Question for travlerajm

I have been gathering data on TT users arm length and MgR/I. The aim is to find a link, or a multiplier between arm length and MgR/I.

I just thought I'd run this by you to see what you think, and to critique my methodology. The answers would be compared against your data, if you are willing, since your MgR/I is fine tuned. Here is the questionnaire I sent out.

What is your swingweight?
Do you wear a wristband? Single wide or double?
What is your forehand grip?
Do you choke up or down from the middle of the handle?
Could you measure from the top of your shoulder to the end of your middle finger?
What is your personal MgR/I value?

I've realized that people have probably been measuring from different points of the shoulder. I've come up with the following method to get accurate arm length results.

To measure use a tape measure with a clip on the end, like this. Guide the clip up your arm until it rests on the tip of your shoulder.Measure from here to the end of your middle finger.

All of the TT users I questioned have fine tuned their MgR/I with lead tape.

I have included swingweight as a factor due to the following post of yours.

travlerajm said:

The calculations in the posts above demonstrate that the arm lever swing frequency is affected by the amount of mass in the handle. Becasue of this, the optimum MgR/I is slightly different for different swingweights. For me, my forehand optimum is about 21.0 for a SW of 360, but 21.4 for a SW of 300. In any case, tuning against the wall is necessary. The effect of handle mass on the arm lever swing frequency compounds the sensitivity of the swing to small changes in balance.

Click to expand...

This seems to indicate that large shifts in swing-weight have quite a big effect on MgR/I.

newyorkstadium said:

I have been gathering data on TT users arm length and MgR/I. The aim is to find a link, or some sort of multiplier.

I've got three replies, with three to come. I just thought I'd run this by you to see what you think, and to critique my methodology. The answers would be compared against your data, if you are willing, since your MgR/I is fine tuned. Here is the questionnaire I sent out.

What is your swingweight?
Do you wear a wristband? Single wide or double?
What is your forehand grip?
Do you choke up or down from the middle of the handle?
Could you measure from the top of your shoulder to the end of your middle finger?
What is your personal MgR/I value?

I've realized that people have probably been measuring from different points of the shoulder. I've come up with the following method to get accurate arm length results. I can't think of another method that doesn't start from the neck, or involve knowledge of shoulder anatomy that I don't possess.

To measure use a tape measure with a clip on the end, like this. Guide the clip up your arm until it rests on the tip of your shoulder.Measure from here to the end of your middle finger.

Click to expand...

I hope you are able to reach your goals.
My SW is 370.
I don't wear a wrist band.
My wingspan is about 72.5". I am 5'11" without shoes.
My forehand grip is between eastern and semiwestern.
I don't choke down or up.
Distance from point of shoulder to tip of finger is about 29".
I play with 21.0 MgR/I, and 22.55 for my 2hb (10cm axis).

If I find some time this summer, I will try tuning MgR/I for few frames at lower swingweights/static weights to see what I get. I am curious about what I'll find.

Thanks travlerajm. What correction factors do I use for the following? Please give me the precise figure if it is a rounded number:

Single wide or double wide wrsitband
Eastern, extreme eastern, SW & W

How much would you guess I should change MgR/I for choking up or down?

Is wingspan a more useful figure then arm length?

I would need to do the experiments and measure carefully to answer your questions.

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Ok, this experiment looks like coming to an abrupt end. I have tried to tune MgR/I again against a practice wall with numerous racket, but got nowhere.

To find a link between arm length and MgR/I, I would need to know how much swingweight, choking up/down handle, wristbands and forehand grip type affect MgR/I.

Btw, I could feel the lagging disconnect in the racket head, when attempting to tune my racket's MgR/I. I just could not distinguish a difference in accuracy. My shot's were going to the right, left and exactly where I intended.

I'm typing this on a portable device, so apologies for any typos.

If anyone does wish to investigate how equipment factors like wristbands affect mgr/i, it would be a good idea to find out if swingweight affects mgr/i first. Say, if you found out that wearing a wristband lowered mgr/i. You would then have to deduct any effect the change in swingweight, from adding or removing lead tape, had on the mgr/i to reach the true number of how much the wristband impacted mgr/i.

I just hit the ball.

