|
Post by dubiousgolfer on Jun 19, 2021 7:00:07 GMT -5
I've found the explanation for why a lateral movement of the shoulder socket could increase clubhead speed. I bought Jorgensen's book 'The Physics Of Golf' and its explained in his topic titled 'Five Experiments'. Coincidentally , it's similar to a previous post of mine quite awhile ago but I didn't take into account the increased speed caused by the braking action (but this is explained in Jorgensen's book). DG The thread where I offered an explanation is here. newtongolfinstitute.proboards.com/thread/805/reach-maximal-speed-sooner-downswing?page=3I've just provided a general approximated description of the kinetics below but obviously one needs to understand how eccentric forces can cause rotation.
|
|
|
Post by dubiousgolfer on Jun 21, 2021 10:01:03 GMT -5
Here is another video by Dr Scott Lynn analysing Kyle Berkshire ground reaction forces (quite interesting).
So having a quick pelvis rotation doesn't necessarily equate to high rotational (torque) ground reaction forces (see 19:10 - 21:17). Dr Lynn said he doesn't fully understand how that could happen for the Thai golfer mentioned (who has quicker pelvis rotation than Rory McIlroy) without him possibly losing contact with the ground while he spun his hips.
How can a golfer spin his pelvis so fast with small torque ground reaction forces? Couldn't this be a superior ability to contract the pelvic girdle muscles while he weight pressured his right leg and hip joint from P4-P5? There would be no need to apply high active shear forces (via the feet) to make the pelvis rotate , but just enough vertical ground force to stabilise the right leg/hip joint while the pelvic girdle muscles contracted.
DG
|
|
|
Post by imperfectgolfer on Jun 21, 2021 16:42:42 GMT -5
I've found the explanation for why a lateral movement of the shoulder socket could increase clubhead speed. I bought Jorgensen's book 'The Physics Of Golf' and its explained in his topic titled 'Five Experiments'. Coincidentally , it's similar to a previous post of mine quite awhile ago but I didn't take into account the increased speed caused by the braking action (but this is explained in Jorgensen's book). DG The thread where I offered an explanation is here. newtongolfinstitute.proboards.com/thread/805/reach-maximal-speed-sooner-downswing?page=3I've just provided a general approximated description of the kinetics below but obviously one needs to understand how eccentric forces can cause rotation. I cannot understand why you have the braking force operating at the level of the left shoulder socket. When MA/TR/SL talk about a braking force they refer to the pelvis braking so that it does not continue to glide left-laterally towards the target - and it is secondary to a negative horizontal GRF happening at the level of the left foot, which requires that a large vertical GRF is simultaneously being generated under the left foot. I do not understand how one can brake the left-lateral pelvis sway motion via a negative horizontal GRF being generated under the lead foot without generating a large vertical GRF at the same time. That pelvis braking action potentially allows a moment arm to operate around a braking point that is at the level of the left pelvic crest, which causes the left-sided mid-upper torso to rotate counterclockwise and thereby elevate the left shoulder socket (presuming that the left side of the mid-upper torso can significantly extend, which depends on a golfer's spinal flexibility). As the left shoulder socket elevates between P5.5 => P7 it can increase the MoF acting centripetally at the level of the club handle and it can potentially increase the speed of release of PA#2. I suspect that the efficacy of this phenomenon is dependent on a golfer's flexibility and that it will work best in a golfer who can arch his upper thoracic spine away from the target so that his head moves downwards-and-away from the target while he simultaneously acquires a large amount of right lateral bend.
