Optimum Racquet Balance for Performance II - MgR/I Data for ATP Pros

ok ..

i tried it and i have to say it didnt work for me. i didnt like it at all ^^, went straight back to my old setup.

also i dunno which pros u measured and how bc u dunno the sw from every pro. but for example gonzo was a long time top 10 player and his MgR/I is nowhere near 21. aswell as nadal is rank 1 and his MgR/I is not even 20,1 its a bit lower. ferrer MgR/I 20,4... and i could measure a lot more pros like this. i just dont want to count more lol
(i measured their MgR/I's with the "perfect" sw of 360 and juras specs)

 

The MgR/I method only works if you take the time to tune it precisely for your stroke. That is - if your optimum MgR/I vlaue for your stroke is 20.9, then 21.0 will feel difficult to control. So will 20.8. It only works if it's spot on. For me, I always take the time to tune my racquet against a wall -- this is because small variations in grip position for different racquets mean that I can't always get the effective MgR/I value accurate enough without on-court tuning.

Also, please keep in mind that my method for estimating swingweights is not that accurate, because the SW can vary a lot for a given mass and balance. Sometimes my estimate is high, sometimes it is low, and sometimes it is accurate. This creates a lot of noise in the data, but even so, averaged out over 100 players, the estimates are accurate enough to give the trends.

Also, players like Nadal, who use full western grips, seem to be able to control the ball just fine with very low MgR/I values. For players like Ferrer, who I don't have accurate swingweight data for, it cannot be assumed that the MgR/I value is accurate (but it's probable that it is reasonably close).

I should point out that the smaller subset of data that includes measured swingweights from Greg Raven gave an even more distinct advantage to players in the 20.6-21.0 MgR/I range, with less noise. This can be easily verified by anyone who plugs in the numbers.

 

i dont want to be bad with u. i appreciate ur posts its very interesting.

but nadal doesnt use full western. he uses semiwestern.

and even if ferrers sw would be 350 his MgR/I would still only be 20,77. and like i said i could count lots of more pros with less than 21 MgR/I

 

According to Fig 2 of the OP, about 40% of all ATP pros have MgR/I in the 20.8-21.1 range (and more than 50% in the 20.7-21.1 range). But more than 50% are < 20.8.

My point is that the pros who are in the 20.7-21.1 range have, on average, better rankings, especially when considering only those with high swingweight.

It doesn't mean that there are not exceptions to the trend.

 

One more important point about David Ferrer...

He plays with a wrist band on his right wrist. This effectively adds to the weight of the hand, necessitating a much lower MgR/I value than without one. If you think that this sounds ridiculous, go try hitting your normal forehand while wearing a wrist band -- it noticeably alters your stroke.

 

mh i just dunno if this is right for every1. bc there are some big exceptions. i dont rly want to discuss this further, this was just my opinion about it

 

yes it sounds a bit ridiculous lol^^. there are many pros who wear wristbands i guess its more than 50%.... how big do u think it influence the MgR/I rating?

with this aspect some of ur pros who r in the range of 21 have a too high MgR/I rating. etc.

 

Holy crap - I just did a spot check of all the pros from my subset from Greg Raven's list (where I have measured SW data).

Almost all of the top-10 guys who had low MgR/I values wear wrist bands. And all of the top-10 guys in the 'optimal' range don't wear them. The only guy in the optimal range near 21.0 on the list that does wear one is Hyung-taik Lee, and he was screwing up my perfectly separated result with his crummy ranking. So this might explain why!

I might need to recrunch my results - giving perhaps a 0.3 boost for the guys with wristbands. Curious to see how the numbers would turn out -- my guess it that it will clean up some of the noise.

 

Hmm - it looks like if I give a correction factor of about 0.3 for small wrist bands, and about 0.5 for large wrist bands, then almost every pro on Greg Raven's list comes out in a very narrow MgR/I range.

 

Is this a .3 for the small wrist ban added to 21, so if you had your racquet at 21 it would now be 21.3 or is it in your figures?

 

Hmmm - this sort of post-analysis data 'grooming' comes dangerously close to 'torturing the data untill it confesses'...

 

With a quick search on youtube, i was able to find videos of top pros using wrist bands of different length in some matches or not wear at all sometimes or wear them higher on their forearm. So, if a difference of 0.1 in MgR/I makes so much difference in someones ability to control the racket, the pros that used a shorter or longer wrist band than their usual or didnt wear any, they should have a great difficulty according to you to control the racket that day. All this sounds a bit exaggerating to me.

 

So you ARE talking about a pendulum action in the horizontal plane afterall!!?

