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Post by imperfectgolfer on Aug 26, 2019 12:12:49 GMT -5
What is the correct definition of "lag tension"? During the backswing of a full golf swing action, a golfer usually upocks (radially deviates) the left wrist in the plane of the intact LAFW and during the downswing this lag angle between the clubshaft and the left arm decreases so that it is basically eliminated by impact. When I state "basically eliminated" I mean that the clubhead catches up to the left arm so that they are straight-line aligned by the low point of the clubhead arc. If the golfer places his golf ball at low point (which is usually vertically situated below the left shoulder socket) in his driver swing action, then the clubhead and left arm will be straight-lined aligned at impact - as seen in the following capture image of Adam Scott's driver swing. Note that Adam Scott's clubhead, clubshaft and left arm are straight line aligned at impact (image 1) and also at P7.2 (image 2). That means that the clubhead has caught up to the left arm by impact and it is no longer lagging. The question then becomes-: Is the clubshaft under a state of lag tension during the downswing when the clubhead is lagging behind the left arm, and should that lag tension still be present at impact? Consider an analogy. Imagine a child pulling a toy car behind him as he walks so that the car is pulled along by a string, the end of which the child is holding in his hand. The string will be taut when he pulls the car along and the tension in the string will depend on the mass of the toy car and the speed of acceleration of the car. If the child walks faster, then the tension in the string will become larger as the car accelerates. If the child suddenly stops walking, then the string will become lax, but the car will still continue to temporarily move forward at its acquired speed because it has already gained forward momentum during the lag phase. It is easy to determine whether lag tension is present in the string because a taut string means that lag tension is present and a lax (loose) string means that lag tension is absent.
How do we determine whether lag tension is present in a clubshaft during the downswing between P4 (end-backswing) and P7 (impact)? The correct answer is that lag tension is present when the peripheral clubshaft is bend backwards relative to the proximal clubshaft and lag tension is absent is when the peripheral clubshaft is bent forward relative to the proximal clubshaft.
Here is a capture image from David Tutelman's website. A positive wrist couple means that that a positive wrist torque is present and that means that the golfer is still applying a "force" to the club handle in order to get the clubhead to catch up to the hands. A negative wrist couple means that a negative wrist torque (no lag tension) is present, and the peripheral clubshaft is bent forward because the clubhead is traveling faster than the hands. It is very important to appreciate the fact that the presence of lag tension is dependent on studying the relationship of the peripheral clubshaft relative to the proximal clubshaft and it has nothing to with the alignment relationship between the overall clubshaft and the left arm. So, in the 3rd image one can see that the overall clubshaft is lagging behind the left arm in the late downswing and it has not yet caught up to the left arm - so a condition of forward shaft lean is present at that time point. In other words, the presence of forward shaft lean does not automatically mean that lag tension is present in the clubshaft. Now, consider this video by Brendon Devore.
Note that Brenson claims that he measured a golfer's lag tension at impact by measuring the relationship between the left arm and the clubshaft. Brendon incorrectly states that if the golfer comes into impact with forward shaft lean, so that the clubshaft is angled back relative to the left arm, then that means that lag tension is present and he also incorrectly states that the magnitude of lag tension is proportional to the degree of forward shaft lean. Brendon is making another fundamental error by also claiming that the golfer is in control of his clubshaft when he comes into impact with forward shaft lean (which he equates with the presence of lag tension being applied by the golfer pulling the club handle actively forwards) and he infers that lag tension is not present if the clubshaft flips passed the left arm. I agree with Brendon that flipping pre-impact is a major swing fault, which a golfer should avoid, but the absence of flipping pre-impact does not mean that lag tension is present in the later downswing and immediately before impact. Consider these capture images of Rory McIlroy's downswing. Image 1 shows Rory at the P4 position. Note that his entire clubshaft is straight-line aligned, which means that there is no torque being applied to the club handle by Rory's hands.
Image 2 is at the P5 position and image 3 is at the P5.5 position - note that the peripheral clubshaft is bent backwards because Rory is using his hands to apply a torque to the club. Under those conditions, lag tension is present in the clubshaft. Image 4 is a the P6 position and one can now see that the clubshaft is starting to bend in the opposite direction, and this is much more apparent by P6.5 (image 5). That means that a condition of a negative wrist torque is present in the later downswing after P6, and the clubhead is now traveling faster than the hands, which means that lag tension is absent. The clubhead is still lagging behind the left arm between P6 and impact, but clubhead lag relative to the left arm is a different golf instructional concept and it is not the same golf instructional concept as lag tension (which implies the presence of a positive wrist torque).
I believe that virtually all pro golfers have a negative wrist torque, and the absence of lag tension in their clubshaft, during the late downswing between P6 and impact when swinging a driver, and it has nothing to with the degree of forward shaft lean at impact. The average pro golfer has a negative clubhead attack angle of -0.5 degrees at impact when swinging a driver, but some pro golfers prefer to have a positive clubhead attack angle of a few degrees at impact, which means that they will likely have a different degree of shaft lean at impact. The different degree of forward shaft lean at impact nothing to do with the presence/absence of lag tension (because all pro golfers come into impact with negative lag tension) and it only relates to the timing and efficiency of the club release phenomenon (PA#2 release phenomenon) and it is also affected by ball position. What causes the club to release in a pro golfer's driver swing action? The correct answer is that it happens according to a law of physics and that particular law of physics is described by different names (eg. law of the double pendulum, law of the flail, D'Alembert's principle law). I prefer using nmgolfer's personal description of that law (see nmgolfscience.tripod.com/release.htm ) because it basically emphasises the fact that the golf club acquires angular momentum during the early-mid downswing in direct proportion to the change in hand arc path per unit time as the hands travel down the hand arc path between P4 and P6. If a golfer is skilled and correctly controls the speed of motion of his hands down the hand arc path and also controls the shape of his hand arc path (especially between P4 and P5.5), then he can control the speed of release of PA#2 so that the clubhead can catch up to the left arm by impact (or near impact if the ball position is not at low point).