I am not surprised that SL cannot explain why that Thai golfer can generate large pelvic rotary speeds without first generating a large "spin" torque - because he does not take into account the possibility that the pelvis can be induced to rotate counterclockwise via the activation of the right-sided lateral pelvic rotator muscles and not solely via the horizontal GRFs being generated under the feet (right forefoot pushing away from the ball-target line while the left forefoot pushes towards the ball-target line). Jeff.
|
|
|
Post by imperfectgolfer on Jun 21, 2021 17:11:28 GMT -5
I am assiduously studying the golf swings of on-top pro golfers to try and find an example of a golfer whose trail elbow is higher than the lead elbow during the early-mid downswing. I have not found an example. Here are two prototypical examples of on-top pro golfers. Patrick Reed Note that his trail elbow is higher than his lead elbow at P4, but it drops below the level of the lead elbow at P4.5, P5 and P5.5 - even though he is using a punch elbow motion with the trail elbow in a position of rear-linkage at P5.5. Angel Cabrera Note that his trail elbow is higher than his lead elbow at P4, but it drops below the level of the lead elbow at P4.5, P5 and P5.5 - even though he is using a punch elbow motion with the trail elbow in a position of rear-linkage at P5.5. An interesting new insight - note that they both have more trail forearm supination at P5.5 than they had at P4- but their trail palm still looks like it is facing groundwards. I now believe that it is biomechanically due to the fact that have their trail wrist well extended and significantly radially deviated, which causes the trail wrist to be rotated counterclockwise due to the presence of a trail wrist circumductory roll motion. That fact, when combined with an on-top trail hand position, causes the trail palm to face groundwards - and it does not necessarily mean that their trail forearm is pronated at P5.5.
Jeff.
|
|
|
Post by dubiousgolfer on Jun 21, 2021 18:00:28 GMT -5
Dr Mann
From the videos I've seen Dr Lynn does say that golfers generate large vertical GRFs while the braking GRFs occur and some of the 'Swing Catalyst' graphs do seem to validate that claim.
I am assuming that when a golfer extends his legs and pushes horizontally against the ground away from the target that it helps move his whole body targetward (that includes his left shoulder socket).
I am therefore also assuming that the reverse can occur when the golfer pushes his legs against the ground towards the target, that it will help brake his body's targetward movement (including his left shoulder socket).
I personally think that your statement below is the cause of some of the grf forces (not the other way around).
"I suspect that the efficacy of this phenomenon is dependent on a golfer's flexibility and that it will work best in a golfer who can arch his upper thoracic spine away from the target so that his head moves downwards-and-away from the target while he simultaneously acquires a large amount of right lateral bend."
DG
PS. My previous posted image showing MOF relates to the assisted release of PA#4 .
|
|
|
Post by dubiousgolfer on Jun 21, 2021 18:16:30 GMT -5
I am assiduously studying the golf swings of on-top pro golfers to try and find an example of a golfer whose trail elbow is higher than the lead elbow during the early-mid downswing. I have not found an example. Here are two prototypical examples of on-top pro golfers. Patrick Reed Note that his trail elbow is higher than his lead elbow at P4, but it drops below the level of the lead elbow at P4.5, P5 and P5.5 - even though he is using a punch elbow motion with the trail elbow in a position of rear-linkage at P5.5. Angel Cabrera Note that his trail elbow is higher than his lead elbow at P4, but it drops below the level of the lead elbow at P4.5, P5 and P5.5 - even though he is using a punch elbow motion with the trail elbow in a position of rear-linkage at P5.5. An interesting new insight - note that they both have more trail forearm supination at P5.5 than they had at P4- but their trail palm still looks like it is facing groundwards. I now believe that it is biomechanically due to the fact that have their trail wrist well extended and significantly radially deviated, which causes the trail wrist to be rotated counterclockwise due to the presence of a trail wrist circumductory roll motion. That fact, when combined with an on-top trail hand position, causes the trail palm to face groundwards - and it does not necessarily mean that their trail forearm is pronated at P5.5.
Jeff.
