Bertie,
In this post I am going to analyse (in great detail) some of your opinions that you expressed in your vimeo-video. Although I agree with many of your opinions, I disagree with a number of your opinions and I will mainly focus this post on our points of disagreement.
At the start of your vimeo-video, you quote John Jacobs, who stated that the "
sole purpose of the golf swing is to create a correct impact". I disagree! I think that the primary purpose of the golf swing is to hit the ball far enough and also very accurately so that the ball can land very close to a golfer's intended target. I do agree that correct impact geometry is an important subsidiary goal that is needed to hit the golf ball accurately straight at one's intended target, but I would define good impact geometry (needed for a straight ball flight) somehwat differently to you. From my personal perspective, the correct impact conditions for a straight ball flight should primarily include a zeroed-out clubhead path and a zeroed-out clubface angle and a ball strike on the sweetspot of the clubface. I would take it one step further and state that although ball-clubface contact only lasts 4/1000th of a second, and where the clubhead travels about 0.75" (presuming a clubhead speed of 100mph) while the ball is still in contact with the clubface, that it is potentially very advantageous to keep the clubface stable through impact into the early followthrough, which means that the clubface should have a low ROC during that early followthrough time period. In your vimeo-video, you demonstrated a desirable clubhead path and clubface behavior through impact where the clubface remained square to the clubhead arc during the early followthrough. So, I surmise that we seemingly agree on this point. Also, like you, I believe that left wrist extension (left wrist flipping) through impact will cause the clubshaft to flip passed the lead arm, which means that the left wrist joint becomes the fulcrum of the clubshaft's motion. That will create a short lever scenario (rather than a long lever extending from the clubhead to the left shoulder socket), which will cause the clubface to rotate much more through impact to *P7.2 (which I arbitrarily define as the end of the immediate impact zone). That will create a high clubface ROC scenario through impact, which we both seemingly agree is very disadvantageous.
(* I presume that you are familiar with the P system of classifying body/arm/clubshaft positions - if not, you can refer to the following review paper at
perfectgolfswingreview.net/wrist.htm )
Both you and I seemingly agree that left wrist flipping through impact is disadvantageous and that it represents a significant swing fault that should be avoided, and we both seemingly agree that the golfer should attempt to establish maximum control of the clubface through impact so that the clubface can have a very low ROC through the immediate impact zone to P7.2+, but we seemingly have very different opinions on how best to achieve this goal.
You seemingly believe in two major principles when it comes to maximising clubface control at impact, and through impact. The first principle that you seemingly believe in is the principle that a golfer must sustain lag tension throughout the entire downswing. What is your definition of lag tension?
Here is a capture image from your vimeo-video where you define lag tension.
You define lag tension as existing when the clubshaft lags behind the lead arm. This capture image shows a golfer at the P5.5 position where lag tension is large, and you stated in your video that lag tension will decrease throughout the late downswing between P5.5 and impact as the club releases (representing the release of PA#2 in TGM terminology). However, you seemingly believe that a finite degree of lag tension will still exist at impact if the clubshaft has not quite caught up to the left arm. This "idea" of "sustaining lag" all the way into impact is a fundamental TGM principle that Homer Kelley referred to as the "secret of golf". Homer Kelley believed that a golfer should "sustain lag" all the way into impact, so that the line of compresion through the ball can be maximised. You seemingly endorse Homer Kelley's belief that a golfer should be applying a positive wrist torque during the late downswing and that lag tension must be sustained all the way into impact. I was previously a TGM literalist and I also previously believed that that most pro golfers were applying a positive wrist torque all the way into impact by using a TGM handle-dragging technique - whether they were using a driver or a wedge. I have recently changed my opinion on this issue and I now believe that a positive wrist torque (positive couple) scenario does not happen in the late downswing of the driver swings of most professional golfers.
Here is the "evidence" to support my revised opinion on this issue.
Consider two pro golfers - Rory McIlroy and Luke List - as representative examples of pro golfers.
