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Post by imperfectgolfer on Jan 22, 2022 12:04:10 GMT -5
In this post, I am going to propose a novel hypothesis of how increasing the lead foot's v-GRF between P5 => P6 can increase clubhead speed at impact. In a previous post, I posted this image produced by Scott Lynn that shows that there is a low correlation coefficient R value of 0.33 between the lead foot's v-GRF at clubshaft vertical (~P5.2) and clubhead speed at impact in a number of pro golfer driver swings. I also stated that increasing the lead foot's v-GRF at P5 => P6 happens very late in the torque generation phase that Kwon claims is necessary to rotate the torso around the body's COM in the frontal plane, which means that it probably does not significantly contribute to an increase in the speed of torso rotation in the frontal plane, and thereby an increase in the speed of release of PA#4.
However, I suspect that increasing the lead foot's v-GRF to a high level between P5 => P6 may increase the speed of release of PA#2 by the following mechanism. Here is a Kwon graph showing the MoF due to the lead hand pulling the club handle down the hand arc path, and which is in play at the level of the club handle during the mid-late downswing. The MoF (which Kwon calls the net mid-hand force) becomes positive after ~P5.5 and it causes the clubshaft to rotate counterclockwise during the later downswing after P6. That MoF (represented by the black arrows) can be broken down into two sub-forces - a tangential force and a centripetal force.
The centripetal component of the MoF is the dominant force causing the club release phenomenon (release of PA#2).
So, theoretically, if one can increase the centripetal component of the MoF that is operating between P5.5 => P6.5, it could potentially increase the speed of release of PA#2. How can this be accomplished biomechanically? In a previous post, I stated that J B Holmes had a super-efficient release of PA#2 - based on the following table showing his clubshaft accelerations values. Note that J B Holmes has a clubshaft acceleration value of 247 rads/sec-sec between P6 => P7, which is much higher than that produced by other pro golfers. I do not really know how he accomplishes that feat, but here is my proposed novel explanation of how he could potentially be releasing PA#2 super-efficiently. Image 1 is at P4. I have placed a small green circle over his lead shoulder socket. Image 2 is at P5. I have placed a small yellow circle over his lead shoulder socket. Note that his lead shoulder socket is moving horizontally towards the target between P4 => P5, and it helps him to release PA#4 during the early downswing. Image 3 is at P5.5. I have placed a small while circle over his lead shoulder socket. Note that he is starting to move his lead shoulder socket upwards. Image 4 is at P6. I have placed a small red circle over his lead shoulder socket. Note that his lead shoulder socket is moving mainly upwards.
Image 5 is at P6.5. I have placed a small blue circle over his lead shoulder socket, and it shows that his lead shoulder is still moving upwards. What is causing his lead shoulder socket to move progressively upwards between P5.5 => P6.5? I think that a major causal factor is the progressive straightening of the lead leg, which elevates the lead hip joint and then secondarily the lead shoulder socket.
We know that force must precede motion, so the force used to cause elevation of the lead hip joint secondary to lead leg straightening must involve an increased degree of v-GRF under the lead foot, which must start to happen between P5 => P5.5. Theoretically, it could be that if a golfer significantly increases the v-GRF under the lead foot at that time during the downswing, that it can significantly increase the speed and efficiency of lead shoulder socket elevation, and thereby increase the centripetal component of the MoF, which is causally responsible for the release of PA#2.
The key point is that this must involve a shortening of the hub radius (= slight elevation of the hand arc path) between P5.5 => P6.5, and not later after P6.5.
Some pro golfers elevate their lead shoulder socket abruptly after P6.5 by "jumping up" through impact and that can cause a shortening of the hand arc path radius just before impact - as seen in the following diagram. The red dots show the phenomenon of hub path radius shortening, but it is happening very late in the downswing after P6.5 and it produces a very small increase in clubhead speed (due to the phenomenon called parametric acceleration of the club). What I am proposing is very different - the hub path radius must be decreasing between P5.5 => P6.5, which can potentially cause an increase in the centripetal component of the MoF and thereby the speed of release of PA#2.
Whether that phenomenon is really happening in JB Holmes's driver golf swing action is unknown, but I think that it would be a very interesting hypothesis for golf researchers to explore. Jeff.
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Post by dubiousgolfer on Jan 22, 2022 13:12:23 GMT -5
Dr Mann
Aren't there other ways to change the hand path rather than just the extension of the lead leg? For example , more right side lateral flexion to make the shoulder plane more inclined?
