|
Post by imperfectgolfer on Jan 10, 2022 9:00:01 GMT -5
I noted that DG and Jay Dubeck are having a back-and-forth argument in the comment section of one of Kwon's videos. I have no reason to comment on their opinions, but I am bothered by Jay's claim made in the following paragraph-: "You know what sounds like mentally ill...someone who writes the elderly parents of a well respected golf instructor and tells them their son is a misguided person. That person is Jeff Mann. Why would he do that? Sounds like he needs help and you can maybe take him in to be evaluated...while you're there you might want to get checked as well."
That is a wild accusation that is untrue! Where is his "evidence" that I personally wrote to the elderly parents of a respected golf instructor in order to tell them that there son is a misguided person?
Jeff.
|
|
|
Post by imperfectgolfer on Jan 10, 2022 9:11:34 GMT -5
Janik, You wrote-: " However I can clearly see Jim is performing this 'holding-on' action all the way to P8 in his mini swings (see app. 39:45 in the video). Maybe this is his practice 'feel' to achieve the DH action, which just lasts until P7.2 as he can't keep up to P8?" It is obvious that if one is using a DH-hand release action where the arm/clubshaft motion is slow after impact that one can more easily maintain an intact LFFW to P8+. That happens in Jim Sheridan's mini-swing and it can often happen in many pro golfer DHers when they hit wedge shots with a short iron. Some even keep their LFFW intact to P8.5+. However, it is very rare to see a pro golfer DHer keep their LFFW intact to beyond P7.4 when using a driver. Here are capture images of Cameron Champs' driver swing. Note that he still has an intact LFFW at P7.4 (image 3) and the clubshaft is only starting to bypass his lead arm in image 4 (P7.6). Jeff.
|
|
|
Post by dubiousgolfer on Jan 10, 2022 11:02:56 GMT -5
Dr Mann
I have been in discussion with Jay Dubeck on Dr Kwon's you-tube comments section and although this individual keeps using insulting personal attacks he did refer me to this video (which I've seen before and may have also previously posted in another thread) where SMK talks about ROC from 11:30- 21:00. I have deleted the comments now because of his continued insults and reported him to you-tube.
The one thing I failed to notice before was SMK's comment regarding a claim of 800 deg/sec ROC being impossible because typically the minimum of rate of closure for a PGA golfer swinging at 100 mph (without any lead forearm supination or wrist extension/flexion) will be around 1600 deg/sec. Obviously this is because they swing on an inclined plane and not on a vertical one like a Ferris wheel.
But then I recall Jon Sinclair sending a graph of one of the PGA players on his database with the lowest ROC and I mistakenly thought 877.7 deg/sec represented the ROC but in fact it represented the lead wrist velocity for 'flexion/extension'.
So shouldn't there really be a comparison made between D-Hers and non-DHers for the following (just before and after impact):
1. 'Handle Twist Velocity' vs 'Dispersion' 2. 'Lead Wrist flexion/extension Velocity' vs Dispersion' 3. 'Rate of Closure (due only to swing speed and swing plane inclination at impact)' vs 'Dispersion'
There should also be a measurement made of the lead and trail hand grip strength for all golfers when conducting these measurements.
Amalgamating all the above into one graph 'ROC vs Dispersion' doesn't provide enough detailed data to discern a possible cause and effect of dispersion.
Further the measurement of 'Driving Accuracy' should not relate to % fairways hit (like in Phil Cheetham's dissertation) but measured in a way that reflects the true outcome of how wayward the strikes are from an intended target.
DG
|
|
|
Post by dubiousgolfer on Jan 10, 2022 18:17:58 GMT -5
I noted that DG and Jay Dubeck are having a back-and-forth argument in the comment section of one of Kwon's videos. I have no reason to comment on their opinions, but I am bothered by Jay's claim made in the following paragraph-: " You know what sounds like mentally ill...someone who writes the elderly parents of a well respected golf instructor and tells them their son is a misguided person. That person is Jeff Mann. Why would he do that? Sounds like he needs help and you can maybe take him in to be evaluated...while you're there you might want to get checked as well." That is a wild accusation that is untrue! Where is his "evidence" that I personally wrote to the elderly parents of a respected golf instructor in order to tell them that there son is a misguided person? Jeff. Dr Mann Although the comments have been deleted , he claimed that the respected golf instructor was Michael Jacobs. DG
|
|
|
Post by dubiousgolfer on Jan 11, 2022 11:09:58 GMT -5
Another interesting video showing how Dr Kwon analysed the ground reaction forces for a female pupil to try and optimise her lower body movement to increase her clubhead speed.
