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Povl Carstensen 01-20-2013 06:27 AM

Racket head acceleration through impact
 
I find it rather revealing that some people have to make up that others propose that you hit the ball backwards, to have something to critisize and be right about. But it made me think about racket head acceleration. During the debate someone put forward (I can't find it now) that the foreward velocity decreases after impact, while the upwards increases. And ofcourse the sideways speed accelerates as the racket goes across the ball and/or body. And it is only natural that the foreward vektor goes down as the upwards and sideways goes up. If you factor them together, I think it is very likely that the combined sum goes up, meaning that the racket in a lot (most?) of typical modern forehands (and other shots as well) accelerate after and through impact. Maybe this is obvious to some, perhaps others disagree. I wonder if the movement in all three planes have been factored together?

dominikk1985 01-20-2013 07:18 AM

I have read a study somewhere that it is a good sign when the racket decelerates a lot at contact because that means you have a good energy Transfer and all the energy is in the ball (just like the shoulders and hips decelerate to Transfer energy to the arm).

however while that might be true from a Point of physics I still think that the old fashioned swing through the ball is a better advice since it ensures that you don't decelerate before Impact although technically the swing is over at contact and the follow through does nothing with the ball. but the Body is not a machine and when you don't accelerate through the ball there will something bad happen before or at Impact.

sureshs 01-20-2013 07:51 AM

Quote:

Originally Posted by Povl Carstensen (Post 7139813)
I find it rather revealing that some people have to make up that others propose that you hit the ball backwards, to have something to critisize and be right about. But it made me think about racket head acceleration. During the debate someone put forward (I can't find it now) that the foreward velocity decreases after impact, while the upwards increases. And ofcourse the sideways speed accelerates as the racket goes across the ball and/or body. And it is only natural that the foreward vektor goes down as the upwards and sideways goes up. If you factor them together, I think it is very likely that the combined sum goes up, meaning that the racket in a lot (most?) of typical modern forehands (and other shots as well) accelerate after and through impact. Maybe this is obvious to some, perhaps others disagree. I wonder if the movement in all three planes have been factored together?

In that study, sideways numbers were not supplied. I went back and calculated the resultant velocity of the forward and upward components at impact and it was 36 m/s. After impact, the first decreased and the other increased (up to a point) as noted by you above. I calculated the resultant velocity again when the upward component reached its maximum value, and it was 26 m/s. So, at least for the case when the sideways is ignored, there seems to be a net deceleration.

Povl Carstensen 01-20-2013 08:04 AM

Quote:

Originally Posted by dominikk1985 (Post 7140069)
I have read a study somewhere that it is a good sign when the racket decelerates a lot at contact because that means you have a good energy Transfer and all the energy is in the ball (just like the shoulders and hips decelerate to Transfer energy to the arm).

Yes, of course the hit with the ball deccellerates the racket. And the more solid hit, the more decelleration. I suppose with a brush of the ball there is less.
Someone suggested actually shadow swinging should be measured. Allthough perhaps not 110 % scientific, I think a valid suggestion.

Povl Carstensen 01-20-2013 08:10 AM

Quote:

Originally Posted by dominikk1985 (Post 7140069)
however while that might be true from a Point of physics I still think that the old fashioned swing through the ball is a better advice since it ensures that you don't decelerate before Impact although technically the swing is over at contact and the follow through does nothing with the ball. but the Body is not a machine and when you don't accelerate through the ball there will something bad happen before or at Impact.

Agreed. I would say acceleration into the ball would increase ball contact, maybe even dwell time.

sureshs 01-20-2013 08:21 AM

Quote:

Originally Posted by Povl Carstensen (Post 7140295)
Agreed. I would say acceleration into the ball would increase ball contact, maybe even dwell time.

Actually the opposite. While trying to find some info on dwell time last week, I found a paper (by Rod Cross I think) which stated that dwell time decreases with the speed. I don't remember exactly what speed was, but probably the relative speed of the ball wrt racket.

Povl Carstensen 01-20-2013 08:26 AM

Yes, but disregarding speed, acceleration might increase dwell time, alltough perhaps marginally. The racket plays catchup with the ball during contact.

julian 01-20-2013 12:03 PM

Majority of reasearch disagrees with you
 
Quote:

Originally Posted by Povl Carstensen (Post 7139813)
I find it rather revealing that some people have to make up that others propose that you hit the ball backwards, to have something to critisize and be right about. But it made me think about racket head acceleration. During the debate someone put forward (I can't find it now) that the foreward velocity decreases after impact, while the upwards increases. And ofcourse the sideways speed accelerates as the racket goes across the ball and/or body. And it is only natural that the foreward vektor goes down as the upwards and sideways goes up. If you factor them together, I think it is very likely that the combined sum goes up, meaning that the racket in a lot (most?) of typical modern forehands (and other shots as well) accelerate after and through impact. Maybe this is obvious to some, perhaps others disagree. I wonder if the movement in all three planes have been factored together?

