Print Page | Close Window

Concave vs. Convex Loop (Which is which/better?)

Printed From: Alex Table Tennis - MyTableTennis.NET
Category: Pictures & Videos
Forum Name: Videos
Forum Description: Post table tennis video download information here.
Moderator: mickd
Assistant Moderators:

URL: http://mytabletennis.net/forum/forum_posts.asp?TID=51139
Printed Date: 09/20/2021 at 1:29am
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com


Topic: Concave vs. Convex Loop (Which is which/better?)
Posted By: king_pong
Subject: Concave vs. Convex Loop (Which is which/better?)
Date Posted: 06/21/2012 at 3:44am
      Not sure I'm following it when people use these terms.  I was wondering of someone could point me in the right direction.  
      I notice at least two distinct main looping styles of the CNT.  The first is an aggressive loop-drive, in which the hand starts low and ends very high with the blade vertical and very high above the head.  The crux of the elbow is often right in front of the nose on the follow-through (think Ma Long, Yan An, Fan Bo).  I consider this one to be "concave".  
      Then there is a loop which also starts low, but when the stroke terminates the blade ends more across the head horizontally, with the elbow pointed outwards, almost like they're throwing the ball rather than hitting it (think Wang Hao, Zhang Jike, Chen Qi).  Maybe this is more of a "pure-loop".  I consider this one to be the "convex".

      Two distinct styles (Ma Long vs. Chen Qi):
http://www.youtube.com/watch?v=1-8ECXb9n9w - http://www.youtube.com/watch?v=1-8ECXb9n9w

       It seems these two distinctive styles may have developed from two of the sports' and two China's most heralded players -- Kong Linghui and Liu Guoliang.  When I watch them in their video series -- "Excellent World Champions Teach You How To Play Table Tennis (16DVDs)", I noticed how different the two players' forehands were.  

      Kong Linghui "whipping hand/wrist loop"--
http://www.youtube.com/watch?v=ebNMGlBCd2U&feature=related#t=9m30s - http://www.youtube.com/watch?v=ebNMGlBCd2U&feature=related#t=9m30s  (Chinese)
http://www.youtube.com/watch?v=c5q0xdSwiXM&feature=related - http://www.youtube.com/watch?v=c5q0xdSwiXM&feature=related  (Chinese)
http://www.youtube.com/watch?v=rszTmfzdluY&feature=related#t=05m11s - http://www.youtube.com/watch?v=rszTmfzdluY&feature=related#t=05m11s  (Japanese)

      Liu Guoliang "driving loop"--
http://www.youtube.com/watch?v=YL3j8wJnH4Q&feature=results_video&playnext=1&list=PLC2C1B5656A6B4262#t=25m46s - http://www.youtube.com/watch?v=YL3j8wJnH4Q&feature=results_video&playnext=1&list=PLC2C1B5656A6B4262#t=25m46s

      I understand that Guoliang was more of a hitter, while Kong was a pure looper, but Guoliang's style (what I believe to be the "Concave-style FH") seems to be emerging as the more dominant top-spinning FH amongst today's CNT shakehanders, with its more open striking of the ball and elliptical path of the recovery arm.  
      Maybe someone could speak to this, explaining this for this for those of us who are a bit newer to the game.  Might spare from trying to mimic extinct or outgoing FH technique styles.  Thank you.  Smile



Replies:
Posted By: doraemon
Date Posted: 06/21/2012 at 3:49am
Sorry, but when I read "concave" vs "convex" loop, I am immediately terrified that "person" is back with haunting threads.....   Smile

All of you know who I meant......

Sorry King_Pong, for the irrelevant reply....


Posted By: kenneyy88
Date Posted: 06/21/2012 at 3:50am
I don't think many pros do any of these anymore. Closest thing is like Ma long swinging up, then on followthrough he closes the racket face.


Posted By: king_pong
Date Posted: 06/21/2012 at 5:30am
Originally posted by kenneyy88 kenneyy88 wrote:

I don't think many pros do any of these anymore. Closest thing is like Ma long swinging up, then on followthrough he closes the racket face.

Do "which" anymore?  Can you elaborate?  Thank you.


Posted By: zeio
Date Posted: 06/21/2012 at 6:32am
This is in fact a legit topic worth digging for.

The Japanese magazine http://www.world-tt.com/ - 桌球王国 World Table Tennis has published articles regarding the differences in the loop stroke when playing tacky and grippy rubbers.

It is claimed that the grazing loop stroke is more suited for tacky rubbers, whereas the hitting loop stroke is suitable for high tension or tensor rubbers.

A picture of Wang Liqin pulling off a loopkill is even included.

Parts of those articles have been in wide circulation among various forums.
http://www.pingpang.info/bbs/dispbbs.asp?id=215087&authorid=83433&boardid=2 - http://www.pingpang.info/bbs/dispbbs.asp?id=215087&authorid=83433&boardid=2
http://www.pingpang.info/bbs/TopicOther.asp?t=5&BoardID=235&id=201008 - http://www.pingpang.info/bbs/TopicOther.asp?t=5&BoardID=235&id=201008
http://sundns.org/discuZ/viewthread.php?action=printable&tid=266525 - http://sundns.org/discuZ/viewthread.php?action=printable&tid=266525

-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: popperlocker
Date Posted: 06/21/2012 at 6:43am
Depends on your equipment and physical attributes. The CNT members all use slightly different body mechanics. The only person that can answer your question is yourself. Try out both concave and convex and decide which one you like better. 
Some rubbers are great for concave looping and others for convex looping. So it depends what you're using too. 
As I was watching your example video, I feel it's a crime to classify the CNT members as convex or concave. I view it more complex than that, like walking. Every person walks a little different, because they have different: body weights, height, muscles, bone structure, training, influences, handicaps, injuries, abnormalities, personalities, mood, etc. 


Posted By: JohnnyChop
Date Posted: 06/21/2012 at 10:44am
Isn't LGL short pip forhand? That would definitely change the stroke!!!

-------------
Nittaku Fastarc G1 Butterfly Cypress Max


Posted By: king_pong
Date Posted: 06/21/2012 at 10:58am
Originally posted by zeio zeio wrote:

This is in fact a legit topic worth digging for.

The Japanese magazine http://www.world-tt.com/ - 桌球王国 World Table Tennis has published articles regarding the differences in the loop stroke when playing tacky and grippy rubbers.

It is claimed that the grazing loop stroke is more suited for tacky rubbers, whereas the hitting loop stroke is suitable for high tension or tensor rubbers.

A picture of Wang Liqin pulling off a loopkill is even included.

Parts of those articles have been in wide circulation among various forums.
http://www.pingpang.info/bbs/dispbbs.asp?id=215087&authorid=83433&boardid=2 - http://www.pingpang.info/bbs/dispbbs.asp?id=215087&authorid=83433&boardid=2
http://www.pingpang.info/bbs/TopicOther.asp?t=5&BoardID=235&id=201008 - http://www.pingpang.info/bbs/TopicOther.asp?t=5&BoardID=235&id=201008
http://sundns.org/discuZ/viewthread.php?action=printable&tid=266525 - http://sundns.org/discuZ/viewthread.php?action=printable&tid=266525

That's great, but what do these threads say?  I saw in the last one that it appeared that they were addressing the issue of blade angle during the stroke (either closing or opening).  It appeared that they were implying that the closing-stroke made a lower trajectory, but I couldn't read the text.  Can you translate? Smile


Posted By: Leshxa
Date Posted: 06/21/2012 at 11:20am
I think this will help a lot. Look at the section 14.

http://protabletennis.net/content/mechanics-table-tennis


-------------
Back to table tennis...


Posted By: racquetsforsale
Date Posted: 06/21/2012 at 11:56am
I think the concave and convex trajectories occur naturally --- the more you swing forward and less upward, the more convex ("positive" arc in the article Leshxa referenced) your swing is; and the more you swing upward and less forward the more concave ("negative" arc) your swing is.

You probably already use the concave stroke when brush looping against underspin and the convex stroke when looping against topspin close to the table. 


Posted By: king_pong
Date Posted: 06/21/2012 at 3:08pm
Originally posted by Leshxa Leshxa wrote:

I think this will help a lot. Look at the section 14.

http://protabletennis.net/content/mechanics-table-tennis


Thank you.  This is very informative.  The author definitely knows what he is talking about.  It is a little bit over my head, but I will read it more than once. 

      I think I've trained in a FH stroke that follows the negative-arc trajectory, but have recently become aware that many powerful top pros' FHs follow a more positive-arc (Ma Long being the most outstanding).  I'm experimenting with that stroke trajectory now.  It seems to be a more powerful FH, with the additional benefit of recovering to a more neutral position for a possible backhand should the opponent force the situation.  The article mentions the importance of stroke recovery, but does not specify which stroke arc is to be preferred for that.  I feel that the positive-arc gives the best advantage for a potential follow-up backhand. 




Posted By: racquetsforsale
Date Posted: 06/21/2012 at 4:29pm
Originally posted by zeio zeio wrote:

It is claimed that the grazing loop stroke is more suited for tacky rubbers, whereas the hitting loop stroke is suitable for high tension or tensor rubbers. 
 
This seems to go against the perception that most Chinese players drive or hit through the ball more than their European counterparts when looping. Even a famous Chinese coach has stated the same thing.


Posted By: king_pong
Date Posted: 06/21/2012 at 6:41pm
Originally posted by racquetsforsale racquetsforsale wrote:

Originally posted by zeio zeio wrote:

It is claimed that the grazing loop stroke is more suited for tacky rubbers, whereas the hitting loop stroke is suitable for high tension or tensor rubbers. 
 
