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Post by dubiousgolfer on Jan 29, 2020 12:57:11 GMT -5
Dr Mann I've been reading this critical review by the 'swingengineer' www.theswingengineer.com/faq7.htmlWhat interested me was his opinion (using Sasho's research finding data) that the active rolling of the lead forearm did generate more clubhead speed (ie. PA#3 ). "Simulation 3’s clubhead speed at impact was also much higher than Simulation 1’s. This demonstrates the contribution forearm muscles make to clubhead speed through impact." When I looked at SMK's research paper (link below) ,the clubhead speed for Sim 3 was 44.1 m/s , while Sim1 was 36.2 m/s , and that was with a 0 degree PA#3 angle at impact. www.sashomackenzie.com/publications/MacKenzie%202012%20Club%20position%20relative%20to%20the%20golfer's%20swing%20plane%20meaningfully%20affects%20swing%20dynamics.pdf Doesn't this suggest that PA#3 is not only a clubface squaring accumulator but also one that increases clubhead speed? SMK's experiment seems to have a zero PA#3 angle at impact but I suspect not too many tour golfers (apart from DeChambeau) create a zero PA#3 angle at impact. Is the retention of a PA#3 angle (and higher MOI of club around the longitudinal axis of the lead arm) maybe from P6.7-P7 by the majority of tour golfers the reason why you think PA#3 is primarily a club squaring accumulator? DG
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Post by imperfectgolfer on Jan 29, 2020 14:06:51 GMT -5
DG,
Your link to Sasho's paper is not working.
Jeff.
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Post by dubiousgolfer on Jan 29, 2020 14:33:58 GMT -5
Dr Mann
The other issue I have problems conceptualising is how SMK's model could keep a constant hand path plane and still rotate the lead forearm without causing some 'toppling effect' of the clubshaft.
If one kept an intact LAFW in the downswing with a 'constant hand path plane steepness angle' (as in SMK's model for SIM3) with a PA#2 angle (ie. less than 180 degrees) any left arm supination after P4 and before P7 (in the downswing) will cause the clubshaft to 'topple' the LAFW out of the hand path plane.
Wouldn't 'real' golfers who kept an intact LAFW, have to pitch their left arm while releasing PA#2 (if they were also supinating the lead arm) to keep the clubhshaft clubhead on plane? That they might also have to keep pitching slightly as they released PA#3 between P6.7-P7 (if they had a PA#3 angle) to keep the clubshaft on plane (clubhead droop would have to be taken into account)?
In SMK's model there is no lead arm pitching and I can only assume that PA#2 has been fully released (sometime in the downswing) with a zero PA#3 angle, and then the forearm rotated.
How else could the clubshaft and lead arm end up in a straight line relationship by impact?
DG
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Post by dubiousgolfer on Jan 29, 2020 15:16:52 GMT -5
DG, Your link to Sasho's paper is not working. Jeff. Dr Mann Try this link www.sashomackenzie.com/Click into 'Recent Publications' Then select the below from the list (13th on the list). MacKenzie, S. J. (2012). Club position relative to the golfer’s swing plane meaningfully affects swing dynamics. Sports Biomechanics, 1-16, iFirst Article. DG
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Post by dubiousgolfer on Jan 29, 2020 20:48:01 GMT -5
Dr Mann The other issue I have problems conceptualising is how SMK's model could keep a constant hand path plane and still rotate the lead forearm without causing some 'toppling effect' of the clubshaft. If one kept an intact LAFW in the downswing with a 'constant hand path plane steepness angle' (as in SMK's model for SIM3) with a PA#2 angle (ie. less than 180 degrees) any left arm supination after P4 and before P7 (in the downswing) will cause the clubshaft to 'topple' the LAFW out of the hand path plane. Wouldn't 'real' golfers who kept an intact LAFW, have to pitch their left arm while releasing PA#2 ( if they were also supinating the lead arm) to keep the clubhshaft clubhead on plane? That they might also have to keep pitching slightly as they released PA#3 between P6.7-P7 (if they had a PA#3 angle) to keep the clubshaft on plane (clubhead droop would have to be taken into account)? In SMK's model there is no lead arm pitching and I can only assume that PA#2 has been fully released (sometime in the downswing) with a zero PA#3 angle, and then the forearm rotated. How else could the clubshaft and lead arm end up in a straight line relationship by impact? DG Dr Mann Please ignore the above