In this post, I am going to analyse in great depth some of the opinions expressed by Terry Rowles (TR) in the following video.
If you follow that link, you will find a 2:29 minute Terry Rowles video, where he talks about the golf swing biomechanics that must happen as a result of adopting an on-top (weak) trail hand grip. I mainly disagree with 3 claims made by TR in that video and his 1st claim happens at the 0.26 - 0.32 minute time point of the video when TR states "that the trail hand grip has the biggest effect on what the clubface does during the golf swing". The 2nd claim that TR makes happens between the 1:32 - 1:50 minute time point of the video when TR claims that an on-top trail hand grip is a face-opener grip and that means that the golfer will have to perform a clubface-closing mechanism during the downswing to counter that clubface-opening effect that is due to adopting an on-top trail hand grip. The 3rd claim that TR makes happens between the 1:50 - 2:00 minute time point of the video when TR describes the clubface-closing phenomenon that he believes is needed to provide the clubface-closing mechanism - when he states that when the trail arm extends (= straightens at the elbow joint) during the later downswing ( = roughly between P5.5 => P7) that it will cause the trail forearm to pronate, and that when the trail forearm is pronating during the later downswing that the counterclockwise rotating trail forearm will cause the clubshaft to rotate counterclockwise about its longitudinal axis and that will cause the clubface to close more relative to the clubhead path so that the clubface can become square relative to the clubhead path by impact.
It is very important to note that when I talk about the topic of "clubface control" I am mainly talking about how the clubface must close during the later downswing (between ~P5.5 => P7) relative to the clubhead path so that the clubface can become square relative to the clubhead path by impact and I am not talking about "clubshaft/clubhead control" which mainly affects the clubhead path and swing direction. It also important to understand that in this post I am only talking about the golf swing action performed by pro golfers (eg. PGA tour golfers) and not the golf swing action performed by amateur hackers.
I strongly disagree with TR's assertion that the trail hand grip strength has the biggest effect on the clubface-closing phenomenon routinely seen in the later downswing of pro golfers and I believe that it is the lead hand grip strength that is the main factor that affects the "amount of clubface closing relative to the clubhead path" phenomenon that always happens during the later downswing after ~P5.5.
I will first analyse those 3 claims made by TR before I start to explain why I believe that it is the lead hand grip strength that is the biggest determining factor involved in the amount of clubface-closing that happens in the later downswing in all pro golfers.
I will start off this analysis by analysing what TR seemingly means when he talks about an on-top trail hand grip being a face-opener grip.
Here are capture images from the TR video.
Image 1 shows TR holding a golf club handle using an on-top (weak trail hand grip) where the clubface is facing the target, which means that it is neither open-or-closed.
Image 2 shows what happens when TR rotates his trail hand clockwise (when viewed from his perspective) so that the back of his trail hand becomes more vertical and that causes the clubface to open.
What does this mean to you?
What it means to me that if a golfer adopts an on-top (weak) trail hand grip - as seen in image 1 where the clubface is neutral (square) to the clubhead path (presuming that the clubhead path is directed towards the target) - that if the golfer swings his trail arm towards the target (as seen in the P6 => P7 time period of a pro golfer's swing) that the clubface will remain square to the clubhead path if the grip does not rotate clockwise (as seen in image 2 where it is rotating clockwise to an open clubface alignment) or rotate counterclockwise (where it will rotate to a closed clubface alignment).
That phenomenon of the clubface remaining square (neutral to the clubhead path) is what happens in the grip verification test performed by Mike Adams (MA).
In this grip verification test video, Mike Adams explains how you know that you have "dialed-in" the correct trail hand grip strength. Note that he starts with a strong trail hand grip and he then swings the club from waist-high-to-waist-high using only his trail arm. He states that if you "feel" the clubface closing during the clubshaft's travel passage from waist high-to-waist high, then the trail hand grip strength is too strong. He then suggests that you weaken the trail hand grip until the clubshaft remains quietly stable with no tendency to roll closed during the trail arm-only swinging action. MA seems to be suggesting that if the clubface does not roll when using an on-top trail hand grip that the trail hand grip is correct (= stable) for that particular golfer. That claim suggests to me that MA believes that if there is no tendency for the clubface to roll either open-or-closed during that the grip verification test when using an on-top trail hand grip, then that means that the on-top trail hand grip allows the clubshaft to swing across the front of the body without being subjected to any face-opening force or face-closing force.