This seems to go against the perception that most Chinese players drive or hit through the ball more than their European counterparts when looping. Even a famous Chinese coach has stated the same thing.


I think the statement is correct -- that it is easier to get a blistering brush-loop with tacky rubber, while bouncy-grippy rubber more easily facilitates a loop-drive -- but since it is possible to do either with either rubber, the CNT has discovered that driving with their harder-tackier rubber is, for some reason, better than the traditional brush-looping.  Perhaps it is the arc that it produces, outlined in the article that Lexsha posted above -- http://protabletennis.net/content/mechanics-table-tennis - http://protabletennis.net/content/mechanics-table-tennis .


Posted By: zeio
Date Posted: 06/22/2012 at 8:38am
Originally posted by king_pong king_pong wrote:

Originally posted by zeio zeio wrote:

This is in fact a legit topic worth digging for.

The Japanese magazine http://www.world-tt.com/ - 桌球王国 World Table Tennis has published articles regarding the differences in the loop stroke when playing tacky and grippy rubbers.

It is claimed that the grazing loop stroke is more suited for tacky rubbers, whereas the hitting loop stroke is suitable for high tension or tensor rubbers.

A picture of Wang Liqin pulling off a loopkill is even included.

Parts of those articles have been in wide circulation among various forums.
http://www.pingpang.info/bbs/dispbbs.asp?id=215087&authorid=83433&boardid=2 - http://www.pingpang.info/bbs/dispbbs.asp?id=215087&authorid=83433&boardid=2
http://www.pingpang.info/bbs/TopicOther.asp?t=5&BoardID=235&id=201008 - http://www.pingpang.info/bbs/TopicOther.asp?t=5&BoardID=235&id=201008
http://sundns.org/discuZ/viewthread.php?action=printable&tid=266525 - http://sundns.org/discuZ/viewthread.php?action=printable&tid=266525

That's great, but what do these threads say?  I saw in the last one that it appeared that they were addressing the issue of blade angle during the stroke (either closing or opening).  It appeared that they were implying that the closing-stroke made a lower trajectory, but I couldn't read the text.  Can you translate? Smile

For a start, the first two threads are reviews done by a renowned reviewer from Taiwan under the name of http://ooakforum.com/viewtopic.php?p=133655#p133655 - 桂花田 .  He often cites material from that magazine to support his assertions.  While I find most of those insights informative, certain portrayals within those articles are exaggerated and hence not representative of what is really taking place in reality.  The picture in which the lady demonstrates the service motion where the ball literally rolls over the rubber from end to end is one such depiction, as opposed to http://www.youtube.com/watch?v=fJb38EPOy00&feature=player_detailpage#t=32s - this real-world example .

The last one is about how the thread starter feels the European stranglehold on the forehand loop stroke is ruined at the hands of the current crop of loopers, e.g. Boll, Maze etc.  He uses the tacky/grippy image to help illustrate that their having the blade face parallel with the endline of the table as the root cause of poor power and jerky transition, as opposed to the angled contact of the Chinese, when seen from the side.  Yet, the picture of Wang Liqin's loopkill clearly shows otherwise.  What the OP fails to take into account is the fact that different situations call for different strokes.  Shot placement, contact point, body stance and so on all have an effect on one's swing.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: Imago
Date Posted: 06/22/2012 at 10:24am
Quote Explosive speed is an inherited characteristic
 
Kind of eugenic/rasist statement.


Posted By: zeio
Date Posted: 06/22/2012 at 12:46pm
Originally posted by king_pong king_pong wrote:

Originally posted by racquetsforsale racquetsforsale wrote:

Originally posted by zeio zeio wrote:

It is claimed that the grazing loop stroke is more suited for tacky rubbers, whereas the hitting loop stroke is suitable for high tension or tensor rubbers. 
 
This seems to go against the perception that most Chinese players drive or hit through the ball more than their European counterparts when looping. Even a famous Chinese coach has stated the same thing.


I think the statement is correct -- that it is easier to get a blistering brush-loop with tacky rubber, while bouncy-grippy rubber more easily facilitates a loop-drive -- but since it is possible to do either with either rubber, the CNT has discovered that driving with their harder-tackier rubber is, for some reason, better than the traditional brush-looping.  Perhaps it is the arc that it produces, outlined in the article that Lexsha posted above -- http://protabletennis.net/content/mechanics-table-tennis - http://protabletennis.net/content/mechanics-table-tennis .

I can understand where racquetsforsale is coming from.  Liu Guozheng has been quoted for commenting on Chen Qi having more of a wrapping motion than other players, yet he happens to generate more power than would have been thought possible.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: racquetsforsale
Date Posted: 06/22/2012 at 12:57pm
This is what I'm referring to: Wu Jing Ping on the FH; at the end of the article, he mentions that Chinese players tend to brush more because they use tacky rubbers, as opposed to their European counterparts who drive more with their grippy and elastic rubbers.

http://www.mytabletennis.net/forum/forum_posts.asp?TID=33003&PN=1&title=national-coach-wu-jingping-on-chinese-fh - http://www.mytabletennis.net/forum/forum_posts.asp?TID=33003&PN=1&title=national-coach-wu-jingping-on-chinese-fh




Posted By: V-Griper
Date Posted: 06/22/2012 at 1:37pm
I may be wrong but it seems to me that the the curve of the stroke, and the relatively closed or open paddle condition, is largely determined by where the ball is taken off the bounce. 

If you take the ball early, anywhere up to, and including, slightly after TOB (top of bounce) and the ball is above net height, I think it would be preferable to have "positive" arc loop stroke and emphasize a relatively closed paddle face. It also facilitates over the table looping. 

If the ball is taken much after TOB and below net height it would then be preferable to use the "negative" arc loop stroke with a more open paddle face. The arc of the ball as it descends requires a more vertical "lifting" action. Also, of course, when you are stroking underspin.

Of course each individuals adjustment is different.


 Mechanics of Table Tennis


Examples-

Positive arc







Negative arc







Posted By: king_pong
Date Posted: 06/22/2012 at 6:51pm
Excellent point, excellent post, V-griper!  Thanks.  I think you're right.  Smile

Originally posted by V-Griper V-Griper wrote:

I may be wrong but it seems to me that the the curve of the stroke, and the relatively closed or open paddle condition, is largely determined by where the ball is taken off the bounce. 

If you take the ball early, anywhere up to, and including, slightly after TOB (top of bounce) and the ball is above net height, I think it would be preferable to have "positive" arc loop stroke and emphasize a relatively closed paddle face. It also facilitates over the table looping. 

If the ball is taken much after TOB and below net height it would then be preferable to use the "negative" arc loop stroke with a more open paddle face. The arc of the ball as it descends requires a more vertical "lifting" action. Also, of course, when you are stroking underspin.

Of course each individuals adjustment is different.


 Mechanics of Table Tennis


Examples-

Positive arc







Negative arc







Posted By: zeio
Date Posted: 06/23/2012 at 8:48am
Originally posted by racquetsforsale racquetsforsale wrote:

This is what I'm referring to: Wu Jing Ping on the FH; at the end of the article, he mentions that Chinese players tend to brush more because they use tacky rubbers, as opposed to their European counterparts who drive more with their grippy and elastic rubbers.

http://www.mytabletennis.net/forum/forum_posts.asp?TID=33003&PN=1&title=national-coach-wu-jingping-on-chinese-fh - http://www.mytabletennis.net/forum/forum_posts.asp?TID=33003&PN=1&title=national-coach-wu-jingping-on-chinese-fh



Wu Jingping's article, at the time of writing(2005 as indicated by one http://pingpongworld.friendhood.net/t33-topic - source ), did point out that the forehand loop of Chinese penholders lacked power, a trait common among players owing to the short-pips hitter style.  And so he had made it a first priority and had forced Wang Hao and Ma Lin to practice hitting harder.

The notion that the Chinese hit harder probably first took root a decade ago along with Wang Liqin's first claim of the WTTC title.  Duan Xiang(段翔), deputy director of R&D of the CTTA, uses the term " http://mil.eastday.com/epublish/gb/paper97/20010828/class009700008/hwz388001.htm - 扭轉爆發鞭沖技術(Rotation-induced Explosion Whip-like [Forward"> Loop Technique, literally) " to separate Wang Liqin's forehand loop from the rest whom he describes as "加速制動擺沖技術(Acceleration-Braking Pendulum-like [Forward] Loop Technique)".  The latter is likely an extension to the term " http://www.datangtt.com/dv_rss.asp?s=xhtml&boardid=3&id=11858&page=19&star=1&count=15 - 加速制動(Acceleration-Braking) ", first coined by Zhuang Zedong, who takes a minimalistic approach to stroke mechanics where great emphasis is placed on maximizing acceleration before contact and brakes to a halt as soon as the ball takes off to reduce the time of recovery.  According to Duan's words, what sets Wang Liqin apart is the unique[at that time] http://uconnsportsmed.uchc.edu/injury/prevention/kinetic_chain.html - kinetic chain he uses to harness the rotational kinetic energy by coupling the arm, waist, crotch and so on.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: bluebucket
Date Posted: 06/23/2012 at 9:44am
There is no such thing as a convex or concave loop, if you have the spare time and muscles to make that shape movement when looping you are simply doing it wrong.


