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Post by imperfectgolfer on Feb 9, 2023 9:19:23 GMT -5
DG,
I cannot understand what you are saying because I do not clearly understand how GEARS measures rib cage bend and side-bend.
Jeff,
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Post by dubiousgolfer on Feb 9, 2023 19:12:08 GMT -5
DG, I cannot understand what you are saying because I do not clearly understand how GEARS measures rib cage bend and side-bend. Jeff, Dr Mann Looks like AMG have published a video about Milo Lines opinions on shallowing . There are some interesting points being made regarding shoulder line angles versus ribcage side bend where one of their 'scratch golfer models' did his best to rotate in the backswing/downswing without trying to do any thoracic bend. I also have my doubts about how AMM3D and GEARS measure ribcage side bend as there is still no detailed explanation. DG PS. Here is a video that I think measures lateral flexion of the spine anatomically with reference to the lumbar spine. If AMM3D and GEARS don't use this type of comparison , then maybe they should rename their metrics such as 'Ribcage Side Bend' or 'Thorax Side Bend' because it can be misleading. |
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Post by imperfectgolfer on Feb 9, 2023 23:37:05 GMT -5
DG,
That AMG video looks very interesting and I think that Milo is going to have a very difficult time defending his opinions.
I am presently on a 4-day golf trip and I do not have the time to analyse this very interesting AMG video. I will analyse it over a period of a few days when I return home, and I will then comment on the AMG golf instructor's opinions.
Jeff.
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Post by dubiousgolfer on Feb 10, 2023 19:04:59 GMT -5
I've been looking at the Golfwrx thread regarding MILO and AMG videos and one forum member 'GungHoGolf' answered a question about how GEARS measures ribcage side bend. I've copied and pasted his post below but also included images (for reference purposes) of the AVATARS with the sensors .  My company has owned a Gears system for a couple of years. Anatomically speaking, there’s no distinction between “rib cage bend” and spinal bend. Rib cages don’t bend, so that’s just referring to the thoracic section of the spine. The spine is capable of a remarkable degree of lateral bending and flexion/extension:  Theoretically, it may be possible to consciously bend just the thoracic or lumbar sections of the spine a tiny bit to the side independently of other, but practically, side bend is going to result in the entire spine bending, and that is all we’re talking about by “side bend”. The three markers on the Gears suit needed to measure this spinal bend are the two on the rear hip bones, and the one at the top center of the spine between the shoulder blades. When at least 3 of the 8 Gears cameras can locate these markers (not a problem), their 3D positions are determined and define the bottom and top of the spine, along with the starting direction of the lumbar spine, which is perpendicular to a line drawn between the two lower markers, since the hip bone is rigid across both sides. A safe assumption can then be made that the spine is smoothly curved (or not) left or right along its entire length to meet the top center marker. Your point about markers shifting on the body is a valid one, and may result in very small artifacts, but the bib and other wraps to which the markers are attached with velcro are pretty snug. For more precise research purposes, markers are attached directly to skin (like Dr. Kwon does, mostly - he requires men to go shirtless and wear spandex shorts, and women wear a sports bra). But even skin can shift a bit over the muscles and bones underneath. What would be cool is a whole-body fluoroscopy (real-time x-ray imaging) study of the golf swing, so we could see exactly what the bones are doing. But of course nobody would/should volunteer for that. ------------------------- I'm not convinced the above explanation is what GEARS uses to measure ribcage side bend because there is no mention on their website about measuring this parameter relative to the starting direction of the lumbar spine. DG |
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Post by imperfectgolfer on Feb 11, 2023 10:19:30 GMT -5