Can you explain to me why you think this pendulum action is primarily affected by gravity, and hence g, and not by the acceleration of the racket by the player? How does gravity affect the angular velocity omega2?

 

Definition of omega2

Please let me where is omega2 defined

 

LOL..no it does not. I have used a wristband for years and when it's not on there is no difference.

There is so much over thinking in this thread that it scares me.

 

Ok - I went into the racquetball court to investigate how much of a difference a wrist band makes. I tied a sock around my arm, and then tweaked my RDS001MP until it felt right again. I actually liked the feel -- made the swing of my arm feel more like a heavy pendulum and more repeatable than when I tuned my racquet without the band. But didn't like the restricted feeling on serves. Anyway, I came back and took measurements: the MgR/I value for the wrist-band tuned racquet was 20.6.

Based on this, the expectation was that there should be a higher percentage of players in the wrist band group with MgR/I shifted about 0.4 below the optimum.

So I sorted the 99 players on my spreadsheet into those who play with wrist bands and those who don't.

70 players with wrist bands (I was surprised it was this many!).
27 players without.
And 2 players omitted from analysis due to double handed forehands (Gambill & Knowle).

Sure enough, I found a big spike at MgR/I = 20.4-20.6 in the wrist band group:
18 out of 70 players (26%) had MgR/I in the 20.4-20.6 range.

How many had MgR/I = 20.4-20.6 in the bare wrist group? Zero for 27.

 

Good question, I should have said your (trav's) omega2...

 

I've tried figuring out if there is any substance to this theory, but I'm rapidly losing hope...

 

More basic questions

Kaiser,
1.your question is reasonable
2.A more basic question is:
what is a definition of a word "frequency"?
Please note that a frequency can be time dependent.
i.e omega2 is really omega2(time)
If so an analytic expression quoted by OP is only an approximation.
The same applied for a phrase "period" used

 

A "correct numbers" for swingweight and mass

Another aspect to think about.
Please see a quote from TW Professor
There is no such thing as "the real" weight, balance, swingweight, etc. of a racquet. Every racquet is different and, depending on the measurement of interest, the range can be up to +/- 5%. For weight, that would be as much as 30 grams between the lightest and heaviest possible racquets for a 300 gram "spec" racquet. Most racquets fall closer to the middle of the range, but you never know.

That is partly why the dynamic specs (like power potential, sweet zone size, and vibration frequency) are more accurate predictors of performance. They are measurements during impact that are the result of the composite contributions of every other spec (weight, balance, swingweight, RDC flex, pattern, etc.). As such they are performance specs that tend to average out the tolerances in the individual static specs.

 

I was referring to Cross's omega2, which he uses to denote the angular velocity of the racquet about the vertical axis (I cannot post greek symbols or exponents).

 

I think you'll be hard-pressed to find a top-10 pro who switches back and forth. Show me a pro who wears wrist bands for some of his matches but not for others, and I'll show you a pro with a crummy ranking.

 

To summarize this thread: wristbands plus heavy racquet = goat?

 

I'm skeptical about any of this. First of all two pendulums are involved, as it was pointed out, the full arm from shoulder down including the racket and the second made up with the wrist including the racket. So, one can't just take these formulas and plug the numbers for the racket alone. The length and mass of the arm will need to be taken into account for the first pendulum and for the second the mass is a combined mass of the wrist and the racket. The wrist is pretty heavy and people differ in wrist's mass substantially. I think if one were to try to use these numbers/formulas in practice the error would be huge, rendering the approach utterly useless. One can argue there is a third component here that is completely ignored - the torso, which is also rotating. That's not even to say that the energy for the stroke comes from the legs to begin with. As scientific as this sounds, I can't really take any of this seriously in terms of practical application when a player want's to find the best racket to play with.

 

2009 Rolland Garros 4th Round : http://www.youtube.com/watch?v=WHwgdhD4SP0

Nadal didnt wear his watch in this match and many others, but i am posting this one so you can tell me that he lost because of that. His watch weighs just 20 grams, which is the weight of a small wrist band(i weighed one of mine), so 0.3 difference in MgR/I.

And a couple of practice videos of federer and nadal without wrist bands, i know its not matches, but why would they practice in a way that would make it really really difficult for them to control the ball?

http://www.youtube.com/watch?v=SJVF3vqD_kI
http://www.youtube.com/watch?v=-eq4PAMA5A8&feature=fvst

A couple Monfils photos too :


And the pickiest person of all time about his equipment :

 

Nadal wears his watch on his non-hitting arm.
Not trying to invalidate the rest of your argument though.

