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Post by syllogist on Dec 10, 2019 7:15:49 GMT -5
Dr. Mann,
Apologies - I meant to type "adduction."
Evidence for release? Well, I don't have the tools to measure the increasing pounds of force that the clubhead acquires throughout the downswing but surely 100 lbs or so at the onset on release can't be too far off for a full swing. Logic would dictate that if the club were weightless, the clubhead would not release unless positive torque were applied at the wrist joints. Is it a coincidence that, in a double pendulum model under, let's say, the force of gravity, both the mass and length of the two segments are variables to be input?
S
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Post by syllogist on Dec 10, 2019 8:47:04 GMT -5
Hi DG,
Apologies for the ambiguity. There's nothing wrong with Dr. Mann's summary of a "swinging technique" and White is correct as well.
You wrote: "So do you believe in a swing where PA#4 and PA#2 retain their 'loading' ('out of line' geometry) while the golfer uses his 'torso pivot' to rotate those loaded PA's in the downswing until the pivot slows down and blasts the lead arm off the chest (release of PA#4)? Then the release of PA#2 happens later (and passively without any active wrist torque) due to D'Alemberts principle? "
S: PA 4 and PA 2 retain their "while the torso begins to rotate. It is more likely that the major factor for torso slowing is the release of PA 4 and PA 2 (movements of distal segments farther from proximal segments). I also wouldn't characterize the lead arm as "blasting off the chest" - the phenomenon is not as explosive as the phrase suggests. There is no active, positive wrist torque during wrist release. In physics terms, the major reason for wrist release is the increasing momentum of the clubhead. I think that D'Alembert's principle of force differential applies to the entire downswing.
You wrote: "Are you saying that you can control a late release of PA#4 (and therefore a late release of PA#2) by rotating your torso against the inertia of the arms/club until the opportune moment in the downswing? That if you time the release of PA#4 correctly , it will provide your lead arm with enough angular velocity so that there is optimal forward shaft lean by impact? "
S: The torso and left arm begin to rotate as a "unit," - as one distinct mass per se. You don't time the release of PA 4; forces will take care of that. The lead arm will outrace the club shaft will a delayed release. Beyond that, shaft lean is a function of "effective ball placement" in relation to the body.
You wrote: "With regards Bertie's lag tension concept, I personally cannot accept that Vimeo Video explanation because it doesn't make sense from a physics perspective (if Dave Tutelman's assertions are correct). We will just have to wait and see if Bertie (or his R&D colleagues) can disprove DT's statements.
S: That concept was a mass of confusion though I understood what he meant. Further, personally, I'm not much for concepts such as left hand stabilization or changes in location of hand pressure. My awareness diminishes in proportion to the progression of the downswing. :-)
S
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Post by syllogist on Dec 10, 2019 17:27:17 GMT -5
To all, After doing a quick search, I came to realize why D'Alembert's principle has been consistently used in this forum to explain why the golf club releases. The analysis contained in the link below used such math to simplify the solution to angular acceleration. nmgolfscience.tripod.com/release.htm#:~:targetText=d'Alembert's%20principle%20says%3A%20the,external%20forces%20acting%20on%20it. Please do not attribute the release of the club to D'Alembert's principle. The clubhead is undergoing angular acceleration. It has a specific mass and acceleration attributed to the force applied to move the club over distance. In other words, the clubhead has momentum. Momentum is the mass of an object multiplied by its velocity. It is the momentum of the clubhead, (which happens to increase during the downswing), that causes release. There is nothing else that can cause the clubhead to release. Of course the wrists must be cocked. S
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Post by imperfectgolfer on Dec 10, 2019 23:11:18 GMT -5
S, I still cannot quite comprehend your perspective. If I change the word "abduction" to "adduction", then I presume that you are claiming that if the upper torso rotates counterclockwise between P4 and P5 while keeping the left arm adducted that it will produce a delayed release. I disagree because it is possible that the hand arc path will be too circular under those conditions during the P4 => P5 time period and a circular hand arc path will induce the release of PA#2 (according to the principle of the double pendulum). I believe that the hand arc path must be more "straightish" between P4 and P5.5 to prevent an early release of PA#2 and I know of no better biomechanical method of creating a "straightish" hand arc between P4 and P5.5 other than increasing the downward component of the release of PA#4 via an active right arm adduction maneuver that is combined with external rotation of the right humerus and an right elbow pitch motion - as seen in these capture images of Cameron Champ's early-mid downswing action. During the eventual release of PA#2 the clubhead starts to travel faster than the hands which means that the clubhead acquires more angular momentum than the amount derived from the release of PA#4 and I believe that the only mechanism that can rationally explain why it acquires an increased amount of angular momentum is via the D'Alembert principle (change in the direction of the hand arc path) - presuming that the golfer does not manually uncock the left wrist.
