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Post by dubiousgolfer on Jun 25, 2022 9:06:02 GMT -5
I re-read the article (link) below and now understand a few things a golfer should not try and do. sashomackenzie.com/publications/delayedrelease.pdfExamining the delayed release in the golf swing using computer simulation (E. J. Sprigings and S. J. Mackenzie)1. Not try and hold the PA2 angle with active use of the wrists only2. If a golfer tries to hold the lag angle using active wrist torque only until point of release and then revert to passive wrists, the loss of clubhead speed will be 13% less than if the golfer had used a 'natural release'. SMK didn't detail exactly what a natural release was, but I suspect it's using passive wrists other than the hand couple required (as a stopper) to prevent the jack-knifing of the club during the downswing and just allowing the 'In Plane MOF' to trigger the release of the PA#2. So basically, if the golfer tries to hold the PA2 angle using the wrists only, he must not resort to having passive wrists after release happens and will need to actively use them to prevent a substantial decrease in clubhead speed by impact. He does mention that Pro golfers use other means to retain lag (PA2 angle) other than actively using their wrists and I am assuming that means altering the hand path to prevent early PA#2 release. DG
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Post by imperfectgolfer on Jun 25, 2022 9:17:46 GMT -5
I re-read the article (link) below and now understand a few things a golfer should not try and do. sashomackenzie.com/publications/delayedrelease.pdfExamining the delayed release in the golf swing using computer simulation (E. J. Sprigings and S. J. Mackenzie)1. Not try and hold the PA2 angle with active use of the wrists only2. If a golfer tries to hold the lag angle using active wrist torque only until point of release and then revert to passive wrists, the loss of clubhead speed will be 13% less than if the golfer had used a 'natural release'. SMK didn't detail exactly what a natural release was, but I suspect it's using passive wrists other than the hand couple required (as a stopper) to prevent the jack-knifing of the club during the downswing and just allowing the 'In Plane MOF' to trigger the release of the PA#2. So basically, if the golfer tries to hold the PA2 angle using the wrists only, he must not resort to having passive wrists after release happens and will need to actively use them to prevent a substantial decrease in clubhead speed by impact. He does mention that Pro golfers use other means to retain lag (PA2 angle) other than actively using their wrists and I am assuming that means altering the hand path to prevent early PA#2 release. DG DG, You wrote-: " So basically, if the golfer tries to hold the PA2 angle using the wrists only, he must not resort to having passive wrists after release happens and will need to actively use them to prevent a substantial decrease in clubhead speed by impact." How is it biomechanically possible to use the wrists actively after PA#2 has been released during a pivot-induced TGM swinging action? Jeff.
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Post by dubiousgolfer on Jun 25, 2022 11:20:47 GMT -5
I re-read the article (link) below and now understand a few things a golfer should not try and do. sashomackenzie.com/publications/delayedrelease.pdfExamining the delayed release in the golf swing using computer simulation (E. J. Sprigings and S. J. Mackenzie)1. Not try and hold the PA2 angle with active use of the wrists only2. If a golfer tries to hold the lag angle using active wrist torque only until point of release and then revert to passive wrists, the loss of clubhead speed will be 13% less than if the golfer had used a 'natural release'. SMK didn't detail exactly what a natural release was, but I suspect it's using passive wrists other than the hand couple required (as a stopper) to prevent the jack-knifing of the club during the downswing and just allowing the 'In Plane MOF' to trigger the release of the PA#2. So basically, if the golfer tries to hold the PA2 angle using the wrists only, he must not resort to having passive wrists after release happens and will need to actively use them to prevent a substantial decrease in clubhead speed by impact. He does mention that Pro golfers use other means to retain lag (PA2 angle) other than actively using their wrists and I am assuming that means altering the hand path to prevent early PA#2 release. DG DG, You wrote-: " So basically, if the golfer tries to hold the PA2 angle using the wrists only, he must not resort to having passive wrists after release happens and will need to actively use them to prevent a substantial decrease in clubhead speed by impact." How is it biomechanically possible to use the wrists actively after PA#2 has been released during a pivot-induced TGM swinging action? Jeff. Dr Mann I don't really know for certain but I suspect his model (which only has one lead arm and wrist torque generator), includes the possible wrist torque that could be applied by the trail arm too. So theoretically, couldn't the trail wrist be used to temporarily add to the release of PA#2? DG PS . Would probably be like a temporary hit action PA#1 type release but it would need impeccable timing and it would have to happen during the slow phase of the release of PA#2 and before the club shaft has forward bend. cloud2.golfloopy.com/wp-content/uploads/2013/02/TW-Downswing-Combo-sm1.gif
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Post by imperfectgolfer on Jun 25, 2022 15:59:45 GMT -5
DG, You wrote-: " So basically, if the golfer tries to hold the PA2 angle using the wrists only, he must not resort to having passive wrists after release happens and will need to actively use them to prevent a substantial decrease in clubhead speed by impact." How is it biomechanically possible to use the wrists actively after PA#2 has been released during a pivot-induced TGM swinging action? Jeff. Dr Mann I don't really know for certain but I suspect his model (which only has one lead arm and wrist torque generator), includes the possible wrist torque that could be applied by the trail arm too. So theoretically, couldn't the trail wrist be used to temporarily add to the release of PA#2? DG PS . Would probably be like a temporary hit action PA#1 type release but it would need impeccable timing and it would have to happen during the slow phase of the release of PA#2 and before the club shaft has forward bend. cloud2.golfloopy.com/wp-content/uploads/2013/02/TW-Downswing-Combo-sm1.gifYou seem to be implying that a straightening right wrist could apply a positive PA#2 releasing force during the release of PA#2 between P5.5 => P6.5+. That would need an active right wrist straightening action and a positive hand couple torque being produced by the trail hand between P5.5 => P6.5, but we know that the trail hand's positive hand couple torque becomes negative after P5.5 in a pivot-induced TGM swinging action. Jeff.
