3D motion capture and the resulting measurements......

[Michael Finney]

HUGE issue:

From Dan Parks comments on Joyce, Ball, et al.......enjoy

"What is unclear from this portion of the patent is how the rotational angles are defined. In Joyce et al.(2010) it is argued that in biomechanics and human movement applications “sequence dependency” needs to be considered whenever measuring a rigid body in space where there are three translations (displacements along the X,Y, and Z axes) and three independent and successive rotations which correspond to rotation about the X,Y, and Z axes (Cardan angles). Joyce et al. (2010) writes,
**** In human movement applications these three rotations typically correspond to flexion/extension, lateral bending and axial rotation. To provide anatomical meaning these angles need to be defined in a specific order of rotation (ZYX, ZXY, YZX, YXZ, XYZ or XZY). It is the order in which these angles are defined which may affect the actual value of the rotations reported...This is of importance as for movements with large magnitudes of rotations about each orthopaedic axis (such as golf), as the magnitudes of rotation reported for each Cardanic sequence may vary considerably as the choice of which rotational sequence is appropriate for a particular movement pattern."

Considerably

 

[SteveT]

It tells me that the kinematic axes and sequencing must be defined for the golfswing for the patent to be valid. What does it tell you?

 

[Michael Finney]

It tells me that the Matt System, Zenolink, AMM, GBD, KVest, 4DSwing and the 20 other "for profit" 3D motion capture companies are probably not measuring the same sequences and therefore there are some confused programmers, owner/operators, teachers, students, and golf forum junkies.........

 

[TeeAce]

It tells me that the Matt System, Zenolink, AMM, GBD, KVest, 4DSwing and the 20 other "for profit" 3D motion capture companies are probably not measuring the same sequences and therefore there are some confused programmers, owner/operators, teachers, students, and golf forum junkies.........

I totally agree with you. The measuring points are different, the definitions of axis and some directions are different and that way we can't say that one is right (specially in rotation speeds) and one is wrong.

What I can say about measurements of 4DSwing, we decided to measure the shoulder rotation around the vertical axis so we can see the rotation from the top down camera also. Another thing is that we measure shoulders from outer part of shoulder joints and not from the spine, and it gives also different results. In few weeks we gonna include the rotation speed also around the spine, but it seems not much difference in results.

3Dmeasurement is something I can call really challenging to define. It feels simple at beginning when we are used to see and think like we do, but gets more complicated when going deeper to that world. For example spine is not rigid and it bends to many directions and to define how to measure it really well "around the spine angle" there is no really simple solution. Around the lower spine or upper part of that will also give different numbers and even to define what is tilt and what is forward bend is quite impossible when everything is changing all the time.

Those are the reasons we got so many other graphs like lateral speeds from different joints, because sometimes those are more informative than pure rotations. The main point is still that whatever system we use, we have to understand how the measurements are defined and only compare apples to apples, not to oranges. When we learn to read one systems graphs and compare those from player to player, we can get the benefits out of them to help people getting better and that's the main goal we all should have. That way we can see if the deceleration of the shoulder speed for example is caused by real deceleration or because the change of moving direction when right shoulder drops and pops up later on.

 

[wulsy]

To be fair, Teeace has been saying this for months here on Brian's forum. And has been unfairly slated for saying it sometimes.

 

[Kevin Shields]

Oh, yeah, let's. He's been soooooooo fair to people here on other boards.

 

[Michael Finney]

To be fair, Teeace has been saying this for months here on Brian's forum. And has been unfairly slated for saying it sometimes.

I agree - he has agreed with me a few times saying that all the systems were not measuring the same things. HOWEVER, his partners (maybe not by choice but by circumstance) Miyahara and Martin (we will now refer to them as the M&Ms) have filibustered on the fact that their "elite" strikers of the ball have no decel in their most proximal body parts.

Well, how in the hell are we supposed to believe that contention when EVERY other 3D measurement company has said it happens and that the summation of speeds principle (proximal to distal sequencing) is in fact valid? Tapio has admitted that his system is most likely measuring these rotations and translations in their own proprietary way.

The moral to the story is don't base your challenge to the the golf instruction industry on a system that produces numbers which may mislead the target audience. Just because you say that the "elite" strikers of the ball have a consistent rotational speed to and through impact (or maybe even a positive acceleration to and through impact) doesn't make it so.