Jeff.
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Post by syllogist on Dec 11, 2019 8:23:50 GMT -5
Dr. Mann,
Briefly, left arm adduction of course will move toward abduction because of 1) the golfer's chosen three-dimensional hand path and 2) forces exerted on the arms by the accelerating and "folded" golf club. So, the movement toward abduction and resultant degree of right arm straightening imply some hand path whose radius is continuously changing.
Wrist cock release is solely due to the momentum of the club. Further acceleration of the club occurs during release and is due to two phenomena. One, the release motion that the wrists make (if we isolate that motion without regard to hand travel) is a circle-like motion having the shortest radius of the entire swing - much shorter than the radius of hand path just prior to release. Two, there is also a degree of energy transfer from arms to the club as the release of the club slows the hands (as we would see in a double pendulum model).
S
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Post by imperfectgolfer on Dec 11, 2019 9:03:59 GMT -5
S,
You wrote-:
"Briefly, left arm adduction of course will move toward abduction because of 1) the golfer's chosen three-dimensional hand path and 2) forces exerted on the arms by the accelerating and "folded" golf club. So, the movement toward abduction and resultant degree of right arm straightening imply some hand path whose radius is continuously changing."
There should no/negligible left arm abduction and no right arm straightening happening between P4 and P5.5 because that will produce a more circular hand arc path and a sweep release of PA#2 (early release of PA#2). Note that neither biomechanical phenomenon is happening between P4 and P5.5 in either Dustin Johnson's and Cameron Champ's early-mid downswing.
Jeff.
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Post by dubiousgolfer on Dec 11, 2019 9:50:56 GMT -5
Hi S Might be worthwhile checking out this article by Nesbitt below (especially the section I've copied and pasted below). www.jssm.org/vol8/n2/11/v8n2-11pdf.pdf"Artificially controlling and optimizing the hub path of the better golfer in the group indicated that a non-circular hub path was superior to a constant radius path in minimizing the kinetic loading while generating the highest possible club head velocity.This results presented in this study support the notion that the non-circular nature of the hub path is fundamental to the golf swing, and properly configured an essential element in achieving the maximum transfer of energy from the golfer to the club. These finding have important implications for golf instruction, and possibly for equipment design (achieving variable equilibrium paths) and injury prevention (minimizing kinetic loading)."
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Post by imperfectgolfer on Dec 11, 2019 10:39:13 GMT -5
Hi S Might be worthwhile checking out this article by Nesbitt below (especially the section I've copied and pasted below). www.jssm.org/vol8/n2/11/v8n2-11pdf.pdf"Artificially controlling and optimizing the hub path of the better golfer in the group indicated that a non-circular hub path was superior to a constant radius path in minimizing the kinetic loading while generating the highest possible club head velocity.This results presented in this study support the notion that the non-circular nature of the hub path is fundamental to the golf swing, and properly configured an essential element in achieving the maximum transfer of energy from the golfer to the club. These finding have important implications for golf instruction, and possibly for equipment design (achieving variable equilibrium paths) and injury prevention (minimizing kinetic loading)." DG, Those were 4 amateur golfers in the Nesbit study, and not pro golfers. Look at how rounded their hand arc path is between P4 and P5.5 and it does not look like DJ's and CC's hand arc path, which is more vertically downward over a longer time period creating a longer "straightish" section of the hand arc path between P4 and P5.5. Their more rounded hand arc path is not conducive to the delayed release of PA#2 that is seen in many pro golfers. Also, look at figure 7 and look at the theoretically optimised hand arc path and note that is has a "straightish" section that is more vertically aligned. That optimised hand arc path (in green) looks more like DJ's hand arc path in the sense that it doesn't go too far away from the target between P4 and P5 and it therefore looks more vertically "straightish" between P4.5 and P5.5. Jeff.