DG
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Post by imperfectgolfer on Jan 22, 2022 16:47:52 GMT -5
Dr Mann Aren't there other ways to change the hand path rather than just the extension of the lead leg? For example , more right side lateral flexion to make the shoulder plane more inclined? DG Yes. If a golfer changes the degree of secondary axis tilt and trail side bend, then that will affect the hand arc path because they do affect the motion of the lead shoulder socket. However, it will not necessarily make the hand arc path between P6 => P7 less horizontal and tilted slightly upwards in the same way - where elevation of the left shoulder socket is primarily due to lead leg straightening happening while the upper torso is rotating counterclockwise between P5.5 => P6.5. Also, active lead leg straightening secondary to a large lead foot v-GRF can potentially affect the speed of lead shoulder elevation in a much more dramatic manner. Jeff.
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Post by dubiousgolfer on Jan 23, 2022 20:26:08 GMT -5
Dr Mann I just found an article that better describes Dr Kwon's beliefs relative to other golf biomechanical theories(so I thought I'd post it for reference purposes). I bold highlighted certain sections which I found questionable and raised comments below. Also noted that you've already read this article before in 2015. leejhlee.wordpress.com/2015/03/14/findings-from-dr-kwons-golf-biomechanics-instructor-training-program-level-1/Findings from Dr. Kwon’s Golf Biomechanics Instructor Training Program Level 1 Posted on March 14, 2015 *Dr. Young-Hoo Kwon is a professor at the Texas Women’s University. He is hailed by many, including Chris Como, as the foremost expert in the field of bio-mechanics. The dynamic team of Dr. Kwon and Chris Como (coach to Tiger Woods) was picked by Golf.com as the Biggest Innovators in Golf. I recently took a part in the Dr. Kwon’s training program in Bangkok, Thailand (Mar. 8 & 9th, 2015). I would like to thank Dr. Kwon and everyone involved for such insightful and enlightening couple of days. With such vast amount of new findings presented during the seminal, it is amazing to think that it’s only a tip of the iceberg in his research. I am sure we are all in agreement that it will take a good part of our professional lives to digest and absorb Dr. Kwon’s findings. In the following section, I have compiled a list of my understandings from the Level 1 Program. I tried to deconstruct them into a common language that relates only to the practical implication/application and I have left out the scientific lingos, which I had a hard time following. I would love to have someone take a look and guide me as to whether I’m on the right track. Please feel free to add any materials that I have missed out (and I’m sure there are a lot of them). 1. Golf Biomechanics The research focuses on contribution and analysis of bio-mechanics in the golfer’s body and swing motion What Does This Mean? The research of Dr. Kwon focuses on the relationship between the inner mechanics of golfer’s body and swing motion Other models of bio-mechanics, as presented by TPI and others organizations, put too much emphasis on the relationship between anatomy and the swing motion which, in effect, works only to improve muscular compensation to hide mechanical fault.
My Comment Is Dr Kwon assuming his step drills to optimise the GRF patterns (according to his own opinion) will create mechanical efficiency and remove muscular compensations? If he has the evidence , then I'd like to see it published.
Countermovement To counter-act the Stretching-Shortening Cycle. Focuses on the importance of backswing to engage muscles to pre-stretch prior to the start of the downswing and eliminate Electromechanical delay (EDM). What Does This Mean? Movements in the backswing needs to serve as an important mechanism to “load” up the correct muscles that can fire immediately at the start of the downswing, without wasted time caused by the effect of Electromechanical delay (slight lag time between eccentric and concentric contraction of a muscle). This will maximize the energy (muscle force and contraction velocity) to be translated into achieving maximum velocity quicker and earlier in the downswing. Early cocking limits pre-stretching. It refutes the notion of the backswing sequence starting first with the club (K-Vest).
My Comment: Dr Phil Cheetham graphs shows a kinematic sequence in the takeaway that starts with the club and I am assuming is predominantly what he's found in PGA Tour swings.Ground Reaction Force Mass of body and club remains constant throughout the swing and External Ground Force (foot/ground interaction) is the only controllable variable that can intentionally be changed in the realm of maximizing the force output.
What Does This Mean? Foot/Ground interaction and the position of the Center of Mass (COM) are the most important elements in maximizing the force exertion and creating efficient force expenditure. Movement of pelvis and its effect on the position of Center of Mass is highlighted, as oppose to focusing on singular position/movements of shoulder, head, trunk, weight distribution (vertical position), or etc.
My Comment: The COM is not necessarily positioned on the body or a moveable joint that can achieve rotation to match the physics/maths . Yes , one can calculate the angular momentum being created by using the measured grfs/moments/torques generated (ie. via musculature contractions) to achieve the intended movement . But the human body can also do a variety of movements to create the same grf forces (and angular momentum) which suggests to me there could be innumerable controllable variables that can be intentionally changed.
