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Post by imperfectgolfer on Sept 9, 2013 10:36:06 GMT -5
See this Jeffy forum thread. jeffygolf.com/showthread.php?787-Questions-for-DuffeyKM obviously harbors a great deal of antipathy towards MD and he wants to show that he knows much more than MD about golf swing biomechanics. MD may not be able to cope with KM's attacks, but I can easily show that KM is wrong or that his arguments are weakly incomplete. KM asked this question-: " What muscles cause the pelvis to rotate?" MD answered-: "I t is a nice question, but the real answer can not be given here. That particular movement is pretty complex - almost certainly it is a combination of femoral external rotation on one side and internal rotation on the other, so you have almost opposite muscle groups acting from one side to another. In addition, so don't have many muscles that create a pure rotation, for example, the gluteus maximus acts to externally rotate the femur, but it also also acts as a powerful hip extensor (its better known function), so that action must be coupled with a hip flexor.
The answer would be a nice, first year PT graduate student presentation that would likely take an hour or two if done well." KM then responded-: " We've got the most intelligent and knowledgeable readership on this forum. Many of us have been there done that. So we know truth vs. marketing or plain BS. Pelvic rotation can come from direct muscle contractions and from indirect movements of the hip/legs which I have written extensively about. The answer I was looking for pertains to the first method and requires only citation of a certain Russian nuclear physicist and his theory of human locomotion. It would take 10 seconds if you knew the answer.
Could one of our readers please help Duffey with the answer? " Note how he is taunting MD. KM implies that the correct explanation is Gracovetsky's spine engine model. However, KM is wrong!!! Look at KM's article - www.aroundhawaii.com/lifestyle/health_and_fitness/2011-04-whats-a-hip-turn-part-2.htmlIn the section on the transition and early downswing pelvic motion, he uses Sam Snead and Ben Hogan as examples. He has very nice animated images (that I cannot show here) of Sam Snead and Ben Hogan performing their early downswing pelvic motion, which I have labelled the "left hip clearing action ala Hogan" move or the "hip squaring" move. That move does not involve the spine engine at all. It simply involves a counterclockwise rotation of the left thigh that moves the left femoral head (and therefore the left acetabular socket) away from the ball-target line and then away from the target. The spine is not involved in this motion, although the "spine engine" does transmit forces from the pelvic motion to the mid-upper torso. Then, KM argues that there is an alternative method of moving the pelvis - leg movements - and he claims to have described those actions. Where? I presume that he is referring to this article - www.aroundhawaii.com/lifestyle/health_and_fitness/2011-04-whats-a-hip-turn-part-2.html - where he writes about dual external rotation of both hip joints. However, he doesn't really explain how to get into a state of dual hip joint ER (hip squaring phenomenon - Sam Snead sit-down look). In other words, he doesn't provide the sequence of biomechanical events that really affect the pelvis at the transition. I think that his explanation about pelvic motion at the transition is very unsatisfactory and incomplete. Jeff.
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Post by konrad on Sept 9, 2013 19:44:01 GMT -5
The more KM posts at Jeffy's the more credibility he's losing IMO.
KM and Jeffy...two peas in a pod!
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Post by chipitin on Sept 9, 2013 23:25:50 GMT -5
The more KM posts at Jeffy's the more credibility he's losing IMO. KM and Jeffy...two peas in a pod! You got that right! KM isn't about real debate and discussion, he's only trying to make Mike D. look bad. The funny thing is Mike answered the question about what makes the pelvis rotate and K.M. because he is so bent on trying to show Mike doesn't know what KM. knows missed the answer and then tried to say Mike doesn't know. K.M. comes off as arrogant and mean spirited, but isn't that the main theme of that Micro forum. The whole thing is so transparently a farce, asking endless questions with no other purpose other than showing Mike as a clueless biomechanist according to K.M. The amazing thing is Dr. Mann has shown much of Kelvin's work and theories to be full of holes. Would be nice if Mike D. did join here.