However, TR seems to be implying that there is naturally a "face-opening force" in play during the late downswing if a golfer adopts an on-top trail hand grip that mandatorily requires a corrective clubface-closing phenomenon to be actuated to counter that "face-opening effect". I have no idea what's the nature/cause of that "clubface-opening force" that TR must have in mind if he believes that an on-top trail hand golfer must mandatorily provide a clubface-closing force to counter any tendency of the clubface to be too open during the P6 => P7 time period.
Seeing that I have no clear idea why TR believes that a corrective clubface-closing force is needed if a golfer adopts an on-top trail hand grip, I will move onto the next topic by discussing what I perceive TR is claiming regarding the biomechanical mechanism of performing that corrective clubface-closing action.
TR uses the analogy of a straightening trail arm when performing a boxing punch action to help explain the rationale for his proposed clubface-closing mechanism.
Here are capture images of his boxing punch demonstration.
In image 1, note that TR has flexed his right elbow while holding his closed fist in a vertical alignment where his finger knuckles are vertically aligned.
In image 2, he fully straightens/extends his right arm and you can see that his fist rotates ~90 degrees counterclockwise (as viewed from his viewing perspective). What explains why his fist rotates counterclockwise? TR seemingly suggests that it is a natural/automatic biomechanical phenomenon that is due to a passive pronatory motion of his right forearm.
When I perform his test maneuver, I find that I can easily straighten my right arm fully without any tendency of my fist to rotate if I keep my right humerus vertically aligned alongside the right side of my torso with the right humerus in a neutral rotary position. However, if you look at image 2, note that his trail upper arm is slightly abducted away from the side of his torso. When I mimic that abducted right upper arm alignment, then I also note that my fist will automatically rotate counterclockwise by ~90 degrees during my right arm straightening action. What I perceive is happening biomechanically is that the right humerus starts to rotate internally during the arm straightening action and that secondarily causes the right forearm to pronate as the right arm straightening action proceeds further.
That forearm pronatory motion is what theoretically happens in a punch elbow motion of the trail elbow during the later downswing - according to TR's reasoning. Homer Kelley in his "The Golfing Machine" book described a pitch elbow motion of the trail arm during the P4 => P6 time period and also a punch elbow motion, but he never defined the difference clearly. I also have never heard TR clearly define the difference between a pitch elbow motion versus a punch elbow motion between P4 => P6 other than to infer that the trail elbow leads the trail hand all the way down to P6 without the trail hand bypassing the trail elbow when performing a pitch elbow motion, while in a punch elbow motion he infers that the trail humerus will start to internally rotate when the trail arm straightens and that it will cause the trail hand to bypass the trail elbow before P6. It is my experience that pro golfers only start their trail arm straightening action between P5.2 - P5.5 and never in the early downswing and that it mainly happens to a greater degree after P5.5 - P6. Then, I perceive that TR seemingly believes that when the trail arm continues to straighten much more between P6 => P7 while the trail humerus continues to internally rotate, that it will induce the trail forearm to passively pronate during the later phase of the trail arm straightening action, which mainly happens between P6.5 => P7. If the trail forerarm pronates, it will obviously produce a clubface-closing phenomenon that TR believes is mandatorily required if a pro golfer adopts an on-top/weak trail hand grip (face-opener grip). By contrast, TR seemingly believes that if a pro golfer adopts an under/strong trail hand grip (face-closer grip) that he must definitely avoid performing a punch elbow motion and that he must mandatorily use a pitch elbow motion of the trail arm.