I've been looking at the Golfwrx thread regarding MILO and AMG videos and one forum member 'GungHoGolf' answered a question about how GEARS measures ribcage side bend. I've copied and pasted his post below but also included images (for reference purposes) of the AVATARS with the sensors . My company has owned a Gears system for a couple of years. Anatomically speaking, there’s no distinction between “rib cage bend” and spinal bend. Rib cages don’t bend, so that’s just referring to the thoracic section of the spine. The spine is capable of a remarkable degree of lateral bending and flexion/extension: Theoretically, it may be possible to consciously bend just the thoracic or lumbar sections of the spine a tiny bit to the side independently of other, but practically, side bend is going to result in the entire spine bending, and that is all we’re talking about by “side bend”. The three markers on the Gears suit needed to measure this spinal bend are the two on the rear hip bones, and the one at the top center of the spine between the shoulder blades. When at least 3 of the 8 Gears cameras can locate these markers (not a problem), their 3D positions are determined and define the bottom and top of the spine, along with the starting direction of the lumbar spine, which is perpendicular to a line drawn between the two lower markers, since the hip bone is rigid across both sides. A safe assumption can then be made that the spine is smoothly curved (or not) left or right along its entire length to meet the top center marker. Your point about markers shifting on the body is a valid one, and may result in very small artifacts, but the bib and other wraps to which the markers are attached with velcro are pretty snug. For more precise research purposes, markers are attached directly to skin (like Dr. Kwon does, mostly - he requires men to go shirtless and wear spandex shorts, and women wear a sports bra). But even skin can shift a bit over the muscles and bones underneath. What would be cool is a whole-body fluoroscopy (real-time x-ray imaging) study of the golf swing, so we could see exactly what the bones are doing. But of course nobody would/should volunteer for that. ------------------------- I'm not convinced the above explanation is what GEARS uses to measure ribcage side bend because there is no mention on their website about measuring this parameter relative to the starting direction of the lumbar spine. DG Why do not think that GEARS measures rib cage bend in that manner? There are two causes of rightwards bend of the spine - i) secondary axis tilt where the lumbar spine/thoracic spine tilt rightwards due to changes in the degree of pelvic position relative to the upper swing center and ii) right lateral bend where the thoracic spine bends relative to the lumbar spine. I cannot understand how the GEARS rib cage bend measurement can distinguish between these two causes if it only measures changes in the tilt of a marker placed over the upper thoracic spine relative to markers placed on the back of the upper pelvis. Jeff. |
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Post by dubiousgolfer on Feb 11, 2023 11:29:45 GMT -5
Dr Mann GungHoGolf has explained how he thinks GEARS measures ribcage bend but it's not defined like that on their website. When I look at GEARs metrics on their website, they are measuring the tilt of the pelvis/ribcage/spine relative to the horizontal plane (of a 'Global Frame Of Reference'), and there is no mention of measurements made relative to any other body segments. Also, ML says he spoke to Michael Neff who has now agreed to investigate a better way to measure ribcage side bend , therefore one might assume that the existing method being used in GEARS is flawed. Even more confusing is the measure of lateral tilt of pelvis/spine and I've underlined/bolded the important part of their explanation below.  Lateral Tilt is a projection angle on the Y-Z plane (i.e. face on). A projection angle allows you to turn a 3D object into a 2D representation of it. Thus, Lateral Tilt is like the Side Bend metric, but it is a projected angle instead of a global angle. We display values for the lateral tilt of the pelvis and the ribcage. The underlined/bolded section seems to infer that 'Side Bend' is a global angle , not a projected one. I will have edit this post again with some more images to explain the difference between a projected vs global angle (that may take some time). On reflection, I am unable to explain global angles in any understandable way (just too complicated to draw diagrams). If I find a video that explains it simply , I will post it but most of them involve complicated vector maths which is too confusing. DG |
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Post by imperfectgolfer on Feb 12, 2023 10:11:20 GMT -5
DG - I find the GEARS definition of lateral tilt interesting because it is not a true measure of latriflexion of the thoracic spine, and and it is a spinal side-bend measure that is projected onto the frontal plane.
I have returned home from my golf trip and I am starting to analyse the AMG video. I think that the GEARS rib cage side-bend measurements are worthless because they do not really measure thoracic spine latriflexion, although they are affected by the presence of any T-spine latriflexion.
I will have lot to say and it may take me 5 -7 days to produce multiple capture images and a very long post where I will comment on the strengths and weaknesses of the AMG video.
Jeff.