post because I've just noticed the following in the article: "In Sim3, the forearm angle showed a small decrease during the first half of the downswing due to gravity pulling the club below the swing plane. The forearm supination torque generator was then activated at approximately 0.16s which resulted in the forearm rapidly supinating and the clubface becoming square at impact."This means that the shaft was slightly below plane of the hand plane so any 'toppling effect' caused by left arm supination before PA#2 is completely released might have got the shaft back on hand plane by impact. SMK did not specify whether the SIM3 and SIM5 scenarios created an overall 'out to in' clubhead path into impact because all he said was the clubface was 'square at impact'. Plus he said the below which imho is only a comparison between SIM3 and SIM5 and doesn't specify whether there was an overall out-in clubhead path into impact: "For the normal swing, the steeper swing plane (Sim5) resulted in a 0.78 reduction in the inside-to-outside path of the clubhead compared to Sim3, as well as a 0.78 increase in the downward path of the clubhead at impact. "But then he says later " As demonstrated in Sim5 and Sim6, coming over the top places the club above the golfer’s swing plane and impedes the squaring of the clubface."As far as I am aware SIM3 and SIM5 are identical except SIM3 had a hand plane 135 degrees while SIM5 was 125 degrees. I am therefore assuming that both SIM3 and SIM5 produced OTT swing paths but SIM 5 less so by 0.78. On reflection , maybe he meant to say "As demonstrated by Sim6 compared to Sim5, coming over the top places the club above the golfer’s swing plane and impedes the squaring of the clubface." So maybe SIM3 and SIM5 were not OTT paths and rather 'in-out' (I suspect only Sasho can confirm this). I do find these research articles very difficult to interpret. DG
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Post by imperfectgolfer on Jan 30, 2020 12:11:13 GMT -5
DG, You wrote-: " What interested me was his opinion (using Sasho's research finding data) that the active rolling of the lead forearm did generate more clubhead speed (ie. PA#3 ).
"Simulation 3’s clubhead speed at impact was also much higher than Simulation 1’s. This demonstrates the contribution forearm muscles make to clubhead speed through impact."
When I looked at SMK's research paper (link below) ,the clubhead speed for Sim 3 was 44.1 m/s , while Sim1 was 36.2 m/s , and that was with a 0 degree PA#3 angle at impact." You have seemingly concluded that active left forearm supination (due to the active contraction of the left forearm's supinator muscles) increases clubhead speed!!!! Compared to what? It is only true when compared to simulation one where the release of PA#3 is passive. In other words, if you take a golfer who adopts a weak-neutral left hand grip, and who therefore needs to execute a PA#3 release action in order to square the clubface by impact, it is reasonable to conclude that he he will be able to generate a greater clubhead speed at impact if he uses an active PA#3 release action rather than a passive PA#3 release action. However, that computer-generated simulation study does not prove that a PA#3 release action increases swing power - because he did not compare his simulation 3 to another simulation where the golfer adopts a very strong left hand grip (like Jamie Sadlowski) and who therefore does not have to perform a PA#3 release action during the downswing. Do you have any evidence to support a "belief" that if a golfer adopts a weak-neutral left hand grip (and who therefore generates his maximum clubhead speed by the sequential release of PA#4 => PA#2 => PA#3) can generate a faster clubhead speed at impact than a golfer who adopts a very strong (4-knuckle) left hand grip (and who therefore generates his maximum clubhead speed by the sequential release of PA#4 => PA#2)? Do you really believe that Jamie Sadlowski could generate higher clubhead speeds at impact if he changed his very strong left hand grip to a weak-neutral left hand grip? Also consider the following argument. Sasho showed that the left forearm had rotated to 90 degrees by impact (in simulation 3) in order to get a square clubface by impact and that the left forearm was pronated by ~10 degrees during the early downswing, which means that ~100 degrees of left forearm supination must have happened between P4 and impact. That's a lot of left forearm supination thereby implying that his computer-generated simulation golfer must have adopted a weak-neutral left hand grip.
