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Post by syllogist on Nov 3, 2019 7:49:01 GMT -5
In 2008, both Sasho Mackenzie and Professor Robin S. Sharp developed triple-pendulum models consisting of the torso, left arm, and wrist. MacKenzie used torque parameters to match a consistent, low-handicap golfer while Sharp used torque parameters to match the three professional golfers shown in the book, "In Search for the Perfect Swing." From both models, the basic swing sequence for the downswing is torso, then arm, then wrist. Additionally, Sharp concluded that none of the three professionals had to delay the uncocking of the wrists through the use of negative wrist torque. Obviously the models were crude given that it cannot be known how much torque was actually applied through each of the three segments of the triple pendulum and how long and in what degree the torques accelerated and diminished. The Mackenzie model was briefly discussed here in the thread, "Why isn't the pivot classified as a power accumulator?" Although the topic I will address has nothing to do with this question, the pivot (torso rotation) is a power accumulator per Kelley's logic. Kelley's power accumulators consist of an action and "opposite" action, i.e., cocking/uncocking, bent arm/straight arm, pronation/supination, and arm on chest/arm off chest. The torso can be considered rotated in one direction/rotated to the other direction. MacKenzie's 2008 model, referenced on Tutelman's website via the link, www.tutelman.com/golf/swing/models3.php, assumes the release of PA 4 via the straightening of the right arm per Tutelman. I have no qualms with this statement. MacKenzie's model shows a torque at the left shoulder called "Shoulder M" as well as torque through torso rotation called Torso M. Given that the right arm was omitted from the model, MacKenzie applied slightly more torque (85 Nm) to Shoulder M (vs 80 Nm being maximum torque previously reported) to account for the release of PA 4. Tutelman stated that by doing so, MacKenzie was certainly aware of the contribution of the straightening right arm, which he didn't model. Tutleman stated that the torque than causes left arm abduction would be from either or both: 1) Shoulder M, or muscles in back of the left shoulder that "swing" the left arm 2) Right arm extension Tutelman then stated that for the left arm to separate from the chest via the use of muscles in back of the left shoulder, right arm extension must be accomplished while pulling with the left arm and without pushing with the right hand in a way that does not create an undesirable torque at the grip end of the club, which can be tricky. Except for any incidental right arm straightening during the downswing caused by body position given the use of a given hand/arc path, is the final straightening of the right arm though the release zone motivated by Shoulder M? Although the answer is that one can certainly pull/push in the release zone, I would contend that right arm straightening in the release zone in an optimal, efficient swing is actually motivated by the increasing and overwhelming forces from the accelerating club acting on the right arm. S
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Post by imperfectgolfer on Nov 3, 2019 10:59:06 GMT -5
In 2008, both Sasho Mackenzie and Professor Robin S. Sharp developed triple-pendulum models consisting of the torso, left arm, and wrist. MacKenzie used torque parameters to match a consistent, low-handicap golfer while Sharp used torque parameters to match the three professional golfers shown in the book, "In Search for the Perfect Swing." From both models, the basic swing sequence for the downswing is torso, then arm, then wrist. Additionally, Sharp concluded that none of the three professionals had to delay the uncocking of the wrists through the use of negative wrist torque. Obviously the models were crude given that it cannot be known how much torque was actually applied through each of the three segments of the triple pendulum and how long and in what degree the torques accelerated and diminished. The Mackenzie model was briefly discussed here in the thread, "Why isn't the pivot classified as a power accumulator?" Although the topic I will address has nothing to do with this question, the pivot (torso rotation) is a power accumulator per Kelley's logic. Kelley's power accumulators consist of an action and "opposite" action, i.e., cocking/uncocking, bent arm/straight arm, pronation/supination, and arm on chest/arm off chest. The torso can be considered rotated in one direction/rotated to the other direction. MacKenzie's 2008 model, referenced on Tutelman's website via the link, www.tutelman.com/golf/swing/models3.php, assumes the release of PA 4 via the straightening of the right arm per Tutelman. I have no qualms with this statement. MacKenzie's model shows a torque at the left shoulder called "Shoulder M" as well as torque through torso rotation called Torso M. Given that the right arm was omitted from