AMG - Clubshaft shallowing

[dubiousgolfer]

Some interesting posts I saw on the Golfwrx thread regarding the AMG video. Thought I'd post a few questioning GEARS data versus Tyler Ferrell, Dr Rob Neal and Dr Kwon 3D system data.

glk
I had questions on how amg was measuring ext/int shoulder rotation back in august when they posted their short instagram clip At that time i asked tyler ferrell his take which was basically the shoulder is difficult to measure especially when the arms get above the shoulder and too little information. So i asked again with this recent video. Tyler did some digging and had two main questions 1) how are they measuring and what standard is being used, 2) and ditto for forearm pronation/supination.


tyler talked with dr rob neal who's system has the general pattern of ext rotation in early downswing. He also has dr kwon's graph which shows ext in early downswing, and third, some amm/tpi graphs showing ext in early downswing The amounts are small as expected but the opposite of what amg is showing Tyler did talk to the gears creator and found that gears does not measure ext/int shoulder rotation - so the question is what is amg using? Tyler started a closed facebook group discussion on this which include mike and sean. 3d systems dont all do the same thing in terms of their measurement and data so, i understand, this is not the first time that differences have arisen.

Simpsonia
I mean isn't that why Dr. Kwon built his own 3D system that attaches sensors to bare skin, because AMM and GEARS were nowhere near accurate enough, right? Even with the GEARS harness, shoulders and shoulder blades can slide and move (small amounts) underneath the clothing without necessarily reflecting those movements via the sensors.

glk
I found that both tyler and dr kwon rarely dismiss new information out of hand They both are more interested to learn from the information. That was tyler take on this stuff - this is different, why? Asked dr kwon about mike adams work and though dr kwon has his own data that shows no correlation to swing on anthropometric data he still asked if i knew if mike had any statistical analysis information - best i could do was point him at dr scott lynn whom has been working with adams and has talked about the possibility of doing a joint paper.

AMG made the claim that zero of their swings in their library show external rotation in the downswing






glk
Yes the data shown in this thread has small amounts of er in the early downswing before internal takes over. Amg says that they see none except in the backswing (not defined but dr kwon, for example, includes transition as part of his definition of the backswing others may consider it part of the downswing) and have small amounts of internal.


DG

[imperfectgolfer]

DG,

I find your images showing the relationship between the chest and pelvis to be incomprehensible.

Look at this image.

I think that chest bend in that avatar shows chest side-bend relative to the lumbar spine and not the pelvis.

That's the only way that I can conceptually understand the concept of chest side-bend.

However, I cannot understand how it is measured at P4.

Here are DTL images of Adam Scott at P1 and P4.

I have drawn  a red line parallel to his lumbar spine and a blue line roughly parallel to his thoracic spine at his P1 position (image 1).

I can therefore see that he probably has ~11 degrees of chest bend at address where the thoracic spine is bent forward relative to the lumbar spine. Is that how PC measures chest side-bend at address?

Then, how does he measure chest side-bend in image 2 at P4? I cannot see any angle that makes me think that AS has 36 degrees of chest side-bend at P4.

Can you get PC to clarify this issue?

Regarding external rotation of the trail humerus between P4 => P6, I think that it does not necessarily happen in most pro golfers, especially if they get their trail elbow more alongside their trail hip area at P6  - as seen in the following capture images of Rory McIlroy at P6.

The same applies to Patrick Cantlay

 

However, I think that a small degree of external rotation of the trail humerus happens near P6 if a pro golfer  gets his trail elbow more in front of his trail hip area at P6 - as seen in these capture images of Tony Finau and Brooks Koepka.

Jeff.

[dubiousgolfer]

Dr Mann

I agree with you that Thorax side bend should be relative to lumbar but it is never mentioned on PC's website or other articles I've read. Therefore I am assuming he is using some other method which I am trying to clarify, but to be frank, I'm not expecting any replies from PC.

I'm afraid one has to understand the concept of a local frame of reference (LFOR) and global frame of reference (GFOR) and how the LFOR moves in 3D space relative to the static GFOR. It can be very challenging to picture movements of LFOR in 3D space. You must also understand and become acquainted with the 6 degrees of freedom and the terminology that AMM3D is using as per image below.