Now, consider whether an active left forearm supinatory action can increase clubhead speed if a golfer adopts a weak-neutral left hand grip - by watching the following Lynn Blake video. Watch the video between the 1:37 - 1:40 minute time period. Note how very actively LB is rotating his left forearm counterclockwise during his demonstration. Under those demo-circumstances, I can easily imagine that a golfer can generate an increased clubhead speed by adding a very active left forearm supinatory action to his PA#4 => PA#2 release sequence. However, that remarkably high degree of active left forearm supination is not practically useful because it would make it very difficult (if not impossible) to consistently square the clubface by impact. It would also obviously be impossible to have a stable clubface that is square to the clubhead arc through the immediate impact zone between P7 and P7.2 under those conditions when the left hand is rotating very fast counterclockwise through impact. So, the "real life" reality is that pro golfers (who adopt a weak-neutral left hand grip) are likely using very little active left forearm supination during their downswing action. Consider Tiger Woods driver swing action. This video dates from the early 2000s when Tiger's golf swing was at its best and when he used a weak/neutral left hand grip. Note that he uses a non-delayed full-roll hand release action through impact (where the clubface roll between P7 and P7.2 is mainly due to external rotation of the left humerus and not due to left forearm supination). That suggests that his left forearm supinatory action happening between P6 and P7 (representing his PA#3 release action) could not be very active because that would produce an uncontrolled roller subtype of non-DH hand release action through impact. Under those "real life" conditions of a "far less than maximally active left forearm supinatory action", I know of no evidence that the PA#3 release action (which is obviously needed needed to square the clubface by impact) increases clubhead speed! How could it? If a pro golfer decided to use a very active left forearm supinatory action pre-impact and an uncontrolled roller hand release action through impact, then I can imagine that he could generate a faster clubhead speed at impact - but likely at the very great expense of a significantly decreased driving accuracy rate.
Jeff.
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Post by dubiousgolfer on Jan 30, 2020 16:37:47 GMT -5
Many thanks Dr Mann
I agree with you.
But also, after reflecting again on SIM1 and SIM3 , I think SwingEngineer may have made the wrong assumption from a pure physics perspective.
SIM1 is where the golf shaft starts the downswing under the hand plane while only forearm torque generator switched off creating a clubhead speed of 36.2m/s at impact, clubface square.
SIM3 is where the golf shaft starts on the same plane as the hand plane and all torque generators including the forearm are switched on creating a clubhead speed of 44.1 m/s at impact, clubface square. There might be a very small underplane change in the shaft due to the effect of gravity but to all intents and purposes its virtually on the hand plane.
I cannot imagine that forearm rotation can happen in either of the above scenarios until PA#2 is fully released in the hand plane with zero PA#3 angle (to prevent an OTT) . Imho, only after the latter geometry is reached can the shaft be rotated passively in SIM1 or actively in SIM3 within the hand plane.
Further, I cannot imagine that an active forearm rotation of shaft (SIM3) with zero PA#3 angle can create an extra 44.1-36.2 = 7.9m/s clubhead speed compared to SIM1. In fact I cannot imagine any significant increase in clubhead speed even if the forearm rotation is quite large (because it will be a 90 degree clubface rotation around the longitudinal axis of the shaft - zero PA#3 angle).
I can imagine a simple reason for the speed discrepancy as follows:
Lets assume the energy supplied by the 3 torque generators (ignoring the forearm generator for the moment) is the same for SIM1 and SIM3 to release PA#2 .Lets call that energy 'X'
SIM3 : All of 'X' energy is required to release PA#2 within the hand plane
SIM1 : A certain amount 'Y' energy is used to move the club from underplane to the hand plane , then the rest of 'X-Y' energy is used to release PA#2.