Consider this image of Rory McIlroy and Dustin Johnson that TR featured in one of his Ultimate Golf Lesson webinar videos.
Rory McIlroy is on the left side. Note that his trail elbow is positioned in a rear linkage position above-and-behind his trail hip joint area at P6 and TR states that he is using a punch elbow motion because his trail hand is closer to the target than his trail elbow and that his trail humerus is internally rotated. Then note how Rory is straightening his trail arm between P6 => P7 while manifesting an internally rotated trail humerus. According to TR's reasoning that earlier trail arm straightening action using a punch elbow motion will cause the trail forearm to passively pronate in the later downswing, which TR asserts is a mandatory requirement because Rory uses a face-opener trail hand grip that TR believes necessitates a clubface-closing phenomenon that will be provided by the trail forearm's pronatory motion.
Dustin Johnson is on the right side. Note that his trail elbow is in a pitch location above-and-forward of his trail hip joint area at P6 and that he is using a pitch elbow motion because his trail elbow is closer to the target than his trail hand. That results in a later trail arm straightening action and it also helps to avoid a clubface-closing phenomenon due to trail forearm pronation that Dustin must avoid because he uses an under/strong (face-closing) trail hand grip.
TR's reasoning seems to be logical if one follows the sequential path of his line of reasoning, and it therefore seems reasonable to infer that if a golfer adopts an on-top trail hand grip (face-opener grip) that he must use a punch elbow motion of his trail arm earlier that will secondarily result in a passive trail forearm pronatory motion between ~P6.5 => P7, which will consequently provide the clubface-closing phenomenon that TR believes is a mandatory requirement if one wants to square the clubface relative to the clubhead path by impact using the trail arm/forearm's clubface-closing action.
There is one major problem with TR's theory about how the trail arm's punch elbow motion, that is naturally/automatically combined with a later passive trail forearm pronatory motion, is causally responsible for the clubface-closing phenomenon (relative to the clubhead path) that routinely happens during the P6.5 => P7 time period in all pro golfers - and that is the indisputable fact that the trail forearm does not normally pronate between P6.5 => P7 in any pro golfer irrespective of whether they use a weak-or-strong trail hand grip.
I am now going to present substantial evidence that shows that
there is no significant counterclockwise rotation of the trail forearm during the P6 => P7 time period in pro golfers who use an on-top trail hand grip.
I will start off by examining Rory McIlroy's later downswing action.
Here is a link to a Rory McIlroy driver golf swing video -
www.youtube.com/watch?v=MiPq0zmI_BoCapture image of Rory McIlroy at his P6 position
Note that his trail elbow is located in a rear linkage position and that his trail hand is marginally closer to the target than his trail elbow, which indicates that he is performing a punch elbow motion.
I have drawn a red line down the middle of his trail arm's antecubital fossa and a blue line over his lower radial bone in his lower trail forearm. Note that the blue line is rotated clockwise relative to the red line, which means that his trail forearm is supinated at his P6 position. How can the back of Rory's trail hand be facing the ground at P6 if his trail forearm is markedly supinated? I think that it is only the thenar eminence area of his trail palm that is actually facing groundwards because his thumb metacarpal is held in closer opposition to his trail palm by ~45+ degrees. If you look at his true trail palm area (= palm area just proximal to the base of his 3rd - 5th fingers) it is facing partly skywards and partly facing the aft side of the club handle.
Capture image of Rory McIlroy at his P6.5 position
Note that the blue line seems to possibly be rotated minimally more clockwise relative to the red line, which suggests that Rory's trail forearm is rotating in a clockwise (more supinatory direction) and not in a pronatory direction (counterclockwise direction).
Capture image of Rory McIlroy at impact.
Note that the back of his lead hand has rotated counterclockwise to a small degree between P6.5 => P7 secondary to a lead forearm supinatory motion. The amount of lead forearm supination required to square his clubface relative to his clubhead arc between P6.5 => P7 is very small because Rory McIlroy uses a moderately strong lead hand grip.