Dr Mann Angel Cabrera's trail palm doesn't look as if its facing groundwards at P5.5. DG
|
|
|
Post by imperfectgolfer on Jun 21, 2021 18:51:01 GMT -5
I am assiduously studying the golf swings of on-top pro golfers to try and find an example of a golfer whose trail elbow is higher than the lead elbow during the early-mid downswing. I have not found an example. Here are two prototypical examples of on-top pro golfers. Patrick Reed Note that his trail elbow is higher than his lead elbow at P4, but it drops below the level of the lead elbow at P4.5, P5 and P5.5 - even though he is using a punch elbow motion with the trail elbow in a position of rear-linkage at P5.5. Angel Cabrera Note that his trail elbow is higher than his lead elbow at P4, but it drops below the level of the lead elbow at P4.5, P5 and P5.5 - even though he is using a punch elbow motion with the trail elbow in a position of rear-linkage at P5.5. An interesting new insight - note that they both have more trail forearm supination at P5.5 than they had at P4- but their trail palm still looks like it is facing groundwards. I now believe that it is biomechanically due to the fact that have their trail wrist well extended and significantly radially deviated, which causes the trail wrist to be rotated counterclockwise due to the presence of a trail wrist circumductory roll motion. That fact, when combined with an on-top trail hand position, causes the trail palm to face groundwards - and it does not necessarily mean that their trail forearm is pronated at P5.5.
Jeff.
Dr Mann Angel Cabrera's trail palm doesn't look as if its facing groundwards at P5.5. DG His trail palm does not look like it is facing groundwards at P5.5 - but that is due to the camera angle where the camera is positioned well below the level of his waist and where the camera is looking upwards at him. Here is a swing video where the DTL camera angle is more neutral, and higher than waist level. Stop the video at the 0:15 minute time point when he is at his P5.5 - P6 position. Jeff.
|
|
|
Post by dubiousgolfer on Jun 21, 2021 19:10:17 GMT -5
Many thanks Dr Mann
This video below is even better to show the trail palm position between P5.5-P6.0 and confirms it is pointing more groundwards.
DG
|
|
|
Post by dubiousgolfer on Jun 22, 2021 8:00:46 GMT -5
Dr Mann With reference to what you said below in the previous post "I am not surprised that SL cannot explain why that Thai golfer can generate large pelvic rotary speeds without first generating a large "spin" torque - because he does not take into account the possibility that the pelvis can be induced to rotate counterclockwise via the activation of the right-sided lateral pelvic rotator muscles and not solely via the horizontal GRFs being generated under the feet (right forefoot pushing away from the ball-target line while the left forefoot pushes towards the ball-target line)." I'm surprised that the 'Swing Catalyst' didn't show an increased reactive 'counter clockwise ground torque' mainly in the right foot for that Thai golfer (from an above view). I wonder if Dr Lynn just analysed the net horizontal forces from each foot rather than what is called the individual 'foot contact moments' (see Dr Kwon's image in link below). -------------------- Foot Contact Moments The foot contact moments are the GRMs directly acting on the feet due to the torsional interactions between the feet and the ground. These moments are the smallest in magnitude among the moments acting on the body during the swing. The foot contact moments act on the feet in the counterclockwise direction in the backswing and in the early part of the downswing but turns clockwise near the impact. This is how a pelvic rotator muscle contraction torque would translate to the reactive ground foot torque. DG
|
|
|
Post by imperfectgolfer on Jun 22, 2021 9:05:18 GMT -5
Dr Mann With reference to what you said below in the previous post "I am not surprised that SL cannot explain why that Thai golfer can generate large pelvic rotary speeds without first generating a large "spin" torque - because he does not take into account the possibility that the pelvis can be induced to rotate counterclockwise via the activation of the right-sided lateral pelvic rotator muscles and not solely via the horizontal GRFs being generated under the feet (right forefoot pushing away from the ball-target line while the left forefoot pushes towards the ball-target line)." I'm surprised that the 'Swing Catalyst' didn't show an increased reactive 'counter clockwise ground torque' mainly in the right foot for that Thai golfer (from an above view). I wonder if Dr Lynn just analysed the net horizontal forces from each foot rather than what is called the individual 'foot contact moments' (see Dr Kwon's image in link below). -------------------- Foot Contact Moments The foot contact moments are the GRMs directly acting on the feet due to the torsional interactions between the feet and the ground. These moments are the smallest in magnitude among the moments acting on the body during the swing. The foot contact moments act on the feet in the counterclockwise direction in the backswing and in the early part of the downswing but turns clockwise near the impact. This is how a pelvic rotator muscle contraction torque would translate to the reactive ground foot torque. DG It could also be possible that the amount of foot torque being generated under the right foot is less when it happens in reactive response to contraction of the right sided lateral pelvic rotator muscles - compared to the situation when a golfer deliberately pushes the right foot back away from the ball-target line in order to generate a horizontal GRF (which is different to the counterclockwise foot contact moments shown in the Kwon diagram, which are much less significant and much smaller in magnitude). Jeff.