Posted By: mikepong
Date Posted: 06/23/2012 at 9:57am
Originally posted by V-Griper V-Griper wrote:

I may be wrong but it seems to me that the the curve of the stroke, and the relatively closed or open paddle condition, is largely determined by where the ball is taken off the bounce. 

If you take the ball early, anywhere up to, and including, slightly after TOB (top of bounce) and the ball is above net height, I think it would be preferable to have "positive" arc loop stroke and emphasize a relatively closed paddle face. It also facilitates over the table looping. 

If the ball is taken much after TOB and below net height it would then be preferable to use the "negative" arc loop stroke with a more open paddle face. The arc of the ball as it descends requires a more vertical "lifting" action. Also, of course, when you are stroking underspin.

Of course each individuals adjustment is different.


 Mechanics of Table Tennis


Examples-

Positive arc







Negative arc






wow thanx man, i really didnt understand what we were talking about here until i saw the illustration,  and i agree that the choice of loop depends on what ball is coming to you


-------------
Viscaria

FH: Tenergy 05 black

BH: Tenergy 05 red





Posted By: zeio
Date Posted: 06/23/2012 at 1:21pm
For those who have chosen to jump to conclusions, I invite them to answer the following question.

Given two balls released from the top at the same time, which one reaches the bottom in the shortest time, Red or Green? Why?

Which_one_reaches_the_bottom_first_Red_or_Green


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: vvk1
Date Posted: 06/23/2012 at 1:41pm
A famous English dude figured this out in 1696 :-)


Posted By: V-Griper
Date Posted: 06/23/2012 at 6:50pm
Originally posted by zeio zeio wrote:

For those who have chosen to jump to conclusions, I invite them to answer the following question.

Given two balls released from the top at the same time, which one reaches the bottom in the shortest time, Red or Green? Why?

Which_one_reaches_the_bottom_first_Red_or_Green

Sliding or rolling? Friction?

Off the cuff I would say green(if they are rolling, or sliding with no friction). Larger initial acceleration(linear and rotational) in the beginning and greater momentum and inertia at the end to maintain velocity. The green ball is accelerating/moving/rolling a lot faster.

You will have to explain the relevance. I don't get it. 


Posted By: pnachtwey
Date Posted: 06/23/2012 at 8:56pm
Originally posted by bluebucket bluebucket wrote:

There is no such thing as a convex or concave loop, if you have the spare time and muscles to make that shape movement when looping you are simply doing it wrong.
I think it is impossible to avoid convex or concave loops because our arm rotate around sockets.  However, I I agree you are probably doing it wrong if you have much of a convex or concave loop.  If your timing isn't perfect the ball will go low or high if you paddle attitude is changing during the stroke.   I try to keep the attitude of my paddle constant during the time that impact can occur and my swing in a plane so that my stroke is not as timing dependent.    If I hit the ball a millisecond early or late it won't make any difference.

I find this thread amusing.  So those of you that argue one way or another,  how do you justify your statements?   How can you justify the potential errors due to the ball hitting a few millisecond earlier or latter?   What difference does a 0.1 degree difference in the paddle attitude make over 3 meters or more?

I also know that the ball doesn't care about the stroke leading up to and after impact.  Only the attitude and rate of change in attitude of the paddle make a difference as well as the stoke and rate of change in the stroke directions DURING the stroke make a difference.  



-------------
I TT therefore I am


Posted By: BH-Man
Date Posted: 06/23/2012 at 9:06pm
Originally posted by zeio zeio wrote:

For those who have chosen to jump to conclusions, I invite them to answer the following question.

Given two balls released from the top at the same time, which one reaches the bottom in the shortest time, Red or Green? Why?

Which_one_reaches_the_bottom_first_Red_or_Green
 
 
Good comparison. Red ball has shorter path to go to finish and has constant acelleration if friction is a non-factor. Green ball has a longer path, but achieves higher velocity before halfway point.


-------------
Korea Foreign Table Tennis Club
Search for us on Facebook: koreaforeignttc


Posted By: icontek
Date Posted: 06/23/2012 at 10:37pm
Originally posted by pnachtwey pnachtwey wrote:


I also know that the ball doesn't care about the stroke leading up to and after impact.  Only the attitude and rate of change in attitude of the paddle make a difference as well as the stoke and rate of change in the stroke directions DURING the stroke make a difference.  


I understand what you are saying, I think...

But why then does followthrough make so much difference in consistency, power and placement of a stroke?

For example:
Takie a mid distance BH topspin, with the backswing from the hip, rotation from the leading shoulder, and uncoiling of the core while contacting the ball in front into a big followthrough that ends with the arm high, out to the right (assuming right handed)...

Why does the larger arc (relative to a smaller backswing and smaller followthrough) require less adjustment against incoming spin?

In other words, why do bigger mechanics seem to ignore incoming spin more than smaller mechanics?

Is it because there is a larger section of the arc where a "reasonably good shot" is possible?


-------------
http://bit.ly/vLMhuB" rel="nofollow - - RC1042 . Virtuoso AC : K1 + EL-P


Posted By: IllSonny
Date Posted: 06/23/2012 at 10:44pm
I gotta say, as a rookie player, this is the most interesting thread I ever read... Sorry for the off topic post... :)

-------------
Stiga Infinity VPS Legend
H3
Galaxy Moon


Posted By: pnachtwey
Date Posted: 06/23/2012 at 11:53pm
Originally posted by icontek icontek wrote:

Originally posted by pnachtwey pnachtwey wrote:


I also know that the ball doesn't care about the stroke leading up to and after impact.  Only the attitude and rate of change in attitude of the paddle make a difference as well as the stoke and rate of change in the stroke directions DURING the stroke make a difference.  


I understand what you are saying, I think...

But why then does followthrough make so much difference in consistency, power and placement of a stroke?
Easy.  If the paddle is going to maintain the same attitude and speed during the stroke then you can't change anything until AFTER impact.  After impact it is best to get back to the ready position.

Quote
For example: 
Takie a mid distance BH topspin, with the backswing from the hip, rotation from the leading shoulder, and uncoiling of the core while contacting the ball in front into a big followthrough that ends with the arm high, out to the right (assuming right handed)...
Yes,  but that is due to the limitations on how fast you can decelerate the paddle AFTER the impact.

Quote
Why does the larger arc (relative to a smaller backswing and smaller followthrough) require less adjustment against incoming spin?
I am not sure what you mean.  I don't think the length of the arc has much do do with being less sensitive to the spin except for the fact it is easier to move the paddle forward faster with a bigger stroke.  It requires less acceleration and deceleration.    Spin causes the ball to move tangentially to the ball impact.   The impact itself causes the ball to 'reflect' off the paddle.   Assume the ball is hitting the paddle straight on or normal to the paddle and there is spin on it.   The ball will spin off to the side at a certain rate.   If if spins off to the side at the same rate it bounces back in the normal direction the ball will bounce off the paddle at an angle of 45 degrees.   Now what if the ball hits with the same spin but you hit the ball so the ball is returning 10 times faster in the normal direction.   Then the paddle angle will be only 5.7 degrees from normal.  ATAN(normal speed/tangential speed)  It is the same principle behind why faster paddles have lower 'throw angles', but it really depends on how fast you hit the ball.

Quote
In other words, why do bigger mechanics seem to ignore incoming spin more than smaller mechanics?
No it is simple vector trigonometry.   

Quote
Is it because there is a larger section of the arc where a "reasonably good shot" is possible?
No,  it is simply that hitting the ball faster means the spin has less effect on the angle of return.   If you could hit the ball infinitely fast the spin would have almost no effect on the return angle of the ball.   I think there are many that intuitively realize this when they say 'hit through spin'.



-------------
I TT therefore I am


Posted By: V-Griper
Date Posted: 06/24/2012 at 1:18am
Here is WLQ counter hitting. He is clearly guiding his paddle in a modified circular path. I say modified because the take back is like a semi circle but the forward part is flattened out. 



Again. This time the well referenced ML slow mo FH.  Similar motion. Starting from the ready position. Paddle goes down, then back beside the right knee. Then slightly up and then flattens out as it moves forward into the ball.



So the question is why do a circular motion at all? Why not do more of a straight back and strait forward motion? 

Like this.



Or this.



Iwill grant you that Timo and BP are still making a slightly squashed oval, albeit slight, but it looks nothing like what WLQ and ML are doing.

Some related questions-
Why is ML's elbow so close to the body on the take back? why does the paddle usually stop beside the knee? Why does ML's knee seem to collapse inward slightly?(So does RSM's btw  https://www.youtube.com/watch?v=RMVzq-OnBcM&feature=player_embedded - https://www.youtube.com/watch?v=RMVzq-OnBcM&feature=player_embedded )


I am interested in peoples opinions. 

P.S. Please refrain from playing the "Chinese vs Euro" card. It gets old. I want you guys to think not recycle arguments.




Posted By: power7
Date Posted: 06/24/2012 at 1:33am
Because ML elbows are at a fixed angle when he is loop driving.  So the forward rotation is done with the shoulders.  They are taught to use the shoulder as major pivot point of their swing, not the elbow.

TB flexes his elbow more during the swing for forward motion.  That's why his stroke seems more linear in the video following the same path hitting and retracting.




-------------
DHS PG-7, H3 Neo, 729-5

Butterfly Power-7, Red TG2 Neo 39degree, Black Donic Bluefire M1


Posted By: V-Griper
Date Posted: 06/24/2012 at 2:16am
Originally posted by power7 power7 wrote:

Because ML elbows are at a fixed angle when he is loop driving. 
I would not say "fixed" because he does straighten his arm on occasion. Even in the vid he flexes his arm. slightly but I get your point.