With regards Adam Scott I don't think AMM3D measures forward chest bend relative to the lumbar spine . I think it would be measured relative to the frontal/coronal plane of the golfer when he stands upright and where both the LFOR at his thorax would be calibrated to align with the GFOR. That means the LFOR 'XYZ' axis whose origin is based in the centre of T4 vertebrae are all computer aligned with the 'XYZ' axis of a static GFOR situated behind the golfer (ie. the transmitter).

So in your Adam Scott image at address, the forward chest bend would be the angle made by the blue line relative to a vertical line (in the coronal plane), not the red lumbar line (they don't have any segment in AMM3D to represent the lumbar spine).

To measure image 2 chest side bend is also very difficult to explain in words so look at the below where I have gone through the stages of :

1. Aligning the LFOR with the GFOR
2. Show how the LFOR tilts when AS takes his address position
3. Show how the LFOR rotates and tilts its 'x' axis so that it makes an angle with the Transverse/Horizontal plane. That angle is the 'Thorax/Ribcage/Chest' SIDE bend angle that AMM3D is measuring.




To calculate the exact forward tilt and side bend angles relative to the Coronal and Transverse planes is actually more complicated than what I've said above and involves projecting vectors on planes , etc (more complicated maths and just not worth delving any deeper).

I think my explanation is correct but I cannot be certain without clarification from PC or Dr Greg Rose.

DG

[imperfectgolfer]

DG - Another question.

What is the relationship between the chest bend angle and the shoulder turn angle?

One can see that AS has a very horizontal shoulder turn angle at P4, but according to PC the chest bend angle at P4 is greater than it is at P7 even though we know that the shoulder turn angle at P7 is usually greater if a lot of right lateral bend is present between P5.5 => P7.

I am not sure that I can even perceive the value of measuring chest bend angles if there is no correlation with shoulder turn angles.

Jeff.

[dubiousgolfer]

Jan 30, 2023 22:18:26 GMT -5 imperfectgolfer said:

DG - Another question.

What is the relationship between the chest bend angle and the shoulder turn angle?

One can see that AS has a very horizontal shoulder turn angle at P4, but according to PC the chest bend angle at P4 is greater than it is at P7 even though we know that the shoulder turn angle at P7 is usually greater if a lot of right lateral bend is present between P5.5 => P7.

I am not sure that I can even perceive the value of measuring chest bend angles if there is no correlation with shoulder turn angles.

Jeff.

Yes , this doesn't make sense . If the average chest side bend is 36L at P4 then becomes 31T at P7  why does the shoulder line look flatter at P4 than at P7?

I actually mentioned to Dave Tutelman that if AMM3D did measurements as explained in my previous post , then it would be flawed from an anatomical perspective. 


Here are some of the contents of my email to DT.

--------------------------------------------------------------------------------------------------------------------

www.philcheetham.com/aligning-the-sensors-to-the-golfer/
www.philcheetham.com/two-spine-models-rigid-and-two-segment/

PC states the 'Spine' angles are relative angles calculated from the thorax with respect to the pelvis. That confused me because I'm picturing a 'Spine' line connecting the origins of the local frame of reference between thorax and pelvis. The length of that line could differ depending on the golfer bending his/her spine in 3D space and it doesn't seem to reflect what is actually happening anatomically (see extreme positional image below). Maybe, its the best data we can get using these systems because they must be incredibly expensive.






PC also says:

1. All of the motions of each body segment can be measured with respect to this global reference frame (mentioned in the 1st url link above)

2.The side bend angle of a segment is the angle between a side-to-side anatomical axis and the horizontal plane (mentioned in the 2nd url link above)



Point 1 made sense to me but not point 2 for the reason explained below.



When he says 'horizontal plane' I first thought is must be the 'Transverse Plane' in the 'Global Frame Of Reference' but that didn't make sense when I imagined a position like below image . As the thorax frame of reference rotated so that the side-side axis became parallel to the horizontal plane any tilt of the side-side axis would not cause an angle with the horizontal plane




Hope you can see the images I pasted in my email and understand my confusion


-----------------------------------

If I've interpreted PC's articles correctly,  the way AMM3D measures chest side bend seems obviously flawed because it bears no relationship to the anatomical orientation of the real golfers spine.

For example , what happens to the LFOR if the golfer just bends one leg and straightens the other , thereby tilting the pelvis/lumbar/thoracic together at some inclined angle.  There is no anatomical thoracic side bend happening but the LFOR will have rotated in space. The AMM3D system would still register chest side bend when there isn't any!