Here are capture images from a swing video of Rory McIlroy's driver swing.
Image 1 is at P4, image 2 is at P5, image 3 is at P5.5, image 4 is at P6 and image 5 is at P6.4.
I have drawn a yellow line along his proximal clubshaft.
Note that his entire clubshaft forms a straight line with that yellow line at his P4 position, which means that no positive alpha torque is being exerted at this time point.
Note that his peripheral clubshaft is bent back a lot at P5 and to a lesser degree at P5.5, which means that he is applying a positive alpha torque during his early-mid downswing between P4 and P5.5.
However, note that his clubshaft is marginally bent forward at P6 and significantly bent forward at P6.4 (and it remains bent forward all the way to impact). This means that the change from having a positive alpha torque to having a negative alpha torque happens around P5.5 - P6 and one can reasonably conclude that Rory McIlroy is applying a positive alpha torque during the "swing power generation phase" of his downswing between P4 and P5.5 (as a result of his pivot-induced release of PA#4 that is combined with an active right arm adduction maneuver) and that his club then releases (due to the release of PA#2 phenomenon) at roughly the P5.5 time point of his downswing. During his later downswing, his clubhead is traveling faster than his hands as a result of the increased clubhead momentum gained from the release of PA#2 and he therefore cannot be applying any positive wrist torque (any positive couple) as he approaches impact.
Here are capture images from a swing video of Luke List's driver swing.
Image 1 is at P4, image 2 is at P5.2, image 3 is at P5.5, image 4 is at P6, image 5 is at P6.3 and image 6 is at P6.8.
I have drawn a yellow line along his proximal clubshaft.
Note that his entire clubshaft forms a straight line with that yellow line at his P4 position, which means that no positive alpha torque is being exerted at this time point.
Note that he must be applying a positive alpha torque at P5.3 and P5.5 because his peripheral clubshaft is bent back. However, note that he must be experiencing negative alpha torque (negative hand couple) in his later downswing between P6 and impact because his peripheral clubshaft is bent forward at all time points between P6 and impact.
Here is an image (created by David Tutelman) showing the correlation between the presence of positive/negative wrist torque and the direction of peripheral clubshaft bending.
Note that positive wrist torque ( = positive hand couple) only exists if the peripheral clubshaft is bent backwards and that scenario only exists in the early-mid downswing, and not the late downswing, of pro golfer's driver swings.
The "belief" that positive wrist torque cannot exist if the peripheral clubshaft is bent forward (which happens between P6 and impact in most pro golfers' driver swings) is not a "belief" that I originated. I secondarily derived that "belief" from David Tutleman, who described this issue in great detail in the following articles -
www.tutelman.com/golf/swing/nesbitKwon1.php and
www.tutelman.com/golf/swing/nesbitKwon2.php . If you read those articles, you will note that Sasho MacKenzie also agrees with David Tutelman that a positive wrist torque (positive hand couple) does not exist at impact. I cannot find any flaws in David Tutelman's reasoning. If you do not agree with David Tutleman's opinion, then I would like to see you produce a counterargument that demonstrates why you believe that his reasoning is flawed.
When David Tutelman first wrote about this topic he only used the term "positive wrist torque" and he never equated it with the term "positive hand couple". You seemingly believe that pro golfers are stabilising the clubface through impact by using a positive hand couple phenomenon.
Here is a capture image from your vimeo-video.
You have labelled that image "optimal handle position" and I presume that it reflects your "belief" that the clubshaft must be lagging relative to the lead arm (represented by the dotted red line) at impact and that you believe that this represents a desirable condition of lag tension, and you also seemingly believe that the two hands stabilise this lag tension scenario by acting as a positive hand couple about the coupling point (where the lead hand is applying lag pressure against the club handle at the level of the lead hand's hypothenar eminence in a direction that is away from the target and where the rear hand is applying a positive push-pressure against the aft side of the club handle below the coupling point in a direction that is towards the target). You seemingly believe that if the two hands are working in this coupled manner about the coupling point (which is the point on the club handle midway between the two hands) that it can stabilise the club handle through impact and allow the golfer to maintain a stable clubface that is square to the clubhead arc between impact and P7.2 (or even further into the early followthrough).