I believe that the PA#2 release phenomenon (based on the law of physics called the D'Alembert law) applies to the full golf swing of a pro golfer - whether it is a driver swing or an iron swing with a long iron or mid-iron. The only difference is that most pro golfers will have more forward shaft lean at impact with shorter irons (compared to a driver swing). Why must the degree of forward shaft lean at impact be greater with shorter irons? The correct answer relates to the way that iron golf clubs are manufactured - such that if an iron club's sole is flat on the ground, then the clubshaft will automatically be in a state of forward shaft lean. The degree of forward shaft lean is inbuilt into the clubshaft, with shorter irons having a greater degree of forward shaft lean than long irons - presuming that their soles are all correctly flat on the ground. Therefore, if a skilled pro golfer wants to hit the ball with the correct amount of forward shaft lean that is appropriate for a particular iron club so that the sole is flat-on-the-ground at impact, then he has to perfect his PA#2 release action for each club. Flipping pre-impact is a major swing fault due to an inefficient PA#2 release action, and pro golfers try to routinely avoid that swing fault. However, perfecting the PA#2 release phenomenon so that the degree of forward shaft lean is "correct" for each iron club has nothing to with lag tension! Although virtually all pro golfers have a negative wrist torque, and therefore the absence of lag tension, in their later downswing and at impact when hitting a driver, fairway woods, long irons and mid-irons, some do selectively come into impact with a positive wrist torque when hitting a short iron. So, for example, if a golfer wants to come into impact with an exaggerated degree of forward shaft lean and a larger negative clubhead attack angle when hitting a shorter iron, then he may deliberately use a manually-induced positive wrist torque swing technique during his entire downswing and he will avoid using a PA#2 release phenomenon in that swing action. Consider an example - Jordan Spieth using a handle-dragging technique to hit a short iron. Note that Jordan Spieth has placed the golf ball well back in his stance so that he can strike the ball with a lot of forward shaft lean and where the leading edge of the clubface will dig into the ground because of the exaggerated amount of forward shaft lean and a negative clubhead attack angle. To accomplish that goal, he uses a handle-dragging technique where he moves his left hand sufficiently fast into impact while preventing the club from releasing according to the law of physics that underlies a PA#2 release action.
It is perfectly acceptable to use a handle-dragging technique for certain short iron shots or punch shots out of the woods (when a golfer wants the ball to come out low in order to avoid hitting overlying tree branches), and when using a handle-dragging technique lag tension is present throughout the entire downswing and also at impact. However, I do not believe that a handle-dragging technique is appropriate for a driver swing. Interestingly, Anthony Taggart (a TGM-literalist who recently published a book called "The Complete Golf Swing Enchirdion") recommends a handle-dragging technique (based on the TGM principle of "sustain the lag") for all full golf swings, including the driver swing. He wrongly believes that if the peripheral clubshaft is not bent backwards at impact (implying the presence of a positive wrist torque) that a golfer is not accelerating the clubhead into impact, and he wrongly believes that it will result in a massive loss of swing power. However, his "belief" is obviously false and one does not have to have the clubhead accelerating at impact in order to have a high clubhead speed at impact. In fact, it has been shown that clubhead speed reaches its maximum value at about the 92-94% time point of the downswing in the average pro golfer's driver swing action, and that negative wrist torque (no lag tension) is present at impact.
Jeff.