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Post by syllogist on Dec 11, 2019 11:03:31 GMT -5
Hi DB,
I've read everything Nesbit published. As you know, that study involved a handful of recreational golfers of various abilities. Prior to "optimization," they all had non-circular hand paths. Nesbit calculated optimized paths for each for gains in clubhead speed. Minimization of kinetic loading appears to be Nesbit's term for delaying the release, which is essentially to release over a short arc vs. a longer one. Even if the release arc were the same length for an early release vs. delayed release, the delayed release would have greater resultant clubhead speed because the momentum of the clubhead will have become greater later in the downswing.
Understand that very few recreational golfers, even the more skilled ones, have a downswing start sequence relating to torso and left arm as was indicated in White's and Sharp's modeling of the "secret to the perfect swing." Such sequence will yield something near an "optimal" hand path and a resultant desirable release delay. What we don't know from Nesbit's study is exactly how he would have the test subjects improve their hand paths. Of course we can't possibly know if the test subjects altered other aspects of their swings to gain speed.
S
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Post by dubiousgolfer on Dec 12, 2019 12:01:44 GMT -5
Hi DB, I've read everything Nesbit published. As you know, that study involved a handful of recreational golfers of various abilities. Prior to "optimization," they all had non-circular hand paths. Nesbit calculated optimized paths for each for gains in clubhead speed. Minimization of kinetic loading appears to be Nesbit's term for delaying the release, which is essentially to release over a short arc vs. a longer one. Even if the release arc were the same length for an early release vs. delayed release, the delayed release would have greater resultant clubhead speed because the momentum of the clubhead will have become greater later in the downswing. Understand that very few recreational golfers, even the more skilled ones, have a downswing start sequence relating to torso and left arm as was indicated in White's and Sharp's modeling of the "secret to the perfect swing." Such sequence will yield something near an "optimal" hand path and a resultant desirable release delay. What we don't know from Nesbit's study is exactly how he would have the test subjects improve their hand paths. Of course we can't possibly know if the test subjects altered other aspects of their swings to gain speed. S Hi S Not sure I understand what you meant by the below: "Even if the release arc were the same length for an early release vs. delayed release, the delayed release would have greater resultant clubhead speed because the momentum of the clubhead will have become greater later in the downswing."How could one have an early or late release for the same arc length? I'm also having difficulties (from a physics perspective) understanding your comment below. "While we're on the subject of release delay, when the golfer effectively and dynamically delays the release, we must then release the clubhead. Forget about D'Alembert's mathematical expression. It becomes the momentum of the clubhead through the delay that forcefully uncocks the wrists. The momentum of the clubhead increases its MOI, or "effective weight," which the wrists cannot overcome over the curvilinear path."I can readily imagine that the clubheads COM has acquired momentum in the early downswing and its instantaneous linear momentum (mass x velocity) will be constrained because of the clubshaft being pulled in a different direction via forces on the grip by the hands/fingers (note that there will also be real 'club COM inertial forces' being applied through the golfshaft on the hands- this is actually the 'centrifugal' force). But in terms of physics, the rotation of the clubs COM around the lead wrist joint (ie. release of PA#2) is caused by eccentric forces applied to the club (ie. applied forces to the club but not through its COM). DG
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Post by dubiousgolfer on Dec 12, 2019 12:53:18 GMT -5
Dr Mann
I asked Dave Tutelman to provide some feedback on Bertie's vimeo video and he says:
* Berties product is a good one * Agrees with most of his ideas
Has some reservations about :
* Positive couple just before impact. It goes against everything I'm hearing. (Except from Jacobs and Manzella)
* Yes, hands-forward at impact is good. But the reason for hands-forward is not control. (a) It provides higher margin for error in a strike. That's geometry, not control. (b) It allows continuing centrifugal acceleration.
