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Post by dubiousgolfer on Nov 13, 2019 8:26:46 GMT -5
Found this website which imho provides useful articles on Pressure/Force/COP/Weight Shift/Vertical Forces/GRF's etc. www.swingcatalyst.com/learning-center/articlesFound there was a distinction between Weight Shift vs Pressure Shift (I thought they meant the same thing but apparently not). Unsure whether I wholly agree with the underlined part of this particular article (unless the golfer was actively trying to create some extra tension in the clubshaft by pulling up via the shoulder socket- extra parametric acceleration). More likely that the golfer is applying increasing vertical pushing forces on the ground 'reacting' to the increased 'Centrifugal Pull Force' on the hands by the increased tension in the golf shaft due to optimal 'hand speed/path; (ie. an effect rather than a cause). www.swingcatalyst.com/learning-center/articles/vertical-forcesScreenshot of animation provided by Dr. Sasho Mackenzie At this point in the golf swing, the golfer is almost entirely pulling straight up on the golf club with close to the maximum amount of force that is applied to the club at any point during the swing. In order to produce these large vertically directed forces on the club, it most likely critical that a golfer utilizes the large muscles of the lower body to push into the ground and create the appropriate reaction forces on the body that can then be transferred to the club. DG
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Post by imperfectgolfer on Nov 13, 2019 10:13:34 GMT -5
DG, I am flabbergasted to note that you stated that you didn't previously know that there is a difference between weight shift and pressure shift! I thought that you were an ardent student of my golf website's review papers. Have you not read topic 13 of the following review paper? perfectgolfswingreview.net/2014Revision.htmI wrote that review paper over 5 years ago and I clearly demonstrated the difference between weight shift and pressure shift. Those Swing Catalyst articles are simply SC-propoganda and they do not provide any "evidence" that increasing vertical GRFs under the lead foot is causally responsible for increasing clubhead speed at impact. I presume that you watched Dr. Scott Lynch's more recent videos on GRFs that he did with Brendon DeVore for his BeBetterGolf channel. They were much informative and they demonstrated to me that there are many flaws in his argument that having high vertical GRFs under the lead foot is primarily responsible for long driving distances in long-drive competitors. He even admitted that many pro golfers (eg. Gary Woodland), who drive the ball a long way, do not have high vertical COP measurements under their lead foot during their downswing action. Jeff.
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Post by dubiousgolfer on Nov 13, 2019 20:21:56 GMT -5
Many thanks Dr Mann- Obviously I didn't read all of your articles properly. So 'weight shift' is really 'mass shift' and pressure plates alone cannot differentiate between pressure caused by:
a. Movement of actual body/club mass b. By muscular forces and dynamic movements c. A mix of both a and b.
So would one need to use Doug Marsh's method to assess real 'weight shift' during the golf swing?
DG
PS. So when you mention the below in your article "Critical Update: How to Optimally Rotate the Pelvis during the Downswing" , do you mean the golfer has to move his mass over the right leg or is it a push into the ground or both?
" I believe that diagram B is very applicable to the right hip joint/femur between P4 and P4.5 if weight-pressure loading of the right leg (due to the golfer actively pushing down into the ground under the right foot) causes the right leg to become "stabilised"
*** Found your video on weight shift on you tube which answers my PS. question. I understand these are old videos and some of the content no longer reflects your evolved thinking but it does explain weight shift to the right side****
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Post by imperfectgolfer on Nov 14, 2019 10:13:45 GMT -5
Many thanks Dr Mann- Obviously I didn't read all of your articles properly. So 'weight shift' is really 'mass shift' and pressure plates alone cannot differentiate between pressure caused by: a. Movement of actual body/club mass b. By muscular forces and dynamic movements c. A mix of both a and b. So would one need to use Doug Marsh's method to assess real 'weight shift' during the golf swing? DG PS. So when you mention the below in your article "Critical Update: How to Optimally Rotate the Pelvis during the Downswing" , do you mean the golfer has to move his mass over the right leg or is it a push into the ground or both? " I believe that diagram B is very applicable to the right hip joint/femur between P4 and P4.5 if weight-pressure loading of the right leg ( due to the golfer actively pushing down into the ground under the right foot) causes the right leg to become "stabilised" *** Found your video on weight shift on you tube which answers my PS. question. I understand these are old videos and some of the content no longer reflects your evolved thinking but it does explain weight shift to the right side**** I should probably stop using the term "weight-pressure" because it can give readers the wrong impression that it signifies a weight shift (mass shift) and I should only use the term "pressure-loading". In the backswing, one uses increased "pressure-loading" of the right leg/foot to stabilise the right leg/foot, thereby enabling contraction of the right-sided lateral pelvic rotator muscles at the start of the downswing to rotate the pelvis counterclockwise away from the "stabilised" right leg/foot. It is even possible to efficiently pressure-load the right leg/foot at P4 with a left-loading pelvic motion pattern. That "weight-shift" video is outdated (I didn't even know about the existence of the lateral pelvic rotator muscles at that time) and it contains incorrect golf instructional information (eg. pushing off the right foot in a targetwards direction at the start of the downswing). Jeff.