the model, MacKenzie applied slightly more torque (85 Nm) to Shoulder M (vs 80 Nm being maximum torque previously reported) to account for the release of PA 4. Tutelman stated that by doing so, MacKenzie was certainly aware of the contribution of the straightening right arm, which he didn't model. Tutleman stated that the torque than causes left arm abduction would be from either or both: 1) Shoulder M, or muscles in back of the left shoulder that "swing" the left arm 2) Right arm extension Tutelman then stated that for the left arm to separate from the chest via the use of muscles in back of the left shoulder, right arm extension must be accomplished while pulling with the left arm and without pushing with the right hand in a way that does not create an undesirable torque at the grip end of the club, which can be tricky. Except for any incidental right arm straightening during the downswing caused by body position given the use of a given hand/arc path, is the final straightening of the right arm though the release zone motivated by Shoulder M? Although the answer is that one can certainly pull/push in the release zone, I would contend that right arm straightening in the release zone in an optimal, efficient swing is actually motivated by the increasing and overwhelming forces from the accelerating club acting on the right arm. S I personally reject the value of SMK's triple pendulum model for a number of reasons as it pertains to a TGM swinging action. First of all, it measures the contribution of M shoulder to the "force" required to release of PA#4 only in the plane of left adduction => abduction when the reality is that most of the left arm motion happening during the release of PA#4 is in a downwards direction secondary to the motion of the left arm happening as a result of the left arm moving from its elevated alignment at P4 to its depressed alignment at impact. Secondly, most of the left arm abduction actually happens in the later downswing after P5.5 (when the right arm is increasingly straightening) but I think that any swing power responsible for the sequential release of PA#4 => PA#2 is mainly generated between P4 and P5.5. So, when DT writes-: "Another point to note: the large-muscle torques, the shoulder and especially the torso, continue to provide accelerating torque right through impact. In fact, the torso torque is increasing until immediately before impact." he is implying that it is contributing to clubhead speed. I disagree - because I cannot envisage how any torso torque that is being applied in the later downswing near impact can contribute to increasing clubhead speed (which I believe is secondary to the sequential release of PA#4 => PA#2). I also think that any muscular torque being applied to cause upper torso rotation during the later downswing mainly affects how open the shoulders are through impact - so Cameron Champ, who has more open shoulders at impact than Phil Mickelson, presumably applies more upper torso torque during his later downswing. That allows Cameron Champ to better be able to perform a DH-hand release action between P7 and P7.2+ than Phil Mickelson (who uses a roller subtype of non-DH-hand release action). But, the type of hand release action used between P7 and P7.2+ has not been shown to correlate with clubhead speed at impact. Why should it?
You also wrote-: "Although the answer is that one can certainly pull/push in the release zone, I would contend that right arm straightening in the release zone in an optimal, efficient swing is actually motivated by the increasing and overwhelming forces from the accelerating club acting on the right arm."
I cannot understand why you believe that the accelerating club causes right arm straightening in the later downswing. I think that right arm straightening between P5.5 and impact is mainly due to movement of the left hand/club handle (and attached right hand) in a targetwards direction so that the distance between them and the right elbow increases. If the right shoulder socket moves further downplane and the right elbow also glides further targetwards across the front of the torso between P5.5 and impact, then less right arm straightening will need to happen during the later downswing.
Jeff.
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Post by syllogist on Nov 3, 2019 18:10:30 GMT -5
Dr. Mann,
The accelerating (or moving) club is a result of torso rotation, Torso-M. The torque generated from the torso places a torque of the club. The force of the club from the torque placed on it affects the arms, one of which is the bent right arm. To see this empirically, make a moderately paced swing while trying to retain arm bend. You will notice a large force that "works back into the right arm." The centripetal force of the club is the same force that uncocks the wrists.
I agree with you that in order to be open at impact, as in Champ's swing, Torso-M must continue longer than the square-shoulder to target line impact position as shown in Tutelman's article.