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Post by imperfectgolfer on Sept 9, 2013 23:33:40 GMT -5
Konrad, I agree that KM is simply embarrassing himself. MD replied as follows in the Jeffy forum thread-: " The answer to your question "what muscles cause the pelvis to rotate?" is long and complex It does not take 10 seconds - your answer, which lists zero of the roughly 20 muscles that cross the hip and directly create hip rotation and probably at least 30-40 that will be involved in that motion- is a quite general answer to a somewhat different question.." MD is correct to state that the answer is very complex. KM implies that he knows the answer, but he doesn't. He often gets the biomechanics totally wrong. In that article, he even claims the following-: " For example, during the squat move, the firing of the anterior fibers of the gluteus maximus produces external rotation of the hip while the posterior fibers are being stretched to create a SSC for the hip extension later in the downswing." I would like to seem him prove that wild claim. The idea that one part of a muscle can be contracting while another part of the same muscle is being is passively stretched so that it can subsequently contract more efficiently at a later stage has no scientific validity. KM's answers are also devoid of any explanatory content. For example, in the next paragraph, KM states-: "What occurs in transition in both leg/hips is external rotation". That's true in golfers like Sam Snead and many PGA tour golfers. But, why does that occur, and how would you teach a golfer to achieve that goal? KM provides no explanation! One doesn't need to know the muscle groups involved - one simply has to understand the overall biomechanics. Here is my explanation. Consider Badds at the P4 position. Note that his pelvis has rotated clockwise about 45 degrees during his backswing, and his left femur is relatively neutral relative to the pelvis when his left knee is moved inwards (centrally). The more the left knee bends and moves away from the target during the backswing action, the more the left femur must be in an internally rotated position at the P4 position, but if a golfer only bends the left knee slightly during the backswing, then he will look like Badds. At the start of the downswing, note that he shifts slightly targetwards, and the left knee undergoes the most lateral movement (representing a left femur abduction action). That left femur abduction action will drive the left femur into a condition of external rotation if the left knee moves more targetwards than the left hip joint. While this is happening, the left femur is also rotating counterclockwise (as part of the "left hip clearing action ala Hogan" biomechanical phenomenon) and that will drive the left femoral head, and therefore the left acetabular socket backwards (away from the ball-target line) and also away from the target. That left hip joint motion will drive the left buttocks towards the tush line. In other words, the pelvis becomes square because the left hip joint is driven towards the tush line, and the left femur becomes externally rotated because the left knee moves more targetwards than the left hip joint (which is actually driven away from the target due to the counterclockwise rotation of the left femur). One can see this same phenomenon in Jack Nicklaus's early downswing. JN really had a very bent left knee at the P4 position, so his left femur could be internally rotated (relative to the pelvis) - image 2. Note how much his left knee moves targetwards between image 2 and image 4. While this is happening, his left hip joint is actually moving away from the target due to the counterclockwise rotation of the left femur. The combination of those two biomechanical phenomena will cause the left femur to be externally rotated by P5 (end of the hip squaring phase) - image 3. Now, let's deal with the interesting part. Why does the right femur become externally rotated at the P5 position (rather than internally rotated)? I believe that it will only happen if the right femur is passive and if one doesn't actively drive the right knee towards the ball during the early downswing as some golf instructors teach. If one drives the right knee towards the ball in the early downswing, then that will cause the right femur to become internally rotated. I think that a better biomechanical technique is to hold the flex in the right knee by "holding" one's end-backswing right leg position. That keeps the right buttocks against the tush line, and prevents a premature right pelvis spinning motion due to a premature active rotary motion of the right pelvis away from the tush line. If one keeps the right acetabular joint in place (in more-or-less the same position that it occupied at the P4 position) during the transition by keeping the right femoral head more-or-less in place - and this happens if one pushes off a motionless, but weight-pressure loaded, right leg at the transition, then the right femur becomes externally rotated relative to the pelvis because the pelvis is squared by the "left hip clearing action ala Hogan" phenomenon. In other words, the right femoral head remains relatively stationary, while the left femoral head is actively driving the left acetabular socket (left hip joint) back away from the ball-target line - you can see the "fact" that the right hip joint remains relatively stationary in image 3 of the JN sequence. Expressed differently, the pelvis becomes square by P5 due to the "left hip clearing action ala Hogan" biomechanical phenomenon while the right femur becomes externally rotated due to the fact that the pelvis moves its position relative to the near-stationary right femoral head. Expressed in yet another way, one can think of the "hip squaring phase" that occurs between P4 and P5 as being actively driven by active motions of the left leg that consequently/causally move the pelvis, while the right femoral head, and right hip joint, is kept temporarily near-stationary. The right femur will become internally rotated much later in the downswing when the right buttocks moves away from the tush line. I think that if a golfer understands my biomechanical description, then he doesn't have to know which muscles are actually involved. Only pseudo-scientists (like KM) need to fill their articles with many anatomical photos, and simple-minded descriptions of changes in anatomical positions. Those anatomical photos don't help one understand when a muscle is active versus passive, or whether a joint alignment (between two adjoining bones) changes due to an active movement of the distal bone while the proximal bone remains stationary versus an active movement of the proximal bone while the distal bone remains stationary. KM infers "forces" when he sees golfers in different positions as they move from P4 to P5 and then to P6 --- etc; but he seemingly has no understanding as to which of those "forces" are more likely to be active versus passive. Jeff.