 

[Michael Finney]

For your review:

[video]http://www.amm3d.com/Support/ArticlesandVideos/PhilCheethamThoraxAccelerationCreatesPelvisD.aspx[/video]

 

[Brian Manzella]

Just so everyone is on the same page....

The following happens in EVERY decent golf swing:

The "where" is the only difference.

 

[fadegolfer]

And the "where" is what makes all the difference.

 

[Dariusz J.]

Just so everyone is on the same page....

The following happens in EVERY decent golf swing:

The "where" is the only difference.

Brian, the red line is drawn wrongly, if your intentions were to represent pelvis motion.
It shows now how waist is moving (i.e. boneless segment linking thorax with pelvis).

Cheers

 

[Brian Manzella]

And the "where" is what makes all the difference.

Well, there will be different "wheres" for all 9 ball flights out of a given stance.

 

[TeeAce]

Brian, the red line is drawn wrongly, if your intentions were to represent pelvis motion.
It shows now how waist is moving (i.e. boneless segment linking thorax with pelvis).

Cheers

And that's one of the big differences. When we made decisions about 4DSwing, I absolutely wanted to see hips speed, not waist rotation, because IMO it tells more about how the player uses his feet and legs. It can be surprise how much that middle section is rotated even the shoulders and hips are not. That part can start opening at transition, when hips are still closing when shifting left.

 

[Dariusz J.]

And that's one of the big differences. When we made decisions about 4DSwing, I absolutely wanted to see hips speed, not waist rotation, because IMO it tells more about how the player uses his feet and legs. It can be surprise how much that middle section is rotated even the shoulders and hips are not. That part can start opening at transition, when hips are still closing when shifting left.

Not a word less, not a word more. Waist should be a subject for the soft structure studies. If there is no waist the correct sequentiality of the motion would be very jeopardized.

Cheers

 

[Brian Manzella]

I didn't draw the lines perfectly??

I'll be.....

Listen, I am FRAMING the DISCUSSION. Do you understand that?

 

[TeeAce]

I agree - he has agreed with me a few times saying that all the systems were not measuring the same things. HOWEVER, his partners (maybe not by choice but by circumstance) Miyahara and Martin (we will now refer to them as the M&Ms) have filibustered on the fact that their "elite" strikers of the ball have no decel in their most proximal body parts.

Well, how in the hell are we supposed to believe that contention when EVERY other 3D measurement company has said it happens and that the summation of speeds principle (proximal to distal sequencing) is in fact valid? Tapio has admitted that his system is most likely measuring these rotations and translations in their own proprietary way.

The moral to the story is don't base your challenge to the the golf instruction industry on a system that produces numbers which may mislead the target audience. Just because you say that the "elite" strikers of the ball have a consistent rotational speed to and through impact (or maybe even a positive acceleration to and through impact) doesn't make it so.

First of all Kelvin and Martin has nothing to do with our system and they are not my partners. I got huge respect for Kelvin and has been discussing with him and we agree of many things. No more about that, but please avoid put stamps on something that is not true.

Secon thing about acceleration. Yes there is different ways to measure those things, and one way is to measure lateral speed (toward the target) of something. Everyone can make their own conclusions here if the right shoulder is decelerating or accelerating through impact

So which one is misleading more? To tell people to decelerate the inner circle or accelerate everything through the impact?

 

[Dariusz J.]

I didn't draw the lines perfect??

I'll be.....

Listen, I am FRAMING the DISCUSSION. Do you understand that?

So...framing the discussion justifies wrong presentation ? If yes, I do not understand it. I though we're SCIENTIFIC SOCIETY here. But anyhow - wanted only to be helpful, now I regret it.

Cheers

 

[drewyallop]

First of all Kelvin and Martin has nothing to do with our system and they are not my partners. I got huge respect for Kelvin and has been discussing with him and we agree of many things. No more about that, but please avoid put stamps on something that is not true.

Secon thing about acceleration. Yes there is different ways to measure those things, and one way is to measure lateral speed (toward the target) of something. Everyone can make their own conclusions here if the right shoulder is decelerating or accelerating through impact

So which one is misleading more? To tell people to decelerate the inner circle or accelerate everything through the impact?

Could you show the y axis T?

 

[Michael Finney]

WHO IS TELLING PEOPLE "TO DECELERATE THE INNER CIRCLE"??????? - yes, i am shouting.....

 

[TeeAce]

Could you show the y axis T?

I hope you meant the height of the right shoulder with this