 So the forward rotation is done with the shoulders. 
I would say the whole torso is involved in this action, but gain I see your point.

So your answer to my question is, that is what they were taught. 

Maybe I need to clarify my question. 

I understand how they got their stroke mechanics. What I want to know is why. Why use the shoulder as a pivot point instead of the elbow? 

If you are a coach, and you are teaching young kids how to hit the ball, why would yoou have them do it one way over another? Are they both equally valid ways of hitting the ball? What set of advantages/disadvantages are there?

 




Posted By: power7
Date Posted: 06/24/2012 at 2:52am
I've had a few different coaches that span many different points in my life.  PRC coaches teaches the basic FH that way.  Mostly, shoulder movement.  They don't say lock the elbow, but it just happens, to give more control over the ball, if you pivot with mostly shoulder movement.

Other coaches I've had never really emphasize the stroke Mechanic like that.  Mostly emphasize stiff wrist for control.

As for why?  More powerful muscle group.  Less chance of crossing body with that swing.  Maybe carried over from taichi principles (guess?).  But that's what PRC system teaches.

Or maybe kids start so young there they need to use more shoulder to get blade over the table?



-------------
DHS PG-7, H3 Neo, 729-5

Butterfly Power-7, Red TG2 Neo 39degree, Black Donic Bluefire M1


Posted By: popperlocker
Date Posted: 06/24/2012 at 4:34am
Originally posted by V-Griper V-Griper wrote:

Here is WLQ counter hitting. He is clearly guiding his paddle in a modified circular path. I say modified because the take back is like a semi circle but the forward part is flattened out. 



Again. This time the well referenced ML slow mo FH.  Similar motion. Starting from the ready position. Paddle goes down, then back beside the right knee. Then slightly up and then flattens out as it moves forward into the ball.



So the question is why do a circular motion at all? Why not do more of a straight back and strait forward motion? 

Like this.



Or this.



Iwill grant you that Timo and BP are still making a slightly squashed oval, albeit slight, but it looks nothing like what WLQ and ML are doing.

Some related questions-
Why is ML's elbow so close to the body on the take back? why does the paddle usually stop beside the knee? Why does ML's knee seem to collapse inward slightly?(So does RSM's btw  https://www.youtube.com/watch?v=RMVzq-OnBcM&feature=player_embedded - https://www.youtube.com/watch?v=RMVzq-OnBcM&feature=player_embedded )


I am interested in peoples opinions. 

P.S. Please refrain from playing the "Chinese vs Euro" card. It gets old. I want you guys to think not recycle arguments.



If you've played with both a tacky chinese rubber and Tenergy 05, you will understand. 


Posted By: hobbes203
Date Posted: 06/24/2012 at 5:20am
@Zeio

Couldn't resist answering that question, both objects are of the same mass and has the same qualities (same kinetic and static friction, etc), and the ramps are also equivalent, then both would hit the bottom at the same time whether they slide or roll. Easiest way to do this is energy, but I'll leave it at that.

The important question is what are the accelerations of the objects at the bottom? (Answer should be a vector quantity, magnitude and direction).

Given a very, very general scenario, the comparison of the balls at the bottom of the ramp can be applied to the moment a table tennis ball at a fixed point is contacted by the concave and convex strokes. At this point, I won't try to get into springs, torque, friction, and the magnus effect. Generally, the ballistics of the ball is determined by the magnitude and acceleration at different contacts of a controlled ball. 

I'm no expert but really just try the strokes for yourself, have a robot hit one spot and hit the ball at the same spot with controlled similar-accelerated but different swings.

Also pnachtwey +1 from me Big smile


Posted By: zeio
Date Posted: 06/24/2012 at 6:47am
Originally posted by vvk1 vvk1 wrote:

A famous English dude figured this out in 1696 :-)

It is obvious, isn't it?  I bet he must both be kicking in his coffin and having a good laugh, to see that human nature has not changed all that much since his time.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: zeio
Date Posted: 06/24/2012 at 6:56am
Originally posted by V-Griper V-Griper wrote:

Originally posted by zeio zeio wrote:

For those who have chosen to jump to conclusions, I invite them to answer the following question.

Given two balls released from the top at the same time, which one reaches the bottom in the shortest time, Red or Green? Why?

Which_one_reaches_the_bottom_first_Red_or_Green

Sliding or rolling? Friction?

Off the cuff I would say green(if they are rolling, or sliding with no friction). Larger initial acceleration(linear and rotational) in the beginning and greater momentum and inertia at the end to maintain velocity. The green ball is accelerating/moving/rolling a lot faster.

You will have to explain the relevance. I don't get it. 

Doesn't matter whether there is friction or not.  The end result is the same.

You are correct in picking the green, but you may be surprised to know that the acceleration of the ball down the path is actually constant.  The mass and thus inertia of the ball also does not have any effect on its speed, as evidenced by the http://en.wikipedia.org/wiki/Brachistochrone_curve#Johann_Bernoulli.27s_solution - conservation of energy .  It just so happens that the curve produces the best speed from the acceleration due to gravity.

The curve seen in the image is referred as the Brachistochrone curve, which is Greek for "the shortest time."  The brachistochrone curve happens to be a segment of an inverted cycloid.  Before the brachistochrone was solved, the closely related Tautochrone curve, meaning "same time," was found to be part of a cycloid also. 









For those who are still reading:

The brachistochrone problem was first posed by Johann Bernoulli, in which a point is to start from rest at point a and, solely under the effect of gravity, follow down to point b along a curve that is to be covered in the least time.

Quote http://www-history.mcs.st-and.ac.uk/HistTopics/Brachistochrone.html - The brachistochrone problem was posed by Johann Bernoulli in Acta Eruditorum in June 1696. He introduced the problem as follows:-

    I, Johann Bernoulli, address the most brilliant mathematicians in the world. Nothing is more attractive to intelligent people than an honest, challenging problem, whose possible solution will bestow fame and remain as a lasting monument. Following the example set by Pascal, Fermat, etc., I hope to gain the gratitude of the whole scientific community by placing before the finest mathematicians of our time a problem which will test their methods and the strength of their intellect. If someone communicates to me the solution of the proposed problem, I shall publicly declare him worthy of praise.

The problem he posed was the following:-

    Given two points A and B in a vertical plane, what is the curve traced out by a point acted on only by gravity, which starts at A and reaches B in the shortest time.

...

Johann Bernoulli was not the first to consider the brachistochrone problem. Galileo in 1638 had studied the problem in his famous work Discourse on two new sciences. His version of the problem was first to find the straight line from a point A to the point on a vertical line which it would reach the quickest. He correctly calculated that such a line from A to the vertical line would be at an angle of 45 reaching the required vertical line at B say.


He calculated the time taken for the point to move from A to B in a straight line, then he showed that the point would reach B more quickly if it travelled along the two line segments AC followed by CB where C is a point on an arc of a circle.


Although Galileo was perfectly correct in this, he then made an error when he next argued that the path of quickest descent from A to B would be an arc of a circle - an incorrect deduction.


Quote http://mathworld.wolfram.com/BrachistochroneProblem.html - The brachistochrone problem was one of the earliest problems posed in the calculus of variations. Newton was challenged to solve the problem in 1696, and did so the very next day (Boyer and Merzbach 1991, p. 405). In fact, the solution, which is a segment of a cycloid, was found by Leibniz, L'Hospital, Newton, and the two Bernoullis. Johann Bernoulli solved the problem using the analogous one of considering the path of light refracted by transparent layers of varying density (Mach 1893, Gardner 1984, Courant and Robbins 1996). Actually, Johann Bernoulli had originally found an incorrect proof that the curve is a cycloid, and challenged his brother Jakob to find the required curve. When Jakob correctly did so, Johann tried to substitute the proof for his own (Boyer and Merzbach 1991, p. 417).


Follow the second quoted passage to see the maths behind it.  Equations (16) and beyond consider the condition where friction is present.  The curve is slightly different as a result of that.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: power7
Date Posted: 06/24/2012 at 9:32am
Not really following this argument.  
What aspect of a TT forehand swing is powered by gravity?
So the fastest swing follows the path of a cycloid?

You think any of the top TT players in the CNT can do a simple math proof...

These models are not intuitive at all.


-------------
DHS PG-7, H3 Neo, 729-5

Butterfly Power-7, Red TG2 Neo 39degree, Black Donic Bluefire M1


Posted By: pnachtwey
Date Posted: 06/24/2012 at 10:08am
Nice,  the problem can be solved symbolically and there are only 16 steps!  If I had to solve that problem I would have written the differential equations and solved iteratively using RK4.   That would have been a lot of work.  So many problems I run into don't have a symbolic solution and the problem must be solved using brute force iteration.   With a symbolic solution you have a proof.  With a iterative one you don't because that works with one set if numbers.

What amazes me is those mathematicians from the past didn't have Mathematica.   How did they know there was a symbolic solution?   It is amazing what people can do when their mind is "stupidfied" with TV.  I would imagine this is common knowledge for those that design roller coasters. Zeio, where else would you apply this?   I don't see what this has to do with TT.



-------------
I TT therefore I am


Posted By: mikepong
Date Posted: 06/24/2012 at 10:25am
can someone correlate these math equations or whatever it is to TT? sorry not really good at math

-------------
Viscaria

FH: Tenergy 05 black

BH: Tenergy 05 red





Posted By: pnachtwey
Date Posted: 06/24/2012 at 11:13am
Originally posted by mikepong mikepong wrote:

can someone correlate these math equations or whatever it is to TT?
You can't don't sweat it.