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Post by dubiousgolfer on Jun 25, 2022 18:29:32 GMT -5
Dr Mann Yes, this is confusing! The SIM2 experiment (ie. delayed wrist until release and then positive wrist torque) is described below in his article: The second simulation condition (SIM-2) employed a delayed release strategy where an active wrist torque was used to restrain any change in the relative angle of the wrist joint until that time deemed to be optimal by the search method. At the precise moment when the release point was reached, the torque generator at the wrist was actively recruited to develop torque that aided the release process.Here are the graphs for SIM-2. He also said the following: It is important to note that the point of ‘natural’ release of the clubshaft in a golf swing is a function of the angular acceleration of the segments proximal to the wrist joint. A low handicap golfer may be able to delay the natural release point of the club past that of a high hand golfer by employing a highly coordinated sequence of torso and arm segment accelerations. However, in the present paper, we have addressed the use of a delayed release technique that strictly relies on a resistive wrist torque to delay the natural uncocking of the wrist joint. In SIM-1, the optimization procedure activated a counter-clockwise wrist torque when the arm segment reached an angle of 22° below a horizontal reference line through the shoulder joint. For SIM-2 the optimization procedure activated a counter-clockwise wrist torque 0.05 s later when the arm segment had rotated counter-clockwise through an additional 3.25°. Thus, the duration of a forced delayed release is very small and would, most likely, be difficult to measure in actual practice.If I've interpreted the above correctly: 1. For the natural release swing SIM-1, there was still a need to apply a positive wrist torque at ~P5.5. Why didn't he provide a graph similar to the SIM-2 one above so we could compare the positive wrist torque value and duration? 2. The SIM2 (delayed release and positive wrist torque) had a release point almost imperceptibly later in the downswing (the lead arm moves down an extra 3.25 degrees), which required a positive wrist torque at that point of release all the way into the impact to optimise clubhead speed (look at the wrist torque graph above for SIM2). But we know that the hand couple goes negative after ~P6 as per the inverse dynamic graphs in SMK's vimeo video. There certainly seems to be a contradiction unless I am missing something. DG PS. Could it be that the wrist generated torque in SMK's model is not the same as the hand couple in the inverse dynamic graphs above? The hand couple value above is what is exerted on the grip about the mid-hand point. The wrist torque in that SIM-1 experiment is about the wrist joint not the mid-hand-point.
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Post by imperfectgolfer on Jun 25, 2022 19:55:52 GMT -5
Dr Mann Yes, this is confusing! The SIM2 experiment (ie. delayed wrist until release and then positive wrist torque) is described below in his article: The second simulation condition (SIM-2) employed a delayed release strategy where an active wrist torque was used to restrain any change in the relative angle of the wrist joint until that time deemed to be optimal by the search method. At the precise moment when the release point was reached, the torque generator at the wrist was actively recruited to develop torque that aided the release process.Here are the graphs for SIM-2. He also said the following: It is important to note that the point of ‘natural’ release of the clubshaft in a golf swing is a function of the angular acceleration of the segments proximal to the wrist joint. A low handicap golfer may be able to delay the natural release point of the club past that of a high hand golfer by employing a highly coordinated sequence of torso and arm segment accelerations. However, in the present paper, we have addressed the use of a delayed release technique that strictly relies on a resistive wrist torque to delay the natural uncocking of the wrist joint. In SIM-1, the optimization procedure activated a counter-clockwise wrist torque when the arm segment reached an angle of 22° below a horizontal reference line through the shoulder joint. For SIM-2 the optimization procedure activated a counter-clockwise wrist torque 0.05 s later when the arm segment had rotated counter-clockwise through an additional 3.25°. Thus, the duration of a forced delayed release is very small and would, most likely, be difficult to measure in actual practice.If I've interpreted the above correctly: 1. For the natural release swing SIM-1, there was still a need to apply a positive wrist torque at ~P5.5. Why didn't he provide a graph similar to the SIM-2 one above so we could compare the positive wrist torque value and duration? 2. The SIM2 (delayed release and positive wrist torque) had a release point almost imperceptibly later in the downswing (the lead arm moves down an extra 3.25 degrees), which required a positive wrist torque at that point of release all the way into the impact to optimise clubhead speed (look at the wrist torque graph above for SIM2). But we know that the hand couple goes negative after ~P6 as per the inverse dynamic graphs in SMK's vimeo video. There certainly seems to be a contradiction unless I am missing something. DG PS. Could it be that the wrist generated torque in SMK's model is not the same as the hand couple in the inverse dynamic graphs above? The hand couple value above is what is exerted on the grip about the mid-hand point. The wrist torque in that SIM-1 experiment is about the wrist joint not the mid-hand-point. Isn't SMK's model purely theoretical and only computer-based and he does not explain how an active wrist torque could practically be applied in a "real life" golf swing action? Also, SIM-2 and SIM-3 have similar clubhead speeds at impact, and there is only a 0.02 seconds difference in the duration of the downswing. Jeff.