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Post by dubiousgolfer on Aug 26, 2019 19:20:37 GMT -5
Dr Mann Your thread comment above makes perfect sense although I'm not sure about this sentence below: "A positive wrist couple means that that a positive wrist torque is present and that means that the golfer is still applying a "force" to the club handle in order to get the clubhead to catch up to the hands" The positive wrist torque could be a 'bracing/stopping' torque to stop the clubs continued COM motion in the clockwise direction in the backswing (from a face-on view). It could be a torque that is preventing the clubhead from getting 'too far behind the hands' falling onto the back of the shoulders/neck (see 'Note' below) rather than a torque to make the clubhead catch up with the hands. But it's definitely a positive torque. -------------------------------------------------- Note : The positive torque is mentioned in Rod White's article below: www.tutelman.com/golf/swing/golfSwingPhysics3a.php"Initially some positive wrist torque is required to stop the club from being pulled into the golfers neck (the hub)." ------------------------------------------------- When I think of that positive bracing/stopping torque I normally relate it to the max lead wrist radial deviation reached in the plane of the intact LFFW. It's like the bracing torque you apply to the handle of a Y shaped catapult with one hand , while you are pulling the elastic bands back with the other. The handle is being stabilised by a positive bracing torque but its not actively rotating the Y section. I'm unsure who Brendon Devore believes is correct about clubshaft deflection in the golf swing. Does he believe in Nesbitts research rather than Sasho/Tutelman/Kwon? If Nesbitt's research is proved to be correct , then those Tutelman diagrams would give a false impression of negative/positive torques in the hands. If Brendon believes in this Nesbitt 'shaft deflection' diagram below , then he might be assuming similar bend at the proximal end of the shaft to decide whether there is positive or negative torque at the hands. DG
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Post by imperfectgolfer on Aug 26, 2019 23:31:24 GMT -5
DG, You stated-: " The positive wrist torque could be a 'bracing/stopping' torque to stop the clubs continued COM motion in the clockwise direction in the backswing (from a face-on view). It could be a torque that is preventing the clubhead from getting 'too far behind the hands' rather than a torque to make the clubhead catch up with the hands. But it's definitely a positive torque." Your opinions make no sense to me. The positive wrist torque is being applied in the early downswing between P4 and P5.5 (see those capture images of Rory's early-mid downswing) and it makes the peripheral clubshaft bend backwards. The positive wrist torque is not being applied during the backswing and it makes no sense to me to say that the positive wrist torque is only being applied to prevent the clubhead lag from getting larger. Surely, any positive torque being applied to the club handle by the hands between P4 and P5.5 is the result of the release of PA#4, which will then induce the release of PA#2 (according to the D'Alembert principle). You also wrote-: " If Brendon believes in this Nesbitt 'shaft deflection' diagram below , then he might be assuming similar bend at the proximal end of the shaft to decide whether there is positive or negative torque at the hands." I have no idea what you are claiming? Feel free to expand on this point. By the way, do you disagree with David Tutelman's criticism of Nesbit's opinion on the shaft deflection diagram - as described in this DT article at www.tutelman.com/golf/swing/nesbitKwon2.phpAre you arguing that there may be no legitimacy to DT's opinion "that if the peripheral shaft is bent forward relative to the proximal shaft that it implies that there is a negative wrist torque at the level of the club handle"?
Jeff.
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Post by dubiousgolfer on Aug 27, 2019 6:37:43 GMT -5
Dr Mann
Yes , on reflection my wording 'too far behind the hands' was very vague and incorrect (I've corrected my post as I originally found it difficult to explain what I meant).
Positive torque is actually being applied during the backswing because the angular velocity of the club is reducing to zero (before changing direction to the downswing). Something has to stop the club falling onto the back of the golfers neck and that requires a positive torque.
From a purely 'physics' perspective , the 'positive torque' that releases PA#2 is caused by a 'linear' force (applied by the hands) that is not aligned through the COM of the club. That 'positive torque' is not made by any 'active radial to ulnar deviation' of the left wrist but by the natural tendency of the COM of the club to align itself with that linear force (ie. the clubs COM is moving the wrists from radial to ulnar deviation when PA#2 is released). No-one knows exactly 'how' that 'linear force' (direction and magnitude) is actively created but it may well be secondary to the release of PA#4 .
With regard Nesbit's diagram , if you look closely at the first few inches of the shaft from the grip end, it is showing backwards shaft bend. That would infer positive wrist torque even though one can see forward bend at the distal end. If Brendon believes that is what is actually happening to the shaft (ie. Nesbit's calculations on shaft bend) , then he may well be right in believing that golfers are drag loading (based on possibly incorrect assumptions made by Nesbit).
Personally, I believe that Dave Tutelman has a valid criticism because he has performed some real experiments that seem to strengthen his own claims. But Tutelman , Sasho and Dr Kwon cannot 100% prove their claims are correct until further detailed research is done over a large sample of elite golfers with different swing techniques (as you've mentioned before using force sensors on the gloves/handle).
After seeing a few more of these 'lag tension' videos and hearing Bertie Cordle's replies to Brendon Devore's questions he doesn't seem to have any expertise in biomechanics or physics. Does he and Brendon have any knowledge of TGM regarding optimal PA2# release and Drive-Hold hand release actions?
To be honest , this looks like another marketing gimmick to sell Mr Cordle's inventions.
DG
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Post by imperfectgolfer on Aug 27, 2019 10:01:04 GMT -5
DG, You wrote-: " Positive torque is actually being applied during the backswing because the angular velocity of the club is reducing to zero (before changing direction to the downswing). Something has to stop the club falling onto the back of the golfers neck and that requires a positive torque." It is obvious that a positive torque must be applied during the backswing to slow down the motion of the club, but I regard that positive wrist torque as a minor element and irrelevant to what is happening in the downswing. You wrote-: "From a purely 'physics' perspective , the 'positive torque' that releases PA#2 is caused by a 'linear' force (applied by the hands) that is not aligned through the COM of the club. That 'positive torque' is not made by any 'active radial to ulnar deviation' of the left wrist but by the natural tendency of the COM of the club to align itself with that linear force (ie. the clubs COM is moving the wrists from radial to ulnar deviation when PA#2 is released). No-one knows exactly 'how' that 'linear force' (direction and magnitude) is actively created but it may well be secondary to the release of PA#4." I agree with your first two sentences, but I cannot understand why you are unsure whether the release of PA#4 is responsible for producing the linear force that will subsequently cause the release of PA#2. Look at this one-armed golfer hitting a 300 yard drive.
What can be providing the linear force at the level of the club handle other than the pivot-induced release of PA#4?