|
|
|
Post by dubiousgolfer on Jun 22, 2021 9:39:01 GMT -5
Dr Mann
Yes , that is a very real possibility . I have actually sent Dr Lynn another email referring him to your chapter.
"Critical Update: How to Optimally Rotate the Pelvis during the Downswing"
DG
|
|
|
Post by imperfectgolfer on Jun 22, 2021 9:52:43 GMT -5
Here is a capture image from session number 6 where Jean-Paul Fernandez (force plate expert) and MA were teaching Asian tour golfers in Thailand. This pro golfer had a maximum driver clubhead speed of 115 mph before he was taught how to markedly increase his vertical force from ~140% to ~225% of his body weight with appropriate timing. His clubhead speed went up to 126mph. That significant gain in clubhead speed is probably due to an increased magnitude of his MoF (centripetal direction) that happens between P5.5 and P7. The photo shows his body position when the vertical force peaks and it is just after P6. The effect of the vertical force on body motion is that it will cause the left shoulder socket to move faster upwards and slightly further away from the target (due to the fact that he has secondary axis tilt and right lateral bend) => which will cause the hand arc path to move upwards with greater force and that should increase the MoF acting centripetally => which should speed up the release of the club. I wonder whether this phenomenon explains the difference in clubhead speed patterns between Rory McIlroy and JB Holmes. Here are their kinematic graphs.
Note that they have similar clubhead speeds at impact. Note that JB Holmes has a slower maximum lead hand speed (which usually happens at ~P5.5), but he compensates for that fact by having the ability to generate a faster release of PA#2 after P.5. I wonder whether it is due to the fact that JB Holmes is generating a larger vertical force after P5.5 that increases the MoF (directed centripetally) happening between P5.5 => P7 => speeds up the release of PA#2. I have tried to increase my vertical force in my personal driver swing and it definitely helps to increase the speed of release of PA#2. However, due to a lack of spinal and hip joint flexibility I can easily become unbalanced and lose control of my club. So, I have decided not to pursue that golf instructional idea, which may be perfectly acceptable for a subset of golfers! Jeff.
|
|
|
Post by dubiousgolfer on Jun 22, 2021 10:21:41 GMT -5
Dr Mann I suspect you are correct about that superior PA#2 release by JB Holmes. I've also delved in increasing the vertical force in my golf swing and can sometimes get a perfect strike and a distance increase of 10-15 yards but my consistency is awful and I can get a whole array of errant shots. The timing required to do this is probably too difficult for many recreational golfers. Gary Woodland doesn't use much vertical ground force but is still one of the longer hitters on tour. DG ps. There is a .pdf from Dr Lynn that provides some Swing Catalyst graphs of several players including Gary Woodland. carolinas.pga.com/wp-content/uploads/sites/3/2019/03/Dr.-Scott-Lynn-PhD-Swing-Catalyst.pdf
|
|
|
Post by imperfectgolfer on Jun 24, 2021 10:30:13 GMT -5
In this post, I will be discussing the Kwon/Duffy model of generating vertical GRFs in order to generate a counterclockwise rotation of the body around the body's COM in the frontal plane. Mike Duffy has produced a computer-graphics model to show the effect of varying vertical GRFs on the body's COM and he has produced different models for rear-post, center-post and front-post golfers. Here is an example featuring a rear-post golfer model. The green central dot is the golfer's COM (an imaginary point in 3-D space). The blue vertical arrowed lines represent the vertical GRFs being generated under the feet. The vertical GRFs have magnitude - represented by the height of the arrows, and a directional vector represented by the tilt of the blue arrows. The yellow/orange vertical arrowed lines represents the total COP due to combining the vertical GRFs being generated under both feet. If the yellow arrow points to the left of the COM it will produce a counterclockwise rotary force around the COM - represented by the spinning blue-red wheel in the right-handed diagram. The magnitude of that rotary torque force depends on the magnitude of the vertical yellow arrow and its distance from the body's COM (= moment arm).