Therefore I can assume that the hand speed in SIM1 as it approaches release of PA#2 is inferior to SIM3 and will create a lower clubhead speed after PA#2 release. Therefore the switching on of the forearm generator for SIM3 after the release of PA#2 is a 'red herring' and is not the main cause of the increased clubhead speed.
I cannot prove the above but it makes some sense from an energy perspective.
DG
PS. I've emailed Sasho MacKenzie asking whether my tentative explanation above is nonsensical (I imagine he will say it is).
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Post by imperfectgolfer on Jan 30, 2020 17:55:40 GMT -5
Many thanks Dr Mann I agree with you. But also, after reflecting again on SIM1 and SIM3 , I think SwingEngineer may have made the wrong assumption from a pure physics perspective. SIM1 is where the golf shaft starts the downswing under the hand plane while only forearm torque generator switched off creating a clubhead speed of 36.2m/s at impact, clubface square. SIM3 is where the golf shaft starts on the same plane as the hand plane and all torque generators including the forearm are switched on creating a clubhead speed of 44.1 m/s at impact, clubface square. There might be a very small underplane change in the shaft due to the effect of gravity but to all intents and purposes its virtually on the hand plane. I cannot imagine that forearm rotation can happen in either of the above scenarios until PA#2 is fully released in the hand plane with zero PA#3 angle (to prevent an OTT) . Imho, only after the latter geometry is reached can the shaft be rotated passively in SIM1 or actively in SIM3 within the hand plane. Further, I cannot imagine that an active forearm rotation of shaft (SIM3) with zero PA#3 angle can create an extra 44.1-36.2 = 7.9m/s clubhead speed compared to SIM1. In fact I cannot imagine any significant increase in clubhead speed even if the forearm rotation is quite large (because it will be a 90 degree clubface rotation around the longitudinal axis of the shaft - zero PA#3 angle). I can imagine a simple reason for the speed discrepancy as follows: Lets assume the energy supplied by the 3 torque generators (ignoring the forearm generator for the moment) is the same for SIM1 and SIM3 to release PA#2 .Lets call that energy 'X' SIM3 : All of 'X' energy is required to release PA#2 within the hand plane SIM1 : A certain amount 'Y' energy is used to move the club from underplane to the hand plane , then the rest of 'X-Y' energy is used to release PA#2. Therefore I can assume that the hand speed in SIM1 as it approaches release of PA#2 is inferior to SIM3 and will create a lower clubhead speed after PA#2 release. Therefore the switching on of the forearm generator for SIM3 after the release of PA#2 is a 'red herring' and is not the main cause of the increased clubhead speed. I cannot prove the above but it makes some sense from an energy perspective. DG I don't understand, or I disagree, with a lot of your statements. First of all, I don't like the term "hand plane" as used by Sasho. The TGM definition of the term "hand plane" is a line drawn from the ball to the belt buckle. Sasho wrongly uses the term "hand plane" to describe the hand arc path plane, which is much steeper than the clubshaft plane in most pro golfers. You wrote-: "I cannot imagine that forearm rotation can happen in either of the above scenarios until PA#2 is fully released in the hand plane with zero PA#3 angle (to prevent an OTT) . Imho, only after the latter geometry is reached can the shaft be rotated passively in SIM1 or actively in SIM3 within the hand plane." In a SIM 1 type of golf swing action, the clubshaft is shallowed to below the hand arc path plane between P4 and P5.5 and left forearm rotation can happen well before PA#2 is fully released.