Further, if the golfers ribcage becomes more aligned with the horizontal , chest side bend measurements relative to the horizontal plane diminish (because  the bend is happening within its plane) and that might provide a possible explanation for why the average is 36L at P4 then becomes 31T at P7 , even though it doesn't match what we are anatomically seeing

DG

[dubiousgolfer]

Here is the reply from Dr Greg Rose when I sent him a copy of my previous post with the Adam Scott images with the local and global frames of reference.

--------------------------------

You are correct - we don't use any projected angles.

"The side-to-side tilt of the thorax (upper body) with respect to a horizontal plane; measured as if a bubble level was put on a side-to-side thorax axis; “Trail” is tilting to the side away from the target at address and “Lead” is tilting to the side nearer the target at address; measured in degrees"

--------------------------------

Can you imagine if the spine was tilted horizontal (like in my previous posted image) with a bubble level across the chest (ie. the side-side axis) and then I flexed my thoracic spine 30 degrees within the horizontal plane. The bubble would not move and therefore chest side bend would be measured as zero.

This means that AMM 3D segment side bend measurements might not match with any great accuracy the anatomical reality of what is happening.


DG

[dubiousgolfer]

Here is my clarification email to Dr Rose.

-------------------------------

I seem to have a problem now trying to imagine how thorax side bend could be measured for an extreme anatomical position like the image below. If a bubble level was placed on the side-side axis and then the skeleton man performed thoracic bend within the the horizontal plane , would AMM3D register that as zero ? Obviously I wouldn't expect a real golfer to be in such an extreme position but was just wondering how AMM3D would work in that scenario.



Here is his reply:

That is pretty much correct. Since the chest doesn't get past 90 degrees of side bend in the golf swing, we use the angles with respect to the horizontal plane.

Side bend is the angle between the horizontal plane and a line through the shoulders.
Forward bend is the angle between the horizontal plane and an anterior/posterior line through the chest (at about the upper sternum point).

It would flip out if it goes past 90.

-----------------------------

So if we looked at DJ's downswing images below, is his spine becoming more forward bent in image 2 (ie. becoming progressively more parallel to the horizontal plane) as increased right lateral flexion happens by P7? That forward bend will have a diminishing effect on the measurement of thorax side bend by AMM3D system.




The fact that PC is showing 'visually' less shoulder angle at P4 with increased 'measured' thorax left side bend, versus greater 'visual' shoulder angle and less 'measured' thorax right side bend at P7 , now seems to make some sense . Real thorax side bend measurements (ie. not those measured relative to horizontal plane) are not being measured accurately.  Also , for analysis from an anatomical perspective , we really need these systems to measure thorax side bend relative to the lumbar spine.

DG

[dubiousgolfer]

There is another thread about this AMG video on The Sandtrap forum:

thesandtrap.com/forums/topic/117823-external-rotation-in-the-downswing-amg-shallowing-video/

One thing I noticed (I've bold highlighted below) is what Michael Neff said on some private 'Golf Teaching Professionals' facebook forum.

------------------------------------
Michael Neff (GEARS founder):
"GEARS does NOT REPORT shoulder range of motion. The AMG boys are using their own calculations on this specific segment. …
1. GEARS does not report shoulder rotation in our user interface BUT our clients can export data and get it.
2. We use Phil Cheetham’s algorithm for our thorax and pelvis stuff and it is GLOBAL.
3. Most tour players go external on the backswing and minimal if any on the downswing (depending on your reference frame).
4. It's plausible lowering kills external and the wrist can bend without external.
5. Measuring the shoulder is very hard because of the challenge with the scapula, muscle and facia. Especially when the elbow gets over the shoulder.
6. Most agree that there is minimal external if any on the downswing and that teaching excessive external can really cause problem. Which is really the main story they are trying to say."

------------------------------------

This means that GEARS has the same flaws as AMM3D when measuring thorax and pelvis side bend .

DG

[imperfectgolfer]

DG,

We are seemingly at a dead-end when trying to discover how PC defines chest-bend.

Jeff.

p.s I sent you a PM.

[dubiousgolfer]

Feb 1, 2023 22:09:19 GMT -5 imperfectgolfer said:

DG,

We are seemingly at a dead-end when trying to discover how PC defines chest-bend.

Jeff.

p.s I sent you a PM.