When I looked at her original swing , I thought her stance was too wide and the angulation of her right leg to hip joint prevented her from optimally pressure loading into her right leg to contract her right pelvic girdle rotator muscles.
DG
|
|
|
Post by imperfectgolfer on Jan 11, 2022 11:13:49 GMT -5
DG, You asked-: " So shouldn't there really be a comparison made between D-Hers and non-DHers for the following (just before and after impact):
1. 'Handle Twist Velocity' vs 'Dispersion' 2. 'Lead Wrist flexion/extension Velocity' vs Dispersion' 3. 'Rate of Closure (due only to swing speed and swing plane inclination at impact)' vs 'Dispersion'
There should also be a measurement made of the lead and trail hand grip strength for all golfers when conducting these measurements."
If I recall correctly, Sinclair showed that the "average" rate of lead wrist extension at impact in pro golfers was about 877 degrees/second. We worked out that it represents ~6 degrees of lead wrist extending happening during the P7 => P7.2 time period. That amount is very small and will not necessarily cause the clubshaft to bypass the lead arm by P7.2 if the lead wrist is bowed at impact. So, one can still be a DHer with an "extending lead wrist phenomenon" happening through impact. It would be intellectually interesting to know whether the degree of "lead wrist extending" happening between P7 => P7.2 is smaller in DHers (compared to non-DHers), but it is not really important because the phenomenon of a small degree of "lead wrist extending" happening between P7 => P7.2 will not necessarily cause the clubface ROC to be increased if the lead wrist does not significantly circumduct while it moves in the direction of extending. Many pro golfers (eg. Brandt Snedeker) exhibit a small degree of overt clubshaft flipping action through impact and they still hit the ball straight. It would be much more interesting to know what the clubface ROC is at P6.9, P7 and P7.1 to see if there is a significant correlation between the dispersion rate and a lower clubface ROC (either near-impact, at impact or immediately post-impact). However, the answer to that question would require a very high sampling rate, which modern-day 3D systems are incapable of achieving. I would imagine that the clubface ROC pre-impact at P6.8 - P6.9 is much more important in terms of its likely effect on the dispersion rate than the clubface ROC post-impact at P7.1, but I am willing to change my opinion if scientific studies did not confirm my opinion. It would also be interesting to know whether factors such as lead hand grip strength, trail hand grip strength and a "running-out-of-trail arm" phenomenon could be major causal factors in causing a higher clubface ROC at those time points.
Jeff.
|
|
|
Post by imperfectgolfer on Jan 11, 2022 11:52:41 GMT -5
I noted that DG and Jay Dubeck are having a back-and-forth argument in the comment section of one of Kwon's videos. I have no reason to comment on their opinions, but I am bothered by Jay's claim made in the following paragraph-: " You know what sounds like mentally ill...someone who writes the elderly parents of a well respected golf instructor and tells them their son is a misguided person. That person is Jeff Mann. Why would he do that? Sounds like he needs help and you can maybe take him in to be evaluated...while you're there you might want to get checked as well." That is a wild accusation that is untrue! Where is his "evidence" that I personally wrote to the elderly parents of a respected golf instructor in order to tell them that there son is a misguided person? Jeff. Dr Mann Although the comments have been deleted , he claimed that the respected golf instructor was Michael Jacobs. DG Jay Dubeck seems to assert that I personally wrote to Michael Jacobs' elderly parents to inform them that I think their son has misguided golf instructional opinions. I have never personally communicated with them and I would not know how to do that because I do not know their names or their e-mail addresses. If Jay has "evidence" to the contrary, then he should post his "evidence" in the public sphere. However, I do vaguely recall commenting on a public post that MJ's father made where he praised his son as being a genius who had significantly advanced the scientific knowledge of golf swing mechanics. I cannot exactly remember where he made this publically-available post and it could have been in the comment section of an Amazon book review or a golf forum. I do recall responding to his claim by publically stating that it would be misguided to believe that MJ has made any significant contribution to the knowledge of golf swing mechanics. My public response represents "fair criticism" because I was responding to a public post, and I did not privately contact MJ's father to tell him that I think that his faith in MJ's opinions re: golf swing mechanics is misguided. In reality, I actually believe that MJ is an "idiot" who has expressed totally nonsensical opinions regarding golf swing mechanics - as particularly evidenced by a video where he held a small model airplane and talked about pitch and yaw of the plane as representing the alpha, beta and gamma torques happening during the downswing. I think that that particular video was totally nonsensical. It is interesting that I can no longer find that you-tube video online and I presume that MJ has deleted it.