You wrote-: "With regard Nesbit's diagram , if you look closely at the first few inches of the shaft from the grip end, it is showing backwards shaft bend. That would infer positive wrist torque even though one can see forward bend at the distal end. If Brendon believes that is what is actually happening to the shaft (ie. Nesbit's calculations on shaft bend) , then he may well be right in believing that golfers are drag loading (based on possibly incorrect assumptions made by Nesbit)." I do not see any backward bend of the proximal shaft in the late downswing in "real life" pro golfers' golf swings (eg. That Rory McIlroy swing that I have posted). Also, do you not believe that the major factor causing the forward bend of the peripheral clubshaft is due to the clubhead traveling faster than the hands? If the clubhead is traveling faster than the hands, how can a golfer still be applying a positive torque to accelerate the clubhead?
I don't believe that either Bertie Cordle and Brendon DeVore understand the difference between a "sustain the lag" type of golf swing action (handle-dragging technique) and a pro golfer's TGM swinging action based on the release of PA#2 being due to the D'Alembert principle. Stop the Bertie Cordle interview video at the 4:48 minute time point. Note that the peripheral clubshaft of that golfer is bent forward (implying a negative torque at the level of the club handle) even though there is forward shaft lean at impact. The same "fact" applies to Tiger Woods' peripheral clubshaft between the 17:15-17:30 minute time point of the video when he hits his stinger shot - note that the peripheral shaft is bent forward. From my perspective, it demonstrates i) an absence of lag tension in the clubshaft at impact and ii) where the forward shaft lean at impact is actually due to the correct timing of the release of PA#2 and PA#3.
Another point that Bertie (and TGM literalists) often refer to is the functioning of the trebuchet as being an accurate reflection of what is happening during a full golf swing. However, I think it is not a good comparative model because the large weight (? stone) providing the power to the lever is providing a constant amount of power due to the constant effect of gravity on the large weight. However, in a golf robot club-testing machine and a pro golfer's driver swing (which both work according to the principle of the double pendulum swing model) swing power is only applied to the central arm (lead arm in a golfer) between P4 and P5.5 and the lead arm slows down during the later downswing. Here is the kinematic sequence of a pro golfer. Note that the hands (= left arm) reach their peak speed of 22.6mph at about P5.5 and they slow down in the later downswing. If the hands are slowing down progressively between P5.5 and impact then how do they provide a positive wrist torque that can accelerate the clubhead all the way into impact? Also, consider what Bertie Cordle states between the 18:20- 18:40 minute time point of his interview video. He states that when the clubshaft becomes straight-in-line with the left arm that lag tension is lost and he states that the golfer can no longer control the club, so that flipping is inevitable. However, we know that is not true! Pro golfers who use a DH-hand release action keep the clubshaft aligned with the left arm to well beyond impact (eg to P7.4+) even though lag tension is absent between impact and P7.4. DHers do this by matching the angular velocity of the left arm to the angular velocity of the clubshaft and thereby maintain an intact LAFW.
Another point that Bertie and Brendon do not grasp is the fact that clubhead lag operates in the plane of left wrist radial => ulnar deviation and that the club-releasing plane plane is parallel to the swingplane in the early-mid downswing, but it becomes progressively more perpendicular to the functional swingplane between P6.5 and impact. That means that the ability to maintain lag tension (defined as the relationship between the clubshaft and the left arm) has to take that "fact" into account. Bertie Cordle does not explain how lag tension is maintained all the way into impact when the club-releasing plane (plane of radial => ulnar deviation) is constantly changing its angular relationship relative to the ball-target line during the late downswing. I think that it is much easier to understand the underlying biomechanics when one uses the intact LAFW model. Consider Kelli Oride's late downswing.
Note that the back of her GFLW is rotating counterclockwise between P6.5 and impact due to the release of PA#3 (where the LAFW remains intact during this time period). Note that she has forward shaft lean at impact, and it is partly due to her controlled rate of release of PA#3 (and not PA#2). In other words, an ability to control the release of PA#3 (which is biomechanically due to a left forearm supinatory motion) plays a highly significant role in a golfer's ability to ensure that the clubshaft comes into impact with forward shaft lean and it has nothing to do with controlling lag tension (which operates in the plane of radial => ulnar deviation). Bertie Cordle and Brendon DeVore do not consider the "real life" complexity of this issue! Jeff.
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Post by imperfectgolfer on Aug 27, 2019 12:38:00 GMT -5
Another comment - watch the Bertie Cordle interview video between the 17:46 - 18:24 minute time point. Bertie states that a golfer can only control the clubshaft and clubface if lag tension (which he defines as the clubshaft lagging behind the left arm) is present. However, I believe that his claim is not true if one uses the intact LAFW technique where one continuously controls the golf club by maintaining an intact LAFW throughout the entire downswing and early followthrough. Here is Jim George demonstrating the intact LAFW technique in slow motion.
Note that Jim is maintaining an intact LAFW throughout the entire downswing and early followthrough to P7.2 (image 6).
Between P6 (image 3) and impact (image 5) the clubshaft is always in a straight-line relationship with the left arm (from an angular rotational perspective) and he comes into impact with a small degree of forward shaft lean by controlling the rate of counterclockwise rotation of the entire LAFW while simultaneously controlling the rate of release of PA#2 (which is happening within the plane of the intact LAFW). It is far too simplistic to think that a golfer only controls the golf club by controlling the degree of lag tension in the plane of radial => ulnar deviation. Also, to acquire a greater amount of forward shaft lean at impact that is appropriate for a short iron shot, a golfer has to ensure that the ball position is appropriate and then he needs to control the rate of release of both PA#2 and PA#3 so that the intact LAFW, and therefore the clubshaft, has the desired degree of forward alignment and also rotational alignment relative to the ball at impact.