Quote
 sorry not really good at math
Those that figured this problem out were the best of their time.  The Timo Bolls and Ma Longs of math and physics.   There I related this to TT.



-------------
I TT therefore I am


Posted By: zeio
Date Posted: 06/24/2012 at 1:52pm
I am getting there.

Forget the maths and the gravity.  The keyword here is time.  It is time, not distance, that really matters in producing the best swing.  And for that to happen the best path to follow during a swing is a curve that most closely resembles the brachistochrone.  Concave or convex, positive or negative, however you name it.  It may sound counter-intuitive, but the longer path does produce the least time and we see signs of it in videos of the pros.  And one thing is for sure, that path has never been and probably never will be a straight line as those who are in denial of any curvature in swing mechanics may have imagined.  They could have been doing it all along without even realizing.

The answer is out there, that the way we live, the tools we use, and the many things we come across during our lives are largely http://www.ted.com/themes/inspired_by_nature.html - inspired by Nature .  As it turns out, we humans tend to ignore it and overcomplicate things.  As Johann Bernoulli himself has put it - "Nature always tends to act in the simplest way, and so it here lets one curve serve two different functions, while under any other hypothesis we should need two curves..."

-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: pnachtwey
Date Posted: 06/24/2012 at 2:13pm
Originally posted by zeio zeio wrote:

And for that to happen the best path to follow during a swing is a curve that most closely resembles the brachistochrone.

The brachistochrone works because the brachistochrone allows the ball to drop or accelerate faster initially.  This isn't the case with a swing that opposes gravity.

I know where you are going with this.  You are thinking of the brachistochone with a upwards swing where the swing starts out shallow to get moving and then starts in the upwards direction.  Good one, but if the paddle attitude is always changing the resulting timing errors will result in poor control.  However, if the paddle attitude can be kept constant during the up swing it may work.   The big question is will this make any practical difference?   Most of us can swing far faster than what is necessary anyway.



-------------
I TT therefore I am


Posted By: Baal
Date Posted: 06/24/2012 at 2:15pm
There is more than one way to skin a cat.  That is why several different players who have been in the top five in the world appear to have a different swing, and they all have great forehands.  Also, it is very very hard to remodel a stroke once it is formed -- and in adults in general.  It can be done, but it takes a long time.  That may not be apparent from an engineering perpective, but it is true from a physiological perspective.  Those motor patterns get really engrained.  Tape yourself and find out.  It may feel like you are making big changes in your stroke and when you actually see it, you just look like you.  (Especially once you play a match).  Feel and reality do not always coincide.  The most important things are (1) does your swing produce reasonable spin, pace, and accuracy, and (2) can you maintain your balance so as to be able to hit the next ball?  If you forehand does this with consistency than it doesn't matter if you look like WLQ, ML, or the Dalai Llama.  You will be good.  And Bernoulli, Gauss, and Laplace be damned.    


Posted By: Baal
Date Posted: 06/24/2012 at 2:19pm
The reason why a follow through matters is because a swing that results in a proper follow throw begins before you hit the ball, and therefore affects the way you hit the ball.


Posted By: zeio
Date Posted: 06/24/2012 at 2:20pm
Originally posted by hobbes203 hobbes203 wrote:

@Zeio

Couldn't resist answering that question, both objects are of the same mass and has the same qualities (same kinetic and static friction, etc), and the ramps are also equivalent, then both would hit the bottom at the same time whether they slide or roll. Easiest way to do this is energy, but I'll leave it at that.

The important question is what are the accelerations of the objects at the bottom? (Answer should be a vector quantity, magnitude and direction).

Given a very, very general scenario, the comparison of the balls at the bottom of the ramp can be applied to the moment a table tennis ball at a fixed point is contacted by the concave and convex strokes. At this point, I won't try to get into springs, torque, friction, and the magnus effect. Generally, the ballistics of the ball is determined by the magnitude and acceleration at different contacts of a controlled ball. 

I'm no expert but really just try the strokes for yourself, have a robot hit one spot and hit the ball at the same spot with controlled similar-accelerated but different swings.

Also pnachtwey +1 from me Big smile

Both objects are identical in size, shape, and weight etc.  They are under uniform gravity.  Friction or frictionless does not affect the outcome.

They reach maximum velocities at the bottom.  Assuming no friction, the vertical accelerations of both objects are constant but of different values as they run down the paths.  This difference in vertical acceleration is what separates the two.

Quote http://scienceray.com/mathematics/path-for-shortest-time-of-travel-straight-or-curved-line/ - Our intuition would most likely tell us that any object allowed to fall under the influence of gravity alone would take the natural straight line course despite the  object being  constrained to travel as quickly as possible – travel of least time. And we are inclined to come up with such a conclusion for it’s the seeming natural appearance of events – the Aristotelian method of deducting scientific conclusions.



-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: power7
Date Posted: 06/24/2012 at 4:02pm
Originally posted by zeio zeio wrote:

I am getting there.

Forget the maths and the gravity.  The keyword here is time.  It is time, not distance, that really matters in producing the best swing.  And for that to happen the best path to follow during a swing is a curve that most closely resembles the brachistochrone.  Concave or convex, positive or negative, however you name it.  It may sound counter-intuitive, but the longer path does produce the least time and we see signs of it in videos of the pros.  And one thing is for sure, that path has never been and probably never will be a straight line as those who are in denial of any curvature in swing mechanics may have imagined.  They could have been doing it all along without even realizing.

The answer is out there, that the way we live, the tools we use, and the many things we come across during our lives are largely http://www.ted.com/themes/inspired_by_nature.html - inspired by Nature .  As it turns out, we humans tend to ignore it and overcomplicate things.  As Johann Bernoulli himself has put it - "Nature always tends to act in the simplest way, and so it here lets one curve serve two different functions, while under any other hypothesis we should need two curves..."
This isn't non-Euclidean geometry, so the linear path takes the least amount of time.  Nor is this a gravity power problem with no friction.

The modelling is incorrect.  

The only thing applicable is Bernoulli's principle on the ball spinning creating low pressure systems thus make the ball "curve" in flight...




-------------
DHS PG-7, H3 Neo, 729-5

Butterfly Power-7, Red TG2 Neo 39degree, Black Donic Bluefire M1


Posted By: pnachtwey
Date Posted: 06/24/2012 at 6:47pm
Originally posted by power7 power7 wrote:

This isn't non-Euclidean geometry, so the linear path takes the least amount of time.  Nor is this a gravity power problem with no friction.
You assume that the velocity profiles are the same.   If there is no friction then the speeds will be the same at the bottom of the ramps but the cycloid ramp will allow the ball to accelerate to faster.   The area under the velocity curve,  the distance,  traveled will be greater when comparing with the constant acceleration ramps at the same time.

Quote
The only thing applicable is Bernoulli's principle on the ball spinning creating low pressure systems thus make the ball "curve" in flight..
So far yes,  lets wait for zeio to make his case.



-------------
I TT therefore I am


Posted By: Krantz
Date Posted: 06/25/2012 at 6:52am
Nice observation about brachistochrone curve. For now it tells me that we cannot outright exclude the possibility that a curved motion may be “faster” then a motion along a straight line. Here are few other possible explanations why curved motion (with a long follow-through) can be a good option:

1. It may be easier to aim with that kind of swing. While it’s true that all it really matter is an angle (direction, speed) of a racket at point of contact it may be easier to adjust these factors during longer swing. Compare this to shooting with a rifle and with a pistol. If you adjust your sights perfectly then it doesn’t matter which gun you shoot with, but it is easier to adjust sights of a rifle because of longer distance between a notch and a bead - and this results in overall better accuracy of a rifle. Consecutively, a longer curved swing with a long follow through may just help you in placing the ball at the exact point you aim.

2. Generally, the harder you hit, the more closed the angle of a racket should be. A positive arc of a movement assures just that. At the beginning of a swing the racket’s speed is low, so its angle is open. While you accelerating, you are continuously closing the angle and during the whole swing their combination is just about right to place the ball on the table. Moreover, I would say that this option of closing the angle is on the safe side of an error margin - closed angle is good. If the angle is to low then in order to prevent the ball from hitting the net you have to just hit harder - and hitting harder in order to not miss the table is a win-win scenario. 

3. Natural ready position between shots is with a hand relatively low. Sufficient reason that we don’t wait for a ball with a hand raised high is that it would be to tiring. But quite often we have to hit the top part of the ball – the only way we can do this (from this low hand starting position) is by performing this curved, positive arc motion. 



Posted By: V-Griper
Date Posted: 06/25/2012 at 9:28am
There is also conservation of momentum and energy. 

If you use a more straight forward/straight back motion you have to expend a lot more effort accelerating and decelerating the paddle. 

By following a more circular stroke path momentum and energy are conserved.

There is also adjustment to incoming ball to consider. As an example if you look at ML slow mo vid again, when ML begins the forward part of the stroke, you can see there is more of an virtical component to his stroke. To me this is where the height adjustment is being made for the height of the ball. However there is still a forward component to the stroke. It's just more efficient. 


BTW this is the best thread in awhile. Clap This is where we challenge our assumptions and refine our paradigm. 

Time to get your geek on Tongue


Posted By: V-Griper
Date Posted: 06/25/2012 at 9:41am
I love things that challenge my intuitive assumptions about how things work. Even if this is not substantially relevant to TT it is still cool.