In defense of the modelers like MacKenzie, they were trying to answer certain questions about the swing with models that weren't completely intractable, using torque values whose accelerations and decelerations that cannot be known, and validating as best as possible the models by matching swing positions of real golfers. Such makes discovering precise mechanics impossible. However, I do think that knowing the torque sequence with cause and effect has instructional value for golfers seeking to optimize their swings.
S
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Post by dubiousgolfer on Nov 3, 2019 21:26:49 GMT -5
Dr Mann You said "First of all, it measures the contribution of M shoulder to the "force" required to release of PA#4 only in the plane of left adduction => abduction when the reality is that most of the left arm motion happening during the release of PA#4 is in a downwards direction secondary to the motion of the left arm happening as a result of the left arm moving from its elevated alignment at P4 to its depressed alignment at impact."Question : Not sure I understand what you mean by "in the plane of left adduction => abduction" . Is this the same as the plane of the left arm moving from a 'diagonal abduction' to "diagonal adduction" (as in image below)? You said: "So, when DT writes-: "Another point to note: the large-muscle torques, the shoulder and especially the torso, continue to provide accelerating torque right through impact. In fact, the torso torque is increasing until immediately before impact." he is implying that it is contributing to clubhead speed. I disagree - because I cannot envisage how any torso torque that is being applied in the later downswing near impact can contribute to increasing clubhead speed (which I believe is secondary to the sequential release of PA#4 => PA#2)"When I look at Tutelman's underlined comments below, isn't he implying that its good instruction to feel as if the body is using increased torque all the way through impact to prevent any early deceleration between P4 and P5.5? The danger of not doing so could cause deceleration between P4-P5.5 and the clubhead might not achieve a greater speed just before release. I don't agree with Tutelmans last opinion below when he says " physics says that hand and arm motion is caused by body rotation". Maybe the physics of the models being used but not in a real golfer. -------------------------- TUTELMAN COMMENTS "Another point to note: the large-muscle torques, the shoulder and especially the torso, continue to provide accelerating torque right through impact. In fact, the torso torque is increasing until immediately before impact.[1] That is a lesson we could also learn from the double-pendulum model (see my article on accelerating through impact); but the fact that a speed-optimized model recommends it definitely reinforces the lesson." But note, however, that an accelerating torque does not assure acceleration. For instance, when M_Shoulder kicks in it actually retards the torso rotation. This is basic Newtonian physics; every action has an equal and opposite reaction. In order for the torso to exert torque M_Shoulder to release the left arm, the left arm exerts an equal and opposite torque back on the torso slowing its release. This is analogous to an effect often noted with the double pendulum model; the hands are slowed by the release of the club by a very similar mechanism occurring here. (For animations explaining the latter effect, see Rod White's article on the physics of the swing.) In fact, we can see the torso slowing its rotation in the last tenth of a second of the graph; while Q_Torso is still increasing, its slope (which is velocity) is decreasing. So the net effect is deceleration. A real live human being cannot accelerate the body to impact and not still be accelerating through impact. A golfer thinking only of accelerating to impact is going to quit accelerating before getting near impact. You can't turn off full-body acceleration in .4 milliseconds, probably not even in 100 milliseconds.CONSEQUENCES OF ANGULAR DECELERATIONAbove we discussed the angular acceleration of the body. The argument above maintains that, unless you try to accelerate the body's rotation well through impact, you will in fact lose acceleration well before impact. In golf terminology, you will "quit on the shot." This has a number of consequences: Distance actually is lost. This has nothing to do with the clubhead accelerating through the ball, but rather that less acceleration is applied to the clubhead for tens of milliseconds before impact. The clubhead is deprived of some of the accleration it would have had, in order to build up speed at impact. And clubhead speed at impact is what really matters for distance.The left wrist is cupped, rather than the proper flat or even bowed left wrist. We know that a bowed wrist at impact (or a flat wrist at the very least) is desirable for a solid hit. A cupped wrist, on the other hand, is associated with lost clubhead speed, fat or thin shots, or too-high balloon shots. It is also likely to point the clubface to the left, resulting in a pull or even a pull-hook. (Think about it this way: if the swing plane were perfectly vertical, then a cupped left wrist would add loft. Since the swing plane is not vertical but tilted, some of that "loft" turns into a left-facing angle.) 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.) -------------------------------------------