Note that Rory's trail forearm is still supinated at impact, and there is no evidence that he is pronating his trail forearm during his late downswing between P6.5 => P7. There has been a small amount of counterclockwise rotation of his trail forearm in a pronatory direction, but the amount is very small. Note that Rory still has an incompletely straightened trail arm and a significantly bent trail wrist at impact. In fact, if Rory released his trail arm "early and hard" using TR's recommended punch elbow motion that action could potentially produce an excessive amount of trail arm extension and secondary trail forearm pronation between P6 => P7, which would likely close his clubface too much. I think that Rory cannot afford to close his clubface too much between P6 => P7 because he uses a moderately strong lead hand grip, and I believe that he must reach impact with the back of his lead hand exactly angled as seen in this capture image if he wants to have a square clubface at impact.
Now, let's consider the late downswing action of another on-top pro golfer - Patrick Reed
Capture image of Patrick Reed's late downswing action.
Image 1 is at P6, image 2 is at P6.5, image 3 is at impact and image 4 is at P7.2.
Note that I have drawn a blue line down the middle of his trail antecubital fossa and a red line over his trail lower forearm's radial bone.
Note that PR's trail elbow is located in a rear linkage position at P6 (image 1). Note that the red line is rotated clockwise relative to the blue line, which means that his trail forearm is significantly supinated. Note that the back of his lead wrist is facing towards the ball-target line. How can the back of PR's trail hand be facing the ground at P6 if his trail forearm is significantly supinated? I think that it is only the thenar eminence area of his trail palm that is actually facing groundwards because his thumb metacarpal is held in closer opposition to his trail palm by ~45+ degrees. If you look at his true trail palm area (= palm area just proximal to the base of his 2nd - 5th fingers) it is facing partly skywards and partly facing the aft side of the club handle.
At P6.5 (image 2) his trail forearm is still supinated and there has been no counterclockwise rotation of his trail forearm in a pronatory direction. Note that the back of lead hand is still facing towards the ball-target line to a large degree. Note that his clubface is still open relative to his clubhead path and he still has to perform a clubface-closing phenomenon to square the clubface relative to his clubhead path.
At impact (image 3), his trail forearm is still supinated and the degree of counterclockwise rotation of his trail forearm happening between P6.5 => P7 in a pronatory direction is very small and not enough to explain the degree of clubface-closing that is actually happening during that late downswing time period - look at how much the back of his lead hand is rotating counterclockwise between P6.5 => P7. Note that he still has a significantly bent trail arm and his trail wrist is still extended.
Image 4 is at P7.2. Note that his trail arm is now fully straightening and that his trail forearm is now pronating (as recommended by TR) , but it happens post-impact so the pronatatory motion of his trail forearm cannot explain how he performed a clubface-closing phenomenon pre-impact.
Now, let's consider the late downswing action of another on-top pro golfer - Matthew Fitpatrick
Capture images of Matthew Fitzpatrick's late downswing action.
I have drawn a blue line down the middle of his trail antecubital fossa and a red line over his trail lower forearm's radial bone.
Image 1 is at the P6 position - note that the red line is rotated clockwise relative to the blue line, which means that his trail forearm is supinated at his P6 position. How can the back of Matthew's trail hand be facing the ground at P6 if his trail forearm is significantly supinated? I think that it is only the thenar eminence area of his trail palm that is actually facing groundwards because his thumb metacarpal is held in closer opposition to his trail palm by ~45+ degrees. If you look at his true trail palm area (= palm area just proximal to the base of his 3rd - 5th fingers) it is facing partly skywards and partly facing the aft side of the club handle.
Image 2 is at the P6.5 position - note that his trail forearm is still supinated to roughly the same degree and note that there has been no counterclockwise rotation of his trail forearm in a pronatory direction between P6 => P6.5.