Thanks Zeio.

http://www.youtube.com/watch?feature=fvwp&v=HSRJ8t6nRtU&NR=1 - http://www.youtube.com/watch?feature=fvwp&v=HSRJ8t6nRtU&NR=1

Sorry won't embed.





Posted By: V-Griper
Date Posted: 06/25/2012 at 11:49am
Originally posted by pnachtwey pnachtwey wrote:

Originally posted by zeio zeio wrote:

And for that to happen the best path to follow during a swing is a curve that most closely resembles the brachistochrone.

The brachistochrone works because the brachistochrone allows the ball to drop or accelerate faster initially.  This isn't the case with a swing that opposes gravity.

I know where you are going with this.  You are thinking of the brachistochone with a upwards swing where the swing starts out shallow to get moving and then starts in the upwards direction.  Good one, but if the paddle attitude is always changing the resulting timing errors will result in poor control.  However, if the paddle attitude can be kept constant during the up swing it may work.   The big question is will this make any practical difference?   Most of us can swing far faster than what is necessary anyway.


I would say that the paddle angle can and is kept constant by the better players who seem to be using a more circular motion.

ML seems to hold blade angle more constant throughout his swing cycle than Timo. At least that I can perceive. BP seems to hold paddle angle more constant than ML or TB but I am not sure he could generate the paddle acceleration that ML or TB can.

Imo minimizing timing errors is mainly a nervous system issue. I see a lot of players with very inefficient strokes who have incredible timing because they do exactly what you say, they hold the paddle angle relatively constant. 

I was practicing with a beginner Yesterday and he could do 150 ball rallies. I noticed, however, that in order to keep his paddle condition constant he made all kinds of contortions with his wrist elbow and shoulder.

Then there is the 1800 level player at our club who has to quit training for a couple of days if he does a lot of looping. His loop mechanics are so bad(FH & BH) I worry about him tearing his rotator cuff. He has already had minor tearing in his shoulder muscles. 

The ball may not care what you do prior to and after contact but your body sure does.



Posted By: zeio
Date Posted: 06/25/2012 at 11:51am
To keep things straight, the energy source behind the two balls is actually the potential energy.  Potential energy can exist in quite a few forms, and each of them comes from a particular type of force, namely the conservative force.  In the brachistochrone problem, the force of gravity used to initiate a change of state from rest to motion is a type of conservative force and it gives rise to gravitational potential energy.  As the balls trace down the paths, the potential energy within them is converted into kinetic energy.  By the conservation of energy, in a closed system where friction is neglected, both potential and kinetic energy are conserved.  In layman's terms, the balls are powered by an engine that is 100% efficient with no loss.  Theoretically speaking, they start off at the same level of potential energy and should end up with the same final velocities at the end of the paths.  In an experiment run in Germany where kinetic energy is not conserved due to friction, the final velocity of the ball along the brachistochrone curve has been found to be greater than that of the ball along the straight line, as cited by http://zhidao.baidu.com/question/118994128 - this source .  So it looks like the brachistochrone is also more efficient in aspects other than time.

For table tennis, we draw on a number of potential energy.  When one winds up during a backswing, elastic potential energy is stored in parts of the body, waiting to be released.   Chemical potential energy from food is transformed into kinetic energy when we do work to swing the paddle back and forth.  When players lower their stances, they also gain gravitational potential energy.  Instead of using the gravitational potential energy gained from the force of gravity alone to start motion as in the brachistochrone problem, the goal here is to make the most out of the additional potential energy available to us to overcome gravity in a three dimensional swing.

The timing problem is not really a problem as we have all witnessed.  This is what http://www.youtube.com/watch?v=ue1Y1gk6sWM&feature=plcp - training is for.  http://www.youtube.com/watch?v=ZNSu9wHIdzA&feature=player_detailpage#t=4s - One may be a fluke, http://www.youtube.com/watch?v=ZNSu9wHIdzA&feature=player_detailpage#t=21s - two could be coincidence, but http://www.youtube.com/watch?v=ZNSu9wHIdzA&feature=player_detailpage#t=37s - three is a trend.  Every pro may approach it differently, but the basic rule still holds.  Just because the human nature within most of us tends to think only the pros can do it well should not deter the rest from pondering, discussing, and mimicking, for this is how one gains knowledge.

Of all western sources I've managed to dig up, only those in http://www.espnmediazone3.com/us/2010/02/11/sport-science-looks-at-the-physics-of-a-lindsey-vonn-ski-run/ - skiing and http://engineeringsport.co.uk/2010/10/29/surfing-the-brachistochrone/ - surfing is the brachistochrone curve ever directly mentioned and applied for performance gain.  Not to worry, here is a thesis just about its application in table tennis, titled http://cdmd.cnki.com.cn/Article/CDMD-10043-2009126777.htm - "Kinetics Analysis of the Kinetic Chain of the Execution of Strokes in Succession while in Motion in Table Tennis" by 賈鵬(Jia Peng) and published in 2007.  I do not have access to the full paper, but the abstract will suffice.  Below is an excerpt about the benefits of integrating the brachistochrone curve into stroke mechanics.

(3)人体在移动后动力再链接包含了“引拍、挥拍、还原”的周期过程,尤其在连续击球时,“引拍、挥拍、还原”的线路轨迹、周期长短、频率高低以及击球前的准备充分程度都直接影响击球的效果。在研究过程中把“引拍、挥拍、还原”的轨迹、周期、频率和单摆、锥摆的轨迹、周期、频率运用力学的方法做了详尽的比较分析,也利用“最速降线”对“还原、引拍”进行了力学上的比较分析,得出人体在持拍连续击球的时候,利用近似椭圆的轨迹特点,利于发挥速度、频率优势,在节奏快的激烈对抗中获取时空上的利益,以期能够获得技战术上的优势。
(3) The kinetic chain of the human body after some displacement involves a cycle of "backswing, swing, and recovery".  The path, period, and frequency of the cycle, as well as the level of readiness before each stroke all have a direct effect on its result.  During research, the path, period, and frequency of the "backswing, swing, and recovery" and of the simple pendulum and the conical pendulum are given extensive comparative analysis using kinetics.  The same analysis is also performed using the "brachistochrone curve" for the "recovery and backswing."  The results derived suggest that when the human body executes shots in succession, use of the ellipse-like path facilitates the play of speed and frequency to get the upper hand in space-time during a fast-paced and fierce confrontation in hopes of gaining further technical and tactical advantages.

At this stage, we see the potential advantage of applying the brachistochrone curve for the recovery and backswing before and after a swing.

Other than the thesis above, there is another user by the name "jlw" posting about the brachistochrone curve http://www.chinatt.com/tt/dispbbs.asp?boardid=118&id=102237&move=next - (1) , http://bbs.alltt.com/viewthread.php?tid=198274 - (2) .  The poor dude got practically zero constructive feedback.

-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: pnachtwey
Date Posted: 06/25/2012 at 3:14pm
I find it interesting but we don't swing using gravity alone.   It is would very nice to put a  3D accelerometer on the back of a blade to see what is really happening.  It doesn't surprise me that some of the authors didn't get any attention without hard data.



-------------
I TT therefore I am


Posted By: V-Griper
Date Posted: 06/25/2012 at 3:28pm
Originally posted by pnachtwey pnachtwey wrote:

I find it interesting but we don't swing using gravity alone.   It is would very nice to put a  3D accelerometer on the back of a blade to see what is really happening.  It doesn't surprise me that some of the authors didn't get any attention without hard data.


Alright, you've got the know how, let's get some hard data then. How cost prohibitive is it?


Posted By: power7
Date Posted: 06/25/2012 at 3:37pm
http://www.google.com/products/catalog?q=accelerometer&hl=en&rlz=1C1CHKZ_enUS437US437&prmd=imvnsr&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&biw=1024&bih=673&um=1&ie=UTF-8&tbm=shop&cid=14940118607995515195&sa=X&ei=rb3oT__EF6HY0QG5iPSMCg&ved=0CJQBEPMCMAA - http://www.google.com/products/catalog?q=accelerometer&hl=en&rlz=1C1CHKZ_enUS437US437&prmd=imvnsr&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&biw=1024&bih=673&um=1&ie=UTF-8&tbm=shop&cid=14940118607995515195&sa=X&ei=rb3oT__EF6HY0QG5iPSMCg&ved=0CJQBEPMCMAA

$25 USD...cheaper than some popular rubbers.


-------------
DHS PG-7, H3 Neo, 729-5

Butterfly Power-7, Red TG2 Neo 39degree, Black Donic Bluefire M1


Posted By: V-Griper
Date Posted: 06/25/2012 at 3:42pm
Originally posted by power7 power7 wrote:

http://www.google.com/products/catalog?q=accelerometer&hl=en&rlz=1C1CHKZ_enUS437US437&prmd=imvnsr&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&biw=1024&bih=673&um=1&ie=UTF-8&tbm=shop&cid=14940118607995515195&sa=X&ei=rb3oT__EF6HY0QG5iPSMCg&ved=0CJQBEPMCMAA - http://www.google.com/products/catalog?q=accelerometer&hl=en&rlz=1C1CHKZ_enUS437US437&prmd=imvnsr&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&biw=1024&bih=673&um=1&ie=UTF-8&tbm=shop&cid=14940118607995515195&sa=X&ei=rb3oT__EF6HY0QG5iPSMCg&ved=0CJQBEPMCMAA

$25 USD...cheaper than some popular rubbers.

