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Post by imperfectgolfer on Apr 6, 2020 22:52:23 GMT -5
I've been having some fun with this free double pendulum application below imagining that the central hub was the right shoulder joint, the proximal joint was the elbow and the peripheral joint the wrist/hand (keeping the arm lengths approximately the same and just adjusting the masses). Then I just positioned the proximal arm horizontal and the peripheral arm vertical as if the P4 position of a golfers right arm position (90 degree arm bend). Then just ran it at very slow time rate. www.myphysicslab.com/pendulum/double-pendulum-en.htmlAmazing how you can see the almost linear vertical path of the 'hand' as the proximal arm 'adducted' . Yes there is some extra 'right arm bend' but not much required to generate an almost linear 'hand' path . Obviously you will have to imagine a left arm and shoulder joint attached and how the movement of each shoulder socket might move in a real golf swing but it does help me visualise how a right arm adduction move can help create a less curved hand path in the downswing. DG You made me laugh a lot, which is quite an achievement in these troubled coronavirus times! The idea of applying that double pendulum system to the way that the right arm functions in a golf swing is simply crazy!!!! Jeff.
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Post by dubiousgolfer on Apr 7, 2020 9:16:26 GMT -5
Yes , life has become very surreal indeed.
DG
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Post by dubiousgolfer on Apr 7, 2020 21:15:37 GMT -5
Dr Mann
Just looking at this video of scapula movements 0:33 - 0:36 where there seems to be some flexion of the spine to allow full range of protraction.
If the left scapula is fully protracted while the right shoulder retracted at P4 (and the left shoulder remains protracted while there is an active pivot) will the golfer have to perform some flexion of the spine (as well as lateral flexion) to permit full range of protraction of the right scapula?
DG
On reflection , it seems the model in the video increased spine flexion so that the scapula could slide and protract a bit more over the upper ribcage (which has less breadth and width).
That raises another question - is it better for a golfer who has a poor pivot , to allow his scapula movement to slide over the upper sections of the ribcage and allow the arms more range of motion to adduct and abduct (ie. swing closer to the TSP than the elbow and hand plane)?
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Post by imperfectgolfer on Apr 8, 2020 9:25:54 GMT -5
DG,
I think that some degree of right upper torso flexion may often accompany the right scapular protraction that happens in the early downswing's right arm adduction phase, just as left scapular retraction after P5.5 will likely be associated with extension of the left side of the upper torso.
Jeff.
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Post by utahgolfer on Apr 13, 2020 1:38:29 GMT -5
Hi Jeff,
Sorry for the delayed response. Of course, right forearm supination and right arm ER are effective ways to shallow the club shaft, but the right wrist can also steepen or shallow the club shaft. Anytime the shaft moves farther from the target line (rearward), it is a shallowing effect. Anytime the shaft moves closer to the target line, it is a steepening effect.
Perhaps Milo mixed up the terminology, but I don't think anyone would misinterpret what he meant. If at p4.5, the right wrist performs palmar flexion, the shaft will steepen and tumble across the line. Conversely, at p4.5, if the right wrist performs dorsiflexion, the shaft will shallow and move farther from the target line. It is patently obvious that Milo meant right wrist dorsiflexion, and his audience would probably not want to hear exact, unfamiliar terminology anyway.
UG
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Post by dubiousgolfer on Apr 13, 2020 17:43:03 GMT -5
I think that Milo, and especially Eric, are making many errors in their biomechanical reasoning. In this first critical post, I will again discuss the issue of why the clubhead moves away from the target during the early downswing. Watch this Eric Cogorno video. Between the 11:00 - 13:45 minutes time point of the video, Eric provides two explanations as to why the clubhead moves away from the target as one starts the downswing. He states that the left wrist must uncock (ulnar deviate), but he simultaneously attempts to imply that left wrist uncocking does not represent casting because of a left wrist hinging motion happening simultaneously in the opposite plane where the left wrist becomes more flexed. However, that explanation is pure BS, because casting is measured in the plane of radial => ulnar deviation and it is not significantly affected by small changes in the degree of left wrist flexion/extension. His second explanation is an increase in the degree of right angle bend from 90 degrees at P4 to 110-120 degrees. That's also pure BS! Here is a birds-eye view video of Rory McIlroy's driver swing. Here are capture images of his P4 => P6 time period. Note that his clubhead reaches it furthest distance away from the target at P5.5 (image 4) and not P6 (image 5) as Eric claims. What is causing the clubhead to move away from the target between P4 (image 1) and P5 (image 3)? Here are close-up images of the P4 => P5 time period. I have placed a yellow circle over his left shoulder socket, a blue circle over his right shoulder socket and I have drawn a red line between his right shoulder socket and the club handle just in front of his right hand's placement on the grip.
Note that the clubhead moves away from the target between P4 and P5 even though the left shoulder socket is moving targetwards during that time period. The reason = change in angle of the left arm from being angled at 11:30 o'clock at P4 to being angled at 9 o'clock at P5 - and it has nothing to with any change in the degree of lag. Note that the degree of his left wrist radial deviation does not significantly change between image 1 and image 3, and note that he does not cast between P4 and P5.