I can readily agree with you that this type of positive hand couple phenomenon can potentially be in play in punch shots, short iron shots and selective mid-iron shots (like Tiger Woods' stinger shot), where the golfer uses a handle-dragging technique that allows him to have a positive wrist torque phenomenon happening throughout the entire downswing and all the way into impact. I can also envisage that it is in play when a golfer uses a TGM hitting technique (which is based on the sequential release of PA#1 => manual release of PA#2/3). However, I cannot understand how it can be in play if the golfer comes into impact with the peripheral clubshaft bent forward - which is the scenario commonly seen in the driver swings of most pro golfers and long-drive competitors. According to David Tutelman, a negative wrist couple scenario must exist at impact under those conditions. Do you disagree with David Tutelman and do you believe that he is wrong? If your answer to my question is affirmative - then please explain why he is wrong.
I personally do not believe that most pro golfers use a positive hand couple phenomenon through impact when swinging a driver, and I believe that they use another golf swing technique to stabilise their clubface throughout the immediate impact zone between impact and P7.2+. I believe that many pro golfers primarily use the intact LAFW technique to stabilise their clubface during their driver-clubhead's travel through the immediate impact zone and I believe that it is the fundamental biomechanical basis for their drive-hold (DH) hand release action where their clubface remains constantly square to their clubhead arc, and I also believe that they do not use the principle of a positive hand couple phenomenon to maintain a clubface that is square to the clubhead arc during the clubhead's travel time through the immediate impact zone between P7 and P7.2+.
Consider Adam Scott's driver swing action through impact.
Image 1 is at impact (where his clubshaft is nearly straight-in-line with his left arm) and image 2 is at P7.2 (end of the immediate impact zone). Note that Adam Scott keeps his clubface very stable and square to the clubhead arc all the way between impact and P7.2. How does he achieve that goal? I believe that the correct answer is that he is using a DH-hand release action where he maintains an intact LAFW all the way between P7 and P7.2. How does he keep the clubshaft from bypassing his left arm between P7 and P7.2 considering the fact that the clubshaft has caught up to his left arm, which means that lag tension cannot be present between P7 and P7.2. I believe that the most important factor that makes this possible is that he does not stall his left arm at impact and that he simultaneously ensures that the targetwards momentum of his left arm is perfectly matched (from an angular velocity perspective) to the targetwards momentum of his clubshaft.
To make this point clearer, consider Kelli Oride's superb DH-hand release action in this swing video.
Here are capture images from the video.
Image 1 is the P4 position, image 2 is at the P5 position, image 4 is at the P6 position, image 4 is at the P6.5 position, image 5 is at the P7 position, and image 6 is at the P7.4 position.
Note that Kelli Oride continuously maintains an intact LFFW and *GFLW alignment throughout her entire downswing and early followthrough.
(* You mentioned in your post that Homer Kelley stated that it was imperative that a golfer has a FLW at impact, but what he failed to describe in his TGM book when he talked about the intact LAFW concept [which is a TGM concept] is that the left wrist must constantly be geometrically flat throughout the entire downswing and early followthrough [and not only at impact] if one uses the intact LAFW swing technique for a TGM swinging action)
Note that Kelli Oride is using a DH-hand release action where she keeps the clubface square to her clubhead path between impact (image 5) and P7.4 (image 6) and she does not allow the clubshaft to bypass her left arm from an angular rotational perspective. How does she achieve that desirable goal of maintaining a stable clubface all the way between P7 and P7.4? It cannot be due to the presence of lag tension because the clubshaft is straight-in-line with her left arm during that early followthrough time period.
I think that the following capture images helps to explain how Kelli Oride maintains an intact LAFW all the way between P7 (impact) and P7.4 and how she avoids left wrist flipping.
