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Post by dubiousgolfer on Aug 8, 2021 21:20:14 GMT -5
SMK seems to have suggested a few new things in this video (but most of the content has been repeated before).
1. Consistency of ROC seems to be more important than magnitude of ROC for shot dispersion 2. At 56:20 - 59:44 . That a faster contracting muscle produces less force . LPGA players can move rotate their hips quicker but not create as much angular momentum as PGA men.
*Hmmm..... this is a bit confusing*
Angular Momentum = Moment of Inertia x Angular Velocity
If LPGA players have more angular velocity of the hips than PGA men but are creating less 'Angular Momentum' this means the MOI (rotational inertia ) is much less.
They are basically applying less push force against the ground to just swivel their pelvis while not engaging the torso (ie. larger hula-hula). Therefore they are only rotating the pelvis (small MOI) very fast but not the torso, whereas the men are pushing against the ground far more while also engaging their pelvis and torso (a much larger MOI) because of smaller hula-hula.
The much larger MOI of 'pelvis+ engaged upper torso' in PGA men (even with a slightly inferior angular velocity) generates a net higher angular momentum than LPGA women which can then be used to create clubhead speed.
Note: I thought TPI data also showed on average LPGA ribcage rotation greater than PGA men. If that is the case , then the MOI of the LPGA 'pelvis+torso' must still be (on average) far inferior to PGA men.
3. That a players mass can have a small effect on the ability to create clubhead speed.
DG
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Post by imperfectgolfer on Aug 10, 2021 16:06:55 GMT -5
DG,
I do not learn anything new and useful by thinking about laws of physics (regarding angular momentum) when it comes to trying to understand the differences in pivot motion between PGA and LPGA golfers. I did not gain any new insights from that SMK interview video.
Jeff.
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Post by dubiousgolfer on Aug 10, 2021 22:26:24 GMT -5
Dr Mann I agree but it did pique my interest in the Force -Velocity curve and I've now learned more about how muscles work (fascinating stuff). I was so confused by SMK's explanation why PGA players are able to generate more clubhead speed than LPGA with slower pelvic/ribcage rotation that I sent him an email. It didn't seem to tally with Dr Phil Cheethams explanation in his X-factor podcast or what we thought was the reason in an older thread (ie. LPGA women are less efficient with their release of PA#2 than PGA men). SMK - Seems to infer that PGA men are able to create greater angular momentum from ground reaction forces than LPGA women. He rotated his pelvis loosely but rapidly to replicate an LPGA type pivot seemingly inferring that type of movement doesn't create much angular momentum. Then he forcefully pressed his leg into the ground turning the pelvis and his upper torso almost together to demonstrate what PGA men are doing. Not sure what that demonstration proves apart from the fact that LPGA women have more hula-hula than PGA men so how does that explain the superior clubhead speed generated by PGA men? Phil Cheetham - I've interpreted his reasoning to be that PGA men create more force/torque because their 'X-factor' stretch is faster than LPGA women in the kinematic sequence . I am assuming it is some combined effect of the X-factor stretches during transition and downswing between 'Pelvis/Torso', 'Torso/Shoulder girdle' , 'Shoulder girdle/Wrists' . I've tried to learn more about how to interpret the kinematic sequence graphs from this article below and I can now see how the Force-Velocity curve could be used to assess efficient force production. www.philcheetham.com/variations-in-the-downswing-kinematic-sequence-of-golf-stretching-riding-fanning/DG Note: I might have understood SMK pelvis/torso rotating almost together as a type of 'Riding' as explained in Phil Cheethams link above (extract below). "Examine the middle graph first; if the two curves rise very closely together then these two body segments are turning at about the same speed and accelerating at approximately the same rate (at least for the early portion of the downswing). That means there is no relative speed difference between the two body segments so the thorax is “riding” on the pelvis and the core muscles are in isometric contraction."
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Post by imperfectgolfer on Aug 11, 2021 9:31:31 GMT -5
Phil Cheetham wrote-: " Phil Cheetham - I've interpreted his reasoning to be that PGA men create more force/torque because their 'X-factor' stretch is faster than LPGA women in the kinematic sequence . I am assuming it is some combined effect of the X-factor stretches during transition and downswing between 'Pelvis/Torso', 'Torso/Shoulder girdle' , 'Shoulder girdle/Wrists'." I cannot understand the idea of an X-factor stretch existing between the torso/shoulder and shoulder girdle/wrists as being a factor in generating clubhead speed. This is the results of the Zheng study. PGA golfers do have a slightly faster upper torso rotation, but the largest difference is in the speed of lead wrist uncocking.
Jeff.