DG
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Post by syllogist on Dec 13, 2019 6:49:18 GMT -5
Hi DG,
"How could one have an early or late release for the same arc length? "
As an example, in a downswing with hands starting at 11:00 from a face on view, fully uncocking the wrists from 10:30 to 8:30 vs. uncocking from 8:30 to 6:30 shows releases of the same arc length. This is hypothetical and theses positions are purely arbritrary for purposes of making the point that a delayed release gives greater angular velocity because of the opportunity to build momentum from peak velocity at the onset of release.
Per DT's thoughts, I don't have any reservations about a positive hand couple at release. I think that the idea is incorrect. However, one can apply positive wrist torque at that point and the slower the hand speed, the more the torque can be applied. Hand speed is sacrificed for positive wrist torque. The release is not akin to the use of a tire iron with both hands to remove the lug nuts from the tire of an auto.
With regard to "hands forward," of course there's a greater margin for error at lease with respect to a ball hit off the turf vs. sitting higher on a tee. Hands forward providing for continuing centrifugal acceleration does not make sense unless he puts it in context.
S
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Post by imperfectgolfer on Dec 19, 2019 13:44:40 GMT -5
I have waited nearly two weeks for Bertie to reply to my first lengthy post where I posed many questions. He has not replied, and I must confess that I am not really surprised! I will now in this present post point out the main differences between Bertie's and my thinking on this topic. Both Bertie and I agree that getting to impact with forward shaft lean is desirable. The main reason is that the left arm/left hand must be leading the clubshaft in a TGM swinging action where swing power is generated by a pivot-induced release of PA#4 and then PA#2. The clubshaft must not bypass the lead arm prior to impact because that means that the lead hand is no longer leading the club towards impact, and the clubshaft (which has bypassed the left arm) is therefore no longer being controlled by the lead arm/hand. Therefore, I can readily agree with Bertie's arbitrary definition of lag tension, which Bertie defines as the clubshaft not reaching the left arm (as viewed from a face-on viewing perspective), and I can readily agree that a lagging clubshaft (relative to the left arm) must be operant during the entire downswing and also at impact. Although I agree with Bertie that lag tension (as defined by Bertie as the lead arm/hand being ahead of the clubshaft) must be present throughout the downswing, I do not think that lag tension (defined differently in the standard TGM way as a positive wrist torque phenomenon) must exist all the way into impact. In other words, I believe that a lagging clubshaft is not synonymous with the presence of a positive wrist torque phenomenon, and I believe that Bertie is wrongly implying that a lagging clubshaft implies the presence of a positive wrist torque phenomenon co-existing at the same time. Consider this capture image from Bertie's vimeo-video. I agree with Bertie that the shaft of the club must trail behind the lead forearm at impact and only catch up to the lead arm after impact. However, I disagree with his opinion that a trailing clubshaft (relative to the lead arm) at impact implies that the i) clubshaft is under lag tension at impact (defined in the standard TGM way implying the presence of a positive wrist torque phenomenon at impact) and ii) that the club is accelerating into impact (under the influence of a positive wrist torque that ensures a "sustain the lag" phenomenon).
First of all, when a researcher studied the driver golf swings of PGA and LPGA tour golfers, the researcher found that peak clubhead speed is actually reached at about 94% of the downswing time period, and not at impact, and that the clubhead is actually slowing down fractionally at impact. In other words, there is no evidence that the clubhead is accelerating at impact. Regarding the presence of a positive wrist torque at impact, David Tuteleman has argued that it cannot exist if the peripheral clubshaft has forward bend relative to the proximal clubshaft - as routinely seen in the driver swings of pro golfers.
I have found further evidence that a positive hand couple phenomenon does not likely exist at impact by reviewing Koike's research study where he used an instrumented grip handle that incorporates strain gauges.
