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Post by imperfectgolfer on Mar 1, 2018 21:08:23 GMT -5
Dr Mann Do you know how 3D AMM calibrates the zero point for lead wrist Flexion/Extension? I've been looking for any information I could find about 3D AMM sensor calibration without any luck. Does it use the following method (as per picture below) where a 'visually' flat wrist is calibrated to a zero point ? Or does it use something similar to the middle picture below where the 'zero point' could be determined after a golf club was gripped and clubshaft in line with the lead arm (ie. intact LAFW). If 3D AMM used the first 'visually' flat wrist method above to measure flexion/extension, then wouldn't it always register an 'extension' measurement even if the golfer arrived at impact 'neutral' (similar to middle image above) with an intact LAFW? Very good question! I suspect that they use a visually flat left wrist (without a golf club) to get their zero point. However, this is exactly the type of question that you should ask Phil Cheetham. Jeff.
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Post by dubiousgolfer on Mar 2, 2018 7:37:59 GMT -5
Dr Mann I found this video with Phil Cheetham but it's a bit confusing (to say the least). www.youtube.com/watch?v=zMjDiX19mMgFor P4 position At 0:24 they say " set the tones on when the wrists gets to extended 15 to 30 degrees, if we bow the wrists down we lose it, and that would be where the club would be shut at the top" . They go on to say from 0:51 " if we set the tone to our tour ranges which is 15-30 degress of wrist extension, he's in the proper position" I think they are changing the settings so that sound tones are emitted when extensions/flexions are outside some optimal range at P4 . So that doesn't answer my question on how they calibrate their system to measure actual flexion/extension. I'm going to contact Phil Cheetham again and hope he replies (he ignored my emails last time) . Regards DG Note: If they use a visually flat lead wrist as zero point that means the golfer must still be 'palmar-flexed' (if one uses a bit of commonsense) when the green line passes the x axis post impact on Cheethams graph below.
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Post by dubiousgolfer on Mar 3, 2018 17:04:19 GMT -5
I've received a reply from someone involved in 3D AMM and they say the 'zero point' is the flat back of the wrist in line with back of forearm (ie. imho that is a palmar flexion position).
I think a lot of people looking at the 3D AMM graphs could quite easily misinterpret the data (because of the above calibration method) and picture different wrist flexion/extension positions like the 2nd set of 'hand/wrist/forearm' images I used above.
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Post by imperfectgolfer on Mar 4, 2018 10:06:04 GMT -5
I've received a reply from someone involved in 3D AMM and they say the 'zero point' is the flat back of the wrist in line with back of forearm (ie. imho that is a palmar flexion position). I think a lot of people looking at the 3D AMM graphs could quite easily misinterpret the data (because of the above calibration method) and picture different wrist flexion/extension positions like the 2nd set of 'hand/wrist/forearm' images I used above. Using the anatomically FLW with the back of the left hand straight-in-line with the back of the left forearm is what I expected for a zero point 3-D setup calibration technique. That means that if a golfer has a weak/neutral left hand grip, a GFLW at impact will actually measure a certain amount of left wrist extension even though it is functionally flat. Also, if a golfer adopts a very thick grip handle or a finger grip, it will make the degree of measured left wrist dorsiflexion greater - even if the golfer still has a GFLW. Then, for a golfer with a very strong left hand grip (eg. Daniel Berger), the degree of left wrist extension at impact has no correlation with the "fact" that the clubshaft may be straight-in-line (or not) with the left arm at impact - because the back of the left hand/wrist is parallel to the ball-target line at impact (and not facing the target) and it is the ulnar border of the left hand that is facing the target. I think that many golf instructors who use 3-D systems do not take these complexities into proper account when interpreting their 3-D data. Jeff.
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Post by dubiousgolfer on Oct 14, 2019 7:47:30 GMT -5
Dr Mann
It's still a mystery to me why Cheethams graph is showing increased lead wrist flexion happening from P6-P6.9+
If there is forward shaft bend happening in most tour pro driver swings , then that means the hands cannot keep up with the angular velocity of the clubshaft. So how can there be increased wrist flexion? It seems an improbability.
Something doesn't gel between the data being shown on that graph vs the physics of clubshaft bend. I think any smoothing algorithms they have used to complement the slow 3D AMM data frequency measurements render that graph as suspiciously inaccurate from approx P6.5-P7.4
Have you found any logical reason that may explain increased lead wrist flexion happening from P6.5-P6.9+ ?
DG
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Post by imperfectgolfer on Oct 14, 2019 9:20:07 GMT -5
Dr Mann It's still a mystery to me why Cheethams graph is showing increased lead wrist flexion happening from P6-P6.9+ If there is forward shaft bend happening in most tour pro driver swings , then that means the hands cannot keep up with the angular velocity of the clubshaft. So how can there be increased wrist flexion? It seems an improbability. Something doesn't gel between the data being shown on that graph vs the physics of clubshaft bend. I think any smoothing algorithms they have used to complement the slow 3D AMM data frequency measurements render that graph as suspiciously inaccurate from approx P6.5-P7.4 Have you found any logical reason that may explain increased lead wrist flexion happening from P6.5-P6.9+ ? DG I think that Cheetham's graph fits in with a swing pattern where the left wrist is cupped at P5.5 and where the golfer uses the technique of "combined early left wrist flexion and left wrist palmar flexion" to convert to a flexed left wrist alignment after P5.5 - as seen in the following animated gif of Ben Hogan's golf swing.
Note that the peripheral clubshaft still bends forward after P6 as a result of the PA#2 release phenomenon - even though the left wrist is becoming increasingly more palmar flexed.
I don't think that one should presume that the presence (or absence) of left wrist bowing implies that there is a strict causal relationship between hand speed and peripheral clubshaft speed based on the degree of left wrist bowing present in the late downswing.
Jeff.
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Post by dubiousgolfer on Oct 14, 2019 9:51:37 GMT -5
Many thanks Dr Mann. So could the increased lead wrist 'Flexion/Palmar Flexion' be influenced by the PA#3 release? Where the inertia of the clubhead is dragging against the lead wrist as the arms/hands are swung (and forearms also rotated) from an inside to out arc (from an overhead view) as it 'turns the corner'?
DG
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Post by imperfectgolfer on Oct 14, 2019 11:11:19 GMT -5
Many thanks Dr Mann. So could the increased lead wrist 'Flexion/Palmar Flexion' be influenced by the PA#3 release? Where the inertia of the clubhead is dragging against the lead wrist as the arms/hands are swung (and forearms also rotated) from an inside to out arc (from an overhead view) as it 'turns the corner'? DG In golfers like Ben Hogan, who shallow the clubshaft a lot between P4 and P5.5, and who then convert from a cupped lead wrist to a bowed lead wrist between P5.5 and P6.2, I can imagine that the biomechanical conversion to a bowed lead wrist is assisted by the inertia of the club as the hands "turn around the corner". I would not use the term PA#3 release to describe this early left forearm supination phenomenon that happens between P5.5 and P6.2 and I would prefer to think of the PA#3 release phenomenon mainly happening later in the late P6.5 => P7 downswing phase. Jeff.
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Post by dubiousgolfer on Oct 14, 2019 11:26:28 GMT -5
Many thanks Dr Mann
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