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Post by chipitin on Sept 5, 2013 0:53:16 GMT -5
The biomechanists know nothing according to Jeffy yet he's happy to say they agree with Kelvin's second firing theory. Except they don't the way Kelvin laid it out.
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Post by chipitin on Sept 5, 2013 1:03:34 GMT -5
Below is what Jeffy thinks constitutes agreement with Kelvin on the second firing. If you notice Mike D. basically leads Jeffy by his nose and lets him in on how the second firing is done.
Up until that point on Jeffy's forum Kelvin on facebook in 300 + posts according to M.D. never had the translation and tilt and extension as separate, he had it all as one pure motion about the pelvis vertical axis. Kelvin never had it right, that's a fact.
Mike Duffey Mike Duffey is offline
Join Date Aug 2013 Posts 29
Ok, so if you are confirming that the second fire constitutes motion other than pure (about the pelvis vertical axis) pelvis rotation - for example hip extension and/or pelvis posterior tilt, then I am happy to agree with you and I can tell you that you have cleared up what 300+ posts in two threads on FB did not clear up. This seems like great progress.
You are correct that those motions are not presented in the downswing kinematic sequence graph, which is on page 5 of the AMM biomechanics report. They are on page 11. That information is on pages 9 and 10 in our report and is also on page 10 of the GBD report.
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Post by imperfectgolfer on Sept 5, 2013 8:59:10 GMT -5
Chipitin,
You refer to the AMM and GBD reports. Have you read those reports? Are they publicly available?
The biomechanists may be measuring pelvic rotation as the degree of rotation of the pelvis around a vertical axis. However, the pelvis never rotates around any vertical axis and it changes its 3-D orientation continuously during the downswing as a result of the "left hip clearing action ala Hogan". Using a 3-D machine, one could "interpret" that 3-D pelvic motion from a variety of different/arbitrary axes, but I cannot understand how that type of interpretation is more helpful than visually viewing a golf swing from a variety of viewing angles. Has any biomechanist shown that they have discovered "something" new about pelvic motion that is not discernible using videos taken from multiple angles?
Jeff.
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Post by chipitin on Sept 5, 2013 12:11:38 GMT -5
Jeff -
What you see on video is rotation and translation as one. Rotation, by definition, cannot be translation. Furthermore, rotation, in this context, by definition is around an axis. There was a big debate about which axis to use for the machines (ex. screw axis, etc.) to determine pelvic rotation. Don't fall into the error that Kelvin fell into by merging rotation and translation. (In fact, Kelvin tried to define the biomechanists definition of rotation as "narrow" because his error was exposed by them.) Big difference between translation and rotation and the fact that the left side of the illiac crest moves back and up doesn't mean there's increased rotation per se of the pelvis.
One 2D Video cannot accurately represent rotation. It can show rotation and translation merged together, but biomechanist want to see the movement in 3D or else they would be crucified for missing the obvious that rotation and translation are different (but often found together in a golf swing). You can either guess with one 2D video or try to be more precise with a 3D system like AMM or GBD.
AMM and GBD are 3D systems. There are over 200 readings from one swing on AMM and the body is digitized before the golfer swings. It isn't K-Vest where the location of the sensor determines the readings. I don't have them and they aren't publicly available. Contrary to popular thought, it's very difficult for elite golfers to show up and be tested by a biomechanists.
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Post by chipitin on Sept 5, 2013 12:20:18 GMT -5
Jeff- just a side note.
AMM measures the pelvis in the local axis of the pelvis, not a vertical axis. That's why digitization is so important with AMM, to get where the bones are actually located.
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Post by chipitin on Sept 5, 2013 12:22:07 GMT -5
Kelvin and Jeffy cannot possibly do any of this thru 2d video. That's the reason Kelvin has made errors he used K-vest as his 3d experience and that's just not going to cut it.