Image 3 is at his impact position. Note that his trail forearm is now minimally less supinated and closer to being neutral so there has been a small amount of counterclockwise rotation of his trail forearm happening in a pronatory direction between P6.5 => P7. However, the amount is very small, which is a good thing because MF uses an ultra-strong lead hand grip and he cannot afford to have too much lead forearm supination happening between P6.5 => P7, which would cause his clubface to close too much by impact. Note that the back of MF's lead hand is facing the ball-target line at impact and it is only the ulnar border of his lead hand that faces the target at impact and that same alignment would need to happen even if he used a side-on (neutral) or under (face-closer) trail hand grip.
I have presented the golf swing actions of 3 pro golfers who use an on-top (face-opener) trail hand grip and none of them have any frank pronation happening during their P6.5 => P7 time period as suggested by TR. I can imagine that I could be accused of confirmation bias by selecting only 3 examples that do not show the requisite evidence that there is a large amount of counterclockwise trail forearm rotation happening between P6 => P7 in on-top pro golfers - so let's look at a larger sample of pro golfers.
Here is a capture image of Jon Sinclair's graphs of >100 pro golfers' trail forearm supination/pronation rotary motion pattern - captured using the TPI/AMM 3-D system used by Phil Cheetham.
Supination is above the horizontal zero line, and pronation is below that line. It is hard to read the positions on that graph where "top" is the P4 position, "AP" is the P5 position, "MD" is the P6 position and impact is the P7 position. The vertical white line midway between P6 and P7 is the P6.5 position.
Note that I have yellow-highlighted the P6 to P7 time period.
The blue graph represents the average value and the two green graphs represent the one standard deviation limits, which means that 68% of the pro golfers in Jon Sinclair's collection fall between those two green graphs.
Note that Jon Sinclair has written a note in a red box, which states "Note! Still supinating before impact" and his red arrow is pointing at the P6.5 position.
His trail forearm supination/pronation graph shows that the average pro golfer is increasingly supinating his trail forearm between P6 => P6.5 and that there is a marginal decrease in the amount of supination that is present at P7 compared to P6.5. There is no evidence of a large amount of counterclockwise trail forearm rotation happening between P6.5 => P7 and there is no evidence of any overt trail forearm pronation existing during the late downswing or in the immediate post-impact time period in 68% of those pro golfers.
If I would hazard a guess, I would imagine that strong/under trail hand grip (face-closer) pro golfers would be closer to the top green line while the weak/on-top trail hand grip (face-opener) golfers would be closer to the bottom green line. Either way, the fact is indisputable that most pro golfers do not have any significant counterclockwise trail forearm rotation happening between P6 => P7 (as predicted by TR for the on-top subgroup of pro golfers).
I know that Phil Cheetham must also have a large collection of these trail forearm graphs in his collection of >100 pro golfers' AMM-3D results. I would like to see him publish his graphs to see whether they show the same results as the Jon Sinclair graphs above. In fact, I would like to see him and Jon Sinclair both publish separate graphs for on-top (face-opener) trail hand grip pro golfers versus under (face-closer) trail hand grip pro golfers in order to determine if there is a significant difference in their pattern of trail forearm rotation happening between P6 => P7.
I will now provide yet another reason that explains why I do not believe that the trail hand's grip strength is the major factor that is causally responsible for the degree of clubface closure that happens to a variable degree in all pro golfers between P6.5 => P7 - and that is the indisputable fact that the lead hand's grip strength is more likely to be the major factor that can be causally correlated with the degree of clubface closure that happens in the late downswing between P6 => P7 in many pro golfers.
Here is a diagram showing the usual pattern of clubface closure that happens between P6 => P7 in a pro golfer who uses a weak-or-neutral lead hand grip (irrespective of the strength of the trail hand grip) and who wants to generate a straight ball flight by zeroing-out both the clubhead path and the clubface angle at impact.
The blue line represents the ball-target line and the desired direction of the straight ball flight.
The curved red path represents an in-to-square-to-in clubhead path where the clubhead path is square to the ball-target line at impact (green dot representing the ball).
The short black line represents the clubface angle which is steadily closing during the P6.5 => P7 time period so that the clubface can become square to the clubhead path (and therefore also to the ball-target line) by impact.