Jeff.
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Post by dubiousgolfer on Aug 27, 2019 17:54:36 GMT -5
Dr Mann I agree that the release of PA#4 is the cause of that linear force. "If the clubhead is traveling faster than the hands, how can a golfer still be applying a positive torque to accelerate the clubhead?"Nesbitt & McGinnis seem to think so because it was mentioned on Tutelmans website 'Transient analysis' (see below). Personally , I don't know enough of about physics , damping and standing waves to decide 100% whether Tutelman's critical analysis is correct or not (but Nesbit has not responded or countered Tutelman's opinions). But currently I am more convinced with Tutelmans assertions than Nesbit, that forward bend means that the clubhead is travelling faster than the hands can keep up 'from an angular velocity perspective' (therefore negative torque at the hands). ------------------------ Nesbit and McGinnis talk about "bending modes" in the paper. Bending modes implies a resonant effect leading to standing waves Here is a diagram I think that both Nesbit and I could agree to, at least with the explanation here: For the early part of the downswing, the shaft bend is completely in lag, because the hand couple is needed to get the club moving and turning. At some point, about 100msec before impact, there is a force pulling the head forward along its path. This curves the shaft forward, but initially just at the tip. Because of shaft mass, this "flex wave" has yet to reach the hands. It must propagate up the shaft to the hands. Until it reaches the hands, the curve at the grip remains in lag bend. If the force continues to pull the head forward, eventually, the shaft will be completely in lead bend. According to McGinnis and Nesbit's analysis, impact occurs before the flex wave reaches the hands, so there is still lag bend under the hands at impact. ---------------------------------------------------- DG
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Post by imperfectgolfer on Aug 27, 2019 18:30:11 GMT -5
Dr Mann I agree that the release of PA#4 is the cause of that linear force. "If the clubhead is traveling faster than the hands, how can a golfer still be applying a positive torque to accelerate the clubhead?"Nesbitt & McGinnis seem to think so because it was mentioned on Tutelmans website 'Transient analysis' (see below). Personally , I don't know enough of about physics , damping and standing waves to decide 100% whether Tutelman's critical analysis is correct or not (but Nesbit has not responded or countered Tutelman's opinions). But currently I am more convinced with Tutelmans assertions than Nesbit, that forward bend means that the clubhead is travelling faster than the hands can keep up (therefore negative torque at the hands). ------------------------ Nesbit and McGinnis talk about "bending modes" in the paper. Bending modes implies a resonant effect leading to standing waves Here is a diagram I think that both Nesbit and I could agree to, at least with the explanation here: For the early part of the downswing, the shaft bend is completely in lag, because the hand couple is needed to get the club moving and turning. At some point, about 100msec before impact, there is a force pulling the head forward along its path. This curves the shaft forward, but initially just at the tip. Because of shaft mass, this "flex wave" has yet to reach the hands. It must propagate up the shaft to the hands. Until it reaches the hands, the curve at the grip remains in lag bend. If the force continues to pull the head forward, eventually, the shaft will be completely in lead bend. According to McGinnis and Nesbit's analysis, impact occurs before the flex wave reaches the hands, so there is still lag bend under the hands at impact. ---------------------------------------------------- DG According to DT that flex wave should only last 3 msec in "real life" if the hands are acting as hinged (damping) clamps that absorb the wave phenomenon, and it should have disappeared well before impact. Also, in my personal experience there is no "feel" of a positive torque being applied at the level of the club handle between P6 and impact if one performs a TGM swinging action using a lead arm-only swing action (or a two-handed swing action where the right hand does not apply a push-force against the aft side of the club between P6 and impact). By the way, Nesbit's golfers were amateurs who may be using a swing-hitting technique. It is amazing that he did not do his study using highly skilled pro golfers and that he only used 4 amateur golfers. Jeff.
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Post by dubiousgolfer on Aug 28, 2019 11:15:32 GMT -5
Dr Mann You mentioned the following: "Another point that Bertie (and TGM literalists) often refer to is the functioning of the trebuchet as being an accurate reflection of what is happening during a full golf swing. However, I think it is not a good comparative model because the large weight (? stone) providing the power to the lever is providing a constant amount of power due to the constant effect of gravity on the large weight. However, in a golf robot club-testing machine and a pro golfer's driver swing (which both work according to the principle of the double pendulum swing model) swing power is only applied to the central arm (lead arm in a golfer) between P4 and P5.5 and the lead arm slows down during the later downswing." Are you saying that the torque being applied to the lead arm in a pro golfer's driver swing (via lead shoulder joint) only acts between P4 and P5.5? But when I look at this Sasho Mackenzie modeled graph , one can see positive left shoulder torque happening all the way from P4-P7 DG
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Post by imperfectgolfer on Aug 28, 2019 17:40:37 GMT -5
Dr Mann You mentioned the following: "Another point that Bertie (and TGM literalists) often refer to is the functioning of the trebuchet as being an accurate reflection of what is happening during a full golf swing. However, I think it is not a good comparative model because the large weight (? stone) providing the power to the lever is providing a constant amount of power due to the constant effect of gravity on the large weight. However, in a golf robot club-testing machine and a pro golfer's driver swing (which both work according to the principle of the double pendulum swing model) swing power is only applied to the central arm (lead arm in a golfer) between P4 and P5.5 and the lead arm slows down during the later downswing." Are you saying that the torque being applied to the lead arm in a pro golfer's driver swing (via lead shoulder joint) only acts between P4 and P5.5? But when I look at this Sasho Mackenzie modeled graph , one can see positive left shoulder torque happening all the way from P4-P7 DG I believe that Sasho MacKenzie's forward dynamics computer modeling program is highly flawed. First of all, he only attempts to calculate the amount of muscular torque (presumably involving the shoulder girdle muscles) that would be required to abduct the left arm away from its adducted position at P4 to its more abducted position at impact, and he seemingly implies that it happens steadily throughout the entire downswing (see his angular displacement graphs). He only deals with the horizontal component of the release of PA#4 and he seemingly ignores the downward component of the release of PA#4 and he also does not produce any evidence that he takes into account the "real life" fact that the left arm slows down after P5.5 secondary to the release of PA#2 (based on the COAM principle). Also, he seemingly does not take into account the fact that the counterclockwise torso rotation can power the release of PA#4 without significant use of any shoulder girdle muscles. By the way, I also think that Sasho's M arm torque graph is worthless because he does not take into account the RYKE effect or the significant influence of the accumulator #3 angle on the amount of "force" needed to release PA#3. Jeff.
