Hit-Brush Explained

Part 2 but I have yet to watch it.

http://www.youtube.com/watch?v=hpt-B__Ql1w

Racquetsforsale, what do you mean by closing the blade through contact and why don't you agree it is the essence of the loop?

Do you have a USATT rating or estimate?

I ask both to understand your statement as well as understand whether you can at least reproduce what experts do on a consistent basis since you seem to disagree with either their mechanics or their interpretation of the essence of such mechanics.

NextLevel wrote: Racquetsforsale, what do you mean by closing the blade through contact and why don't you agree it is the essence of the loop? Do you have a USATT rating or estimate? I ask both to understand your statement as well as understand whether you can at least reproduce what experts do on a consistent basis since you seem to disagree with either their mechanics or their interpretation of the essence of such mechanics.

NextLevel,

I do not have an USATT rating.

The instructor in the video explains that one must start to change the blade angle (closing it) before contact and continuing to close it through contact. If my translation or interpretation is incorrect, I welcome a correction.

Please elaborate on what effects you know is produced by closing of the blade as described in the video.

I don't disagree with the mechanics of the pros. I just often disagree with the descriptions of those mechanics when the descriptions are not consistent with what I see.

racquetsforsale,

Thanks.  Some estimate of your playing strength would still be helpful.  I have found in my personal experience that the game people watch as casual observers is not the game that the pros play, and the more I learn, the more I realize I had no clue what was happening. 

Many things that pros do is not easily observed without either slowing down the camera or understanding the amount of practice and physical training they have used to make the difficult become easy.  I gave an example of one of those things in my thread on how serving practice helped improve my game.  It's easy to think that the pros are swing as hard as the ball as they can when they are taking relatively relaxed swings compared to their full power.  Yet many beginners try to hit the ball as hard as they can to emulate pros rather than doing work on their physique and keeping proper form.

What I have found in my practice is that the trajectory of the racket through contact, which is affected either by changing the racket angle or the swing trajectory through contract, can impart more rotational action on the ball (Vs. hitting action). 

Do you roll a ball by just pushing it off center, or pushing it around the center?  Both are possible, but the amount of force that goes into rotating the ball vs driving the ball is larger in the second scenario than the first scenario, all other things being equal.

I used to subscribe to the school of thought that argued that all that was important was what happened at contact until I realized that the trajectory of the stroke can make a difference to the amount of spin imparted as well as the path the ball moved through.


Edited by NextLevel - 09/17/2014 at 7:08pm

If the ball stays on the racket for a few mili-seconds, the ball won't feel the racket angle change, with the rate you're closing it through the swing...

NextLevel,

What differences in your loops do you observe when you do change "alpha" during contact?

NextLevel wrote: racquetsforsale wrote: NextLevel, What differences in your loops do you observe when you do change "alpha" during contact? The ball curves more during flight.  Remember, you can do this while serving as well.

And this cannot be replicated without changing "alpha" during contact?

It comes down to how much alpha can be changed during contact, which is limited by how quickly one can close the paddle, and whether that amount is large enough to influence the ball.

Say changing alpha requires a really fast rotation. Then the next question would be how much effort and follow-thru would be needed to stop that rotation, and what would the physical motion look like.

If the requirement to stop the rotation in time limits the rotation to a certain speed and if that speed is not enough to influence the ball, then the rotation does not produce a special type of contact.

I believe the rotation establishes a particular angle alpha at contact by progressively "getting to it" before contact and then establishing it at contact. Other than perhaps additional acceleration achieved by the rotation, I don't see, at the moment, how this is different from establishing that exact same alpha before and during contact.

By the way, there are looping motions that open the blade through contact. Just wanted to point that out as well.

It occurs to me that there may be one benefit to closing the racket angle just before contact.   For counter-looping against strong topspin the desired angle might be so closed that it would be very easy to hit the edge of the racket (or missing the ball completely).  By closing just before contact you can approach the ball at an angle which poses little threat of hitting the edge of the racket and then by closing it get the full benefit of hitting with the very closed angle that is best for that particular incoming ball.