Why is this clubface-closing pattern between P6.5 => P7 - where the amount of clubface closure is inversely proportional to the strength of the lead hand grip - often seen in many pro golfers who want to zero-out both the clubhead path and clubface angle at impact (as seen in the above diagram)?
Here is the obvious answer.
Consider the swing of a pro golfer who uses a weak-or-neutral lead hand grip.
Tiger Woods driver golf swing action - capture images from his Nike commercial video.
Image 1 is at P1, image 2 is at P4, and image 3 is at impact.
Note that the logo on Tiger's lead hand glove is facing the target at address and that it is approximately straight-line-aligned with his clubface (although it is marginally off because Tiger prefers to hold his hands midway between his thighs at address, which causes his clubshaft to be angled slightly backwards due to the fact that his lead hand is slightly behind his ball position at address). Note that the back of his lead hand is facing the target at address and that it is approximately perpendicular to his hand arc path.
During his backswing's P1 => P4 time period, the back of Tiger's lead hand is going to rotate clockwise so that by the time his lead hand reaches its P4 position it will have rotated ~90 degrees clockwise so that the back of his lead hand is roughly parallel (and not perpendicular) to his hand arc path. Because his clubface continuously stays roughly parallel to the back of his lead hand during the P1 => P4 time period, his clubface will also rotate by the same amount so that it is roughly parallel to his clubhead path at P4, which means that it has rotated clockwise to a very open position. The major biomechanical factor that allows the back of his lead hand to rotate ~90 degrees clockwise between P1 => P4 is a lead forearm pronatory motion, although a certain amount of internal rotation of the lead humerus can contribute to his lead hand's clockwise rotary action.
To get his clubface to become square to the target at impact, Tiger Woods must reverse the process so that the back of his lead hand, and therefore the clubface, will again be square to the target at impact. To reverse the process and rotate his lead hand in a counterclockwise direction, Tiger must perform a lead forearm supinatory motion +/- a certain amount of lead humerus external rotary motion. The necessary lead forearm supinatory motion cannot happen between P4 => P5.5 when the back of his lead hand and clubshaft are continuously aligned parallel to his shallowing swingplane, because that would steepen his clubshaft to an over-the-plane (off-plane) position. So, all the necessary lead forearm supination must happen between P5.5 => P7, and mainly between P6.5 => P7 after the club has significantly completeted most of its release action in the plane of lead wrist radial => ulnar deviation (representing the release of PA#2 in TGM terminology).
Here is a capture image showing Tiger's lead forearm supinatory action (which is called the release of Power Accumulator #3 in TGM terminology).
Image 1 is at P6.5, image 2 is at P6.7, image 3 is at P6.8 and image 4 is at impact.
Note that Tiger's clubface is still open relative to his clubhead path at P6.5 and note that it steadily closes more between P6.5 => P7 in direct proportion to the angular speed of counterclockwise rotation of the back of his lead hand, and note that his clubface remains continuously parallel to the back of his lead hand between P6.5 => P7. What causes his lead hand to rotate counterclockwise between P6.5 => P7? I believe that it is mainly due to lead forearm supination (= PA#3 release action) - look at the degree of rotation of his lead lower forearm's radial bone (just above the top level of his gloved hand) and note that it rotates at the same rotational speed as the back of his lead hand and clubface. I can see no evidence that his trail forearm is rotating counterclockwise by a large amount in a pronatory direction between P6.5 => P7 that would lead an unbiased observer to postulate that it is the major casual factor causing the clubface closing phenomenon (relative to the clubhead path) that is obviously happening between P6.5 => P7.
I think that the biomechnically-induced pattern of clubface closure seen in Tiger Woods driver swing action is identical to the "average" pattern seen in Jon Sinclair's collection of >100 pro golfers.
Consider these Jon Sinclair graphs showing the "average" pattern of lead forearm rotation (green graph) and trail forearm rotation (red graph) seen in his collection of >100 pro golfers.