Image 1 is at impact where she has a minimal amount of forward shaft lean present, which means that any lag tension must be negligible. Image 2 is at P7.2 and image 3 is at P7.4. Note that her clubface is very stable and square to the clubhead arc all the way between impact and P7.4.
Image 4 is a composite image showing the degree of targetwards momentum/travel of her clubshaft between impact and P7.4 and the next accompanying diagram shows that the targetwards angular velocity of her left hand (blue dot) is perfectly matched to the targetwards momentum of her clubhead (orange dot) from an angular velocity perspective so that her clubshaft remains constantly straight-in-line with her clubshaft (representing an intact LAFW scenario) all the way between impact and P7.4. In other words, I believe that the most important biomechanical factor that allows a golfer to maintain an intact LAFW during the early followthrough between P7 and P7.2 (or even further to P7.4) is the biomechanical ability to avoid left arm stalling and the biomechanical ability to simultaneously ensure that the angular velocity of the left arm is perfectly matched relative to the angular velocity of the clubshaft during that early followthrough time period.
To better understand this point, let's consider Sasho MacKenzie's lead arm only golf swing action.
Here are capture images of his followthrough action.
Image 1 is at P7.4, image 2 is at P7.8 and image 3 is at P8.3.
Note that Sasho is maintaining an intact LeadAFW (where the clubshaft is straight-line-aligned with his lead arm from an angular rotational perspective) to well beyond the P7.4 followthrough position and he avoids any lead wrist flipping phenomenon. How is this possible? It cannot be due to the presence of lag tension or due to a positive hand couple phenomenon (which requires the presence of a trailing hand) and it must surely be due to the fact that he is perfectly matching the targetwards angular momentum of his lead arm to the targetwards angular momentum of his clubshaft.
Consider this capture image from your vimeo-video.
In this image the clubshaft has caught up to the golfer's left forearm (representing a scenario which you call "full extension"). Note that you then stated that after full extension, the lead hand, arm and shoulder lose control of the club. I totally disagree with your assertion! I believe that a golfer will only lose control of his club (and therefore automatically lose control of his clubface) if he stalls his left arm and allows the left wrist to flip-bend (extend) after that time point of "full extension". By contrast, if a golfer maintains the forward momentum of his lead arm so that it perfectly matches the forward momentum of his clubshaft (from an angular rotational perspective), then there is no reason why he cannot avoid left wrist breakdown and left wrist flipping and thereby constantly maintain an intact LAFW during his early followthrough time period to P7.4 (or even beyond P7.4 as seen in Sasho's lead arm-only followthrough action).
What potentially useful role can the trailing arm/hand play in a DH-hand release action (where the golfer, who is using a TGM swinging technique, maintains an intact LAFW throughout the early followthrough time period)?
To answer that question, let's consider Tommy Fleetwood's DH-hand release action.
Here are capture images from a Tommy Fleetwood driver swing video.
Image 1 is at impact, image 2 is P7.4, image 3 is at P7.6, and image 4 is at P8.
Note that Tommy Fleetwood is such an efficient DHer that he can keep his clubface square to his clubhead arc all the way to P7.4 (image 2), and that he does not allow his clubshaft to bypass his left arm (from an angular rotational perspective) during that P7 => P7.4 time period.
How does Tommy Fleetwood keep his clubface square to his clubhead arc between P7 and P7.4 from a biomechanical perspective?
Consider these close-up views of Tommy Fleetwood's early followthrough action.
Note that I have placed a green dot in the center of his left antecubital fossa and three red dots in a straight line over the most peripheral 3" of his left lower radial bone. That allows one to see if his left forearm is relatively neutral with respect to his left humerus. Also, if the red dots move significantly more counterclockwise than the green dot during his followthrough time period, that would indicate the presence of a significant amount of left forearm supination.
At impact (image 1) one cannot see Tommy Fleetwood's left antecubital fossa because his left humerus is internally rotated at impact. Note that he has a strong left hand grip, which explains why the red dots are aligned more clockwise relative to the ball-target line and why the back of his left hand faces the ball-target line at impact.