In general, trail foot works to generate horizontal force, and lead foot works to generate vertical force. It refutes the notion of relying data solely on the measurement of vertical weight distribution (most force plates in the market). Horizontal force from foot movements has to be calculated to examine the efficiency of the force output. It refutes the notion of maintaining weight on the leading side (Stack & Tilt). It refutes the notion of X-Factor. Focusing on the upper-body rotation, without taking in consideration for the foot/ground interaction, only suppresses the Ground Reaction Force. Negative correlation was found between X-Factor (traditional understanding and also the X-Factor stretch) and the output (speed/distance/force). It refutes the commonly held teaching philosophy that feet should be firmly planted. Functional Swing Plane Tracking the trajectory (Motion Plane) of the clubhead from the Mid-Downswing (MD) to Mid-Followthrough (MF) as it rotates around the Instantaneous Rotation Center. What Does This Mean? It refutes any other notion of a swing plane, including Ben Hogan’s shoulder plane, Hank Haney’s shaft plane, and Jim Hardy’s shoulder/arm (one or two plane swing) lines, as there are too much variation of movements on the outside phases of swing events (as in, any swing events happening outside of MD to MF phase). My Comment Surely it is more preferable to swing on plane as per Homer Kelley TGM book where one end of the club is tracing the Swing Plane Line? So is it okay if a golfer swings too vertical or flat or in a loop like Matthew Wolff? It refutes the traditional use of the Double or Triple-Pendulum Model in simulation studies as they simplifies the swing too much. Swing events should be looked at in relation to player’s Instantaneous Rotation Center, which is not stationary throughout the swing. In Functional Double-Pendulum model, Mid-Trunk can be used as the hub to relate the position of Functional Swing Plane. Early Acceleration In order to maximize the vector quantities (force, pressure, velocity, and etc.) of the clubhead at Impact (BI phase), the vector in the “tangential” direction should be accelerated to the max in the early part of the downswing (EDA phase) and then, 100 percent of the vector needs to be directed in the “normal” direction at Impact. What Does This Mean? Direction of the energy (needs a better word??) on the downswing has to be directed down towards the ground and at the point of impact, the energy (??) must be directed toward the body. This is done through deceleration of the body prior to impact position. It refutes the commonly held teaching philosophy to “swing through the impact.”
My Comment: If one swings 'to impact' and not 'through', won't one tend to decelerate the lead arm prematurely ? Dave Tutelman says swinging through impact might not be good physics but it could be good golf instruction. Also wouldn't swinging through impact with the lead arm assist with forward shaft lean and prevent flipping? It refutes the idea of multi-peak kinematic sequence model where the speed of different anatomic parts are peaking at different points on the downswing. It confirms the single peak kinematic sequence where the speed of anatomic parts peak at the same time then, decelerates prior to the Impact position.
My Comment Dr Phil Cheetham has produced many graphs of PGA tour players proving the multi-peak kinematic sequence.DG PS. Just noted the following so maybe this article is not Dr Kwon's beliefs - the author said: "this is MY understanding of his research".
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Post by dubiousgolfer on Jan 24, 2022 9:46:13 GMT -5
Here is another video from Be Better Golf with more comments by Dr Kwon . Basically he is talking about external focus on keeping the clubhead swinging on the functional plane using continuous/perpetual motion (using GRFs) and keeping the shoulders closed to the target during transition to prevent an OTT.
DG
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Post by imperfectgolfer on Jan 24, 2022 11:17:44 GMT -5
Here is another video from Be Better Golf with more comments by Dr Kwon . Basically he is talking about external focus on keeping the clubhead swinging on the functional plane using continuous/perpetual motion (using GRFs) and keeping the shoulders closed to the target during transition to prevent an OTT. DG Kwon's golf instructional teaching is nearly identical to my golf instructional approach in terms of the following features-: 1) It is a body driven motion, where the lower body initiates the downswing with a variable degree of torso-pelvic separation (which should give a golfer the "feeling" of keeping the upper torso temporarily closed between P4 => P5 and that will help avoid an OTT move). 2) The arms are swung around the body in synchrony with the body motion, but on a different plane of motion, which for most golfers will probably be from the hand plane at address => TSP (or near the TSP) at P4 => elbow plane by P5.5 => remaining on the elbow plane (= functional swingplane) between P5.5 => P7.5+. However, there is a small difference in our teaching methodology. If the end of the club that is nearest the ground always points at the ball-target line (other than when it is parallel to the ball-target line), then the clubshaft motion will always be on-plane between P4 => P7.5, which is one reason why I think that a golfer should think of clubshaft motion rather than clubhead motion. Also, when one thinks of the concept of a functional swingplane between P6 => P7.5 (or P8), I do not only think that the clubhead motion must be on that plane, and I prefer to think that the entire clubshaft must be on that plane. There are a number of differences in my golf instructional approach as explained below-: 1) Kwon talks of a continuous motion pattern of golf swing action where the lower body is already moving targetwards while the arms/club are still moving back between P3.5 => P4. Although I agree that it is a very desirable pattern of body/arm motion, I think that it is also very accepatable for the golfer to pause at P4 (like Hideki Misuyama) if that pause does not deleteriously affect his body/arm motion during the downswing action.