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Post by dubiousgolfer on Nov 25, 2019 8:46:56 GMT -5
Dr Mann
You said "In the backswing, one uses increased "pressure-loading" of the right leg/foot to stabilise the right leg/foot, thereby enabling contraction of the right-sided lateral pelvic rotator muscles at the start of the downswing to rotate the pelvis counterclockwise away from the "stabilised" right leg/foot. It is even possible to efficiently pressure-load the right leg/foot at P4 with a left-loading pelvic motion pattern."
I'm finding the last underlined sentence difficult to understand . How can one still pressure-load the right leg/foot when one is also using a left-loading pelvic motion pattern?
Are you saying one can still pressure load the right leg 'enough' to stabilise and utilise the right lateral pelvic rotator muscles, even when the COP is favouring the left leg?
DG
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Post by imperfectgolfer on Nov 25, 2019 10:05:17 GMT -5
Dr Mann You said "In the backswing, one uses increased "pressure-loading" of the right leg/foot to stabilise the right leg/foot, thereby enabling contraction of the right-sided lateral pelvic rotator muscles at the start of the downswing to rotate the pelvis counterclockwise away from the "stabilised" right leg/foot. It is even possible to efficiently pressure-load the right leg/foot at P4 with a left-loading pelvic motion pattern."I'm finding the last underlined sentence difficult to understand . How can one still pressure-load the right leg/foot when one is also using a left-loading pelvic motion pattern? Are you saying one can still pressure load the right leg 'enough' to stabilise and utilise the right lateral pelvic rotator muscles, even when the COP is favouring the left leg? DG It is possible to have the a left-loading pelvic motion pattern where the pelvis is left-of-center due to a slanting right thigh, but where the COP measurement under the right foot is higher than that under the left foot - in contrast to the S&T methodology. Jeff.
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Post by dubiousgolfer on Nov 25, 2019 10:38:57 GMT -5
Dr Mann You said "In the backswing, one uses increased "pressure-loading" of the right leg/foot to stabilise the right leg/foot, thereby enabling contraction of the right-sided lateral pelvic rotator muscles at the start of the downswing to rotate the pelvis counterclockwise away from the "stabilised" right leg/foot. It is even possible to efficiently pressure-load the right leg/foot at P4 with a left-loading pelvic motion pattern."I'm finding the last underlined sentence difficult to understand . How can one still pressure-load the right leg/foot when one is also using a left-loading pelvic motion pattern? Are you saying one can still pressure load the right leg 'enough' to stabilise and utilise the right lateral pelvic rotator muscles, even when the COP is favouring the left leg? DG It is possible to have the a left-loading pelvic motion pattern where the pelvis is left-of-center due to a slanting right thigh, but where the COP measurement under the right foot is higher than that under the left foot - in contrast to the S&T methodology. Jeff. Do you mean like Jack Nicklaus's pelvic motion in the below image where at P4, the centre of his pelvis has moved slightly left ? DG
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Post by imperfectgolfer on Nov 25, 2019 12:41:52 GMT -5
It is possible to have the a left-loading pelvic motion pattern where the pelvis is left-of-center due to a slanting right thigh, but where the COP measurement under the right foot is higher than that under the left foot - in contrast to the S&T methodology. Jeff. Do you mean like Jack Nicklaus's pelvic motion in the below image where at P4, the centre of his pelvis has moved slightly left ? DG Yes. When one has a large degree of pelvic rotation (like Jack Nicklaus) it is not unusual for the pelvis to shift leftwards - even though one is primarily pressure-loading the right leg/foot. Jeff.
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Post by dubiousgolfer on Nov 25, 2019 18:51:03 GMT -5
Many thanks Dr Mann
DG
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Post by dubiousgolfer on Apr 17, 2020 8:22:14 GMT -5
Dr Mann
Apologies but I need to revisit this thread again relating to your statement below on your website (How to Optimally Rotate the Pelvis during the Downswing)
" a pro golfer 'stabilises' his right leg/foot by pressing down into the ground"
I cannot see how a golfer can increase right foot pressure vertically into the ground without activating the gluteus maximus, which I assume will straighten the leg and elevate the right side of the pelvis.
However ,if the golfer wishes to retain a flexed 'stabilised' right leg, I can perceive the muscles (specifically the vastus lateralis , gluteus maximus) gradually increasing in isometric contraction as a 'mass weight' is increased above them.
