anderni wrote:

...Physics is an interesting subject but the laws need to be applied with some thought and consideration of what you're attempting to model. 

My proposition is that you cannot model a TT athlete just by modeling objects in motion - you'd need to model the behavior of every muscle group and joint.

I agree, and your post reminds me of two funny things.

This:



And this joke, that I originally heard on this site but had to look it up online to remember all of it:

A group of wealthy investors wanted to be able to predict the outcome of a horse race. So they hired a group of biologists, a group of statisticians, and a group of physicists. Each group was given a year to research the issue. After one year, the groups all reported to the investors. The biologists said that they could genetically engineer an unbeatable racehorse, but it would take 200 years and $100 billion. The statisticians reported next. They said that they could predict the outcome of any race, at a cost of $100 million per race, and they would only be right 10% of the time. Finally, the physicists reported that they could also predict the outcome of any race, and that their process was cheap and simple. The investors listened eagerly to this proposal. The head physicist reported, "We have made several simplifying assumptions. First, let each horse be a perfect rolling sphere . . ."

There is some important truth embedded in this humor that will be overlooked by some of the less talented and inflexible physicists. Fortunately, I have had the pleasure to know many highly talented physicists (and mathematicians) who are very aware of the limitations of their discipline and who are humble and responsible with its application. Smile




Edited by Anton Chigurh - 10/04/2012 at 7:47pm
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     Perhaps engineers should read up on physiology so they don't think this entire argument hinges (literally) on inertia.  But your sentiment is understood and appreciated, pnachtwey. ;) Physics is an interesting subject but the laws need to be applied with some thought and consideration of what you're attempting to model. 

My proposition is that you cannot model a TT athlete just by modeling objects in motion - you'd need to model the behavior of every muscle group and joint.      

Edited by Anderni - 10/04/2012 at 3:07pm
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The loop is generated by the whole body, not just the arm.  After a player hits the loop, they need to be immediately ready for the next shot, which constrains what they can do.  It is obvious from watching real players that the extension of the elbow or not is not the important thing determining the success of the shot or the recovery since World Champions have had strokes that vary considerably in this respect.  And the ones with straighter arms are not all Chinese, dating back to Klampar at least.  Watch also video of Schlager or for that matter, Jorgen Persson on the forehand.  Compare to Kong Linghui or Gatien.  All of these are world champions.

Of course I don't expect these observations to trump overly simplistic theories for some people.   
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I can see you guys can have a good argument without me.

Originally posted by Anderni Anderni wrote:

Quote Let's say the swing took 1 second, just for simplicity. For this 1 second the arm concluded a 1/4 of a full rotation (90 degree swing)

No, you can't simplify human physiology like this. Even a fully fit TT athlete will not be able to make a straight arm 1/4 rotation in the same amount of time he/she uses to make a bent arm 1/4 rotation. The straight arm swing will take longer.

You two are talking past each other and not talking about the same thing. 

Anderni,  given his assumption that the extended and non-extend stroked will alway take 1 second, he is right.  However, that 1 second stroke is a very slow stroke and not energy or strength limited.

You are assuming that the strokes are made with the same amount of energy and very quickly ( high power ) and then you are right.   Why?

Quote Calculating physics is one thing. The problem is applying those physics to a human playing TT. Humans are not robots, we have a complex mix of muscle groups that cannot be modeled the way you do.

I think Anderni should look up inertia and how it is affect when the mass is moved away from the axis of rotation.  It may help him with his argument but that would require learning some physics.

Quote  How many physics classes do you think physiotherapists take?

Not enough.

Quote  It is a fact of human physiology that you can not reduce the behavior of human limbs to simple physics calculations.

True, people are not well defined shapes nor is the density of people consistent.  That makes doing calculations on people difficult but it certainly isn't hard to back your statement with a little physics.  How does the extension of the arm affect the rotational inertia?

 
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Originally posted by FireHorse FireHorse wrote:

To me, I think Gatien did not wait for the ball when in the rally.  I believe that he did wait for the ball when it was coming at him as backspin but once in fast rallies, Gatien topspined everything mostly on top-of-the-bounce.
 
I think the difference b/w Gatien and Wang Liqin is that Gatien staying closer to the table than Wang Liqin.  It could be that Wang Liqin is a little taller and uses straight arm loops while Gatien is a little bit shorter and uses bent arm loops.
 
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Should did edit instead of Post Reply to my original Post.  Sorry about that!

Edited by FireHorse - 10/04/2012 at 2:42pm
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To me, I think Gatien did not wait for the ball when in the rally.  I believe that he did wait for the ball when it was coming at him as backspin but once it's in the fast rally, Gatien topspin everything mostly on top-of-the-bounce.
 
I think the difference b/w Gatien and Wang Liqin is that Gatien staying closer to the table than Wang Liqin.  It could be that Wang Liqin is a little taller and uses straight arm loops while Gatien is a little bit shorter and uses bent arm loops.
 
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Originally posted by bonggoy bonggoy wrote:

Originally posted by Baal Baal wrote:


Two of mt all-time favorite players.  I don't think Gatien's euroloop lacked power (even if he is way past his prime in this clip).  Teen-aged WLQ, has just as much with his chinoloop, and he stays in better balance and wins.  By the way, this is from in the days when people didn't whinge about illegal hidden serves.


The big difference I saw is WLQ always going to the ball vs Gatien's waiting for the ball. Lexsha mentioned this in his post about point of contact. This resulted in WLQ being always in the offensive regardless of who initiated the attack.


I think that's right.  But that had nothing to do with arm position during the loop and more with footwork and mobility (and age difference when this video was made).  The Gatien of ten years earlier was more mobile than in this video, just hard to find good quality video of him then.  One thing for sure, he could rip the crap out of the ball.  Of course, this is also right about the time when WLQ was fast becoming IMHO the greatest shakehand player of all time.
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Quote Let's say the swing took 1 second, just for simplicity.

No, you can't simplify human physiology like this, and say that a fully fit TT athlete will make a straight arm 1/4 rotation in the same amount of time he/she uses to make a bent arm 1/4 rotation. 

Quote That same shot would have been even more powerful with an open arm, and this is not up for your approval and consideration, it is a fact of physics

You're attempting to model something as complex as a TT stroke, which uses a large number of muscles ranging from foot to wrist. And you're modeling it as if it's a mechanical joint powered by a single electrical motor.

You can't just assume that any given person will be able to swing his/her straight arm at the same speed as he/she can swing a bent arm.

Knowing the facts of physics is one thing. The problem is applying those physics to a human playing TT.




Edited by Anderni - 10/04/2012 at 2:51pm
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