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Post by imperfectgolfer on Sept 5, 2013 12:33:47 GMT -5
Chipitin,
I am fully aware that what I am seeing on video with respect to pelvic motion is a combination of translation and rotation. I don't feel a need to precisely separate them into their component parts in order to better understand golf swing biomechanics. I don't believe that there is any value in trying to determine any precise quantitative value for the rotary component (which is complex because different 3-D biomechanists harbor different opinions regarding the appropriate/optimumum axis for measurement). I can simply view a golfer's swing from different angles (eg. face-on, DTL, upline, back view and birds-eye view) and I then have a clear mental picture of how his pelvis is moving in space. I have personally never read a 3-D report that made me understand a golfer's swing action in a better way than the technique of simply viewing multiple videos from different viewing angles. If the 3-D (or 4-D) biomechanists believe otherwise, then I would like to examine their reasoning. I would like to know if there are any "facts" that I do not understand regarding golf swing biomechanics - that has been unearthed by 3-D machines?
Jeff.
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Post by chipitin on Sept 5, 2013 12:39:18 GMT -5
That's fine. I guess you would have to contact them then to find that out.
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Post by virtuoso on Sept 5, 2013 13:15:57 GMT -5
Jeff, you should just request an invite on the facebook page and go talk to them.
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Post by imperfectgolfer on Sept 5, 2013 16:13:43 GMT -5
Virtuoso,
I probably don't know how to get invited to join the closed group. I did send an e-mail to Nick (who I believe owns the group forum) via facebook's internal e-mail system, and I also sent an e-mail to his personal golf blog website's address, but I never received a reply.
Jeff.
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Post by tomdavis76 on Sept 5, 2013 19:49:11 GMT -5
Chipitin, I am fully aware that what I am seeing on video with respect to pelvic motion is a combination of translation and rotation. I don't feel a need to precisely separate them into their component parts in order to better understand golf swing biomechanics. I don't believe that there is any value in trying to determine any precise quantitative value for the rotary component (which is complex because different 3-D biomechanists harbor different opinions regarding the appropriate/optimumum axis for measurement). I can simply view a golfer's swing from different angles (eg. face-on, DTL, upline, back view and birds-eye view) and I then have a clear mental picture of how his pelvis is moving in space. I have personally never read a 3-D report that made me understand a golfer's swing action in a better way than the technique of simply viewing multiple videos from different viewing angles. If the 3-D (or 4-D) biomechanists believe otherwise, then I would like to examine their reasoning. I would like to know if there are any "facts" that I do not understand regarding golf swing biomechanics - that has been unearthed by 3-D machines?
Jeff. What you are doing is qualitative analysis, which is what Kelvin does. The biomechanists simply quantify what the the qualitative analyst asks them to measure. I can see where a quantitative analysis that "benchmarks" elite golfers could be useful in analyzing the swings of non-elites, but it doesn't appear that any of the biomechanists have done that. It also is clear that they don't spend much time challenging their methodology or assumptions. "Biomechanists" do not seem to display the characteristics found in researchers in the "hard sciences".
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Post by tomdavis76 on Sept 5, 2013 19:54:07 GMT -5
The biomechanists know nothing according to Jeffy yet he's happy to say they agree with Kelvin's second firing theory. Except they don't the way Kelvin laid it out. Cray- They know how to measure using their system, and they have measured (and, as a result, recognize) the movements involved in the second fire. Beyond that, they don't know much about the golf swing!
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Post by chipitin on Sept 5, 2013 19:55:33 GMT -5
You believe anything which is a big problem for you. Also the qualatative analysis done by Dr. Mann seems to be quite different in its conclusions compared to Kelvin's... why is that Jaffaray?
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Post by chipitin on Sept 5, 2013 19:57:58 GMT -5
The biomechanists know nothing according to Jeffy yet he's happy to say they agree with Kelvin's second firing theory. Except they don't the way Kelvin laid it out. Cray- They know how to measure using their system, and they have measured (and, as a result, recognize) the movements involved in the second fire. Beyond that, they don't know much about the golf swing! Jaffaray- they are not teachers and don't pretend to be like some others do. Also pure rotation and translation and rotation combined are 2 different things, now you know!
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Post by tomdavis76 on Sept 5, 2013 20:03:01 GMT -5
You believe anything which is a big problem for you. Also the qualatative analysis done by Dr. Mann seems to be quite different in its conclusions compared to Kelvin's...[/b] why is that Jaffaray?"Quite different"? Please elaborate. His critiques are quite modest relative to the broad scope of Kelvin's published work and, for the most part, reflect his desire to find fault in others to provoke "discussion" so he has others to play with.
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