2) Bill Knodle talks of the clubshaft shallowing out automatically/naturally between P4 => P5.5. That clubshaft shallowing phenomenon can be variable (which suggests that it is not necessarily automatic/natural) from my personal perspective because there are three patterns of acceptable on-plane clubshaft motion between P4 => P5.5 from my golf instructional perspective. Pattern 1 is no clubshaft shallowing between P4 => P5.5 (eg. as seen in Phil Mickelson's and Jamie Sadloski's driver golf swing action). Pattern 2 is a slow, and steady, clubshaft shallowing motion between P4 => P5.5 (eg. as seen in Adam Scott's and Henrik Stenson's driver golf swing action). Pattern 3 is a lot of clubshaft shallowing motion between P4 => P5 (eg. as seen in Sergio Garcia's driver golf swing). Although Kwon does not agree that the trail elbow must perform an active right arm adduction maneuver combined with a pitch elbow motion between P4 => P5.5, I cannot easily fathom how a skilled pro golfer can avoid performing that maneuver. Note how well Bill Knolde maintains his bent trail elbow between P4 =P P5.5 and how his trail elbow is driven to a pitch location near his trail hip area by P5.5. 3) Kwon talks about a targetwards pelvic shift motion preceding any counterclockwise pelvic motion during the early downswing between P4 => P4.5+. I believe that the pelvic shift motion should occur concurrently with the pelvic rotary motion (= shurn rhythm motion) as seen in Bill Knodle's golf swing action and as Kwon demonstrated in this following video on the shurn rhythm motion.
Jeff.
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Post by imperfectgolfer on Jan 24, 2022 11:43:14 GMT -5
DG, My reply to some of your comments. You wrote-: "My Comment - Is Dr Kwon assuming his step drills to optimise the GRF patterns (according to his own opinion) will create mechanical efficiency and remove muscular compensations? If he has the evidence , then I'd like to see it published." Kwon never talks/about how different muscular activation patterns can create different pelvic-upper torso motion patterns during the downswing, and I think that it represents a weakness in his ideological golf swing instructional approach. You wrote in response to Kwon's teaching ("Early cocking limits pre-stretching. It refutes the notion of the backswing sequence starting first with the club (K-Vest).)-: "My Comment: Dr Phil Cheetham graphs shows a kinematic sequence in the takeaway that starts with the club and I am assuming is predominantly what he's found in PGA Tour swings." I think that early or late lead wrist upcocking patterns are acceptable, and I do not believe in the phenomenon of a stretch-shorten cycle with respect to the lead wrist's uncocking musculature. I also do not believe that it is imperative that the pelvis should move first before the arms between P1 => P3. You wrote-: "My Comment: - The COM is not necessarily positioned on the body or a moveable joint that can achieve rotation to match the physics/maths . Yes , one can calculate the angular momentum being created by using the measured grfs/moments/torques generated (ie. via musculature contractions) to achieve the intended movement . But the human body can also do a variety of movements to create the same grf forces (and angular momentum) which suggests to me there could be innumerable controllable variables that can be intentionally changed." I agree. You wrote-: "My Comment: - If one swings 'to impact' and not 'through', won't one tend to decelerate the lead arm prematurely ? Dave Tutelman says swinging through impact might not be good physics but it could be good golf instruction. Also wouldn't swinging through impact with the lead arm assist with forward shaft lean and prevent flipping?" I agree.
Kwon talks about thinking of the clubhead moving on the functional swingplane, but I prefer to think of clubshaft motion on the functional swingplane where the clubshaft motion is continuous between P6 => P7.5 and where a golfer can optionally choose to use a DH-hand release action between P7 => P7.2 (or even to P7.4). You wrote-: "My Comment - Dr Phil Cheetham has produced many graphs of PGA tour players proving the multi-peak kinematic sequence." Here is a capture image that Phil Cheetham himself presented on the kinematic sequence of some pro golfers. Note that some of the peaks are sequential while others are more concurrent. I think that there should be no "fixed" rule on that issue.