Here is an example of a SIM 1 type of golf swing action - Sergio Garcia's downswing action. Image 1 is at P5.5 and image 2 is at P6. Note how much he has supinated his left forearm between P5.5 and P6 when PA#2 is only starting to release. Here is another example - Dustin Johnson's downswing action
Image 1 is at P5.5, image 2 is at P6 and image 3 is at P6.5. Note how much he has supinated his left forearm between P5.5 and P6.5 - which is well before the full completion of the release of PA#2. You wrote-: "Lets assume the energy supplied by the 3 torque generators (ignoring the forearm generator for the moment) is the same for SIM1 and SIM3 to release PA#2 .Lets call that energy 'X'
SIM3 : All of 'X' energy is required to release PA#2 within the hand plane
SIM1 : A certain amount 'Y' energy is used to move the club from underplane to the hand plane , then the rest of 'X-Y' energy is used to release PA#2." Regarding your bold-highlighted statement - why do you believe that the clubshaft at P5.5 (which is underplane relative to the hand arc path plane) must steepen to the hand arc path plane between P5.5 and impact? Note that Sergio Garcia's clubshaft does not steepen between P5.5 and impact. I therefore don't think that a certain amount of energy ("Y") is required during the P5.5 => P7 release period as you claim. I also do not understand why you believe that hand speed at P5.5 must be less in a SIM 1 type of golf swing action. Jeff.
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Post by dubiousgolfer on Jan 30, 2020 18:44:35 GMT -5
Dr Mann
I'm only questioning SMK's research experiments because some aspects do not make any sense to me. His SIM1 and SIM3 experiments constrain the downswing to a constant hand path plane with both club/forearm in a straight line by impact (within that 'hand path plane'). Imho his experiments have no bearing to the reality of a real golfers swing like Sergio and DJ above.
I think in his experiment for SIM1 he has released PA#2 early because he says the following:
"While the peak clubhead speeds were similar for Sim1 (37.1m/s) and Sim2 (38.2m/s), Sim2 dropped to 31.8m/s at impact, while Sim1 only dropped to 36.2m/s at impact (Figure 2e; Table II)."
He also makes this comment in his article: " The clubhead speed for Sim3 (44.1m/s) was 22% higher than that generated during Sim1 (36.2m/s), which indicates as to how much active rotation of the forearm from a muscular torque can contribute to clubhead speed"
I think he has made a big mistake by not measuring the hand speed in his Sim1 and Sim3 experiments and then made an assumption about cause and effect of the extra clubhead speed seen in SIM3.
It will be interesting if he replies to my email.
DG
PS. In SG's swing images isn't he pitching his lead arm as he supinates? In SMK's model experiments there is no pitching because the 'hand path plane' is constrained. SMKs model for those particular SIM1-6 experiments, the left arm is only allowed to move in the 'horizontal abduction–adduction' at the shoulder .
I suspect the closest golfers that could represent a SIM3 in SMK's experiment would be a one-planer (with a neutral grip) . How about Moe Norman or De'Chambeau?
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Post by syllogist on Jan 31, 2020 8:34:12 GMT -5
Hi DG,
With regard to centripetal acceleration (with regard to clubhead speed), note that its formula does not include a provision to either axially rotate the club shaft or to axially rotate the hand or forearm.
I believe that how SMK set up his model will result in the conclusion that the rotational velocity of the forearm correlates to clubhead velocity. (He included a forearm torque generator.)
To illustrate, in such a model, if the left hand is positioned at the release point such that the back of the left hand faces the target line (where the knuckles are parallel to the target line), approx. 90 degrees of rotation of the left hand would be required for the club shaft to be perpendicular to the target line to impact the ball. Therefore, in such a model, it stands to reason that the faster the rotational velocity of the forearm, the faster will be the clubhead speed. Remember that he has mathematically calculated that a club shaft shallower than hand path will induce the shaft to align with the left arm abduction angle throughout the downswing (which, in his model, will induce forearm rotation).
I agree that the shallower shaft will seek to align with the left arm abduction angle (even if the hand path were not perfectly planar), but, in my opinion, that is all that should have been concluded. Reality tends to be more complicated that what we are able to simulate.