Jay Dubeck has stated that my opinions re: golf swing biomechanics/mechanics have zero merit because I am not a golf instructor or a golf researcher, and because I do not perform 3D studies. I think that his criticism is meritless. The reality is that I am only an amateur golf swing analyst/theorist who studies golf swing biomechanics and mechanics as a pet hobby interest. I especially make a concerted attempt to analyse, and criticisize, the opinions of many golf instructors/researchers whose opinions are available in the public sphere. Jay Dubeck, and all the other persons who harbor a strong personal antipathy towards me (eg. Malaska-groupies, Manzella-groupies, Jacobs-groupies), resent my brash confidence in my personal opinions and my relentless criticism of many renown golf instructors/researchers, and they often attack me with personal ad hominem attacks (eg. calling me a psychopath or a clown). If they really believe that my personal opinions are nonsensical and meritless, then they should just ignore me. However, they cannot control their antipathy towards me and they relenlessly attack me and mock me via the mechanism of personal ad hominem insults. They remind me of Trump-supporters who live in an "alternative mental universe" and who have zero tolerance for any contrary opinions that contradict their personal opinions! Jeff.
|
|
|
Post by imperfectgolfer on Jan 11, 2022 12:35:40 GMT -5
Another interesting video showing how Dr Kwon analysed the ground reaction forces for a female pupil to try and optimise her lower body movement to increase her clubhead speed. When I looked at her original swing , I thought her stance was too wide and the angulation of her right leg to hip joint prevented her from optimally pressure loading into her right leg to contract her right pelvic girdle rotator muscles. DG I wish that Kwon would publish more of those graphs so I can better understand his point of view. He seems to be plotting the torque forces being produced by vertical GRFs and also the moment arm at very moment of the golf swing, and he is seemingly asserting that those forces/torques produce a counterclockwise rotation of the torso around the COM in the frontal plane. What I cannot understand is how those graphs help us to better understand how to optimally shift-rotate the pelvis in the early-mid downswing where the pelvis is primarily rotating in a much more horizontal fashion. I actually think that she has an excellent golf swing action even though her stance width is wider than her shoulder width. I agree that it is more difficult to drive the trail hip joint into internal rotation if the stance width is so wide and if the clockwise rotation of her pelvis between P1 => P4 is subsequently more limited in magnitude. That theoretically means that her trail side's lateral pelvic rotator muscles may not be optimally pre-loaded. However, whether she would benefit by having a narrower foot stance and a greater degree of clockwise pelvic rotation that would drive her trail hip joint into a greater degree of internal rotation by P4 is unknown to me. It would interest me greatly to see what effect those changes would have on the efficacy of her downswing's pelvic/torso rotary motion, and how it would affect her generation of vertical GRFS/ torques and moment arm.
Jeff.
|
|
|
Post by dubiousgolfer on Jan 11, 2022 20:49:41 GMT -5
I'm finding it difficult to understand what Dr Kwon is saying because of his accent but I think he advised that female golfer that the 'unweighting' phase happens just before the end of the backswing (the transition phase?). I am assuming the transition phase must be the period between the start of counter clockwise rotation of the pelvis and the top of the backswing. Wouldn't that imply that the golfer is actually allowing his body to fall as he demonstrated (ie. the slight flexing of the knees)? So is the contraction of the right pelvic girdle rotary and iliopsoas muscle during the transition phase causing this 'unweighting' effect that he showed in his graphs? I'm assuming Dr Kwon means that the body then has time to prepare itself to create a ground reaction force with a magnitude and direction to maximise the 'moment' about the COM to generate a body driven torque at the right time in the downswing (ie. P5.5 release).
Again , using GRFs is a very abstract way to describe the biomechanics of the golf swing because it doesn't provide any anatomical description of what the golfer is doing to create those GRFs. Because, a far as I am aware , the intended internal anatomical movements of the golfer creates the necessary GRFs to realise those movements.