Dr Mann

We do now know how PC measures chest side bend from a 'geometric/mathematical' perspective but it may not necessarily match what is really happening anatomically (ie. how the thorax side bends relative to the lumbar spine).

DG

[formerbigdaddy]

Jan 24, 2023 17:39:57 GMT -5 imperfectgolfer said:

Jan 24, 2023 16:17:42 GMT -5 playing18 said:

Hi Dr. Mann, 

Youth is not wasted on the young. Nice swing analysis.

Here are few questions to answer/consider as we wait for the snow to melt.

1. How can a player stay on plane as he shallows the shaft. By definition, doesn't shallowing the club shaft cause a brief under-plane swing position from p4 to p5? Maintaining an intact flying wedge seems easy enough, but I'm confused about how a player can remain on plane and shallow at the same time, unless they are slightly over-plane and the shallowing brings them back on-plane.

2. You suggest that the kinematic sequence isn't a major factor involved in shallowing the shaft, while pitching the trail elbow is. What percent contribution would you estimate for the influence of pitching trail elbow on club shaft shallowing, 90%?

3. Isn't the problem with golf instructors stating that the face opens during shallowing more of an issue in how they define an "open face" as compared to how you define it? Isn't this a similar definition-of-terms issue when instructors say the club face is closed when a player bows the lead wrist during the backswing or downswing? 

4. I don't understand how rotating the pelvis promotes or facilitates spinal side bend. To me, it all comes down to the tilting of the pelvis. For example, an elevated trail-side pelvis promotes lead side-bending during the backswing while an elevated lead-side pelvis promotes trail side-bending during the downswing. I can't see how rotating a horizontal or level pelvis, regardless of how much it has rotated, has any positive promoting influence on spinal side-bending. Isn't it only helpful when the pelvis it tilted, which tilts the lumbar spine, which inherently promotes spinal side-bend. How can a horizontal pelvic rotation help with side-bending? 

5. I'm also not sure how any independent trail elbow pitching or any arm motion for that matter has a positive promoting influence on side bending. How can independent arm motion influence spinal motion?

6. It does seem logical that thoracic spinal side-bending, as Milo Lines suggests, could influence club shaft shallowing from p4 to p5. I'm still a little confused on how you define side bending compared to Milo, and you suggest that you can't see any side-bending from p4 to p5, but if a player did a little thoracic side-bending from p4 to p5 as the chest rotates couldn't this assist the trail elbow to pitch even more to increase club shaft shallowing?

7. And finally, what about the lowering effect of the squat move? Could this brief unweighted hip hinge phase conceivably make it easier to pitch the trail elbow due to the brief downward free-falling body momentum? 

Thanks for your expert opinion.

Jim - playing18

1. How can a player stay on plane as he shallows the shaft. By definition, doesn't shallowing the club shaft cause a brief under-plane swing position from p4 to p5? Maintaining an intact flying wedge seems easy enough, but I'm confused about how a player can remain on plane and shallow at the same time, unless they are slightly over-plane and the shallowing brings them back on-plane.

Clubshaft shallowing should not produce a brief underplance condition from P4 to P5 if it is performed correctly. That would only happen if the rate of lead forearm pronation happening between P4 => P5 is far in excess of the rate of lead hand lowering during the same time period. To stay continuously "on-plane" all the way between P4 => P6, the rate of lead forearm pronation must be perfectly balanced with respect to the rate of lead hand lowering during that P4 => P6 time period. I think that it is easier to control those two biomechanical lead arm/forearm events with the trail arm - by controlling the rate of trail arm lowering-and-adduction with the rate of trail forearm supination.

Try a simple experiment. Hold a flashlight in your right hand so that it points at the ball-target line at your simulated P4 position where the right arm/forearm and right wrist are held in a correct P4 positional alignment - like that 10 year-old child in my last post. Then, start lowering your right upper arm using a pitch elbow motion where the right elbow leads the right hand and direct your trail upper arm towards your right shirt seam as you simultaneously start to rotate your torso counterclockwise (like that 10 year-old child). Allow your right forearm to supinate as needed during the right arm lowering action. If you perform all those motions simultaneously and in the correct proportions you should easily be able to keep the flashlight pointing at the ball-target line during the entire P4 => P5.5 time period. 

You suggest that the kinematic sequence isn't a major factor involved in shallowing the shaft, while pitching the trail elbow is. What percent contribution would you estimate for the influence of pitching trail elbow on club shaft shallowing, 90%?