S
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Post by dubiousgolfer on Jan 31, 2020 9:35:58 GMT -5
Hi Syllogist- Yes , your above comment assumes that SMK's model retains some radial deviation as the supination happens in the downswing. But unless the lead arm pitches, the clubhead will topple over and cause an 'out-to-in' path. Unless I've misinterpreted, SMK's model shows the left arm/hand stay on the same plane, his left arm and clubshaft form a straight line with the clubface square by impact. I think a good example of Simulation 3 in a real golfer is Phil Mickelson's downswing in the TSP (Turned Shoulder Plane) Here is an example from one of Dr Manns previous posts on PM, someone who does not pitch his lead arm as he supinates his left forearm. How on earth can Sasho's model create an extra 7.9 m/s clubhead speed (compared to Sim 1 which uses a passive club squaring action) using similar biomechanics as PM between P6.7-P7? I may be wrong but find it very difficult to imagine. Image 1 is just bypassed the P6 position. Note that his clubface is still open to the clubhead arc and that the toe of his clubhead is pointing up (skywards) and that it is also tilted slightly backwards away from the ball-target line. Note that the clubface is parallel to the back of his lead hand and watchface area of his lead lower forearm because he has maintained an intact LFFW. Note that the back of his lead hand, and watchface area of his lead lower forearm, is parallel to the inclined plane, which has a degree of steepness roughly equivalent to the steepness of the TSP because he did not shallow his clubshaft during his early-mid downswing. Image 2 is at the P6.7 position. Note that the clubface is still wide open relative to the ball-target line and also relative to the clubhead arc. Note that the back of his lead hand, and watchface area of his lead lower forearm, is still roughly parallel to the inclined plane, which has roughly the same degree of steepness as the TSP because he is not shallowing his clubshaft between P6 and P6.7. Note that there is no evidence that Phil Mickelson is significantly supinating his lead forearm between P6 and P6.7. Note that he has significantly released PA#2 (in the plane of his intact LAFW) between P6 and P6.7 and that the clubshaft has nearly caught up to his lead arm by P6.7. Image 3 is at impact, where he has squared his clubface by supinating his lead forearm by the amount needed to acquire a square clubface by impact. In other words, Phil Mickelson delays his PA#3 release action and he only significantly supinates his lead forearm between P6.7 and impact. If virtually all of his lead forearm supinatory motion happens in that short pre-impact time period between P6.7 and impact, that means that the amount of clubface roll per unit degree of clubhead travel is very large as his clubhead travels along the last 18" of his clubhead travel path just before impact. That large amount of ROC (rate-of-closure) of his clubface in the last 18" of clubhead travel along the clubhead arc (just before impact) is potentially a great disadvantage because it makes it much more difficult for him to time his clubface roll so that the clubface can be guaranteed to be square at impact. What aggravates the timing of his clubface-squaring phenomenon is the fact that Phil Mickelson needs to use an active muscular force to perform his PA#3 release action's left forearm supinatory motion. Why can Phil Mickelson not use passive forces to square his clubface by impact? First of all, Phil Mickelson cannot use the passive "torque force" (described by Sasho MacKenzie) because he does not shallow his clubshaft during his early-mid downswing. Secondly, he cannot use the passive RYKE phenomenon (described by Kevin Ryan) because he has too small an accumulator #3 angle between P6.7 and impact. So, he is dependent on using an active muscle force derived from an active muscular contraction of his lead forearm's supinator muscles (+/- his rear forearm's pronator muscles if they are used synergistically to assist in the clubface-squaring phenomenon). The amount of active muscular force required is very small because the *moment-of-inertia is very small - and that is because the clubshaft has nearly caught up to his straight lead forearm by P6.7. DG
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Post by imperfectgolfer on Jan 31, 2020 10:57:06 GMT -5
DG, You wrote-: " I'm only questioning SMK's research experiments because some aspects do not make any sense to me. His SIM1 and SIM3 experiments constrain the downswing to a constant hand path plane with both club/forearm in a straight line by impact (within that 'hand path plane'). Imho his experiments have no bearing to the reality of a real golfers swing like Sergio and DJ above.
I think in his experiment for SIM1 he has released PA#2 early because he says the following:
"While the peak clubhead speeds were similar for Sim1 (37.1m/s) and Sim2 (38.2m/s), Sim2 dropped to 31.8m/s at impact, while Sim1 only dropped to 36.2m/s at impact (Figure 2e; Table II)."