So can we assume that the increasing 'mass weight' is caused by the torso loading process + the added weight of arms/club in the backswing?
There is one other issue that bothers me and that is the timing of the relaxing of this isometric contraction so that it doesn't impede the rotation of the pelvis CCW rotation after the hip squaring phase.
DG
PS. On reflection, the timing of the 'relaxation' of the isometric contraction should automatically be felt as the torso 'unloads' and the arms move targetwards.
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Post by imperfectgolfer on Apr 17, 2020 9:22:52 GMT -5
DG,
One does not need to activate the right gluteus maximus in order to load the right leg/foot at P4, as one can simply activate the right knee extensors (quadriceps) to isometrically straighten the right leg against the resistance of the ground. Applying pressure against the ground does not involve adding any additional "mass" to the right side of the center point between the feet. It is even possible to press the right foot firmly against the ground while using a leftwards-centralised upper torso loading pattern.
The same scenario applies to the impact position where some golfers may have most of their COP under their left foot despite having a lot of secondary axis tilt and right lateral bend where most of their "mass" is to the right of the center of one's stance.
Jeff.
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Post by dubiousgolfer on Apr 17, 2020 11:41:56 GMT -5
DG, One does not need to activate the right gluteus maximus in order to load the right leg/foot at P4, as one can simply activate the right knee extensors (quadriceps) to isometrically straighten the right leg against the resistance of the ground. Applying pressure against the ground does not involve adding any additional "mass" to the right side of the center point between the feet. It is even possible to press the right foot firmly against the ground while using a leftwards-centralised upper torso loading pattern. The same scenario applies to the impact position where some golfers may have most of their COP under their left foot despite having a lot of secondary axis tilt and right lateral bend where most of their "mass" is to the right of the center of one's stance. Jeff. Dr Mann - I'm still a bit 'dubious' about the kinetics involved because: 1. I mentioned that I could still rotate my hips relatively freely 'clockwise/anti-clockwise' standing on one leg (which is quite a large pressure loading on my leg and hip socket) 2. Your images 3 and 4 below show that pressure loading your right arm against the wall moved your shoulder socket rightwards . Unless there was an opposing force pushing from right to left on your shoulder socket , it cannot remain stable in space . That same principle can be applied to the right leg pushing increasingly into the ground and I cannot visualise where that opposing force will come from (unless it was mass weight forces) . But as far as I am aware, the COM of pro golfers do not shift much in the golf swing so it isn't 'mass weight forces' so something else could be happening. 3. COP ratio readings do not necessarily mean large forces being applied through the leg (because surface area of foot contact with ground is also a variable between both feet during the golf swing). How about another possibility? Could the activation of the iliopsoas muscle from P4-P5 be the major factor in stabilising the right hip joint in space, if it was dominantly used to apply a clockwise torque on the right femur in the hip socket (with secondary right 'foot/ground' horizontal forces preventing any actual external rotation) ? Then the golfer could still use the pelvic rotary muscles to rotate the pelvis counterclockwise . Is that a possibility? DG PS. I've looked at several hip/pelvis articles and the illipsoas is a weak external rotator (so not really feasible acting alone) . Just need a condition at P4-P5 where the external rotation torque acting on the femur is balanced by the horizontal ground forces . That means the femur is stabilised in space and contraction of the right pelvic rotary muscle will then rotate the pelvis & hip socket around the femoral head.
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Post by imperfectgolfer on Apr 18, 2020 9:10:16 GMT -5
DG,
I find your comments and reasoning to be incomprehensible.
Jeff.
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Post by dubiousgolfer on Apr 18, 2020 9:34:44 GMT -5
DG, I find your comments and reasoning to be incomprehensible. Jeff. Dr Mann I'm not surprised as I'm finding the literature on 'muscles/joint movements/forces & reaction forces at the joints' difficult to fathom. Basically , I'm trying to figure out how the right hip can be stabilised in space while the pelvic rotary muscles are activated in the hip squaring phase from P4-P5 . You've mentioned pressure loaded to keep it stable (and I know it can be physically accomplished) but I'm trying to figure out what biomechanical action (on the kinetics side) is responsible for that stabilisation. From what I've read , it seems that the activation of the iliopsoas muscle keeps that right hip socket close to the tush line from P4-P5 (see middle image and joint force direction). Figure 3. The hip joint reaction force is calculated during a simulation of hip flexion (middle) and hip extension (right) activities DG
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Post by dubiousgolfer on Apr 19, 2020 13:18:02 GMT -5
Dr Mann Is this correct below that the isometric contraction of the hamstrings can keep the leg flexed and are also responsible for the raising and lowering of the thigh from a flexed position? DG
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