Let's see if I get this straight.
MgR/I is a number when tuned right, the pendulum frequency of the racket matches the pendulum frequency of the arm.
Swingweight is in the equation.
So, the only reason I can think of why a higher swingweight might result in a lower MgR/I, is that there must be a change in technique playing with it. Maybe due to the higher swingweight and/or static weight a player might bent the elbow less, thus changing the effective length of the arm.

Maybe, Newyorkstadium, you're having trouble tuning because you vary your elbow angle in the high to low part of the forehand differently with different set-ups.

the green god said:

I just hit the ball.

Click to expand...

I second this. Don't get me wrong -- I'm all for experiments and expanding knowledge. I am a graduate student trying to be in the academia, after all. But tennis environment is impossible to control to scientific standards. In my view, a good study is better than no study, and no study is better than a substandard study.

JohnB said:

Maybe, Newyorkstadium, you're having trouble tuning because you vary your elbow angle in the high to low part of the forehand differently with different set-ups.

Click to expand...

No, I haven't been able to tune my MgR/I with any setup. The problem is that I can't find a clear pattern of where my shots are going. They are going to the left, right and exactly where I aimed. I have now given up on tuning my MgR/I or any MgR/I experiments, as I have tried and failed with multiple rackets.

I have the data from the questionnaires but I can't do anything with it, without knowing how much swingweight, choking up/down handle, wristbands and forehand grip type affect MgR/I. I didn't expect the results to amount to much anyway, as I only had data from eight people. If anyone else wants to take up this experiment, that would be great. If not I will let this thread die.

JohnB, I don't have any knowledge of physics. As far as I can tell, travlerajm's post suggests that a change in swingweight does alter technique, and this is the why MgR/I changes.

newyorkstadium said:

I have been gathering data on TT users arm length and MgR/I. The aim is to find a link, or a multiplier.

I've got three replies, with three to come. I just thought I'd run this by you to see what you think, and to critique my methodology. The answers would be compared against your data, if you are willing, since your MgR/I is fine tuned. Here is the questionnaire I sent out.

What is your swingweight?
Do you wear a wristband? Single wide or double?
What is your forehand grip?
Do you choke up or down from the middle of the handle?
Could you measure from the top of your shoulder to the end of your middle finger?
What is your personal MgR/I value?

I've realized that people have probably been measuring from different points of the shoulder. I've come up with the following method to get accurate arm length results. I can't think of another method that doesn't start from the neck, or involve knowledge of shoulder anatomy that I don't possess.

To measure use a tape measure with a clip on the end, like this. Guide the clip up your arm until it rests on the tip of your shoulder.Measure from here to the end of your middle finger.

Click to expand...

It doesn't get any better than this. Funnier than s***!

I just found this in my subscriptions. Travlerajm, did you ever find out if swingweight affects MgR/I?

After failing to tune my MgR/I, I've settled on the Blade 93 that I'm playing well with now.

NYS, did you ever complete this experiment?

henman_fan said:

NYS, did you ever complete this experiment?

Click to expand...

No. See my qouted post from this thread.

newyorkstadium said:

I have the data from the questionnaires but I can't do anything with it, without knowing how much swingweight, choking up/down handle, wristbands and forehand grip type affect MgR/I.

Click to expand...

It would very useful to know this info for a few reasons, but I have tried numerous times and failed everytime.

1) This could be used to create a spreadsheet that calculates your personal MgR/I value, based on arm length and the equipment factors.

2) I would also be curious to see if the pro's have optimal MgR/I, if you add in all these factors. Travlerajm estimated the effects of forehand grip and arm length on MgR/I, from the differences between pro's racket specs. Though, I don't think you can extrapolate the effects of a single factor like height, based on differences in the pro's MgR/I. The pro's in the 6'1 and 5'8 group could also have different swingweight and forehand grips, which also affect MgR/I. You would need to actually know how these factors affect MgR/I, then input it into the data. Experimenting by wall-testing would be far more accurate.

3) If the theory works, I just want to see it take off. Tennis can be a frustrating sport at recreational level, which detracts some people from the sport. MgR/I could help with this. It won't do, though, unless people can calculate their own MgR/I. Something like the spreadsheet I mentioned above could help.