 
This issue came up in another post and we kicked around the idea of collecting hard data.

pnatwey works with that kind of equipment for a living. He knows exactly what it would take and how to do it. It is a matter whether or not he wants to put in the time. I would be willing to put money in the pot for equipment depending on the cost estimate.


Posted By: king_pong
Date Posted: 06/25/2012 at 8:23pm
I'm enjoying this thread as well.  I was away for the weekend, and see that I've missed a lot.  
The posting below by V-Griper is the closest I've gotten to anyone informing me which are concave and which are convex loops. Smile  Would love to know what people think/believe Smile

Originally posted by V-Griper V-Griper wrote:

Here is WLQ counter hitting. He is clearly guiding his paddle in a modified circular path. I say modified because the take back is like a semi circle but the forward part is flattened out. 



Again. This time the well referenced ML slow mo FH.  Similar motion. Starting from the ready position. Paddle goes down, then back beside the right knee. Then slightly up and then flattens out as it moves forward into the ball.



So the question is why do a circular motion at all? Why not do more of a straight back and strait forward motion? 

Like this.



Or this.



Iwill grant you that Timo and BP are still making a slightly squashed oval, albeit slight, but it looks nothing like what WLQ and ML are doing.

Some related questions-
Why is ML's elbow so close to the body on the take back? why does the paddle usually stop beside the knee? Why does ML's knee seem to collapse inward slightly?(So does RSM's btw  https://www.youtube.com/watch?v=RMVzq-OnBcM&feature=player_embedded - https://www.youtube.com/watch?v=RMVzq-OnBcM&feature=player_embedded )

I am interested in peoples opinions. 

P.S. Please refrain from playing the "Chinese vs Euro" card. It gets old. I want you guys to think not recycle arguments.



Posted By: zeio
Date Posted: 06/26/2012 at 4:19am
Originally posted by power7 power7 wrote:

Originally posted by zeio zeio wrote:

I am getting there.

Forget the maths and the gravity.  The keyword here is time.  It is time, not distance, that really matters in producing the best swing.  And for that to happen the best path to follow during a swing is a curve that most closely resembles the brachistochrone.  Concave or convex, positive or negative, however you name it.  It may sound counter-intuitive, but the longer path does produce the least time and we see signs of it in videos of the pros.  And one thing is for sure, that path has never been and probably never will be a straight line as those who are in denial of any curvature in swing mechanics may have imagined.  They could have been doing it all along without even realizing.

The answer is out there, that the way we live, the tools we use, and the many things we come across during our lives are largely http://www.ted.com/themes/inspired_by_nature.html - inspired by Nature .  As it turns out, we humans tend to ignore it and overcomplicate things.  As Johann Bernoulli himself has put it - "Nature always tends to act in the simplest way, and so it here lets one curve serve two different functions, while under any other hypothesis we should need two curves..."
This isn't non-Euclidean geometry, so the linear path takes the least amount of time.  Nor is this a gravity power problem with no friction.

The modelling is incorrect.  

The only thing applicable is Bernoulli's principle on the ball spinning creating low pressure systems thus make the ball "curve" in flight...



The brachistochrone problem was solved and proven in the Euclidean space in the 17th century.  The classical mechanics was developed during this period as well.  Non-Euclidean space did not emerge until the early 19th century.  What matters though is that the brachistochrone was first experimentally observed under the hypothesis of Galileo in the http://en.wikipedia.org/wiki/Space - physical space , which, by Albert Einstein's theory of general relativity, is curved.  As the balls are traveling at far below the speed of light, the classical mechanics used to solve the problem is extremely accurate.  Unless you are hallucinating or something, I don't see how this model can be labeled wrong.

Yes, the reason a table tennis ball curves can be explained by the Bernoulli's principle.  But the Bernoulli's principle alone is insufficient in describing the sequence of events leading up to the pressure difference.  The http://claesjohnsonmathscience.wordpress.com/article/why-a-topspin-tennis-ball-curves-down-yvfu3xg7d7wt-17/ - boundary layer separation is necessary to fill the void.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: V-Griper
Date Posted: 06/26/2012 at 12:14pm
Notwithstanding pnachtway's objections and the lack of hard data, let's go ahead and form a hypothesis, based on the premise, that the principles underlying the mechanics of the brachistochrone curve apply to what we are doing in TT. 

Let's use the video of WLQ counter hitting. I think this is the least ambiguous with regard to whether or not his stroke follows a curved path.



From the ready position. The paddle/arm follows a curved path down and back. It then follows a less pronounced curve up/forward through ball contact and follow through, at which point the stroke cycle starts again.

If the brachistochrone curve principles apply, then this is the shortest possible cycle time of the stroke. It would be faster to take the paddle back along a curved path than it would be to take the paddle straight back. Needless to say this would be somewhat counter intuitive but it wouldn't be the first time.

Now if we could figure out a reasonable way to substantiate this with some empirical evidence we would have a stronger base for training.




Posted By: racquetsforsale
Date Posted: 06/26/2012 at 2:36pm

Putting physics and metrics aside for a moment and going on feeling alone, I find linking the finish and start of the stroke via a curved path as WLQ is doing requires less effort than stopping the stroke at the end, reversing in the opposite direction, and stopping again before starting the stroke again, all on a more linear path.

Swinging and recovering in a continuous loop also helps with establishing a good rhythm and keeping the rally at a steady pace. This is desirable especially when warming up or drilling the basic counter or loop. In these situations, there's nothing more annoying than a hitting partner who can't more or less feed the same ball to you.


Posted By: zeio
Date Posted: 06/27/2012 at 4:45am
The following is the section of that video http://v.youku.com/v_show/id_XMzM2MTg5ODQ=.html?f=2018622 - where Wang Liqin demonstrates the forehand forward loop.

http://v.youku.com/v_show/id_XMzM2MTg5ODQ=.html?firsttime=57 - 57s in , the trajectory of the ball and the path of his swing are traced out and superimposed on the screen.

Below is the same image overlaid with the http://en.wikipedia.org/wiki/Cycloid - brachistochrone curve grabbed from Wikipedia.  As his swing is carried out in 3D(traveling between different planes) and under real-world constraints, I have expected the curve to exhibit more differences from the 2D brachistochrone curve(static plane).  Much to my surprise, it appears that both curves follow an identical path from start to impact.




-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: racquetsforsale
Date Posted: 06/27/2012 at 5:14am
That concave trace is a result of swinging about the shoulder socket. It's human anatomy and again I don't think one should proactively try to trace that curve because it happens naturally.

For the longest time, I thought my swing was pretty much on a plane (close to tracing a line when viewed from the side like in the picture), but it turned out to be concave. In addition, my swing angle turned out to be larger than what I thought---it was close to 60 degrees but I thought I was swinging at 45 degrees.


Posted By: racquetsforsale
Date Posted: 06/27/2012 at 5:21am
For you KLH fans, traces of his loops @ 17:40. Different angle though.




Posted By: zeio
Date Posted: 06/27/2012 at 7:19am
Originally posted by racquetsforsale racquetsforsale wrote:

That concave trace is a result of swinging about the shoulder socket. It's human anatomy and again I don't think one should proactively try to trace that curve because it happens naturally.

For the longest time, I thought my swing was pretty much on a plane (close to tracing a line when viewed from the side like in the picture), but it turned out to be concave. In addition, my swing angle turned out to be larger than what I thought---it was close to 60 degrees but I thought I was swinging at 45 degrees.

In human anatomy, motion http://click4biology.info/c4b/11/hum11.2.htm#1 - "is produced by the skeletal acting as simple lever machines."   Simple movement like bending an elbow can therefore be defined as rotation about a fixed axis.  More complicated movement can then be defined as a combination of rotations about different axes.  Given these conditions, it follows that the tip of any body part undergoing motion, when traced out, would show a curved path.

However, this naturally occurring phenomenon is being ignored, denied, and attacked by those who hold the notion that their swings couldn't be any straighter.  The rationale behind it is most probably the belief that distance reigns over time, and if that is the case, then any deviation from it is either outright wrong or a waste of effort.  Now that there are signs they may be proven otherwise, they come up with doubts and that evidence be shown.  From his limited access to source material, V-Griper is trying his best to fill those requests.  But as I see it, that curve there is still not enough to get things changed.  Well, as V-Griper puts it, this is nothing new as the history of Science has shown.

Here I have on hand another essay paper(more like a book by its page count) about the biomechanics of the backhand loop stroke written by a German.  He went to great lengths to actually set up a complete environment to collect concrete data of the whole motion of the test subjects outfitted with markers all over their bodies.  It's not as simple as just attaching to the paddle an accelerometer.  I will save it for a separate post.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: reflecx
Date Posted: 06/27/2012 at 8:56am

Here are 3 players with straight forward swing.



Posted By: pnachtwey
Date Posted: 06/27/2012 at 9:33am
Originally posted by zeio zeio wrote:

It's not as simple as just attaching to the paddle an accelerometer.  I will save it for a separate post.
What difference does it make?  A 3D accelerometer will provide a lot of information that video systems can't.   The frame rate of the video system must be very high.   High speed cameras are very expensive.



-------------
I TT therefore I am


Posted By: icontek
Date Posted: 06/27/2012 at 10:21am
Originally posted by racquetsforsale racquetsforsale wrote:

For you KLH fans, traces of his loops @ 17:40. Different angle though.




At 26:50 you can see traces of KLH's CONVEX loop.