Note how much the back of his left hand rotates counterclockwise between impact (image 1) and P7.4 (image 2). What is causing that counterclockwise rotation of his left hand from a biomechanical perspective? The correct answer is that it is mainly due to external rotation of the left humerus, which causes the left antecubital fossa to rotate counterclockwise (as clearly seen in those capture images) - while there is very little left forearm supination happening during that P7 => P7.4 time period (as evidenced by the fact that the red dots are not rotating more counterclockwise than the green dot during that same time period).
So, to become a superb DHer, who maintains an intact LAFW/GFLW alignment between P7 and P7.4, Tommy Fleetwood needs to controllably rotate his entire LAFW (left arm + clubshaft) as a single unitary structure at a particular rate of counterclockwise rotation that will keep his clubface continuously square to the clubhead arc between P7 and P7.4 - while simultaneously avoiding any significant left wrist extension (which will disrupt his intact LAFW alignment) or any excessive amount of left forearm supination.
To keep his clubshaft from bypassing his left arm between P7 and P7.4, Tommy Fleetwood has to carefully match the targetward angular velocity of his left arm so that it perfectly matches the targetward angular velocity of his clubshaft (which has acquired a tremendous amount of foward momentum in a targetwards direction by impact secondary to the sequential release of PA#4 => PA#2). Note how Tommy Fleetwood's left hand continuously moves targetwards between image 1 and image 3 and there is no stalling of the forward momentum of his left arm. If his left arm slowed down too much during that P7 => P7.4 time period, then his left wrist could breakdown (extend) and the clubshaft would bypass his left arm. So, the first biomechanical requirement for a DHer through impact is to maintain the forward (targetwards) momentum of the left arm, and avoid any stalling of the forward momentum of the left arm, during the early followthrough time period. The second biomechanical requirement is that a DHer needs to controllably rotate the left humerus (and therefore the entire LAFW) at a particular counterclockwise rotational speed that will allow him to keep his clubface continuously square to his clubhead path during that early followthrough time period. How is this biomechanical skill acquired? I believe that it is mainly based on an "acquired feel" that is rhythm-dependent. In other words, a golfer, who wants to become a superb DHer like Tommy Fleetwood, needs to practice this rhythm-based biomechanical left arm rotational motion so that he can ingrain it into his golf swing DNA!
An important secondary question then becomes - how can using the right arm (trailing arm) potentially assist a DHer in perfecting the execution of his DH-hand release action?
If you look at Tommy Fleetwood's right arm/hand biomechanics between P7 and P7.4, you will note that he maintains a slightly bent right arm and significantly bent right wrist all the way between impact and P7.4 and he does not "run-out-of-right arm" (where the right elbow and right wrist fully straighten between impact and P7.4). To achieve that very desirable goal, a golfer needs to open up his body and drive his right shoulder under his chin in a targetwards direction between P7 and P7.4 - just look at how much Tommy Fleetwood's right shoulder is moving downplane in a targetwards direction during his entire followthrough time period. That "fact" allows his right hand to more easily keep up with the left hand during the entire P7 => P7.4 time period, and it allows the base of his right palm to potentially be applying a finite amount of push-pressure against PP#1 (which is located over the base of the left thumb) in a continuous manner throughout Tommy Fleetwood's entire P7 => P7.4 time period. If Tommy Fleetwood's right palm is actually applying a finite amount of push-pressure against PP#1 in a continuous manner between P7 and P7.4, then one can easily imagine that it can potentially help him to "stabilise" his left wrist (from a mechanical perspective) while synergistically helping the left arm/hand to more exactingly control its rate of counterclockwise rotation between P7 and P7.4.
It is very important to understand that a DHer who uses the right hand to mechanically stabilise the left hand through impact must only apply push-pressure against PP#1 (which is above the coupling point) and it is critical that he must not apply push-pressure against the aft side of the club handle below the coupling point at, or near, PP#3.