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Post by imperfectgolfer on Nov 4, 2019 1:06:53 GMT -5
Dr. Mann, The accelerating (or moving) club is a result of torso rotation, Torso-M. The torque generated from the torso places a torque of the club. The force of the club from the torque placed on it affects the arms, one of which is the bent right arm. To see this empirically, make a moderately paced swing while trying to retain arm bend. You will notice a large force that "works back into the right arm." The centripetal force of the club is the same force that uncocks the wrists. I agree with you that in order to be open at impact, as in Champ's swing, Torso-M must continue longer than the square-shoulder to target line impact position as shown in Tutelman's article. In defense of the modelers like MacKenzie, they were trying to answer certain questions about the swing with models that weren't completely intractable, using torque values whose accelerations and decelerations that cannot be known, and validating as best as possible the models by matching swing positions of real golfers. Such makes discovering precise mechanics impossible. However, I do think that knowing the torque sequence with cause and effect has instructional value for golfers seeking to optimize their swings. S You wrote-: "The accelerating (or moving) club is a result of torso rotation, Torso-M. The torque generated from the torso places a torque of the club. The force of the club from the torque placed on it affects the arms, one of which is the bent right arm. To see this empirically, make a moderately paced swing while trying to retain arm bend. You will notice a large force that "works back into the right arm." The centripetal force of the club is the same force that uncocks the wrists."
I don't believe that the torso rotation directly "places a torque on the club". I think that the torso rotation moves the left arm, and it is the movement of the left hand (which is at the peripheral end of the left arm) that torques the club as result of its motion along the hand arc path. I don't understand what you mean when you state "---- works back into the right arm". I think that the right hand (if passive and not pushing forwards) only experiences a "force" secondary to the motion of the club handle, which is being pulled by the left hand - presuming that the right hand's palm remains attached to the club handle and does not separate from the club handle as seen in Phil Mickelson's rear hand motion through impact.
Jeff.
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Post by imperfectgolfer on Nov 4, 2019 1:28:09 GMT -5
DG, You asked-: " Question : Not sure I understand what you mean by "in the plane of left adduction => abduction" . Is this the same as the plane of the left arm moving from a 'diagonal abduction' to "diagonal adduction" (as in image below)?" No. I have never previously seen the term "diagonal adduction" before, and when I refer to the plane of left arm adduction => abduction, I am referring to the plane of horizontal adduction => horizontal abduction where the left arm remains at left shoulder socket level. I think that the term "diagonal abduction" could reasonably be used to describe the combination of horizontal left arm abduction combined with left arm depression that happens during the release of PA#4, and I may start to use the term "diagonal abduction" to usefully describe the left arm motion happening during the release of PA#4.
You wrote-: "When I look at Tutelman's underlined comments below, isn't he implying that its good instruction to feel as if the body is using increased torque all the way through impact to prevent any early deceleration between P4 and P5.5?"
I see no reason to believe that DT was claiming that the torso should continue to rotate actively through impact in order to prevent left arm slowing in the early-mid downswing. I presume that he was primarily talking about the late downswing. Also, seeing that the left arm is only attached to the torso at the level of the left shoulder socket, and considering the fact that the left shoulder socket is moving upwards after P5.5, and not targetwards after P5.5, I cannot envisage how an active torso rotation after P5.5 can increase clubhead speed. However, I do think that an active torso rotation that gets the right shoulder further downplane will allow a golfer to avoid a "running-out-of-right arm" situation, which is advantageous in terms of more efficiently performing a DH-hand release action.
Jeff.