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Post by dubiousgolfer on Jun 25, 2022 20:19:19 GMT -5
Dr Mann
SIM-1 and SIM-2 have similar CHS at impact.
It seems amazing that in his model (which I admit is purely theoretical and computer based) shows that by delaying the release by 0.02 secs (using negative wrist torque) means the golfer having to use positive wrist torque all the way to impact. But even in the 'natural release' swing he states that his model still had to generate a positive wrist torque.
I've sent him an email asking whether he has the wrist torque graph for the SIM-1 (natural release model swing). I've also asked him why there is a positive wrist torque in his SIM-2 graph (from release to impact) when his inverse dynamic graphs show negative hand couple from around P6 to impact.
I'm not sure whether you remember a thread, maybe over a year ago, where you thought that the middle of the lead wrist joint should be used as a reference point in 'inverse dynamic' calculations rather than 'mid-hand-point'. If the golf scientists could provide inverse dynamics graphs using that lead wrist joint as a reference point, I am wondering whether it would show a positive wrist torque/couple all the way from release to impact? I've asked SMK that question too in my email and hope he replies.
DG
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Post by dubiousgolfer on Jun 28, 2022 21:18:20 GMT -5
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Post by dubiousgolfer on Jul 2, 2022 6:48:56 GMT -5
I now have an answer about why both research articles with the 3 lever model was showing a positive wrist torque into impact (to optimise clubhead speed within the theorised constraints of human muscle activation). But it wasn't from SMK but Dave Tutelman , who has always been very helpful.
-------------- I'll start by pointing out that this paper was a forward dynamics study, not inverse dynamics. So was Sasho's doctoral thesis. Not a coincidence either; Eric Sprigings and Rob Neal were mentors to Sasho. In fact, Sprigings was Sasho's thesis advisor.
Optimizations are forward dynamics operations. In inverse dynamics, the goal is to match the mathematical model to the kinematics (motion) of an observed golfer's swing, and see the kinetics (force and torque) that was required for the match. Forward dynamics, OTOH, is to input the kinetics and see what kinematics it produces. Optimization consists of tweaking the input (forces and torques) to maximize or minimize something about the kinematics -- typically maximize clubhead speed.
The optimization is limited by the assumed constraints on what the golfer can do. For instance, suppose we assume that the golfer is capable of exerting wrist torque even at the angular velocity of the club at impact. If that is our assumption, it should not be a surprise that exerting such wrist torque just before impact would increase the clubhead speed at impact. But there is lots of evidence that such an assumption would be incorrect. So we can optimize without a realistic constraint and, not surprisingly, get an unrealistic answer. For instance, it is easy to plug in a simple mathematical expression for the torque-velocity curve of something like T=K/V -- an asymptotic curve. If that is the assumption you start with, then you are quite likely to have an optimization that ends up with positive wrist torque at impact. OTOH, if you let the torque-velocity curve cross the zero-axis (that is, torque goes negative if the hands can't keep up), then the angular acceleration has to come from somewhere other than wrist torque.
And that is what inverse dynamics has taught us. Inverse dynamics doesn't have to assume a constraint. It is directly observing the kinematics and finding the kinetics that would make it happen. And those kinetics, for all decent golfers, has negative wrist torque at impact.
And yes, forward shaft bend is part of that observation. I know Rob Neal agrees with this, because he liked my critique of Nesbit's shaft bend paper enough to make an appointment to meet me. We played a round of golf and then spent a few hours over dinner talking about biomechanics.
So then... Faldo. I would be surprised if Faldo didn't have forward shaft bend at impact, implying negative wrist torque. But it is pretty likely that he didn't have as much forward bend as other, longer hitting pros. Faldo was notorious for choosing accuracy over distance, in spite of his impressive height and build, and he did not emphasize whipping the club through impact at all. Still, I don't believe that Faldo had positive wrist torque at impact, and the old 2000 study you cite just made a casual observation -- NOT an inverse dynamics computation based on a motion capture of Faldo's swing.
Hope that answers your question.
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DG
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