Eric states that the right elbow must straighten to cause the clubhead to move away from the target. However, note that the right shoulder socket is moving away from the target between P4 and P5 due to scapula protraction combined with a counterclockwise rotation of the upper torso, but the length of the distance between the right hand and the right shoulder socket (length of the red line) is actually shortening between P4 and P5. How could that happen if the right arm is straightening between P4 and P5? What is causing the distance between the right hand and the right shoulder socket to decrease between P4 (image 1) and P5 (image 3)? I believe that it is due to right arm adduction while maintaining roughly the same degree of right elbow angle bend. "Fact" - note how much the right shoulder socket is further away from the target than the left shoulder socket at P5 - compared to their relative distances away from the target at P4 (where the right shoulder socket is actually closer to the target than the left shoulder socket). The distance between the right shoulder socket and the right hand must decrease (not increase) between P4 and P5 to accomodate to that "fact".
Jeff.
Dr Mann I am confused about what you've said below (the bolded section). "What is causing the distance between the right hand and the right shoulder socket to decrease between P4 (image 1) and P5 (image 3)? I believe that it is due to right arm adduction while maintaining roughly the same degree of right elbow angle bend." If one regarded the right shoulder socket to be central hub and the distance between it and the right hand to be the 'radius' , I cannot understand how just an adduction of the right humerus with the same degree of right elbow bend will cause a decrease in the radius. Wouldn't the elbow have to bend more for the 'radius' to shorten ? DG PS. Look at this diagram 'a' below. If one visualised the 'Hub' was the 'right shoulder socket', the inner arm the right 'humerus' , the outer arm the 'forearm' and m2 the 'right hand'. Also assume that the 'constant elbow bend' = 'θ' , why would an adduction move where ' β' angle is decreased cause any change in 'R' (distance between 'right hand' and 'shoulder socket' )?
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Post by dubiousgolfer on Apr 13, 2020 18:33:49 GMT -5
Dr Mann
If you measure the distances between the yellow/blue circles at P4 and P5 from the clubhead toe (on that black traced clubhead path) at P4, you will find that the yellow circle has moved forward approximately more than twice the distance than the blue circle has moved away.
That suggests to me that the right scapular has not moved much in space compared to the left shoulder socket , which might mean that Rory's ribcage has just slid under his right scapula.
DG
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Post by imperfectgolfer on Apr 15, 2020 10:19:30 GMT -5
DG, You wrote-: " I am confused about what you've said below (the bolded section).
"What is causing the distance between the right hand and the right shoulder socket to decrease between P4 (image 1) and P5 (image 3)? I believe that it is due to right arm adduction while maintaining roughly the same degree of right elbow angle bend."
If one regarded the right shoulder socket to be central hub and the distance between it and the right hand to be the 'radius' , I cannot understand how just an adduction of the right humerus with the same degree of right elbow bend will cause a decrease in the radius. Wouldn't the elbow have to bend more for the 'radius' to shorten ?" No! You are not taking into account the fact that when the right arm adducts that the hands move downwards a lot from an elevated position at P4 to a far less elevated position at P5. You also wrote-: "If you measure the distances between the yellow/blue circles at P4 and P5 from the clubhead toe (on that black traced clubhead path) at P4, you will find that the yellow circle has moved forward approximately more than twice the distance than the blue circle has moved away.
That is not surprising seeing that the left shoulder is moving towards the target while both the clubhead and right shoulder socket are moving in the same general direction away from the target. Jeff.
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Post by dubiousgolfer on Apr 16, 2020 8:00:13 GMT -5
Dr Mann
Are you referencing to the distances between right hand and shoulder socket as per the 'birds eye view' images (where parallax comes into play) or the real physical distances (if we were able to measure them in real time from P4-P5)?
I cannot envisage the 'real physical distance' from right hand to shoulder socket to shorten if the elbow bend remains unchanged (even when adduction takes place).
The ' birds eye view' distance changes between the shoulder sockets are also probably affected by parallax and 'protraction vs retraction' changes between the left and right scapula.
DG
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Post by imperfectgolfer on Apr 16, 2020 11:13:42 GMT -5
Dr Mann Are you referencing to the distances between right hand and shoulder socket as per the 'birds eye view' images (where parallax comes into play) or the real physical distances (if we were able to measure them in real time from P4-P5)? I cannot envisage the 'real physical distance' from right hand to shoulder socket to shorten if the elbow bend remains unchanged (even when adduction takes place). The ' birds eye view' distance changes between the shoulder sockets are also probably affected by parallax and 'protraction vs retraction' changes between the left and right scapula. DG I am referring to "real" physical distances. Here are back-view images of Rory McIlroy's early downswing between P4 (image 1) and P5 (image 2).
I don't think that his degree of right elbow bend has changed between P4 and P5, but I suspect that the distance between his right hand and his right shoulder socket is fractionally less at P5 (compared to P4) because i) his right shoulder socket is more protracted and because ii) his right arm is more adducted.
Jeff.
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