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Post by dubiousgolfer on Feb 12, 2023 12:09:44 GMT -5
DG - I find the GEARS definition of lateral tilt interesting because it is not a true measure of latriflexion of the thoracic spine, and and it is a spinal side-bend measure that is projected onto the frontal plane. I have returned home from my golf trip and I am starting to analyse the AMG video. I think that the GEARS rib cage side-bend measurements are worthless because they do not really measure thoracic spine latriflexion, although they are affected by the presence of any T-spine latriflexion. I will have lot to say and it may take me 5 -7 days to produce multiple capture images and a very long post where I will comment on the strengths and weaknesses of the AMG video. Jeff. Dr Mann I agree that both AMM3D and GEARS measurements are not a true measure of latrification of the thoracic spine. Further , after reading this complicated article by Dr Kwon , who uses a different method, I'm unsure whether any 3D system reflects accurately the sequencing and degree of 'rotation/bend/side-bend' happening in the golf swing. www.drkwongolf.info/technotes/thorax_angles.pdfIt's taken me many hours to try and understand how thorax angles are measured (and I'm still not 100% certain I have understood it correctly), but apparently one has to first make a judgement on the sequencing of the 'thorax section' movements before doing the measurements. If the sequencing is defined differently (ie. bend/rotation/side-bend vs rotation/side- bend/bend vs side-bend/rotation/bend , etc ) the measurements of 'rotation/bend/side-bend' during the golf swing can be different. Dr Kwon uses a different sequencing (while also measuring different defined angles) compared to what he calls the 'popular method' (which I assume AMM3D and GEARS may use) and therefore the measurements of thorax movements in 3D space vs time can be very different. Look at the graphs below using 'Popular Method' (top graph) vs Dr Kwon method (bottom graph).  DG |
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Post by imperfectgolfer on Feb 12, 2023 19:25:15 GMT -5
DG,
That Kwon paper is far too difficult for me to comprehend.
I have one question.
Watch The AMG video between 16:27 - 16:29 minute time point.
Note that they have a scratch golfer standing in a golf posture and he has a spinal bend inclination angle of 58.5 degrees at a simulated P1 position. His rib side-bend angle measures ~3 degrees.
They then instruct him to rotate ~90 degrees clockwise while keeping the same spinal bend inclination angle and while making sure that his does not side-bend his thoracic spine relative to his lumbar spine.
By a simulated P4 position, his rib side-bend angle measures 43 degrees.
If he is not side-bending his thoracic spine relative to his lumbar spine between P1 => P4, how can there be a ~40 degree change in his rib side-bend angle if it is supposed to measure the degree of thoracic spine latriflexion?
Jeff.
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Post by dubiousgolfer on Feb 12, 2023 21:15:30 GMT -5
DG, That Kwon paper is far too difficult for me to comprehend. I have one question. Watch The AMG video between 16:27 - 16:29 minute time point. Note that they have a scratch golfer standing in a golf posture and he has a spinal bend inclination angle of 58.5 degrees at a simulated P1 position. His rib side-bend angle measures ~3 degrees. They then instruct him to rotate ~90 degrees clockwise while keeping the same spinal bend inclination angle and while making sure that his does not side-bend his thoracic spine relative to his lumbar spine. By a simulated P4 position, his rib side-bend angle measures 43 degrees. If he is not side-bending his thoracic spine relative to his lumbar spine between P1 => P4, how can there be a ~40 degree change in his rib side-bend angle if it is supposed to measure the degree of thoracic spine latriflexion? Jeff. Dr Mann If he's not trying to side-bend , then there cannot be a 40 degree change in his rib side-bend angle . I can only assume AMG have some theory that rib side-bend happens unintentionally and is not perceived by the scratch golfer. Maybe Granato and Webb have assumed that GEARS is measuring 'what they think' is ribcage side-bend without actually checking how the metrics are derived. My own opinion is that if the ribcage is rotating around on a plane perpendicular to the forward spinal tilt (without any rib side bend) , it will create an angle between the 'side-side' axis of the T4 'local frame of reference' and the horizontal plane, therefore registering a ribcage side-bend measurement (when there isn't any). I actually sent an email to Dr Phil Cheetham on the 10th Feb, before the AMG video was published, outlining a similar scenario of that scratch golfer (from 16:27-16:29) and asking the question whether AMM3D / GEARS would measure ribcage side-bend (when there isn't any, just pure rotation of ribcage on a tilted plane) , but have not yet received a reply. DG |
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Post by dubiousgolfer on Feb 12, 2023 21:40:28 GMT -5
Dr Mann In the screen image below of that scratch golfer , the white line is the side-side axis going through the T4 position . You can see that it makes an angle with the horizontal blue line plane.  Then we have the GEARS metric diagram below showing how it measures ribcage side-bend.  I am therefore assuming GEARS will measure ribcage side-bend on that scratch golfer when there isn't any. On another thread I posted these images below which is basically saying the same as above.  DG PS. Not sure why, but all the you-tube comments made regarding the AMG video have been deleted - no comments permitted anymore. Something must be amiss! |
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Post by dubiousgolfer on Feb 12, 2023 22:57:57 GMT -5
Milo's you-tube video has now been removed so obviously some discussions going on in the background.