The left-handed image shows a rear-post golfer at his P4 position. He has 80% of his COP under his right foot and that causes the total COP to move rightwards. Note that he has moved his body's COM rightwards during the backswing so that the total COP force (yellow arrow) passes through the body's COM, which means that no rotary torque is being generated.
Here is his downswing scenario. In the early downswing between P4 => P4.5, the golfer will be generating a horizontal GRF under his right foot and that will tilt the total COP arrow to the left side of the body's COM thereby generating a small rotary torque around the body's COM. Shortly thereafter (between ~P5 => P5.5), the golfer can markedly increase the vertical GRF being generated under his left foot, and that will markedly increase the rotary torque being generated in the frontal plane around the body's COM - see the right-sided image where the blue arrow being generated under the left foot increases markedly.
I don't dispute that it is possible to produce a counterclockwise rotary torque around the body's COM in the frontal plane - as described by the Kwon/Duffy model. However, how does that help explain how a golfer produces swing power during his downswing? There is no correlation between a pro golfer's clubhead speed at impact and the magnitude of the vertical GRF being generated under the lead foot - as can be discerned from the following capture image of Gary Woodland's Swing Catalyst measurements. Note that GW generates a significant amount of horizontal force (magenta-colored graph) during his early downswing followed shortly thereafter by a lot of rotary torque (yellow-colored graph) but he produces very little vertical force (cyan-colored graph). GW is one of the longest drivers in the PGA tour and he shows that a golfer does not have to produce a lot of vertical force in order to generate a high clubhead speed at impact with his driver.
Pro golfers differ in the amount of vertical force being generated during their mid-downswing and it is very likely higher in front-post "launchers" who are more dependent on that vertical GRF because they cannot easily generate horizontal and rotary torque forces in order to induce a fast pivot motion.
From my perspective, the Duffy model has very limited practical use and I think that the best way to explain its utility is to think that the counterclockwise rotary force around the COM in the frontal plane is primarily useful to allow a golfer to keep his balance during the downswing.
Consider Jamie Sadlowksi's downswing action. Note how JS progressively arches his mid-upper torso away from the target during his mid-late downswing. I think that it is likely necessary because he only weighs ~140 lbs and he has to perform that mid-upper torso arching motion away from the target during his later downswing to counteract the targetwards-directed force of his released lead arm/club and therefore simultaneously keep in balance. By increasing the vertical GRF under his lead foot (as described by Duffy) he can produce a counterclockwise rotary torque around his body's COM that will allow him to more easily produce that arching maneuver of his upper body that is directed away from the target. So, I can conceive that it is has a very practical value for a golfer like JS. However, Gary Woodland weighs much more than JS and he is very muscular-appearing and he may not require much vertical GRF in order to keep his balance.
There are two main reasons why I think that it is very useful to generate a large vertical GRF (peaking at ~P5.5) in the downswing - i) it produces a counterclockwise rotary torque around the body's COM that allows a golfer to keep his balance during the mid-late downswing and ii) it increases the centripetal component of the MoF if the elevating left shoulder socket shortens the hand arc path radius between P5.5 => P7, thereby increasing the efficacy of the release of PA#2 (as described in my previous post). Jeff.
|
|
|
Post by imperfectgolfer on Jun 24, 2021 14:47:47 GMT -5
I have viewed the majority of the MA/TR webinar sessions about 4x and I now have a reasonably good perspective of their opinions. I am now increasingly opposed to many of their golf instructional opinions, which I think make no sense from a golf biomechanical perspective. In a number of future posts over the next few weeks I will explain why I think that their opinions make no sense. In this post, I will address their opinions on how to decide which trail grip strength a golfer should decide to use for his personal swing. Their basic screening test is the trail arm folding test where they fold their trail elbow when standing with their two hands opposed to each other - as shown by Terry Rowles in the following video.