Consider this image showing the pressure points.
If a golfer wants to use push-pressure exerted by the right hand to help stabilise his left hand's DH-hand release action through impact in order to help maintain an intact LAFW and avoid left wrist flipping, then that push-pressure must only be applied at PP#1 (which is located over the base of the left thumb) and it must not be applied against the aft side of the club below the coupling point (green and blue areas in that image) because that may unintentionally promote left wrist flipping if the right wrist straightens too actively through impact. Consider an example of that undesirable type of "right wrist straightening" scenario by noting how Jordan Spieth flips post-impact.
First of all, let's consider Jordan Spieth's usually superb DH-hand release action by looking at the following capture images from a swing video of his driver swing action.
Image 1 is at impact where the clubshaft is nearly straight-in-line with his left forearm, which means that a negligible amount of lag tension is present.
Image 2 is at P7.3 and image 3 is at P7.5. Note that Jordan Spieth is normally such a superb DHer that he can maintain an intact LAFW (where the clubshaft does not bypass his left arm from an angular rotational perspective), and thereby also maintain a stable clubface that is square to his clubhead arc, all the way between impact and P7.5!
However, even a superb pro golfer like Jordan Spieth (who is normally a superb DHer) can occasionally flip through impact.
Here are capture images from a driver swing video where Jordan Spieth flips through impact.
Image 1 is at impact, image 2 is at P7.2 and image 3 is at ~P7.5. Note how the clubshaft is bypassing his left arm during his early followthrough due to a left wrist flipping phenomenon. What is causing that undesirable flipping subtype of non-DH-hand release action? I can think of two potential biomechanical causes - i) stalling of the forwards momentum of his left arm (as evidenced by the exaggerated degree of chicken-winging seen post-impact) and ii) an over-active right wrist straightening action that produces too much push-pressure against the aft side his club handle below the coupling point - although I cannot really know which of those two potential biomechanical causes is the major factor causing left wrist flipping through impact. What I am definitely sure of is the "fact" that his left wrist flipping action is not due to excessive muscular contraction of his left wrist extensor muscles. I personally don't believe that pro golfers activate their left wrist extensor muscles during their late downswing action when they inadvertently (unintentionally) flip their left wrist through impact and I believe that it is most likely due to a left arm stalling phenomenon and/or an unintentionally over-active right wrist straightening action. Why is this distinction very important?
You commisioned Sasho MacKenzie to create a forwards dynamics model comparing a flipping hand release action action to a non-flipping, lag style type of hand release action through impact. How did Sasho program his computer-generated forward dynamics model to produce to produce a repeatable flipping action through impact? I presume that he did it by activating the model's degree of left wrist extensor muscular activity in the late downswing and that he did not produce left wrist flipping by stalling the left arm by a well-defined, and repeatable, amount? Am I correct, or incorrect? He certainly could not have reproduced (simulated) the "real life" scenario of an over-active right wrist straighening action because his forward dynamics model does not include a trailing arm factor. I think that it is very important for Sasho to clearly describe how his computer-generated model produced a flipping action through impact so that we can better understand whether it has any scientically-valid applicability to a "real life" pro golfer's flipping action through impact (which I believe is an unintentional swing fault most likely due to left arm stalling and/or an over-active right wrist straightening action).
I have another question about your positive hand couple image (seen below).
Note that you have positioned the two hands opposite each so that the two palms are parallel to each other. Under those hand positional conditions, I can understand how the positive hand couple phenomenon can potentially work in a golf swing action (even if I do not personally agree that is regularly happening in the "real life" driver swing actions of pro golfers).
However, I cannot really understand how the positive hand couple phenomenon can work efficiently if the two palms are not parallel to each other, but perpendicular to each other.
Here are capture images of Jamie Sadlowski's late downswing driver swing action.
Image 1 is at P5.5, image 2 is at P6, image 3 is at P6.5 and image 4 is near impact.