I cannot really understand this question in terms of percentages - so I will rephrase it in a way that I can understand. In what sense does the counterclockwise pelvis/torso motion affect the clubshaft shallowing motion being performed by the trail arm? It affects it in the sense that one cannot have the trail shoulder moving outwards in the direction of the ball-target line too fast due to an excessively fast rate of upper torso counterclockwise rotation between P4 => P5 because that would cause an OTT move.

Note that this golfer's upper torso is rotating counterclockwise between image 1 and image 2. During that same time period his trail hand is lowering and moving towards the ball-target line as a direct result of a trail arm lowering-adduction move using a pitch elbow motion. Those two independent biomechanical events have to be perfectly timed so that the two hands can be opposite the trail side of the sternum at P5 - as seen in image 2.

 Isn't the problem with golf instructors stating that the face opens during shallowing more of an issue in how they define an "open face" as compared to how you define it? Isn't this a similar definition-of-terms issue when instructors say the club face is closed when a player bows the lead wrist during the backswing or downswing? 

Yes. I think that many golf instructors look at the clubface and compare its face-direction relative to the ground. By contrast, I only use the term "open face" in a golfer, who uses the "intact LFFW/GFLW swing technique + "on-plane" clubshaft motion", to mean that the clubface is too open relative to the watchface area of the lead lower forearm.  

I don't understand how rotating the pelvis promotes or facilitates spinal side bend. To me, it all comes down to the tilting of the pelvis. For example, an elevated trail-side pelvis promotes lead side-bending during the backswing while an elevated lead-side pelvis promotes trail side-bending during the downswing. I can't see how rotating a horizontal or level pelvis, regardless of how much it has rotated, has any positive promoting influence on spinal side-bending. Isn't it only helpful when the pelvis it tilted, which tilts the lumbar spine, which inherently promotes spinal side-bend. How can a horizontal pelvic rotation help with side-bending? 

I agree with you and I cannot see how a horizontal pelvic motion can produce trail side bend between P4 => P5 unless the pelvis tilts due to a lot of left-lateral pelvic slide motion that causes the pelvis + lumbar spine to tilt to the right and produce secondary axis tilt. 

I'm also not sure how any independent trail elbow pitching or any arm motion for that matter has a positive promoting influence on side bending. How can independent arm motion influence spinal motion? 

I don't think that performing a stone-skipping motion with the trail arm causes side-bending in terms of a direct casual relationship. However, if one mentally pictures performing a stone-skipping right arm throw action so that a thrown stone will skip along the surface of a lake, wouldn't the stone thrower lower the right shoulder simultaneously by side-bending so that the right forearm can become more horizontal and lower to the ground during the later phase of the right arm "stone skipping" throw motion?

It does seem logical that thoracic spinal side-bending, as Milo Lines suggests, could influence club shaft shallowing from p4 to p5. I'm still a little confused on how you define side bending compared to Milo, and you suggest that you can't see any side-bending from p4 to p5, but if a player did a little thoracic side-bending from p4 to p5 as the chest rotates couldn't this assist the trail elbow to pitch even more to increase club shaft shallowing?

I think that thoracic side-bending between P4 => P5 would produce too much tilting of the torso to the right and lead to hanging-back.

Image 1 is at P4, image 2 is at P5 and image 3 is at P5.5.

Note that Dustin Johnson has no side-bending between P4 => P5 and it only happens between P5 => P5.5. However, look at how much his trail elbow has lowered between image 1 => image 2 and it has almost reached down to waist level by P5.

And finally, what about the lowering effect of the squat move? Could this brief unweighted hip hinge phase conceivably make it easier to pitch the trail elbow due to the brief downward free-falling body momentum? 

I cannot understand how it would affect the independent motion of the right arm in the right shoulder socket in a beneficial way.

Jeff.

I am quite honored to have stumbled upon this thread with the breakdown of my sons swing.  Here's an update... he's getting a little long with the swing b/c he's very much into the idea of hitting the ball far, however his move hasn't changed much in the last year.  He does sometimes leave the clubface wide open at impact and that's his miss.  I still think it's mostly b/c his body outraces his arms, however he is starting to understand "the release" and how the wrists works.  So not sure if his fault is not a proper release (not shown in this video obviously), or being stuck as described before.

Love that I found this thread.  And yes... he still has no idea what shallowing means and would look at me like I had 2 heads if I tried to explain it.  He just turned 12.