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Post by dubiousgolfer on Aug 28, 2019 19:27:21 GMT -5
Many thanks Dr Mann
Yes, it seems that graph I posted above was based on an 'optimisation' program to maximise clubhead speed and not based on a real life golfer.
Also his model is using M_Arm based on the whole left arm and not just the forearm which makes his model even less reflective of a real golfers swing.
DG
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Post by dubiousgolfer on Aug 29, 2019 6:19:31 GMT -5
Dr Mann I am now in state of confusion regarding swing power generation and I need to clarify this with you. When I read Tutelmans article below he is suggesting that one needs to apply a steady torque with the body through impact. ----------------------------------- www.tutelman.com/golf/swing/accelerateThru.phpThe body turn involves angular velocity and acceleration, so "accelerate through impact" might refer to body rotation. In this category, I will lump together legs, hips, trunk -- all the way up to the shoulders. That's because all have to be involved to move the shoulders. The muscles of every link in that chain must either create motion or transmit it, up from the ground to the shoulders. ""Accelerate though the ball" is an excellent swing key, for every shot from a drive to a putt. But it is better expressed as "rotate your body through the ball" (or perhaps "accelerate moving your hands beyond the ball"), because it is body rotation or "turning the triangle" where acceleration through the ball is beneficial. Consciously accelerating the clubhead through the ball (especially if you do it with the hands, wrists, or forearms) will probably do more harm than good. You will note that using your hands and wrists to retain the lag (as opposed to forcefully helping release the lag) will actually increase clubhead speed. Also from the examples, note that a side effect is that the wrist cock is not completely released at impact. So -- lo and behold -- you do increase ball speed. But not because you are accelerating the clubhead at impact; it is because you held off centrifugal acceleration until late in the downswing, where it creates the highest clubhead speed. ------------------------------ Also here is a section of guest Rod White article on Tutelman's website ------------------------------------------------ Rod White article www.tutelman.com/golf/swing/golfSwingPhysics3a.php#wristcocklet’s look more closely at a more realistic model of the golf swing, in the interest of clarifying technique. In the actual golf swing, the golfer is applying torque, throughout the swing, to the inner arm of the double pendulum -- by using muscles in the torso to turn the shoulders. The animation shows the swing of a moderately good amateur golfer with a sound golf swing. During the first part of the downswing, the golfer holds the club in a cocked position and accelerates the shoulders and torso. Initially some positive wrist torque is required to stop the club from being pulled into the golfers neck (the hub). Remember the passive, steadily rotating model on the previous page? There, a string (providing negative torque) was needed to keep the club from swinging outward. Here, during the initial build up of speed, some sort of "brace" (providing positive torque) is needed prevent the club from being pulled inward. The positive torque required to brace the club falls rapidly as the club accelerates. When the positive ‘bracing’ torque falls to zero, the club can be allowed to swing out -- ending the first phase. The second phase of the downswing occurs as the club swings out. If the golfer lets the club swing out when the bracing torque falls to zero, then this is described as a swing with a natural release. If the golfer holds the club in the cocked position for a short while longer, this is described as a late release. If the golfer releases the club early, the club will swing in towards the neck for a small moment and then swing out. We won’t look at the effect of release timing because to a good approximation release timing has no effect. The chart below plots the approximate driving distance versus wrist torque with almost all other parameters kept the same. Remember that wrist torque has two effects on clubhead speed. It (a) peaks at a lower clubhead speed and (b) peaks earlier in the downswing. The wrist torque is expressed as a percentage of the shoulder torque. For the model I’ve chosen, 10% corresponds to 1 kg.m of wrist torque in the model. This is a very large torque, but probably typical for male beginners who have yet to learn to let the club swing by itself The blue curve assumes that the golfer changes his swing so impact still occurs at the peak. We shorten or lengthen the swing so that impact will occur at maximum clubhead speed. This golfer is then only bitten by (a) above. The red curve assumes that the golfer simply makes the same length swing no matter what the wrist torque. This golfer is then bitten by both (a) and (b). Negative wrist torque also costs distance because the clubhead speed peaks after impact (i.e., impact is at the black line in the curve above). --------------------------------------- So aren't both suggesting a steady 'body torque' (pivot) all the way through the downswing? I think Dave Tutelman might have made an error here when he said "note that a side effect is that the wrist cock is not completely released at impact". He seems to have made the same mistake as Brendon/Bertie (as explained in your post above concerning Kellie Oride's late downswing). You said "Note that she has forward shaft lean at impact, and it is partly due to her controlled rate of release of PA#3 (and not PA#2)" Tutelman has also mentioned the below which has also confused me because the body rotation is not causing the 'downwards' component of PA#4 release. ------------------------------------ "I subscribe to golf instruction that says that the hands are moved by the body. But that is not the only theory of instruction out there; I have read books that say things like, "The arms do the swinging part of the golf swing... The body does not swing. It reacts to the swing." I may disagree with that, but it might be a productive intent and feel for some golfers. And that makes it valid instruction for those golfers. But -- make no mistake about this -- physics says