Majority of research disagrees with your sentence:
"If you factor them together, I think it is very likely that the combined sum goes up, meaning that the racket in a lot (most?) of typical modern forehands (and other shots as well) accelerate after and through impact. "
Read John Yandell,Andy Fitzell,read some quotes in a paper by Rod Cross
Do NOT talk about intent.

dominikk1985 01-20-2013 12:43 PM

Quote:

Originally Posted by julian (Post 7141193)
Majority of research disagrees with your sentence:
"If you factor them together, I think it is very likely that the combined sum goes up, meaning that the racket in a lot (most?) of typical modern forehands (and other shots as well) accelerate after and through impact. "
Read John Yandell,Andy Fitzell,read some quotes in a paper by Rod Cross
Do NOT talk about intent.

can you summarize their results in one sentence for our convenience?:)

OHBH 01-20-2013 01:02 PM

This thread reminds me of a similar debate in the golfing world. They actually did a study of the top pros swing and found that all but one of the top golfers reached their maximum swing speed just BEFORE impact. The one guy who continue to accelerate past impact was Johnny Miller, a man who just happened to be the very best ballstriker on tour at the time of the study.

Most amateurs, tennis and golf alike tend to reach their maximum head speed too early in the swing

luvforty 01-20-2013 04:17 PM

not sure about the point of all this....

trial and error... aint rocket science to figure out how you achieve max ball speed.

Povl Carstensen 01-21-2013 03:41 AM

Quote:

Originally Posted by OHBH (Post 7141351)
This thread reminds me of a similar debate in the golfing world. They actually did a study of the top pros swing and found that all but one of the top golfers reached their maximum swing speed just BEFORE impact. The one guy who continue to accelerate past impact was Johnny Miller, a man who just happened to be the very best ballstriker on tour at the time of the study.

Most amateurs, tennis and golf alike tend to reach their maximum head speed too early in the swing

Yes but of course the hit slows down the racket/club. But if the racket picks up speed afterwards again, I think it is an indication of that the intention is racket head acceleration through impact (or applying of power through impact if you want). I think intent is a perfectly ok word here btw. But interesting result! And yes swinging too early often results in bad contact I guess.

Povl Carstensen 01-21-2013 03:48 AM

Quote:

Originally Posted by luvforty (Post 7141911)
not sure about the point of all this....

trial and error... aint rocket science to figure out how you achieve max ball speed.

True, trial and error, experience, intuition, I guess is the way most of us go. And from shadow swinging myself, and watching others, it seems acceleration through strikezone is normal (and I am not just talking about Marion Bartoli here...). Also it seems intuitive that you apply more momentum by swinging, accelerating, dare I say pull through impact, than by just letting the hand passively follow the racket at a pace previously achieved.

julian 01-21-2013 07:17 AM

Golf has different constraints
 
Quote:

Originally Posted by OHBH (Post 7141351)
This thread reminds me of a similar debate in the golfing world. They actually did a study of the top pros swing and found that all but one of the top golfers reached their maximum swing speed just BEFORE impact. The one guy who continue to accelerate past impact was Johnny Miller, a man who just happened to be the very best ballstriker on tour at the time of the study.

Most amateurs, tennis and golf alike tend to reach their maximum head speed too early in the swing

Golf has different "DISTANCE" constraints
Please see a quote from today's Wall Street Journal below
Some similarities were discussed by Rod Cross
---->
Distance, it seems, is the handicap golfer's version of happiness, the one part of the game for which they are prepared to pay an ever higher price.