It would seem the Chinese coach intends different strokes for different shots.

Is convex used for driving against underspin? I can't tell from the ball feeds, but I suspect so.


-------------
http://bit.ly/vLMhuB" rel="nofollow - - RC1042 . Virtuoso AC : K1 + EL-P


Posted By: power7
Date Posted: 06/27/2012 at 11:09am
26:50 is about attacking a loop.  The segement was about quick counter hit to loop, followed by attacking a loop.  Ma demostrates the drill, 3 hit counter hit to loop, 3 attacks to loops.
 
17:40 is about FH looping off BH side.  The segment prior was FH loop off the FH side 1 meter back.
 
Zeio, I don't think the answer to the better understanding of TT will be found in relativity, quantum mechanics, or other esoteric fluid dynamic prinicples.  You think the PRC with their millions of engineers graduating every year wouldn't have 1 or 2 TT fanatic pursuing dead-end corolation already.


-------------
DHS PG-7, H3 Neo, 729-5

Butterfly Power-7, Red TG2 Neo 39degree, Black Donic Bluefire M1


Posted By: zeio
Date Posted: 06/27/2012 at 12:26pm
Originally posted by pnachtwey pnachtwey wrote:

Originally posted by zeio zeio wrote:

It's not as simple as just attaching to the paddle an accelerometer.  I will save it for a separate post.
What difference does it make?  A 3D accelerometer will provide a lot of information that video systems can't.   The frame rate of the video system must be very high.   High speed cameras are very expensive.


The difference is huge.  The common elements of motion from velocity, acceleration, and momentum etc. to their angular counterparts are all vectors, which unlike scalar values, have both a magnitude and a direction associated with them.  Whether you're working in a 2D or 3D environment, in order to make correct and useful interpretations of and comparisons between the data collected from different subjects, it is necessary you have a http://en.wikipedia.org/wiki/Inertial_reference_frame - reference point in place to compare against.  This is because the accelerometer measures the http://en.wikipedia.org/wiki/Proper_acceleration - proper acceleration .  Nothing beats cameras when it comes to that.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: zeio
Date Posted: 06/27/2012 at 12:54pm
Originally posted by power7 power7 wrote:

26:50 is about attacking a loop.  The segement was about quick counter hit to loop, followed by attacking a loop.  Ma demostrates the drill, 3 hit counter hit to loop, 3 attacks to loops.
 
17:40 is about FH looping off BH side.  The segment prior was FH loop off the FH side 1 meter back.
 
Zeio, I don't think the answer to the better understanding of TT will be found in relativity, quantum mechanics, or other esoteric fluid dynamic prinicples.  You think the PRC with their millions of engineers graduating every year wouldn't have 1 or 2 TT fanatic pursuing dead-end corolation already.

Excuse me?  First thing first, all physics referred to herein is only high-school level.  I wouldn't have needed to write all this if only those who were quick to point out "what is wrong" would have instead enlightened me on "the right way."  A picture speaks a thousand words?  I doubt it in face of people's superstitions being challenged.


-------------
Viscaria FL - 91g
+ Neo H3 2.15 Blk - 44.5g(55.3g uncut bare)
+ Hexer HD 2.1 Red - 49.3g(68.5g 〃 〃)
= 184.8g


Posted By: V-Griper
Date Posted: 06/27/2012 at 1:01pm
Originally posted by reflecx reflecx wrote:

Here are 3 players with straight forward swing.

 

Actually, and I know I am being picky because I am defending a position, that stroke is still curved. Just not in the plane of reference you are looking at. Well partially. If we were looking from the top down you would clearly see that the paddle travels along an arc. You can partially see this in the pictures where you can see the curved part of the line that is tracing the stroke path. This point is not mutable as the arm has a relatively fixed length. The point you are making, I think, is that in the vertical side plane, or the stroke plane, there is no upward or downward curvature. I would argue that this is still not the case. 

Originally posted by racquetsforsale racquetsforsale wrote:

For you KLH fans, traces of his loops @ 17:40. Different angle though.



Good one but same as above. I would still contend that there is a curve based on what's happening at 4 mins in. What I perceive is that the curve has been compressed and accomplished with the forearm and wrist. To me this seems to occur in the transition between the backwards and forward motion of the swing. 

Same thing with Timo.



His is a little different in that his elbow tends to start moving forward before his wrist, kind of like a mini baseball pitch. The paddle, however, moves through a tight curve pivoting at the wrist. 


Originally posted by icontek icontek wrote:

Originally posted by racquetsforsale racquetsforsale wrote:

For you KLH fans, traces of his loops @ 17:40. Different angle though.




At 26:50 you can see traces of KLH's CONVEX loop.

It would seem the Chinese coach intends different strokes for different shots.

Is convex used for driving against underspin? I can't tell from the ball feeds, but I suspect so.

I agree in part but I think basic personal preference and ball height matter more. WLQ tends to use a downward(negative) curvature on most of his strokes. This is good up until the relative ball height makes this untenable. Once the ball reaches a certain height you need to change to a upward(positive) curvature to "cover" the ball. This is where you see the follow through change to  a more horizontal finish. Reverse all that for underspin.



Originally posted by pnachtwey pnachtwey wrote:

   ...but if the paddle attitude is always changing the resulting timing errors will result in poor control.  However, if the paddle attitude can be kept constant during the up swing it may work.   The big question is will this make any practical difference?   Most of us can swing far faster than what is necessary anyway.
 

This a point I agree with. I think that different players have come up with different solutions. Here is what I am perceiving. If you look at KLH and Timo video above there seems to be a lot of paddle movement in the transitions and just prior to ball contact. Here's the catch, his body is relatively still and the movement is simpler,"straight back/straight forward". Now look ML below. Very little attitude variation at the paddle, but serious body movement to cycle the paddle around. The same with RSM. 

 

https://www.youtube.com/watch?v=RMVzq-OnBcM - https://www.youtube.com/watch?v=RMVzq-OnBcM  
RSM vid will not embed




Originally posted by power7 power7 wrote:


Zeio, I don't think the answer to the better understanding of TT will be found in relativity, quantum mechanics, or other esoteric fluid dynamic prinicples.  You think the PRC with their millions of engineers graduating every year wouldn't have 1 or 2 TT fanatic pursuing dead-end corolation already.

Your naivete is showing. Our whole modern society is based on pursuing so called dead-end correlations. I admit we are amateurs, both in TT and science, or at least I am, but that does not mean the effort is irrelevant.  I will also admit that this is not what you should be thinking about in the middle of a point but it does effect training protocols. 
Example- http://www.wired.com/playbook/2012/06/ff_superhumans/ - http://www.wired.com/playbook/2012/06/ff_superhumans/  Btw Lolo is seriously hot!


I was thinking about this relative to backhands and came up with an interesting conjecture(sorry gotta use it or lose it). SH players almost almost always have to use a downward(negativ) curvature to their stroke. I can't think of an example where this is not the case. So then I thought is there an example of an upward(positive) curvature BH? You guessed it rpb. The screw BH, done most notably done by WH, has a upward/outward(positive) curvature. SH players cannot do this shot without some difficult contortions of the wrist and elbow. I almost never see a SH player do this type of BH on a regular basis. 





Posted By: Loop40mm
Date Posted: 06/28/2012 at 11:33am

This is an amazing discussion.  I would’ve never thought of the concave loop, even though now I realize I am using the concave loop in one or two situations.

 

Concave loop against topspin

 

I watched the Kong Ling Hui 1 hour 23 minutes video.  I saw one clip where KLH used the concave loop.  Instead of the convex counter loop against topspin, he used concave loop to hit. It is not for long distance loop.  Some beginners would’ve smashed the ball against topspin and the ball sails out of the table.  With concave loop, one hits and loops the ball.  The loop neutralizes the topspin. 

 

Concave loop against long pips chop

 

I use convex loop against inverted rubber underspin.  I start with a very low stance. Initially the paddle is open but ends up at a certain angle(perhaps 45 degrees).  The trajectory of the loop varies depending on the lift.

 

Against long pips underspin, I use concave loop to deal with the timing issue. Initially the paddle is open but after extending the arm, the paddle is still open. The combination of bat speed and angle of paddle have to be appropriate, else the ball goes long.

 

The other option to handle the long pips underspin is to use the rolling loop which has a delayed effect in hitting the ball, thus solving the timing issue.  This is the convex loop.

 

Receive serves

 

With penhold, recently I started using concave loops to receive serves on the forehand side.  It seems to be a safer shot for me.

 

Using concave loop for pips

 

I think pips player can make use of the concave loop, since I interpret the initial contact of the concave loop being a hit. 

 

Which one is better?

 

Personally I think the advantage goes to convex loop against topspin.  The topspin with the convex loop with the paddle closing brings the ball back down to the table better than the concave loop.  For convex loop, if the paddle angle is more open than it should be at the time of contact, the balls goes out of the table. 

 

Against inverted underspin, I will experiment with concave loop.  It depends on the skill level of the player. For a control game, concave loop might be a safer shot.  There seems to be more techniques involved in convex loop so the margin of error may be higher.

 

It is a humble experience in playing table tennis.  There is always one mountain higher than another mountain.

 

 

 

 



-------------
Stiga Ebenholz NCT V

FH Tenergy 05

BH DHS Tin Arc 3




Print Page | Close Window

Forum Software by Web Wiz Forums® version 12.01 - http://www.webwizforums.com
Copyright ©2001-2018 Web Wiz Ltd. - https://www.webwiz.net