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Post by dubiousgolfer on Aug 11, 2021 10:55:59 GMT -5
Dr Mann Yes , there is a stark difference in angular rotation of the wrist which does suggest PA#2 release is a major factor. Here is an example of Dr Phil Cheetham's analysis of an LPGA player which I found interesting and does infer some cause and effect X-factor stretch between Pelvis and Torso to create clubhead speed. I wish I could see the end result and whether that LPGA player did increase her clubhead speed after she completed her Core muscle improvement training. philcheethamthe3dguy.blogspot.com/2009/Saturday, December 12, 2009 Changing the Kinematic Sequence with Biofeedback Drills I am currently working with an LPGA player to improve her efficiency in the kinematic sequence and get her more swing speed. Remember that the kinematic sequence is the graph of turning speed of pelvis (red), thorax (green), arm (blue) and club (brown). It is measured in degrees/second along the vertical axis and shows time through the swing along the horizontal axis. (Check my earlier blog articles for more detail or amm3d.com). After capturing her swing with the AMM3D golf motion capture system, I analyzed it with the TPI 3D biomechanics report. Below is the graph of her kinematic sequence with a driver. There are many “expert” characteristics in the graph; transition order is good, peaking order is good, accelerations and decelerations generally look good too. Although she transitions in the correct order; pelvis, thorax, arm, club; you can see that she pauses with her hips before transition (the red curve flattens out), also her transition period is too long, there is minimal downswing loading of any joint and her turning speeds are fanning early in the downswing. This pause really limits the speed contribution of the “stretch-shorten cycle” of the muscles. In an ideal stretch-shorten cycle there should be virtually no time between the eccentric/concentric contraction phases of the muscle; this “amortization” phase or pause should be as short as possible. The lack of downswing joint loading means she is leaving a lot of power on the table and the fanning of the curves means that the relative speed between the body segments is increasing, reducing the amount of force that can be produced in each muscle; (see my article on amm3d.com regarding Riding, Stretching, Fanning, I’ll post it soon on this blog too). So while she was still in the AMM3D system we began using real-time audio biofeedback to see if we could change the sequence and teach her not to pause at the top; hence allowing the smooth acceleration into and out of transition and improving the stretch-shorten cycle. We set the audio tone to sound if she achieved a good core stretch at the beginning of downswing and worked on half backswing drills. Very quickly she was able to coordinate her downswing loading (aka “X-Factor Stretch”) and the curves became smoother before and after transition. We also saw that thorax, arm and shaft “rode” up together (good energy transfer); however, her total transition time was still very long. This means that the drill was definitely successful but that we still need to work on lessening the transition time from about 0.17 seconds to about 0.8 seconds. This will require a combination of half swing drills and strengthening of the core muscles so they can support fast pelvis firing without leaving the thorax behind. Check out the kinematic sequence graph below, this is from one of the half swing drills. Drills can definitely change the kinematic sequence very quickly, but conditioning exercises will also need to be done in the gym to support the change. The trick will be to transfer this to the full swing. --------------------- DG PS. I'm confused about his comment " work on lessening the transition time from about 0.17 seconds to about 0.8 seconds." Isn't that an increase not a lessening? The transition time for the Pelvis is when it crosses the zero horizontal angular velocity line . Therefore he must have made a typo error and meant 0.08 secs. He basically wanted the LPGA player to have a faster stretch shorten cycle between pelvis/torso during transition.
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Post by imperfectgolfer on Aug 11, 2021 14:57:29 GMT -5
Cheetham must have meant 0.08 seconds.
I don't think that it is easy to radically change a golfer's kinematic pattern especially if a golfer has excessive hula hula flexibility that allows the pelvis to outrun the upper torso - as Cheetham proposed for that LPGA golfer.
Jeff.
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Post by dubiousgolfer on Aug 12, 2021 12:56:21 GMT -5
At last I've found the research article by Anderson in 2007 (I haven't read all 149 pages). But he did use 500 golfers in their research with a Hcp of 5 or less. The 'Conclusion' on page 143 did not follow a Proximal-Distal order in angular kinematics, kinetic energy or angular momentum. The only connection point to show a consistent delay in peaks between neighbouring segments was the wrist, or the interface between arms and club segments. That the Arm angular momentum peaks before all other segments and it is unlikely that the Arms segment receives an angular momentum transfer from either the torso or hip segments in the downswing. www.yumpu.com/en/document/read/10580132/anderson-speed-generation-in-the-golf-swing-thesisDG Found the pdf at this link below central.bac-lac.gc.ca/.item?id=MR33963&op=pdf&app=Library&oclc_number=551878509Note : It seems that I found this article before back in 2018 so apologies as I must be going over old ground again. But I think I'm more knowledgeable now to understand parts of the research paper and how it might conflict with Phil Cheetham or SMK's opinions. I've tried reading through this detailed and complex research paper but its beyond my capability. He even recommended a polo grip or hockey (split hands) grip type of swing to increase clubhead speed . I think overall this research has limited value on how to perform a golf swing but it does seem to prove that transfer of energy and angular momentum in a Proximal -Distal body segment sequence is not being primarily used. He is saying that the golf swing is actually like a double pendulum with the body being the proximal segment (ie. hips/torso/arm) and the club being the distal one.
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