Address = P1, Top = P4, AP = P5, MD = P6, and Impact =P7.
I have yellow-highlighted the P6 => P7 time period.
Note that the green graph shows that the lead forearm is supinated at address (P1) and note that it rotates in a pronatory direction between P1 => P4 to become frankly pronated by P4 - as I demonstrated when describing the backswing action of Tiger Woods.
Note that there is very little change in the degree of lead forearm pronation happening between P4 => P6. Note that the slope of the green slope only starts to steepen between P6 => P6.5 and that it becomes even steeper between P6.5 => P7. Note the large amount of lead forearm supination happening between P6.5 => P7, which would cause the clubface to close more rapidly relative to the clubhead path during that time period - as seen in Tiger Woods P6.5 => P7 time period. Note that the trail forearm is not rotating significantly in a pronatory direction between P6.5 => P7 so I have no reason to believe that it could be the major causal factor that would be producing the significant amount of clubface-closure (relative to the clubhead path) seen between P6.5 => P7 in many pro golfers who use a weak-or-neutral lead hand grip - and as seen in Tiger Woods driver swing action.
I think that there are many pro golfers who use a pivot-induced TGM swinging action (lead arm swinging action) like Tiger Woods (who uses a side-on/neutral trail hand grip), but who personally choose to use an on-top trail hand grip.
Consider an example featuring Patrick Rogers.
Capture image of Patrick Rodgers at address.
At address (image 1), his trail humerus is internally rotated to a small degree so that his trail antecubital fossa faces more towards the target and it does not face the ball-target line. Note that he has an on-top trail hand grip and a neutral lead hand grip. Note that the back of his lead hand faces the target at address.
Now, consider the clubface-closing phenomenon seen in his late downswing between P6.5 => P7.
Image 1 is at P6.5, image 2 is at P7 and image 3 is at P7.4.
I have drawn a blue line down the middle of his trail antecubital fossa and a red line along his trail lower forearm's radial bone.
Image 1 shows that his trail forearm is significantly supinated at P6.5 and that the back of his lead wrist is facing more towards the ball-target line, which means that very little counterclockwise rotation of his lead hand happened between P6 => P6.5. Note that his clubface is still significantly open relative to his clubhead path at P6.5.
Image 2 shows that the back of his lead hand is facing the target at impact due to a large amount of lead forearm supination that is happening between P6.5 => P7 - note how much his lead lower forearm's radial bone has rotated counterclockwise between P6.5 => P7. Note that there is a direct proportional relationship between the amount of counterclockwise rotation of the back of his hand happening between P6.5 => P7 and the amount of counterclockwise rotation of the clubface that is happening during the same time period - strongly suggesting a direct causal relationship. Note that very little counterclockwise rotation of his trail forearm in a pronatory direction is happening during the same time period, which suggests that the counterclockwise rotation of his trail forearm cannot be the major causal factor responsible for the clubface-closing phenomenon of the clubface (relative to the clubhead path) that is happening between P6.5 => P7. Look at his trail hand's true palm area (= area just proximal to the base of his trail hand's 2nd - 5th fingers) at P6.5 and P7 - you will note that it rotates at the same rotational speed as the back of his lead hand in a counterclockwise direction. How is that possible if there is so little counterclockwise rotation of his trail forearm happening during that P6.5 => P7 time period? I believe that the correct answer is that his trail wrist is becoming significantly less extended between P6.5 => P7 and that allows the trail palm to roll in a counterclockwise direction, especially if a finite degree of counterclockwise trail wrist circumductory roll motion happens during his trail wrist's partial straightening action.