DG
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Post by imperfectgolfer on Feb 12, 2023 23:37:54 GMT -5
Dr Mann In the screen image below of that scratch golfer , the white line is the side-side axis going through the T4 position . You can see that it makes an angle with the horizontal blue line plane. Then we have the GEARS metric diagram below showing how it measures ribcage side-bend. I am therefore assuming GEARS will measure ribcage side-bend on that scratch golfer when there isn't any. On another thread I posted these images below which is basically saying the same as above. DG PS. Not sure why, but all the you-tube comments made regarding the AMG video have been deleted - no comments permitted anymore. Something must be amiss! You have drawn a line through the T4 vertebra. Why did you draw your line at that level considering that the GEARS system only has one spinal marker located at the level of ~T1/2? Also, in which thread did you post those other two images? Jeff. |
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Post by dubiousgolfer on Feb 12, 2023 23:54:46 GMT -5
Dr Mann I drew those diagrams just to make a point that GEARS cannot distinguish between lateral spinal tilt and ribcage side bend when it makes a ribcage side-bend measurement. The thread I posted those images was in the link below newtongolfinstitute.proboards.com/thread/1003/shoulder-tilts-full-swing-actionHere is my email to Dr Phil Cheetham: ------------------------------------------- On Fri, Feb 10, 2023 at 1:11 Dear Dr Cheetham After emailing Dr Greg Rose I do have a better idea of how Ribcage Side Bend is measured . He gave the analogy of visualising a spirit level being the 'side-side' axis of a local frame of reference placed on the T4 vertebrae. That the measurement of ribcage side bend would be the angle formed by this side-side axis relative to the 'Horizontal Plane', which I'm assuming is the XY plane of the 'Global Frame Of Reference'. But when I thought deeper about this explanation it made me wonder how 'Ribcage Side Bend ' would be measured in the below image scenario. Wouldn't the action of a golfer rotating that side-side axis on a plane perpendicular to forward tilted z axis on the local frame of reference (ie. not actually using any anatomical thoracic bend) still cause AMM3D (and GEARS) to register a 'Ribcage Side Bend' measurement? The side-side axis would end up being tilted with reference to the 'Horizontal XY plane' in my drawn image below, even though there was no side-side rotation about the y-axis.  Am I making a big mistake somewhere or does AMM3D have some means of measuring rotation of the side-side axis about the front-back axis of the local frame of reference at T4? ------------------------------------ DG ps. Note I made a typo error in my diagram and should have said "pointing out of the page away from target". Doesn't really matter as I think Dr Cheetham would understand the point I was making. |
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Post by imperfectgolfer on Feb 13, 2023 10:22:57 GMT -5
DG, You posted this image.
The magnitude of the measured rib-cage side-bend (~44 degrees) is very similar to the magnitude of the spinal bend inclination angle (~58 degrees), which is in turn directly proportional to the amount of hip joint flexion. That would suggest that it is the spinal bend inclination angle of the lumbar spine that mainly determines the magnitude of the rib cage side-bend measurement at P4, and not any significant bending of the thoracic spine relative to the lumbar spine due to thoracic spine latriflexion.
Watch the video again, and note that the ribcage side-bend measurement is less at 60 degrees rotation of the spine (compared to 90 degrees rotation at P4) and even less at 30 degrees of rotation. If the model golfer is simply rotating his torso clockwise while deliberately avoiding any change in his spinal bend inclination angle and while avoiding any side-bending of his thoracic spine between P1 => P4, why would the rib cage side-bend values be constantly changing?
Jeff.
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