Here is a capture image from his research paper. This graph shows the forces being exerted by the right hand and left hand relative to the X axis, which is the direction of clubshaft unloading in the alpha torque plane (in-plane torque plane). Note that the hands reach their maximum force values values at P5.5, which means that that a positive wrist alpha torque exists during the early-mid downswing between P4 and P5.5. Note that the hand force values decrease rapidly during the P5.5 => impact time period and reach a zero value just before impact. In other words, this golf research study (using an instrumented grip handle) supports David Tutleman's opinion that a positive wrist torque phenomenon does not exist at impact in pro golfers' driver swing actions. Now, let's explore this issue further and ask whether a positive hand couple force phenomenon at impact will stabilise the clubshaft and allow a skilled pro golfer to keep the clubface square to the clubhead arc through impact and into the early followthrough - as depicted in the following capture image from Bertie's vimeo-video. Note how the clubface is stable and square to the clubhead arc through impact, which means that the clubface has a low ROC through the immediate impact zone between impact and P7.2+. To ensure a stable clubface (as depicted in that capture image) left wrist flipping must be avoided because it will produce a backwards shaft lean phenomenon through impact, and not a continuously forward shaft lean phenomenon (as shown in that capture image). How can a skilled pro golfer prevent left wrist flipping and ensure a stable clubface through impact by using the hands to help stabilise the club handle through impact? Bertie stated in his vimeo-video that the hands can stabilise the club handle at the level of the left wrist hinge joint through impact by working as a positive hand couple - as depicted in the following capture image from his vimeo-video. Note that Bertie envisages that the lead hand must be applying a positive force against the club handle in a direction that is away from the target while the trailing hand is simultaneously applying a positive force against the aft side of the club handle below the coupling point at a point where the two hand forces are roughly equidistant from the coupling point. What effect will the two positive forces have with respect to the club handle at the level of the coupling point? Note that the yellow arrows drawn by Bertie show that it will produce a counterclockwise rotary force operating at the level of the coupling point, and that means that a positive wrist couple phenomenon will potentially induce a left wrist flipping phenomenon, instead of stabilising the club handle, through the immediate impact zone between impact and P7.2+!
In fact, a positive wrist couple force phenomenon is used by certain golf instructors (like Brian Manzella, Mike Jacobs and Richard Franklin) to induce their rotation-about-the-coupling point type of hand release action.
Consider this Richard Franklin video where he demonstrates how a golfer should perform a rotation-about-the-coupling point hand release action through impact. Here is a capture image from the RF-video. Note how Richard Franklin is demonstrating a left wrist flipping phenomenon post-impact - and which can also be seen in the green (left wrist flexion-extension) graph that shows a marked degree of left wrist extension happening through impact.
Note that a positive wrist alpha torque phenomenon (positive hand couple phenomenon) is operant throughout the entire downswing and that it only becomes negative after impact. In fact, if you watch the RF-video you will note that RF states that the left hand must be pulling back on the club handle (in a direction that is away from the target) while the trailing wrist straightens and simultaneously pushes against the aft side of the club handle below the coupling point - and what he is really describing is a postive hand couple force phenomenon.
I believe that applying a positive hand couple force phenomenon through impact will likely promote left wrist flipping through impact, and I believe that a golfer should optimally apply a negative hand couple force phenomenon through impact if he wants to stabilise the club handle and avoid left wrist flipping through impact. To apply a negative hand couple force phenomenon through impact, a golfer should be applying a force with the left hand against the club handle at PP#2 that is in the direction of the target (and not away from the target) where the ventral aspect of the middle/distal phalanges of the left hand's 3rd, 4th and 5th fingers can be applying a positive force against the aft side of the club handle in a targetwards direction, while simultaneously applying a restraining force with the right hand at the level of PP#3 (situated at the aft side of the club handle below the coupling point) where the force exerted by the right hand is directed away from the target (and not in the direction of the target). How could this negative hand couple force phenomenon be biomechanically enacted through impact?