DG
PS. Just seen this new video that Dr Kwon has published which provides more detail on GRF interactions being created during the golf swing.
|
|
|
Post by imperfectgolfer on Jan 11, 2022 23:35:56 GMT -5
I'm finding it difficult to understand what Dr Kwon is saying because of his accent but I think he advised that female golfer that the 'unweighting' phase happens just before the end of the backswing (the transition phase?). I am assuming the transition phase must be the period between the start of counter clockwise rotation of the pelvis and the top of the backswing. Wouldn't that imply that the golfer is actually allowing his body to fall as he demonstrated (ie. the slight flexing of the knees)? So is the contraction of the right pelvic girdle rotary and iliopsoas muscle during the transition phase causing this 'unweighting' effect that he showed in his graphs? I'm assuming Dr Kwon means that the body then has time to prepare itself to create a ground reaction force with a magnitude and direction to maximise the 'moment' about the COM to generate a body driven torque at the right time in the downswing (ie. P5.5 release). Again , using GRFs is a very abstract way to describe the biomechanics of the golf swing because it doesn't provide any anatomical description of what the golfer is doing to create those GRFs. Because, a far as I am aware , the intended internal anatomical movements of the golfer creates the necessary GRFs to realise those movements. DG PS. Just seen this new video that Dr Kwon has published which provides more detail on GRF interactions being created during the golf swing. In his latest video on GRFs, Kwon shows that the unweighting phase starts before P4 and reaches its maximum value at approximately P4.5 (see 15:57 minute time point of his video). I do not believe that the unweighting phase is causally due to contraction of the iliopsoas muscles that can increase hip joint flexion, but it seems to be due to the fact that the trail foot is decreasing its vertical GRF steadily in the later backswing to reach its lowest magnitude at ~ P4.5. The unweighted phase is also the time period between his two-step phase concept - phase 1 is where the right foot is creating a large GRF (maximised at P2.5) and phase 2 is where the lead foot is creating a large VRF (maximised at ~P5.5).
I personally do not find these graphs helpful in explaining how best to perform a pelvic motion during the downswing. These vertical GRFs supposedly are responsible for causing a torque around the COM which causes the torso to rotate counterclockwise in the frontal plane around the COM. However, that does not explain what we see in a pro golfer's early downswing with respect to pelvic motion.
Here is Jamie Sadlowski's pelvic motion in the early-mid downswing. I have drawn a red line along the back of his trail buttock at P4 (image 1). Note that his pelvis has rotated a lot clockwise (>65 degrees) by P4. Note that his pelvis has nearly squared by P4.5 (image 2) while his trail buttock remains abutted against the tush line. There is nothing in Kwon's V-GRF graphs i) that explains what is causing the ~65 degrees of counterclockwise rotation of the pelvis that is happening in a very horizontal plane between P4 => P4.5 and ii) that explains why the trail buttocks remains abutted against the tush line during the P4 => P4.5 time period. I much prefer my biomechanical explanation that is based on the active muscular contraction of the trail sided lateral pelvic rotator muscles that is happening while pressure-loading of the trail foot is maintained. The contraction of the trail side lateral pelvic rotator muscles causes the pelvis to rotate counterclockwise away from the pressure-loaded trail leg, while the continuous pressure-loading of the trail leg/foot keeps the trail buttock in place.
Jeff.
|
|
|
Post by imperfectgolfer on Jan 12, 2022 11:37:03 GMT -5
Here is my interpretation of the GRF graphs presented in Kwon's latest video. Please correct me if you think that I am misinterpreting Kwon's graphs.
Image 1 is at ~P2.5 when the trail side foot's GRF is at its maximum value. Image 2 is at ~P4.5 when the trail foot's GRF = lead foot's GRF and it is at the end of the "unweighting" time period.
Note that the combined GRF being exerted by both feet (red graph) is less than the body weight between ~P3.5 => ~P4.5, which means that the body is basically "unweighted". Note what is happening to that avatar between P3.5 => P4.5 - note that the pelvis is shifting targetwards in a re-centering manner but the pelvis is not rotating counterclockwise during that time period. In other words, it seems that Kwon is advocating that the golfer should maximise his trail foot's GRF at P2.5 so that he can then push the pelvis targetwards while the body is becoming increasingly more "unweighted", and therefore more "free-floating", between P2.5 => P4.5. That will allow the body (pelvis and mid-upper torso) to more easily re-center while keeping the pelvis still closed (= not rotating counterclockwise).
I definitely do not advocate that technique, and I do not think that it is happening in many pro golfers. Here is Jamie Sadlowski's golf swing action. Image 1 is at P2.5, image 2 is at P3.8 , image 3 is at P4 and image 4 is at P4.5. I have drawn red lines alongside the outer border of his pelvis at P2.5. Note that JS's pelvis is re-centering slightly between P2.5 => P3.8, but it is really due to a continued clockwise rotation of his pelvis rather than any targetwards shift of his pelvis due to pushing off his trail foot. Note that his pelvis is maximally rotated clockwise at P3.8 (image 2).