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Post by imperfectgolfer on Sept 10, 2013 8:44:21 GMT -5
Justin Tang wrote the following in the Jeffy forum thread-: "Not Kelvin but I for one am keen to know these muscles. I find it helpful in teaching someone specific movements when one is able to help identify the responsible muscles or muscular region versus giving vague instructions.
I think its great that you have chosen to come over to our little community where truth always trumps fiction. "
I think that JT is making the same mistake as KM/Jeffy. I know of no value in describing the names of muscles when teaching a golfer how to swing a golf club. Can anyone think of why it would be helpful to name muscles involved in any pelvic rotational/translational motion when teaching a student golfer how to move his pelvis?
Jeff.
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Post by konrad on Sept 10, 2013 18:07:18 GMT -5
Konrad, I agree that KM is simply embarrassing himself. Jeff. Kelvin 
Join Date Feb 2012 Posts 301 What is the right trail hip movement sequence of a tour player? Tell us what movements the movements are in the backswing and downswing. And don't tell us it will take 6 hours. I think all of us here would like to know how much you know about the golf swing. So answer this and we're done with the questions. Get your graphs out and tell us what's going on in a very simple way.
Could you tell us why you need to be here? If you don't like answering questions, then you can leave.This is what I'm talking about. Mike Duffey should respectfully decline answering any more KM questions and never post at that pathetic website again. The reality of the situation is Kelvin Miyahira is a Hawaiian public driving range teaching pro who primarily teaches golfers with poor swings. For him to to claim he's an expert on elite tour player golf swings because he's spent some time analyzing YouTube videos is ridiculous at best. At least meet some of these tour players and get to know them and take your own video in a way that truly reveals what a player is thinking, the type of shot he's actually hitting and the quality of that shot being hit. Anything else is purely guessing and at best personal opinion. As you said, he rarely backs up any of his claims with any solid biomechanics. You're right Jeff, Kelvin is making a fool of himself and now with this new machismo he's expressing to someone who is obviously learned in his field is folly. I recall one time Kelvin saying Jeff Martin was the foremost authority on the analysis of Ben Hogan's golf swing. Just that statement alone is very telling how delusional these two guys are when it comes to them trying to be authorities on anything golf. I hope Mike does come here to NGI and start posting, because he's doing no one any good, including himself, by directing any attention to KM and JM.
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Post by chipitin on Sept 10, 2013 18:10:36 GMT -5
I agree 100%!
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Post by konrad on Sept 10, 2013 18:17:08 GMT -5
This idea that the left and right hip can both be in external rotation in the early downswing is folly IMO. Just doesn't happen. I can appreciate the notion that the right hip and right femur are externally rotated at P4 and the golfer has an intention of holding that position as the left femur begins to externally rotate towards the target. Any proposal that the right hip and femur externally rotate further from the P4 position as the left hip and femur go into ER is incorrect. Just look at the sequence photos of Nicklaus. If image 2 is P4, it is OBVIOUS to me that his right pants pocket has definitely moved towards the ball target line and his right knee has gone further into flexion in image 3 which appears to be P4.5. That is not an ER movement in any way. Jeff, I believe you put the blue and yellow lines on those images illustrating the movement of the sacrum. How can the sacrum move that much away from from the target and the right hip and femur be in ER at the same time? They can't. KM stating that Sam Snead's squat move is ER taking place in both the right and left hip is a flawed idea/observation IMO.