"Our research shows that golfers love to hit it long; distance is the number one reason golfers buy a new driver," Cindy Davis, the president of Nike Golf, said in a recent interview. "Plus, as more golfers determine their purchases based on launch monitor testing and club fitting, distance is measurable and even further influences the purchasing decision."
----> the end of quote

luvforty 01-21-2013 07:27 AM

I don't buy that Johnny Miller being the 'only' guy... if interested, check EA Tischler's work.. he categorize golfers into 3 release types - covering, diagonal and extending..... referring to the full release point where both arms are fully extended, which would also be the point of maximum club speed if player shadow swings without ball contact..... and the release point varies from about a foot past the ball (covering), to 2 ft past the ball (diagonal, tiger style), to club almost parallel to ground (extending, and Zack Johnson comes to mind).

it is therefore perceivable that player with later release points reach the maximum speed later, and possible after impact.

but to Tischler's point, all 3 categories are technically valid.

corners 01-21-2013 07:32 AM

Quote:

Originally Posted by julian (Post 7143863)
Golf has different "DISTANCE" constraints

If a tennis player is sufficiently skilled at spinning the ball he or she also has no distance constraints. Spin takes hitting long out of the equation and allows a player to swing as fast as possible, and presumably to accelerate after contact, although I don't know if this is done.

I remember reading in Steve Tignor's book on the Borg Mac rivalry that Mac was taught by [Palifax I think] to decelerate this racquet into contact, which might account for the peculiar appearance of this strokes.

I also remember reading that Martina N.'s serve stroke reached maximum acceleration just after ball impact, but I don't remember where I read that and don't even know quite what means. :confused:

julian 01-21-2013 07:50 AM

I disagree with the first part of the post
 
Quote:

Originally Posted by corners (Post 7143906)
If a tennis player is sufficiently skilled at spinning the ball he or she also has no distance constraints. Spin takes hitting long out of the equation and allows a player to swing as fast as possible, and presumably to accelerate after contact, although I don't know if this is done.

I remember reading in Steve Tignor's book on the Borg Mac rivalry that Mac was taught by [Palifax I think] to decelerate this racquet into contact, which might account for the peculiar appearance of this strokes.

I also remember reading that Martina N.'s serve stroke reached maximum acceleration just after ball impact, but I don't remember where I read that and don't even know quite what means. :confused:

I disagree with the first part of the post.
To go a little deeper if I may.
For ATP forehand 3 (see the classification of Yandell et al) the vertical component of the racket head speed has to go from 0 to 20 mph in 11 milliseconds.
It is NOT a piece of cake to achieve it.Some shanks are generated.
The banner example is reasonably skilled Fderer who shanks A LOT during some matches.

julian 01-21-2013 07:51 AM

Last sentence
 
Quote:

Originally Posted by corners (Post 7143906)
If a tennis player is sufficiently skilled at spinning the ball he or she also has no distance constraints. Spin takes hitting long out of the equation and allows a player to swing as fast as possible, and presumably to accelerate after contact, although I don't know if this is done.

I remember reading in Steve Tignor's book on the Borg Mac rivalry that Mac was taught by [Palifax I think] to decelerate this racquet into contact, which might account for the peculiar appearance of this strokes.

I also remember reading that Martina N.'s serve stroke reached maximum acceleration just after ball impact, but I don't remember where I read that and don't even know quite what means. :confused:

Last sentence-it is NOT true for a serve of Federer-see Andy Fitzell.

julian 01-21-2013 07:55 AM

Some little problems with a tennis net
 
Quote:

Originally Posted by corners (Post 7143906)
If a tennis player is sufficiently skilled at spinning the ball he or she also has no distance constraints. Spin takes hitting long out of the equation and allows a player to swing as fast as possible, and presumably to accelerate after contact, although I don't know if this is done.

I remember reading in Steve Tignor's book on the Borg Mac rivalry that Mac was taught by [Palifax I think] to decelerate this racquet into contact, which might account for the peculiar appearance of this strokes.

I also remember reading that Martina N.'s serve stroke reached maximum acceleration just after ball impact, but I don't remember where I read that and don't even know quite what means. :confused:

Some little problems with a tennis net for TENNIS (NOT GOLF) should be mentioned as well.

julian 01-21-2013 07:56 AM

LAST TIME I checked
 
Quote:

Originally Posted by luvforty (Post 7143889)
I don't buy that Johnny Miller being the 'only' guy... if interested, check EA Tischler's work.. he categorize golfers into 3 release types - covering, diagonal and extending..... referring to the full release point where both arms are fully extended, which would also be the point of maximum club speed if player shadow swings without ball contact..... and the release point varies from about a foot past the ball (covering), to 2 ft past the ball (diagonal, tiger style), to club almost parallel to ground (extending, and Zack Johnson comes to mind).

it is therefore perceivable that player with later release points reach the maximum speed later, and possible after impact.

but to Tischler's point, all 3 categories are technically valid.

LAST TIME I checked it was the TENNIS forum


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