that hand and arm motion is caused by body rotation. That is actual, as opposed to intent and feel. So, if we are going to analyze the physics of the swing, the motion of the hands and arms is driven by the body rotation. For the first approximation, we do not have to analyze hands and arms separately, just the body rotation -- which we discussed above. (If we were to refine the analysis, which I won't here, we would next account for the left arm's separation from the body late in the downswing. Still nowhere near "arms motivating the swing", but at least there may be some change of the result due to the rotation of the arm not being exactly the same as the rotation of the body.) ------------------------------------- Do you think Tutelman and Rod White are flawed in their thinking about applying a body torque throughout the downswing? Tutelman also confused me when he said the following "You will note that using your hands and wrists to retain the lag (as opposed to forcefully helping release the lag) will actually increase clubhead speed.". I inferred from his statement that one could easily 'hold the lag' and increase clubhead speed without changing other aspects of the swing (but the red curve on Rod White's graph proves otherwise). Holding lag (ie. more negative wrist torque) without altering other aspects of your swing seems to cause a decrease in clubhead speed. DG
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Post by imperfectgolfer on Aug 29, 2019 9:15:11 GMT -5
Dr Mann I am now in state of confusion regarding swing power generation and I need to clarify this with you. When I read Tutelmans article below he is suggesting that one needs to apply a steady torque with the body through impact. ----------------------------------- www.tutelman.com/golf/swing/accelerateThru.phpThe body turn involves angular velocity and acceleration, so "accelerate through impact" might refer to body rotation. In this category, I will lump together legs, hips, trunk -- all the way up to the shoulders. That's because all have to be involved to move the shoulders. The muscles of every link in that chain must either create motion or transmit it, up from the ground to the shoulders. ""Accelerate though the ball" is an excellent swing key, for every shot from a drive to a putt. But it is better expressed as "rotate your body through the ball" (or perhaps "accelerate moving your hands beyond the ball"), because it is body rotation or "turning the triangle" where acceleration through the ball is beneficial. Consciously accelerating the clubhead through the ball (especially if you do it with the hands, wrists, or forearms) will probably do more harm than good. You will note that using your hands and wrists to retain the lag (as opposed to forcefully helping release the lag) will actually increase clubhead speed. Also from the examples, note that a side effect is that the wrist cock is not completely released at impact. So -- lo and behold -- you do increase ball speed. But not because you are accelerating the clubhead at impact; it is because you held off centrifugal acceleration until late in the downswing, where it creates the highest clubhead speed. ------------------------------ Also here is a section of guest Rod White article on Tutelman's website ------------------------------------------------ Rod White article www.tutelman.com/golf/swing/golfSwingPhysics3a.php#wristcocklet’s look more closely at a more realistic model of the golf swing, in the interest of clarifying technique. In the actual golf swing, the golfer is applying torque, throughout the swing, to the inner arm of the double pendulum -- by using muscles in the torso to turn the shoulders. The animation shows the swing of a moderately good amateur golfer with a sound golf swing. During the first part of the downswing, the golfer holds the club in a cocked position and accelerates the shoulders and torso. Initially some positive wrist torque is required to stop the club from being pulled into the golfers neck (the hub). Remember the passive, steadily rotating model on the previous page? There, a string (providing negative torque) was needed to keep the club from swinging outward. Here, during the initial build up of speed, some sort of "brace" (providing positive torque) is needed prevent the club from being pulled inward. The positive torque required to brace the club falls rapidly as the club accelerates. When the positive ‘bracing’ torque falls to zero, the club can be allowed to swing out -- ending the first phase. The second phase of the downswing occurs as the club swings out. If the golfer lets the club swing out when the bracing torque falls to zero, then this is described as a swing with a natural release. If the golfer holds the club in the cocked position for a short while longer, this is described as a late release. If the golfer releases the club early, the club will swing in towards the neck for a small moment and then swing out. We won’t look at the effect of release timing because to a good approximation release timing has no effect. The chart below plots the approximate driving distance versus wrist torque with almost all other parameters kept the same. Remember that wrist torque has two effects on clubhead speed. It (a) peaks at a lower clubhead speed and (b) peaks earlier in the downswing. The wrist torque is expressed as a percentage of the shoulder torque. For the model I’ve chosen, 10% corresponds to 1 kg.m of wrist torque in the model. This is a very large torque, but probably typical for male beginners who have yet to learn to let the club swing by itself The blue curve assumes that the golfer changes his swing so impact still occurs at the peak. We shorten or lengthen the swing so that impact will occur at maximum clubhead speed. This golfer is then only bitten by (a) above. The red curve assumes that the golfer simply makes the same length swing no matter what the wrist torque. This golfer is then bitten by both (a) and (b). Negative wrist torque also costs distance because the clubhead speed peaks after impact (i.e., impact is at the black line in the curve above). --------------------------------------- So aren't both suggesting a steady 'body torque' (pivot) all the way through the downswing? I think Dave Tutelman might have made an error here when he said "note that a side effect is that the wrist cock