 

Well, his right arm is his 2-handed backhand hitting arm and from what i understand MgR/I needs to be tuned for the backhand too.

 

Sampras seemed to wear wrist bands for the last couple years of his career, when his volleys seemed to get better, but his forehand sucked. I haven't been able to find a picture from a match from 1993-1998 where he had wrist bands.

And in my opinion, Monfils is a good example of a guy who could be #1 if he played with a tuned racquet. He wins with his physicality, not with pinpoint accuracy.

 

I could find a lot more examples if i kept on searching and i posted also the videos of federer and nadal who practice without wrist bands, which should be like practicing with very different rackets than what they play with. However, i dont think there is a point on arguing more about how much difference wrist bands or perfectly tuned rackets make.

There might be some truth in your theory, but i dont think it is the main reason that someone is number 15-20 in the world and not number 1-5. Especially in the amateur level there are far more important things people should work on to improve their game. Maybe, your theory has helped some people (or they think that something has changed in their game because of placebo effect), but to convince myself, i tried some of the things you suggest in your threads, but i always came back to my setup, which by the way should be really unsuitable for me according to your theory.

And, to be specific i am 6'3", using a racket of 21.5 MgR/I and i wear a wrist band too. So, the ideal should be around 20.8 for me without a wrist band, 20.4 with a wrist band. A difference of 1.1, i wonder how do i keep playing with it

 

Here is a statistically significant result, showing that wrist band use correlates with racquet setup for top players. All players from my combined list with top-3 career high rankings are included in the result (in cases where a player has switched to wearing wrist band during his career, I used the wrist status during his peak years).

The evidence is there, whether or not you choose to dismiss it.

 

Most players are really in-tune with their bodies and how they feel. And you can feel differences with wrist bands, wrist supports, tape, tape on fingers, etc. Its not just how it feels; it affects ball contact.

 

Travler,

Do you think is better to play with wristband or without wristband?

 

I don't think it matters, as long as you pick one way or the other, then tune up your racquet nicely, and stick with it.

 

I got 20.92734649 for the Donnay Gold 99 when I did the math. I used this in Microsoft Excel to get the balance:
=+(((685.58/25.4)/2)- 6*0.125)*2.54

The 685.58 is the length (close enough for government work), 6 is the points head light the balance is.

I basically created a little spreadsheet with some rackets and started plugging in data from Tennis Warehouse.

I found several racquets that came in at roughly 21 bone stock using TW data.
Volkl DNX9 (21.01)
Dunlop Bio 200 Plus (20.99)
Head IG Instinct S (20.97) - This is the odd one of the group, as it is very light
Pacific X Force Pro (20.97)

I'm sure there are others, but also in my list for close are the T-Fight 320, and original T-Fight 315.

 

Well said, the mechanics of the tennis stroke are MUCH more complex than the simplistic MgR/I formula advocated here!

Also, it beats me why g,the vertical acceleration due to gravity, would would critically control whether "the racquethead moves forward faster (or slower) than the hand during the moment of impact", allegedly causing "small errors in timing will result in changes in racquetface angle, leading to less accuracy of the shot", which appears to be the crux of his reasoning.

Moreover, consider the ideal situation that is sketched here: "If the racquethead moves at the same speed as the hand, then small errors in timing are inconsequential and the ball will still go toward the target". If this were true, the maximum speed of the hand would be the limiting factor controlling the maximum speed of the ball, and we wouldn't be witnessing the huge forehands that we are seeing in modern tennis. In my understanding this is the exact opposite of the argument by Cross, who reasoned that as the forearm and hand (necessarily) slow down just before ball contact, the racket will pivot foreward around the wrist resulting in greatly increased rackethead speed...

 

Yes, but that last second racquet acceleration would lag behind or over-accelerate if mgr/I isn't tuned.

 

deleted...

 

Yes - a tennis stroke is complex - that's exactly why it is so remarkable that the physical pendulum model is so effective for tuning a racquet's performance!

A forehand is a high-to-low-to-high stroke. The reason every pro takes the racquet back high is to take advantage of the potential energy of the extra height beyond the height of ball contact. The high-to-low portion of the stroke is almost entirely gravity-powered. It's only after the swing reaches it's low point does a pro start applying a significant couple to the arm lever to accelerate against gravity.

Yes, I am suggesting that Cross has not accurately modeled his forehand because he is assuming that it is similar to a golf swing, where maximum angular velocity at impact is a good thing. For a forehand, minimizing angular velocity of the racquet (about the z axis) is the key to an accurate forehand. For a typical pro forehand, the angular velocity of the forehand slows down a lot just before impact. This can be easily confirmed by looking at slow-motion videos.