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Post by dubiousgolfer on Nov 4, 2019 6:40:08 GMT -5
DG, You asked-: " Question : Not sure I understand what you mean by "in the plane of left adduction => abduction" . Is this the same as the plane of the left arm moving from a 'diagonal abduction' to "diagonal adduction" (as in image below)?" No. I have never previously seen the term "diagonal adduction" before, and when I refer to the plane of left arm adduction => abduction, I am referring to the plane of horizontal adduction => horizontal abduction where the left arm remains at left shoulder socket level. I think that the term "diagonal abduction" could reasonably be used to describe the combination of horizontal left arm abduction combined with left arm depression that happens during the release of PA#4, and I may start to use the term "diagonal abduction" to usefully describe the left arm motion happening during the release of PA#4.
You wrote-: "When I look at Tutelman's underlined comments below, isn't he implying that its good instruction to feel as if the body is using increased torque all the way through impact to prevent any early deceleration between P4 and P5.5?"
I see no reason to believe that DT was claiming that the torso should continue to rotate actively through impact in order to prevent left arm slowing in the early-mid downswing. I presume that he was primarily talking about the late downswing. Also, seeing that the left arm is only attached to the torso at the level of the left shoulder socket, and considering the fact that the left shoulder socket is moving upwards after P5.5, and not targetwards after P5.5, I cannot envisage how an active torso rotation after P5.5 can increase clubhead speed. However, I do think that an active torso rotation that gets the right shoulder further downplane will allow a golfer to avoid a "running-out-of-right arm" situation, which is advantageous in terms of more efficiently performing a DH-hand release action.
Jeff.
Dr Mann Hasn't Dr Sasho MacKenzie taken into the account the downward component of the PA#4 torque by programming his model to have a shoulder rotational axis that is more inclined to the vertical (ie. more horizontal) than the torso (see diagram below)? So is he is using some projected angle from his left arm onto a 'Transverse Plane' that cuts through the level of his shoulders to measure Q_Shoulder (the angle between the torso and the left arm)? If you look at the last diagram below , the green vector line could represent the lead arm, the x-y plane could represent the 'Transverse Plane' going through the shoulder line. The alpha angle (ie. a projected angle from the left arm) could represent the 'Q_Shoulder' angle. ---------------- Some Details of the Model Here are a couple of pictures adapted from MacKenzie's paper, showing the 3D aspect of the model and the four ways motion can occur Three Dimensionality
The torso rotates about an axis 30º from vertical. The shoulder "hinge pin" is 50º from vertical, and stays in that orientation throughout the downswing. That's 20º more towards an upright swing plane than the torso rotation. In addition -- though #1 and #2 already constitute 3D -- the left arm is itself an axis of rotation DG
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Post by syllogist on Nov 4, 2019 6:42:59 GMT -5
Dr. Mann,
I implied that a torque is placed on the club via the acceleration of the left arm which moves as a result of torso rotation, Torso-M, since the club is held in the hands.
"Works back into the right arm" means that the torque on the club affects the right arm just as the torque on the club affects the wrists. As the club moves faster and further from its axis of rotation (torso), its mass feels heavier and the bent right arm cannot (should not) overcome the force and remain in a position of significant bend. Since this was brought up in the context of the later release of P4 in the model, the straightening of the right arm is what moves the hands, and thus arms, along the arc independent of body rotation. (The straightening of the right arm causes hand/arm travel.)
DG,
You said, "I don't agree with Tutelmans last opinion below when he says " physics says that hand and arm motion is caused by body rotation". Maybe the physics of the models being used but not in a real golfer. "
First, to clarify so that there's no confusion, hand and arm motion are one in the same as the downswing gets underway. Tutelman might as well have stated arms. Given that arm motion highly coincides with body rotation as the left arm adduction angle changes little and may actually become more acute in the beginning of the downswing, the statement is valid. If this did not happen and one were to power the arms via muscles that move the arms independent from torso rotation, then, in the first stage of the downswing, the arms would move further away from the axis of rotation and rotary speed would be sacrificed. In addition, the timing of swing events would change.