Note that his left palm is on top of the club handle, and that his left palm is roughly at right angles to his right palm, all the way between P6 and impact. You have stated that all skilled pro golfers are using a positive hand couple phenomenon in the late downswing and through impact. How is this positive hand couple efficiently possible if the two palms are at right angles relative to each other during the late downswing and at impact?
Let's again consider Tommy Fleetwood's followthrough capture images.
You believe that he is using a positive hand couple technique through impact, while I believe that he is using aTGM swinging action combined with a DH-hand release action. Who is correct? I suspect that neither you, or I, can provide scientific evidence to prove our personal opinions. How can we scientifically resolve this issue? I think that the best approach would be to design a golf research study where pressure sensors are placed on PP#1 (located at the base of the lead thumb), on the aft side of the clubshaft at/near PP#3, and on the lead palm's hypothenar eminence area and on the ventral aspect of the lead hand's distal finger tips (representing PP#2). If a pro golfer is tested, and he is using a TGM swinging action combined with a right hand-assisted DH-hand release action, then I would expect to see positive readings at PP#1 and PP#2, but not at PP#3 or on the lead hand's hypothenar area. If a pro golfer is using a TGM handle-dragging technique (lag tension swing with a positive lead wrist torque into impact using a positive hand couple technique through impact)then I would expect to see positive readings at PP#1 and at PP#3 and at the lead hand's hypothenar area, but not at PP#2. This type of research study could possibly distinguish whether a pro golfer is using a TGM swinging technique combined with a right hand-assisted DH-hand release action or whether he is using a TGM handle-dragging technique. What do you think of the potential utility of my proposed golf research study?
I would particularly like to see this type of study performed on Cameron Champ.
Here are capture images of Cameron Champ's driver swing's followthrough.
Cameron Champ has a lot of forward shaft lean at impact with his hands well forward at impact and with clearly discernible lag tension characteristics (clubshaft angled back relative to the lead arm). Although I personally suspect that Cameron Champ is using a TGM swinging action combined with a right hand-assisted DH-hand release action, I could be proven wrong if the golf research study shows that he is more likely using a TGM handle dragging technique and a positive hand couple phenomenon through impact.
This type of research study may also identify pro golfers who could be using a TGM hitting technique for their driver swing action. I have never been able to identify a TGM hitter among the large group of PGA tour professional golfers, and I have wondered whether any exist. This type of study may help us identify a pro golfer who is surprisingly using a TGM hitting action for his driver swing action.
I will now move on to discuss other issues where I disagree with some of the statements that you made in your vimeo-video.
Consider these two capture images from your vimeo-video.
First image
Second image
In the first image, you state that a reverse torque phenomenon develops at the level of the hands when a golfer has a left wrist flipping phenomenon happening through impact and you then claim that the reverse torque phenomenon causes stalling of left hand speed and stalling of the body rotation through impact. In the second image, you state that the reverse torque effect will also cause the left shoulder to not rotate as much up-and-away. I agree that a reverse torque phenomenon must exist at the level of the left wrist during a left wrist flipping action, but I cannot understand how it can produce body rotational stalling and a decreased elevation of the left shoulder socket's up-and-away motion from a "cause-and-effect" perspective. I believe that left arm stalling at impact, body rotational stalling at impact and a poor quality left shoulder up-and-away motion may occur in golfers who do not use a TGM swinging action, but who use an amateurish "hit at the ball" or an amateurish "try to scoop the ball up" swing technique, and those deleterious body/arm motions represent associated swing faults. However, I believe that those associated swing faults cannot be directly caused by the reverse torque phenomenon that is happening locally at the level of the left wrist.
Now, I would like to discuss the issue of how best to maintain maximum clubhead lag during the early-mid downswing so that a golfer can maintain his maximum degree of lag until he reaches the P5.5 position. Both you and I agree that casting is a major swing fault and we both agree that a golfer should optimally maintain his maximum degree of clubhead lag to at least the P5.5 position. In your vimeo-video, you stated that this can be achieved by the combination of a good quality "weight shift, pelvic and upper torso rotation" between P4 and P5.5. I disagree! I believe that the best biomechanical method to maintain the maximum degree of clubhead lag to P5.5 is to appropriately shape the hand arc path.