mjamja wrote: It occurs to me that there may be one benefit to closing the racket angle just before contact.   For counter-looping against strong topspin the desired angle might be so closed that it would be very easy to hit the edge of the racket (or missing the ball completely).  By closing just before contact you can approach the ball at an angle which poses little threat of hitting the edge of the racket and then by closing it get the full benefit of hitting with the very closed angle that is best for that particular incoming ball. This still requires a high level of timing skill.  But I think it is more plausibly accomplished than rotating the racket while the ball is in contact with the rubber.   Another reason that I believe that you do not want to be rotating the racket while in contact with the ball stems from what I have seen of where the ball contacts the blade.  Slow motion video I watched indicates that the ball is struck slightly below the center of the racket (below the centerline running from handle through tip).  If you are rotating the racket closed during contact you are actually moving the blade backwards (at least relative to how it would be traveling without rotation).  That would seem to be taking a lot of power away from the shot. I have another idea why this closing might be helpful.  I have observed a natural tendency for the racket face to slightly open as the swing goes forward.  It actually takes a little effort to keep the racket angle constant.  Having the thought of closing the racket at contact might help in making sure that the racket angle does not open as you approach the contact point. Anyway that is my two-cents worth. /DIV] Mark

Good points, mjamja.

NextLevel,

1. "Technically true but misses the practical point. One may not be literally hitting then brushing the ball, but there is probably nothing like a pure hit and nothing like pure spin - the real question is whether it allows one to add significantly more spin to the ball or not by converting a hitting motion into a spinning motion."

Do you agree that, all else being equal, the larger alpha is, the more one's hitting the ball, and the smaller alpha is, the more one is brushing the ball? Do you also agree that spin is maximized when alpha is zero? I don't believed I've missed the point. I pointed out the possibility that the arm action of closing the blade might create additional acceleration, contributing to additional ball speed and/or spin.

2. "This still needs to be proven. There is no reason that the trajectory of the racket isn't a vector input to the ball trajectory as well as opposed to a scalar input."

I agree that it still needs to be proven. I'm looking forward to the day we have actual footage. I AM treating the trajectory of the racket as a vector, not just as a scalar. I mentioned "a particular" swing angle at contact," meaning the swing vector AT contact. Yes, you can change this vector. All I'm saying is I don't think you can change it enough during contact to affect the ball, because contact is so short. Again, waiting for the footage.

3. "This is related to point 1 and I hinted at it, but you are still overstressing the physics at the expense of the pedagogy. Even if one ceded the physics, the point of table tennis is to be consistent and make dangerous shots. The best speed comes from hitting the ball hard. The best spin comes from off center contact. The most blade face for contacting the ball comes from flat contact. So changing the angle while approaching the ball allows you to make safe contact while trying to contact the ball off center, giving the best of both worlds.   It might also create additional acceleration or other things, but when you think about the hitting element and to the hitting element, you add the off-center contact/brushing element that comes with changing the angle through the stroke, you can see why one might consider that closing of the paddle the essence of looping."

I'm not missing the pedagogy. I take issue when the reasoning or justification behind what is being taught or revealed is possibly bogus. There are many folks out there who still believe that you first hit the ball into the sponge, THEN START closing the blade! You mention that "changing the angle while approaching the ball allows you to make SAFE contact. The instructor in the video advises that this technique should be done only when the incoming ball is SLOW, when looping underspin for example. He demonstrates this in the video. He also explains that this technique is risky when the incoming ball is fast, because if the blade is not closed enough, the ball might go out, and if too closed, the ball might go into the net. It doesn't sound like to him that the added value of this technique is additional safety margin.

5. "I was thinking more along the lines of the practical benefit of a given technique like the risk of missing the ball. Moreover, as I have pointed out, people have claimed that there is no benefit to covering the ball. But what one has to explain is not whether there is any benefit or not, but why a stroke that covers the ball seems to arc differently from one that does not. I see it in my practice, but I can be misconceiving what is happening. I just would prefer that your explanation take into account and explain what people see rather than starting from a position based on what is expected to be true."

Arcing differently...that just means the parameters AT contact, the ones I mentioned before, are different from those you produce with your regular swing. Perhaps when you're closing the blade through contact, you unconsciously swing at a different speed, swinging at a different angle, establishing a different blade angle at contact, changing your timing, etc, whatever. All these things can be accomplished without closing the blade through contact as well.

Can you add full subtitles of the coach? I think it is better to see full of conversation for suitable evaluation.

Edited by winterdrops - 09/20/2014 at 6:23am

NextLevel wrote: tom wrote: I see a lot of discussions back and forth,but does any current player of note use this hit brush? It's the standard looping stroke.  Advanced players do everything so fast you need to slow things down to see them do it on camera.

really? This seems like an interesting topic so I asked an ex Chinese provincial player about the term ”hit brush" in English since my Chinese is poor. Right away she stated the term in Chinese and said this is a technique taught to little kids, herself included to help with their physical limitation to generate more power. Can you post a link that shows this technique in competitioun, preferably in slow-mo

Edited by tom - 09/20/2014 at 12:26pm

Tom, read the whole thread.