S
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Post by dubiousgolfer on Nov 4, 2019 7:54:28 GMT -5
Dr. Mann, I implied that a torque is placed on the club via the acceleration of the left arm which moves as a result of torso rotation, Torso-M, since the club is held in the hands. "Works back into the right arm" means that the torque on the club affects the right arm just as the torque on the club affects the wrists. As the club moves faster and further from its axis of rotation (torso), its mass feels heavier and the bent right arm cannot (should not) overcome the force and remain in a position of significant bend. Since this was brought up in the context of the later release of P4 in the model, the straightening of the right arm is what moves the hands, and thus arms, along the arc independent of body rotation. (The straightening of the right arm causes hand/arm travel.) DG, You said, "I don't agree with Tutelmans last opinion below when he says " physics says that hand and arm motion is caused by body rotation". Maybe the physics of the models being used but not in a real golfer. " First, to clarify so that there's no confusion, hand and arm motion are one in the same as the downswing gets underway. Tutelman might as well have stated arms. Given that arm motion highly coincides with body rotation as the left arm adduction angle changes little and may actually become more acute in the beginning of the downswing, the statement is valid. If this did not happen and one were to power the arms via muscles that move the arms independent from torso rotation, then, in the first stage of the downswing, the arms would move further away from the axis of rotation and rotary speed would be sacrificed. In addition, the timing of swing events would change. S Hi S It is sometimes difficult to decipher Dave Tutelman's comments and whether they relate to physics or his own qualitative opinions. Tutelman has made comments suggesting that the left arm is pushed around by contact with the left pec in the downswing (which is questionable because of the downward component of PA#4) But if he talking about the physics of 'Torques' on the arms/hands (and equal and opposite torques ), then he is correct. One does require a torque to the arm which , in the end, will require a torque from the ground up (and through the body). The difficulty is explaining anatomically how these torques get manifested , and I think Dr Mann's cause and effect via the pelvic rotary muscles for the hip squaring phase and other detailed muscle contractions for the 2nd phase makes sense. DG PS. Have you seen Dr Mann's article below? perfectgolfswingreview.net/TylerReview.htmlSpecifically this 3D analysis of Jon Rahm's swing. -------------------------------------------- Now, let's examine Jon Rahm's kinematic sequence graph (which I copied from that TPI video). The vertical line under the word "top" represents the start of the downswing. The red graph line represents pelvis motion. The green graph line represents thorax motion. The blue graph line represents left arm motion. Note that the pelvis starts to rotate counterclockwise during the late backswing (before the P4 position) so that the pelvis is rotating faster than the thorax at the start of the downswing. That phenomenon increases Jon Rahm's dynamic X-factor, which many golf instructors believe is a desirable phenomenon. However, that degree of torso-pelvic separation is not unusual in a professional golfer. Note that his left arm and thorax are rotating at the same speed at the P4 position, and therefore at the very start of the transition to the downswing. However, note that the blue graph line (representing left arm motion) immediately becomes much steeper than the green graph line (representing thorax motion), which means that the left arm is accelerating much faster than the thorax from the very beginning of his downswing. This observation suggests to me that his left arm is not being exclusively pulled downward-and-forward by the pivoting thorax via the left arm's attachment to the upper torso at the left shoulder socket, and that it is moving somewhat independently, and faster, than the left shoulder socket. This observation suggests to me that his left arm's downward motion at the start of his downswing is mainly being powered by his shoulder girdle muscles (both right and left) that are both causally responsible for moving the left arm in a mainly downwards direction between P4 and P5.25 (as seen in Jon Rahm's hand arc path image) and that it is not primarily due to the pivot action's counterclockwise rotation of the upper torso that passively pulls the left arm around the body via the left arm's connection to the upper torso at the left shoulder socket. It also suggests to me that the peak speed of his left arm motion (which probably happens at ~P5.5) will probably better correlate with the efficiency/speed of contraction of his shoulder girdle muscles rather than the efficiency/speed of rotation of his pelvis and upper torso. --------------------------------
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Post by syllogist on Nov 4, 2019 9:12:19 GMT -5
Hi DG,
I hadn't read Dr. Mann's suppositions but I agree that the left arm begins to move "faster" than the torso rotates. Given the constraint of hand path, the right elbow begins to straighten which, in turn, represents "independent arm movement." If some elite golfers contract shoulder girdle muscles during left arm movement, so be it - that's not an area I focus on. I'm much more interested in efficient generation of force, how and why it's harnessed, and its relationship to the clubhead "finding" the ball in the least chaotic way - if that makes sense. As the 2008 triple pendulum models suggest, "hitting from the top" (trying to accelerate the arms independently may not be the way to achieve the best results in my area of interest.