Note that Patrick Rodgers is performing a DH-hand release action between P7 => P7.4 where the clubshaft is not bypassing his lead arm from an angular rotational perspective, and that allows him to more easily keep his clubface square to his clubhead path between P7 => P7.4. He is not using a handle-dragging "hold-off" hand release action where the lead wrist is held fixedly/rigidly in the same degree of lead wrist flexion and he is allowing his lead wrist to extend during the early followthrough time period between P7 => P7.4, but only by a small amount that will not cause the clubshaft to bypass his lead arm (from an angular rotational perspective). Note how he is able to retain a partly bent trail arm and a partly extended trail wrist all the way to P7.4, and that is only biomechanically possible because he does not "run-out-of-trail arm" - due to the fact that he moves his trail shoulder far enough downplane so that the distance between his trail shoulder and his trail hand does not get too large (considering the additional fact that there is a significant amount of targetward motion of his lead hand happening between P7 => P7.4). By maintaining roughly the same degree of bent trail arm and the same degree of extended trail wrist through the impact zone between P7 => P7.2 it potentially allows his hand couple to work as a negative hand couple through impact, which could have a mechanical-stabilising effect on his lead wrist and make it less likley to extend too much in the immediate post-impact time period. Note that to perform a DH-hand release action as efficiently as Patrick Rodgers, that he has to ensure that he rotates both his pelvis and upper torso counterclockwise by a sufficiently large amount between P7 => P7.4.
Most importantly, note that his use of an on-top trail hand grip does not prevent him from performing a DH-hand release action in a very efficient manner.
Let's compare Patrick Rodgers late downswing action to the late downswing action of another pro golfer who uses a weak-or-neutral lead hand grip, but who uses a strong (face-closer) trail hand grip - Justin Thomas.
Capture images of Justin Thomas's late downswing action.
Image 1 is at P6, image 2 is at P6.5, image 3 is at impact and image 4 is at P7.4.
Note that I have drawn a blue line down the middle of his trail antecubital fossa and a red line along his trail lower forearm's radial bone.
Note that JT's trail forearm is markedly supinated at his P6 position (image 1). Note that the back of his trail hand is facing the ball-target line. Note that his trail elbow is above-and behind his trail hip joint area, and that it is in a rear-linkage position.
Note that the back of his trail hand is still facing the ball-target line at P6.5 (image 2) and note that there has been very little counterclockwise rotation of his lead hand happening between P6 => P6.5. Note that his trail forearm is still supinated at P6.5 and there has been no significant counterclockwise rotation of his trail forearm in a pronatory direction. Note that his clubface is still open relative to his clubhead path.
Note that the back of his lead hand is facing the target at impact (image 3) secondary to a lead forearm supinatory motion (= release of PA#3) and that a large amount of counterclockwise rotation of his club handle is consequently happening between P6.5 => P7 to ensure that he squares his clubface relative to his clubhead path by impact. However, note that his trail forearm is still supinated at impact and I therefore think that the very small amount of trail forearm rotary motion happening between P6.5 => P7 cannot be deemed to be causally responsible for the large amount of clubface-closing happening between P6.5 => P7 relative to his clubhead path. The amount of clubface-closing happening relative to his clubhead path between P6.5 => P7 better correlates with the amount of lead forearm supination happening during that time period.
If you compare the amount of trail forearm rotation in a counterclockwise direction happening between P6.5 => P7 in Patrick Rodger's and Justin Thomas' driver swings, note that there is a negligible difference. In an email message to another golf swing theory enthusiast (DG), TR wrote the following regarding the choice of a trail hand grip-: "We test this until we arrive at a trail hand that delivers the face squarely with the least effort and conscious intervention. Baddeley calls this a “quiet” face. A mismatched grip will close the face too early or not in time." The true real-life reality is that the clubface cannot be "quiet" between P6.5 => P7 if a pro golfer adopts a weak-or-neutral lead hand grip because the clubface needs to close by a significant amount relative to the clubhad path during that time period - irrespective of the strength of the trail hand grip. However, I do agree that the trail forearm motion should optimally be "quiet" between P6 => P7 and it is obviously very quiet in both Patrick Rodgers and Justin Thomas' P6 => P7 time periods - where there is very little change in their degree of trail forearm supination happening (and the same "quiet" trail forearm rotary motion phenomenon is clearly depicted in Jon Sinclair's trail forearm pronation/supination graph).
Jeff.