is not completely released at impact". He seems to have made the same mistake as Brendon/Bertie (as explained in your post above concerning Kellie Oride's late downswing). You said "Note that she has forward shaft lean at impact, and it is partly due to her controlled rate of release of PA#3 (and not PA#2)" Tutelman has also mentioned the below which has also confused me because the body rotation is not causing the 'downwards' component of PA#4 release. ------------------------------------ "I subscribe to golf instruction that says that the hands are moved by the body. But that is not the only theory of instruction out there; I have read books that say things like, "The arms do the swinging part of the golf swing... The body does not swing. It reacts to the swing." I may disagree with that, but it might be a productive intent and feel for some golfers. And that makes it valid instruction for those golfers. But -- make no mistake about this -- physics says that hand and arm motion is caused by body rotation. That is actual, as opposed to intent and feel. So, if we are going to analyze the physics of the swing, the motion of the hands and arms is driven by the body rotation. For the first approximation, we do not have to analyze hands and arms separately, just the body rotation -- which we discussed above. (If we were to refine the analysis, which I won't here, we would next account for the left arm's separation from the body late in the downswing. Still nowhere near "arms motivating the swing", but at least there may be some change of the result due to the rotation of the arm not being exactly the same as the rotation of the body.) ------------------------------------- Do you think Tutelman and Rod White are flawed in their thinking about applying a body torque throughout the downswing? Tutelman also confused me when he said the following "You will note that using your hands and wrists to retain the lag (as opposed to forcefully helping release the lag) will actually increase clubhead speed.". I inferred from his statement that one could easily 'hold the lag' and increase clubhead speed without changing other aspects of the swing (but the red curve on Rod White's graph proves otherwise). Holding lag without altering other aspects of your swing seems to cause a decrease in clubhead speed. DG Although DT has great expertise when it comes to the physics of the golf swing, I have zero respect for his opinions when it comes to golf swing biomechanics because I think that he is TGM-illiterate and also clueless about many aspects of human biomechanics. I think that his opinions in his article that the body must be applying a steady torque through impact is unsound and I find his opinions very unconvincing. He does not explain in a rational cause-and-effect manner how body motions actually transfer energy to the club handle. Most importantly, we have "real life" evidence from 3-D kinematic sequence graphs that the pelvis, thorax (upper torso) and arms decelerate in the late downswing. Here is Jamie Sadlowski's kinematic sequence graphs. It is clearly apparent that all those body parts are decelerating in the late downswing prior to impact. Why would you be confused by this issue if you agree that a TGM swinging action generates swing power by the sequential release of PA#4 => PA#2? How could a golfer benefit by moving the body, and therefore the left arm, faster during the late downswing? I think that it would get the hands to impact before a golfer could complete the release of PA#2 => PA#3, and then the golfer would reach impact with too much forward shaft lean and an open clubface, which would predispose to pushes and push-slices. A point that you need to remember is that the release of PA#2 is never completed by impact if you think of the word "complete" as being maximum ulnar deviation (maximum uncocking). If a golfer has a neutral left hand grip then the plane of radial => ulnar deviation is actually perpendicular to the ball-target line at impact and it results in the accumulator #3 angle if left wrist uncocking is incomplete. Sergio Garcia has a large accumulator #3 angle at impact so he never completely releases PA#2 in the plane of left wrist uncocking. I agree with Rod White that it is a mistake to try and hold lag between P4 and P6 in an artificially-restrictive manual manner (by activating forearm muscles that keep the left wrist cocked up) because it will decrease clubhead speed at impact. However, one can hold lag for longer in a beneficial manner by shaping one's hand arc path - as seen in the following capture image of Dustin Johnson's driver and short iron swings. Note how Dustin Johnson shapes his hand arc for his driver swing (image 1) where the hands move downwards to below waist level between P4 and P5.5 with no targetwards motion of the hands between P4 and P5.5. That allows him to more easily retain lag for longer (presuming that he uses an active right arm adduction maneuver combined with a pitch elbow motion).
Jeff.
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Post by imperfectgolfer on Aug 29, 2019 10:45:45 GMT -5
I decided to search for golf swing videos to see if I could find a swing video where the peripheral clubshaft was bent back in the later downswing just prior to impact. I could never find one! Every swing video demonstrated that the peripheral clubshaft is bent forward (implying a negative wrist torque and an absence of lag tension). I especially concentrated my you-tube search on Phantom camera videos which have a high frame rate and no shutter lag problem. I, unfortunately, found very few Phantom camera videos of the golf swing. Here is one example. Here are capture images from that video. Note that the peripheral clubshaft is bent forward during the later downswing.
Here are two other two Phantom camera slow motion videos showing the same phenomenon. Lucas Glover driver swing.
Justin Rose iron swing.
If anybody can find a swing video showing a double bend in the clubshaft (which Nesbit claims is a "real life" phenomenon) or a peripheral clubshaft bent backwards (implying positive lag tension) in the later downswing, please bring it to my attention. Jeff.
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Post by dubiousgolfer on Aug 29, 2019 17:34:30 GMT -5
Many thanks again Dr Mann
DG
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