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Post by imperfectgolfer on Sept 10, 2013 21:32:35 GMT -5
Konrad, You wrote-: " This idea that the left and right hip can both be in external rotation in the early downswing is folly IMO. Just doesn't happen." I respectfully disagree. Let's consider Sam Snead's early downswing pelvis and thigh motion. I captured 4 images from KM's Sam Snead animated sequence - from P4 (image 1) to P5 (image 4). I have added a diagram - representing the orientation of the pelvis and each thigh as viewed from a face-on perspective. The blue line represents the tush line - the right buttocks is against the tush line at the P4 position. The red line represents the front of the pelvis and its orientation. The green line represents the front of each thigh and its orientation. The dotted grey line represents the reference line that defines if the thigh is internally/externally rotated relative to each hip socket joint. It is drawn at 90 degrees relative to the pelvis line. The curved red arrow shows the directional motion of the left hip joint when a golfer uses a "left hip clearing action ala Hogan" maneuver. The curved green arrow represents the translational motion of the left knee in a targetwards direction at the start of the early downswing. Image 1 - P4 position. Note that the right thigh is internally rotated, while the left thigh is externally rotated. Image 2 - P4.3 position. The left knee is moving targetwards, and the left thigh is starting to rotate counterclockwise. The left hip joint is moving towards the tush line. At this time point, the right thigh is still internally rotated, and the left thigh is externally rotated. Image 3 - P4.7 position. Note that the right thigh has moved from an internally rotated position to a near-neutral position - because the change in pelvis orientation angle is greater than the change in right thigh orientation angle. Image 4 - P5 position - end of the hip-squaring phase. The left pelvis has been pulled back to the tush line, and now the pelvis is square to the ball-target line. Note that both thighs are externally rotated at this time point - when Sam Snead is in his "sit-down" look. Note that the right thigh becomes externally rotated because the degree of change in pelvis orientation angle exceeded the degree of change in right thigh orientation angle during the early downswing. Jeff.
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Post by virtuoso on Sept 11, 2013 11:09:42 GMT -5
I think you nailed the analysis Jeff. It doesn't matter if the femur is moving away from the pelvis or the pelvis is moving away from the femur. It's external rotation in each instance.
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Post by imperfectgolfer on Sept 11, 2013 21:44:51 GMT -5
Virtuoso,
You wrote-: "It doesn't matter if the femur is moving away from the pelvis or the pelvis is moving away from the femur. It's external rotation in each instance."
We perceive that reality in the same way.
Addendum added later: It is not really moving away/towards because that represents abduction and adduction. It is whether the anterior thigh is more rotated outwards than 90 degrees relative to the front of the pelvis to be correctly labelled "external rotation" - irrespective of whether it is the pelvis or femur that is responsible for the differential degree of rotation.
Another point is that it is easy to make the mistake of using the wrong referential points. For example, Konrad stated regarding those Jack Nicklaus' photos-: "I can appreciate the notion that the right hip and right femur are externally rotated at P4". However, how does he know that the right femur is externally rotated? Relative to what? It is obvious that the right thigh appears to have rotated clockwise, and that will cause some observers to state that it is externally rotated - but that is only true with reference to the outside enviroment eg. ball-target line or tush line. It is not necessarily externally rotated relative to the pelvis. To determine that "fact" one needs to establish a reference axis for the pelvis, and the appropriate axis would be a line drawn between the center of the hip joints, and that line should be parallel to the front of the sacrum and also parallel to a line drawn between the anterior superior iliac spines of each pelvic crest. When one uses that line as the reference point, then it becomes obvious that the right femur is internally rotated at the P4 position.
Another point that is important to one's understanding of the downswing pelvic motion is realizing that the right hip joint (right femoral head and acetabular socket) is relatively stationary between P4 and P5 (during the "left hip clearing action ala Hogan" pelvic motion). That allows one to think of the pelvic motion between P4 and P5 being like a door closing with the hinge joint for the door being located at the right hip joint area that is in close proximity to the tush line. When the door closes, the left buttocks moves back to the tush line, where the right buttocks is located. What allows one to keep the right hip joint area nearly stationary during the P4-P5 time period is the "fact" that the right leg is dynamically weight pressure-loaded at the transition. KM doesn't discuss any of these issues in his articles on pelvic motion - and he only describes what happens visually (eg. dual external rotation of both thighs) without explaining why it happens.