Here is an example of an appropriate hand arc path that can be used to optimise the maximum degree of clubhead lag at P5.5 - featuring Dustin Johnson.
Image 1 is at P4, image 2 is at P5 and image 3 is at P5.5.
Note that his hands are not closer to the target at P5.5 than they were at P4, and that his hands are below waist level at P5.5 and about 12" outside his right thigh. To get to that very desirable hand position at P5.5, he needs to move his hands mainly downwards, and not targetwards, between P4 and P5.5 - as demonstrated by the long "straightish" section of his hand arc path between P4 and P5.5. How is this long "straightish" hand arc path achieved (facilitated) biomechanically? I believe that it is best facilitated by an active right arm adduction motion between P4 and P5.5 that is combined with external rotation of the right humerus + a pitch elbow motion of the right elbow where the right elbow is closer to the target at P5.5 than the hands. Note how DJ's right forearm is angled away from the target at P5.5 due to the pitch elbow motion of his right elbow.
Compare the Dustin Johnson image at P5.5 to your GEARS-image of a golfer at the P5.5 position.
Note that the golfer's hands are closer to his right thigh (compared to Dustin Johnson's hands) and that his hands are also closer to the target than his right elbow due to his use of a punch elbow motion (rather than a pitch elbow motion). Note how the right forearm is angled towards the target (and not away from the target) due to his use of a punch elbow motion. I think that a punch elbow motion is not conducive to a "maximum clubhead lag" type of golf swing action.
Now, let's compare Dustin Johnson's hand arc path in his driver swing and his wedge swing.
Note the marked difference in the shape of his hand arc path in his wedge swing where it is directed diagonally towards the ball between P4 and P5.5. I believe that this type of diagonally-directed hand path is not conducive to maintaining the maximum degree of lag until at least P5.5, but I believe that it is very conducive to a TGM handle-dragging technique where one can most efficiently control the clubhead attack angle.
Here are capture images of Jordan Spieth hitting a short iron shot.
I strongly suspect that Jordan Spieth is using a TGM handle dragging technique (positive wrist torque technique during the later downswing combined with a positive hand couple technique through impact) for this short iron shot. I suspect that he is manually inducing the release of PA#2 and that he is not using the double pendulum type of PA#2 release technique (based on the D'Alembert principle's PA#2 release mechanism) that he likely uses for his driver swing action.
Finally, I would like to discuss the topic of whether body rotation can square the clubface by impact. At the 31:29 minute time point of your vimeo-video you start to discuss the problem of a clubhead path that can be too much inside-out and that can lead to shanks. You correctly state that this problem can occur if a golfer tries to get the hands ahead of the body at impact to ensure an optimal hand positional alignment at impact where lag tension is still present (clubshaft lagging behind the lead arm). To prevent that problem you correctly state that a golfer can use more body rotation to ensure that the clubhead path is not too much in-to-out, but you actually used the term "clubface-squaring" in your verbal description at the 32:57 minute of your vimeo-video. I believe that the issue of clubface-squaring is a differrent/separate issue that is best used with respect to biomechanical actions needed to square the clubface relative to the clubhead arc (and not relative to the ball-target line) and I believe that body rotation cannot be used to square the clubface relative to the clubhead arc, although it can obviously be used to square the clubface relative to the ball-target line as a secondary end-result of changing the clubhead path.
One final comment. You stated in your post-" "Importantly, I haven’t relied only on the study from Dr. MacKenzie, I thought it important that another study was undertaken independently using live golfers, this was performed by Blake Isakson at Boccierri Golf’s R&D facility. Please feel free to review the results on our website." I cannot locate that study on your website. Could you please post a link to that study's paper in your reply?
Jeff.