In that video, TR demonstrates a "trail arm folding" screening pattern that determines that he should use an "on-top" trail hand grip pattern. I think that the screening test makes no sense because it only tests what pattern of right arm folding may possibly happen in an individual golfer during a right arm folding takeaway action. It does not mean that the tested golfer, who tests positive for an "on-top" trail hand pattern, cannot perform a "side-on" or "under" trail grip pattern equally easily (= in a biomechanically comfortable/natural manner) during a simulated backswing arm folding action, and it does not prove that it is the best decision for the golfer to choose that particular trail grip pattern during his downswing action. I will discuss this issue in greater detail in a future post. What I plan to discuss in this post is the grip verification test that MA demonstrates in a short 25 second you-tube video (which is unlisted). Here are capture images from the MA-video. Mike states that one should perform a short golf swing action from waist-high-to-waist high using only the right arm. He states that one should start with an "under" grip pattern and then "feel" if the clubface is closing during the short swing action. Then, one should repeat the short swing action using a "side-on" grip pattern if the clubface is still closing and then finally an "on-top" grip pattern if the clubface is still closing. The "correct" trail grip strength is verified if the clubface does not "feel" like it is rolling closed during the short swing action. What is MA actually testing during that verification test procedure? I think that he is only testing how much the right forearm automatically/passively/naturally pronates during the trail arm-only swinging action, and he seemingly infers that the correct amount of pronation is the amount that prevents the clubface from rolling closed too much during the test.
However, we know two facts regarding the clubface closing phenomenon of a pro golfer during the late downswing of his full golf swing action. Fact number 1: The amount of clubface closing happening between P6 => P7 correlates highly with lead hand grip strength - being greater in amount if the lead hand grip strength is weak and smaller in amount if the lead hand grip strength is strong. We also know that there is high correlation between the amount of lead forearm supination happening between P6 => P7 and the amount of clubface closing.
Fact number 2: The trail forearm does not pronate during the P6 => P7 time period in most pro golfers. Here is Jon Sinclair's graph of trail forearm supination during a full golf swing action performed by >100 PGA tour golfers. Top = P4, AP = P5, MD = P6 and impact = P7. The blue graph is the average value and the green graphs show the one standard deviation limits (which incorporates 68% of the pro golfers). Note that they all have a supinated trail forearm during the P6 => P7 time period, and that the degree of supination actually increases between P6 => roughly P6.7 before decreasing slightly just before impact.
Now, consider these capture images of an "on-top" pro golfer - Kevin Stadler. Image 1 is at P6, image 2 is at P6.5, image 3 is at impact and image 4 is at P7.2. Note that KS uses a neutral lead hand grip and an intact LFFW/GFLW swing technique between P6 => P7 - which means that the degree of clubface closing (relative to the clubhead arc) happening between P6 => P7 must have a very high correlation value with respect to the degree of lead forearm supination that is happening between P6 => P7. I have drawn a blue line down the middle of his right antecubital fossa and a short red line over his lower radial bone in his right lower forearm. Note that his right forearm is supinated at P6, at P6.5 and at P7 - and it is never pronated. Note that his trail wrist is radially deviated and highly extended at P6 and that it is ulnar-deviated and far less extended at impact. That means that his trail wrist is rolling clockwise (and not counterclockwise) between P6 => P7 when he is performing his trail wrist's circumductory roll motion.
Note that his trail palm is parallel to his lead palm at impact, which means that the degree of closing roll of his trail palm must be approximately equal to the degree of closing roll of his lead palm (which is causally responsible for squaring his clubface by impact). The amount of closing roll of his trail palm between P6 => P7 is causally due to the combination of the i) decrease in the degree of trail forearm supination happening between P6 => P7 and ii) the degree of trail palm rolling secondary to a trail right wrist circumductory roll motion happening between P6 => P7 - and the amount of closing motion of his trail palm must accomodate itself to what is happening with respect to the amount of closing motion of his lead palm.
Jeff.
|
|