Jeff.
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Post by imperfectgolfer on Sept 12, 2013 11:10:14 GMT -5
KM asked MD how the 3-D systems measure spine movements. He wanted to know how many markers they used over the spine.
MD replied as follows-: "In our system, 10. But as you point out, we typically look at motion of the pelvis, motion of the upper torso, and then calculate the difference between those two segments. We say that difference is spread out through the vertebrae between those two segments. We do not look at motion at an individual vertebra. It is not likely that there could be much movement within the spine that wouldn't be captured using this process. There are a few methods out there that use multiple markers along the spinal column that do this, but to my knowledge this is not being done with a golf application."
KM then replied-: "Ummm, that's not representative of the spine movements then."
I don't understand KM's perspective. If MD has 10 markers aligned along the length of the spine, then he is generating a lot of data regarding the movement of the 10 markers that are aligned along the length of the spine. He may be grouping/bunching his data for a selective interpretation of the movement of the upper torso relative to the lower torso. However, he could study his spine marker data more closely to get a better idea of how the spine is spiraling/bending between the T1 vertebra and the L5 vertebra. I don't think that his data collection would necessarily be inferior to video analysis using multiple viewing angles. So, what point is KM trying to establish?
Jeff.
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Post by tomdavis76 on Sept 12, 2013 12:19:21 GMT -5
KM asked MD how the 3-D systems measure spine movements. He wanted to know how many markers they used over the spine. MD replied as follows-: " In our system, 10. But as you point out, we typically look at motion of the pelvis, motion of the upper torso, and then calculate the difference between those two segments. We say that difference is spread out through the vertebrae between those two segments. We do not look at motion at an individual vertebra. It is not likely that there could be much movement within the spine that wouldn't be captured using this process. There are a few methods out there that use multiple markers along the spinal column that do this, but to my knowledge this is not being done with a golf application." KM then replied-: " Ummm, that's not representative of the spine movements then." I don't understand KM's perspective. If MD has 10 markers aligned along the length of the spine, then he is generating a lot of data regarding the movement of the 10 markers that are aligned along the length of the spine. He may be grouping/bunching his data for a selective interpretation of the movement of the upper torso relative to the lower torso. However, he could study his spine marker data more closely to get a better idea of how the spine is spiraling/bending between the T1 vertebra and the L5 vertebra. I don't think that his data collection would necessarily be inferior to video analysis using multiple viewing angles. So, what point is KM trying to establish? Jeff. You misread Duffey's post. He doesn't have 10 markers "along the spine", just markers at "either end" of the spine.
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Post by imperfectgolfer on Sept 12, 2013 19:18:07 GMT -5
Jeffy,
In post #6 of the relevant Jeffy-forum thread, MD stated 10. I quoted the reply in an unedited manner and he replied as follows-: "In our system, 10."
Where do you get the idea that he is only using two markers - at the top and bottom of the spine?
Jeff.
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Post by tomdavis76 on Sept 12, 2013 20:20:51 GMT -5
Jeffy, In post #6 of the relevant Jeffy-forum thread, MD stated 10. I quoted the reply in an unedited manner and he replied as follows-: " In our system, 10." Where do you get the idea that he is only using two markers - at the top and bottom of the spine? Jeff. I didn't say "two markers", Duffey wasn't specific. But in post #8, he confirms that there are not markers running along the spine. "As I said, if you want to look at movement between individual vertebrae, our systems rarely do that. If you want to know what happen at either end, we do that. What would be great is if you gave us a specific and useful example of what can do what you say." His initial response in post #6, which you quoted, was a bit misleading, IMO. But he makes it clear in the following sentences that markers are not along the spine. "But as you point out, we typically look at motion of the pelvis, motion of the upper torso, and then calculate the difference between those two segments. We say that difference is spread out through the vertebrae between those two segments. We do not look at motion at an individual vertebra. It is not likely that there could be much movement within the spine that wouldn't be captured using this process. There are a few methods out there that use multiple markers along the spinal column that do this, but to my knowledge this is not being done with a golf application."
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