Note that his pelvis is starting to rotate counterclockwise between P3.8 (image 2) => P4 (image 3) without any targetwards shift of his pelvis. Note how much his pelvis has rotated counterclockwise by P4.5 (image 4) and it almost square to the ball-target line. Note that he does not shift his pelvis targetwards during this hip-squaring phase that is happening between P3.8 (image 2) and P4.5 (image 4). I don't have access to Jamie Sadlowski's vertical GRF graphs, but I doubt that they look similar to Kwon's featured GRF graphs. I strongly suspect that JS is maintaining a high degree of pressure-loading of his trail foot between P3.8 (image 2) and P4.5 (image 4) and that he is using his trail side's lateral pelvic rotator muscles to rotate his pelvis counterclockwise during that P3.8 => P4.5 time period without performing any targetwards shift of his pelvis.
Jeff.
|
|
|
Post by imperfectgolfer on Jan 12, 2022 16:34:16 GMT -5
Here is another example of how I disagree with Kwon's golf instructional teaching. Consider how Kwon is talking about this student-golfer's (Kennedy's) golf swing action.
Here is Kwon reviewing her GRF and torque graphs.
Image 1 is at the start of her "unweighting phase" - which is where the red graph in the middle-section graphs starts to drop below her body weight. It is happening at her P4 position. Kwon states this is too late because she is apparently not pressure-loading her right foot adequately at P2.5, which should cause the combined V-GRF graph (red graph in the middle section graphs) to be greater than body weight at P2.5 - according to Kwon's teaching philosophy. Kwon seemingly wants a golfer to maximise the trail foot V-GRF at P2.5 so that the golfer can push the pelvis/body targetwards in a left lateral shift-manner during the "unweighting phase", which he wants to happen between P3.5 => P4.25.
Image 2 shows her at the end of her "unweighting phase", which is happening at ~P4.5. Note that she is generating her maximum torque value (see red graph in the top section of graphs) and maximum moment arm value (see red graph in the lowest section of graphs) at P4.5.
Here are capture images of her pelvic motion.
Image 1 is at P3.8. Note that her pelvis is rotated clockwise to a significant degree and that her trail hip joint is in a condition of internal rotation, which means that she could be optimally pre-loading her trail side's lateral pelvic rotator muscles.
Image 2 is at P4. Note that she is already rotating her pelvis counterclockwise without any preceding left-lateral shift of her pelvis.
Image 3 is at her P4 position. I have drawn a red line along the back of her trail buttock and it represents the tush line.
Image 4 is at her P4.5 position. Note that she has rotated her pelvis a lot counterclockwise, but her trail buttock is not prematurely leaving the tush line as happens in a "hip spinning" pelvic motion pattern.
I think that she is manifesting the pro golfer's pattern of rotary pelvic motion where any targetwards shift of the pelvis happens simultaneously while the pelvis is rotating counterclockwise, and I think that her pelvic motion pattern is superb!
I don't agree with Kwon's instruction where he wants her to more assertively load her trail foot by P2.5 so that she can then push her pelvis targetwards before she starts to initiate her downswing's counterclockwise pelvic rotary motion.
Jeff.
|
|
|
Post by dubiousgolfer on Jan 12, 2022 23:01:23 GMT -5
Dr Mann
Yet after doing these step drills she improved her clubhead speed from 94 - 110 mph but that was when she was using a very energetic trigger backswing action (which she cannot do when playing on course). I think the main reason for her clubhead speed increase is the fact that she has to create a lot of force via her hands to stop the backswing and therefore she has a ready made large linear force to start her downswing (without having to ramp it up from a lower force). A larger linear force applied over virtually the same hand path means more 'work' done on the club to increase its kinetic energy.
SMK did the same with Cordie Walker:
DG
|
|
|
Post by dubiousgolfer on Jan 12, 2022 23:40:54 GMT -5
Dr Mann
I do have some Jamie Sadlowski GRF images on 'hackers paradise' forum . I'll see if I can post them onto this website.
DG
|
|
|
Post by dubiousgolfer on Jan 13, 2022 9:14:10 GMT -5
Dr Mann These are the only images I have but you can see that the COM (red dot) doesn't seem to shift targetwards as P4 is reached. DG
|
|