He also makes this comment in his article: " The clubhead speed for Sim3 (44.1m/s) was 22% higher than that generated during Sim1 (36.2m/s), which indicates as to how much active rotation of the forearm from a muscular torque can contribute to clubhead speed"
I think he has made a big mistake by not measuring the hand speed in his Sim1 and Sim3 experiments and then made an assumption about cause and effect of the extra clubhead speed seen in SIM3." I think that you are making a huge mistake by trying to analyse Sasho's study as if it were an useful study that has scientific and practical legitimacy. I personally think that it is a worthless study that has zero value with respect to helping us better understand the golf swing.
First of all, it is a theoretical study based on computer-generated modelling and not based on the observation of "real life" pro golfers. Therefore, your statement that he didn't measure "hand speed" is somewhat meaningless.
Here are a few criticisms of his study that explain why I think that it was a futile exercise that has no value in helping us better understand golf swing biomechanics/mechanics.
His idea of comparing an under-the-plane clubshaft to an above-the-plane clubshaft (relative to the hand arc path) is basically stupid because I could easily predict that starting the downswing with the clubshaft positioned above the plane of the hand arc path would not work and that it would result in a lower clubhead speed and an open clubface at impact.
Secondly, he compared hand arc paths with different pitches and he presumed that the hand arc path would have a constant pitch throughout the downswing. That only happens in a small percentage of pro golfers.
Thirdly, he attempted to compare a passive PA#3 release phenomenon to an active PA#3 release phenomenon where he presumed that the left forearm's muscles would be providing the active supinatory torque. However, he used a standard amount of active muscular supinatory torque where he did not specify how he determined the appropriate amount of active torque application and also the appropriate timing and duration of active torque application. Surely, it must depend on the strength of the left hand grip and also the accumulator #3 angle (which depends on whether the golfer has the left arm more extended or more vertically oriented between P6 and impact and which also depends on whether the golfer uses a mid-palmar versus a finger grip).
Finally, one of his endpoints was the need for his computer-model to produce a square clubface at impact. I think that requirement is inadequate because an uncontrolled roller hand release action (due to an active left forearm supinatory torque) may produce a square clubface at impact, but it obviously does not produce a stable clubface that is square to the clubhead arc between P7 and P7.2, which may be very important in terms of consistent ball flight accuracy from a swing-after-swing perspective. If you disagree with my criticisms, then please explain how Sasho's study has improved our understanding of golf swing biomechanics or mechanics. Jeff.
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Post by dubiousgolfer on Jan 31, 2020 12:17:43 GMT -5
I agree with you Dr Mann - I am wasting too much time on some of these scientific articles and these limited golf models.
DG
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Post by imperfectgolfer on Jan 31, 2020 15:14:14 GMT -5
DG, Another point. You stated that Phil Mickelson's driver swing action best exemplifies Sasho's SIM 3 model's golf swing action. I agree with you! As I wrote in my analysis of PM's PA#3 release action, it happens very late in the downswing between P6.7 and P7 and it does not require much active lead forearm supinatory torque because the MOI is going to be small when the clubshaft has nearly caught up to the lead arm by P6.7. So, why does Sasho state that the left forearm supinatory torque must start to be applied at ~P5.5 (soon after the start of the release of PA#2) and must be continued for such a long time period - as shown in the following graph. Jeff.
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Post by syllogist on Jan 31, 2020 17:29:55 GMT -5
Hi DG,
I understand about "unless the lead arm pitches." However, SMK intentionally made the left arm plane planar in order to show ONLY that a shaft shallower than the hand path induces clubface squaring and that a steeper shaft than the hand path hinders clubface squaring as well as to show that the slope of the plane did not affect clubface squaring. There is nothing else to conclude from the model. One can critique any other assumptions he made based on the model's output as well as his thoughts about what pros may or may not do per his vimeo presentation on this subject.
S
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