Consider Cameron Champ's DH-hand release action through impact. Image 1 is at impact, image 2 is at P7.2 and image 3 is at P7.4. Note that he still maintains a small degree of lag tension (where the clubshaft is slightly lagging behind the left arm) all the way between impact and P7.4. How does he achieve this non-flipping hand release action (DH-hand release action) between impact and P7.4? I believe that the main biomechanical factor that makes it possible is that he does not stall the targetwards motion of his left arm through impact and he maintains the targetwards angular motion of his left arm so that it matches the targetwards angular motion of the clubshaft (from an angular rotational perspective). I also strongly suspect that he may be using a negative hand couple force phenomenon to help him stabilise the club handle during the impact => P7.4 time period - by using his left hand to pull the club handle in a targetwards direction and by simultaneously using his right hand to apply a negative hand couple force in the opposite direction (away from the target) by maintaining a bent right wrist and thereby rigidly avoiding any active right wrist straightening action through impact. It is important to appreciate the fact that any negative hand couple phenomenon happening through impact is only a subsidiary phenomenon that can synergistically help a DHer to stabilise the club handle through impact, but it cannot be the primary clubshaft-stabilising mechanism because the wrist/hand muscles used to enact a negative hand couple force phenomenon are not strong enough to overcome any potential clubshaft-flipping forces (eg. left arm stalling and/or an over-active right arm/wrist straightening action) that may be present.
I would love to see a golf researcher test my hypothesis that pro golfers, who are DHers, may likely be using a negative hand couple force phenomenon through impact - and not a positive hand couple force phenomenon as suggested by Bertie Cordle - by placing pressure sensors at PP#1, PP#2, PP#3 and on the leading side of the club handle where it abuts against the left hypothenar eminence (heel pad). Then, as a result of this type of golf research study, we would likely gain a better understanding of the golf swing biomechanics used by pro golfers, who are DHers (like Cameron Champ). Jeff.
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Post by syllogist on Dec 20, 2019 6:46:05 GMT -5
Dr. Mann,
I agree that Bertie made some eyebrow-raising scientific assertions. I have viewed several of Richard Franklin's videos including his working with Chip Beck. A major problem with the advent of biomechanical analytics is that its data, if reasonably correct, can be and is misinterpreted.
With regard to the idea of a "couple" between the hands and whether one FORCES the left hand to extend or FORCES its continued travel so as to prevent the club from passing the hand, I think that, ideally and practically, neither situation exists in the case of the tour pro.
If memory serves, Champ's stock driver swing is a low fade with a low-lofted driver. I wouldn't hypothesize what he does or doesn't do with his hands from viewing a video clip or, for that matter, from a collection of digital data. I think that it is far more likely that he does absolutely nothing with his hands.
With regard to whether or not the club passes the hands at a given point in the swing, I'm not so sure that one can conclude anything useful or instructional from a two-dimensional, face-on view.
Maybe in the end, what we see is just a matter of the velocity of the release coupled with the momentum of the hands during the release.
S
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Post by imperfectgolfer on Dec 20, 2019 10:10:23 GMT -5
S,
You wrote-: "With regard to the idea of a "couple" between the hands and whether one FORCES the left hand to extend or FORCES its continued travel so as to prevent the club from passing the hand, I think that, ideally and practically, neither situation exists in the case of the tour pro."
I disagree with your assertion that pro golfers, who use a DH-hand release action like Cameron Champ, are not continuing to actively swing their left arm targetwards between impact and P7.4 in order to maintain an intact LAFW and to prevent the clubshaft from bypassing their left arm (from an angular rotational perspective). I don't believe that it simply happens by chance! Whether Cameron Champ is using a negative hand couple force phenomenon to help stabilise his clubshaft during the early followthrough is unknown, but I am simply arguing (on theoretical grounds) that if he uses a hand couple phenomenon then it would likely be a negative couple and not a positive couple, which will more likely promote a left wrist flipping phenomenon. When I perform, and teach, a DH-hand release action, I prefer to use the biomechanical elements that consitutute a negative hand couple force phenomenon - by deliberately i) ensuring that the left arm does not stall at impact, ii) by ensuring that the left wrist is either geometrically flat or bowed and iii) by ensuring that the right wrist is still significantly bent post-impact and that any push-pressure being exerted by the right hand is exerted above the coupling point (at PP#1) and not below the coupling point (at PP#3).
You also wrote-: "With regard to whether or not the club passes the hands at a given point in the swing, I'm not so sure that one can conclude anything useful or instructional from a two-dimensional, face-on view."
I disagree!
Jeff.
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