 

You need to know your swing weight to complete the forumula.

 

Really?? Why does this MgR/I matter? What's the relevance of r in it?

 

?? Sofar I've only seen you give your own subjective experience as evidence for that statement. I'm sorry to say I find your fudged statistics (multiple back-and-forth corrections of the data to obtain the desired result) rather unconvincing.

When you hit the ball on the rise chest to shoulder high, as happens very frequently in the modern topspin/power game, the high-to-low part of the forehand is almost non-existent and it's almost entirely in the horizontal plane. You see e.g. Federer do this all the time in a match.

Moreover, you said yourself that your MgR/I-tuning is intended to avoid slight variations in the angle of racketface around a vertical axis through the wrist. However, your MgR/I formula completely ignores the strong horizontal component in the accelleration of the racket (supplied by the player) which necessarily plays a primary role in determining the angle of the racket face at impact. This horizontal component will vary considerably between players depending on their strength, ability and forehand stroke mechanics.

Do you have any objective, empirical evidence for this? When I look at those videos I see that the wrist remains laid back until just before impact with the ball, after which it is relaxed completely in the follow-through. Are you suggesting that the angle of the golf club at impact is not important for the accuracy of the stroke???

 

A recent paper by Rod Cross

Kaiser,
a paper by Rod Cross is available from
http://www.physics.usyd.edu.au/~cross/PUBLICATIONS/49. TennisDPend.pdf

 

deleted....

 

Typo corrected.

 

deleted...

 

deleted....

 

I have taken great pains to ensure that my data is as accurate as possible. Any subsequent corrections of the data are only to fix errors that I discover (such as un-updated rankings). Or for example, I initially had Kafelnikov listed in the wrist band group, but then later discovered that he won both of his majors with bare wrist, so I moved him to the bare wrist group after my initial post of the data.
Please do not carelessly accuse me of "fudging," as this is a serious accusation. My statistical findings can be easily checked by anyone willing to make the effort, since the raw data are already publicly available.

The pendulum model is being applied to the racquet lever, which typically starts at about 7 feet high, so gravity still contributes to the pro forehand, even on chest high balls.

No - I am not completely ignoring the horizontal component. When a pendulum swings downward, potential energy is converted to horizontal velocity. As I have stated many times, the player provides a strong couple to the arm lever, but this couple is not very large until AFTER the racquet has already dropped below the ball due to gravity and gained a lot of momentum due to pendulum physics.

And yes, the stroke mechanics vary from player to player, but not by as much as you might think.

A golf club is hitting a stationary object, so high angular velocity at impact is not a problem. For a forehand return, this is not the case. The best returners in the game are the ones who have the lowest angular velocity at impact (check out slo-mo of Ferrer's forehand, who has led the tour in return game % multiple years). Ferrer's angular velocity is almost zero compared to most players. Compare him to Gonzalez, who has a great forehand against slow balls, but he's not as good a returner as Ferrer. Slo-mo analysis of Gonzalez's forehand shows that he has higher angular velocity at impact than Ferrer.

The whole point of this thread is that by tuning your racquet properly, you can just fling your arm toward the ball with a floppy wrist, and your wrist will naturally move in a way that keeps your racquetface at the same angle through the hitting zone. It's a good feeling when you get it tuned right - please show some respect and take the time to try it, you might like it.

 

travlerajm: again nice to see you around here

But I have a question for you:

I have this setup(lead+silicone) in a Dunlop 300T:
- 350 grams
- 357 SW
- 33,1 mm BP
Wich give me:
MgR/I = 20,54
MR^2= 384,48

like you can see, my MR^2= 384,48 this is an optimal value. BUT my MgR/I = 20,54.

How about it?

Best Regards

 

I know this is an older thread at this point (3 months since last post), but I thought it worth mentioning.

I've been experimenting with tuning racquets to as close to 21 MgR/I as possible and trying to retune from there.

What I have found, and it makes perfect sense from a physics standpoint, is that when I got a little above 21 (I am 5'11" tall) even as high as 21.36 I can really snap through the serve better.

So it seems that you can use the information to tune for specific parts of your game to optimize for one thing or another.

For me, optimizing for my serve seems to help the most.

 

Nice work. That means your ideal MgR/I might actually be 21.36 or so. I'm 5'10" and I find my ideal to be around 21.09-21.12.

I have had mine up to 21.2, and it did feel noticeably quicker thru contact on serves. It felt a little too quick on forehands though...

Edit Feb 2012: I have found through more testing that ~20.9-20.95 is better for my forehand.