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Post by imperfectgolfer on Nov 4, 2019 10:13:45 GMT -5
DG,
You asked-: "Hasn't Dr Sasho MacKenzie taken into the account the downward component of the PA#4 torque by programming his model to have a shoulder rotational axis that is more inclined to the vertical (ie. more horizontal) than the torso (see diagram below)?"
Although SMK has tilted his shoulder pin axis to 50 degrees from vertical, I presume that he has calculated that the left arm is abducted away from that axis at a 90 degree angle to that axis (Sz). However, in many pro golfers who shallow their clubshaft a lot between P4 and P5, the hand arc path is presumably more vertically downwards and not at 90 degrees relative to the Sz axis. However, this "fact" could be leading me towards non-useful nitpicking because I personally suspect that it does not significantly affect the calculations of M shoulder torque because I presume that it is not "energy-intensive" to have a more downward hand arc path.
Jeff.
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Post by imperfectgolfer on Nov 4, 2019 10:23:02 GMT -5
S, You wrote-: ""Works back into the right arm" means that the torque on the club affects the right arm just as the torque on the club affects the wrists. As the club moves faster and further from its axis of rotation (torso), its mass feels heavier and the bent right arm cannot (should not) overcome the force and remain in a position of significant bend. Since this was brought up in the context of the later release of P4 in the model, the straightening of the right arm is what moves the hands, and thus arms, along the arc independent of body rotation. (The straightening of the right arm causes hand/arm travel.)"
I disagree with your bold-highlighted statement. I believe that the left hand (holding the club handle) moves targetwards between P5.5 and impact (when the right arm is straightening) due to the release of PA#4. The right arm must obviously straighten in order to not impede this targetward motion of the left hand/club handle from happening between P5.5 and impact. Straightening of the right arm can cause the left hand/club handle to move targetwards if the release of PA#1 is active (which happens during a TGM hitting technique), but it should not happen during a TGM swinging technique.
Jeff.
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Post by imperfectgolfer on Nov 4, 2019 10:32:11 GMT -5
Consider this SMK graph. Why does the M shoulder graph have a secondary peak between P5.5 and impact - considering the "fact" that the left slows down in the later downswing as can be seen in the following 3-D graph of Jamie Sadlowski's driver swing?
Jeff.
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Post by syllogist on Nov 4, 2019 11:15:00 GMT -5
Dr. Mann,
The M Shoulder graph shows a peak just before impact because MacKenzie used that torque in his model to increase the left arm adduction angle. He didn't model the right arm. I merely gave a logical, and in my view, more realistic reason for the increase in that angle. Of course such does not mean that one is not free to keep pulling or pushing the grip until just before impact.
Bear in mind that in order for Mackenzie to model torso and arm rotation, he had to apply separate torques to torso and arm to match rotational velocities of torso and arm in the real golfer. His torque profiles of acceleration and deceleration are arbitrary. For example, Professor Sharp assumed linear changes in his model.
You are saying that active muscular contraction to straighten the right arm causes hand travel but that forces that straighten the right arm do not? That I do not agree with.
S
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Post by dubiousgolfer on Nov 4, 2019 12:02:49 GMT -5
I'm confused about the SMK graph . So did he tweak 'torso/shoulder/arm/wrist' torques to complement the effects of a missing right arm in his model?
Did his tweaked model match the movement of a real golfers 'torso/left shoulder/left arm/left wrist' positions in space using camera images or did it just replicate the movement of the club in space (or both)?
I do not understand the usefulness of complementing the real life effect of a golfers 'right shoulder joint/arm/wrist' by adjusting the torques (and the timing of their application and duration) of the models torso and left 'shoulder/arm/wrist'. How do we know whether there is a 'Closed Loop ' phenomenon happening? That is, different combinations of torques (and subtle timing/duration of their applications) to provide the same outcome?
DG
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