Jeff.
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Post by dubiousgolfer on Jan 26, 2022 10:13:31 GMT -5
Here is BBG recent Dr Kwon's video where he talks about the wrists in the downswing from 09:30 onwards. He says "if in the end you can add wrist motion it will complete your swing".
I am assuming he means the added wrist motion is generated from the concentric contraction phase of a wrist 'stretch-shorten cycle' developed when slowing down a more energetic backswing. That by using a body pivot driven swing where rotation happens before the end of the backswing, this will assist in the eccentric contraction phase of the SSC .
But he hasn't explained how the golfer is supposed to retain that SSC until later in the downswing and seems to be suggesting that it happens automatically if you use a body pivot driven swing correctly (ie. using his step drills).
Then he demonstrates how the body's angular velocity has to slow down to transfer energy to the club but imho I think that gives the non-physicist golfer the wrong impression. The golfer may assume if he actively slows the body rotation very quickly that it will automatically make the club go faster and that seems incorrect to me.
I have heard a few golf instructors (Mike Adams included) saying it is similar to a passenger in a car (without a seat belt) that crashes into a wall propelling the passenger at a greater speed than the car speed just before impact, which imho is incorrect. If the car and passenger are moving at 100mph just before impact , the car will stop and the passenger will continue at 100 mph , there will be no increase in his speed.
I think the kinematic sequence explains what is happening quite well.
1. The pelvis body segment rotates the 'ribcage/shoulders/arms/club' unit in the early downswing 2. Then the internal/external obliques contract to assist the angular acceleration of the 'ribcage/shoulders/arms/club' unit. To do this, they have to twist against a platform (ie. the pelvis) which will decelerate the pelvis. 3. The shoulder girdle muscles will then contract to accelerate the 'arms/club' unit . To do this they have to twist against a platform (ie. the ribcage) which will decelerate the ribcage. 4. A lead wrist SSC contraction might assist in a small increase in the angular velocity of the club. If it does , it will twist against the platform of the arm and slow its angular velocity. But the predominant increase in the angular acceleration of the club (and release of PA#2) is caused by the linear forces transmitted via arms/hands across the grip of the club . The net force across the grip will cause an 'In Plane Mof' which will apply torque/twist to the club but (because of Newtons 3rd Law) means the grip will also apply an 'equal and opposite' torque/twist to the lead arm which will predominantly slow it down (completely separate to any SSC wrist contraction).
There is no active slowing down of the body pivot to make the club move faster , the body segments optimally only slow down after they've first transferred some of their energy to other segments and club. The proximal segments are further slowed down when the more peripheral segments contract to speed up their motion.
DG
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Post by imperfectgolfer on Jan 26, 2022 15:27:03 GMT -5
Here is BBG recent Dr Kwon's video where he talks about the wrists in the downswing from 09:30 onwards. He says "if in the end you can add wrist motion it will complete your swing". I am assuming he means the added wrist motion is generated from the concentric contraction phase of a wrist 'stretch-shorten cycle' developed when slowing down a more energetic backswing. That by using a body pivot driven swing where rotation happens before the end of the backswing, this will assist in the eccentric contraction phase of the SSC . But he hasn't explained how the golfer is supposed to retain that SSC until later in the downswing and seems to be suggesting that it happens automatically if you use a body pivot driven swing correctly (ie. using his step drills). Then he demonstrates how the body's angular velocity has to slow down to transfer energy to the club but imho I think that gives the non-physicist golfer the wrong impression. The golfer may assume if he actively slows the body rotation very quickly that it will automatically make the club go faster and that seems incorrect to me. I have heard a few golf instructors (Mike Adams included) saying it is similar to a passenger in a car (without a seat belt) that crashes into a wall propelling the passenger at a greater speed than the car speed just before impact, which imho is incorrect. If the car and passenger are moving at 100mph just before impact , the car will stop and the passenger will continue at 100 mph , there will be no increase in his speed. I think the kinematic sequence explains what is happening quite well. 1. The pelvis body segment rotates the 'ribcage/shoulders/arms/club' unit in the early downswing 2. Then the internal/external obliques contract to assist the angular acceleration of the 'ribcage/shoulders/arms/club' unit. To do this, they have to twist against a platform (ie. the pelvis) which will decelerate the pelvis. 3. The shoulder girdle muscles will then contract to accelerate the 'arms/club' unit . To do this they have to twist against a platform (ie. the ribcage) which will decelerate the ribcage. 4. A lead wrist SSC contraction might assist in a small increase in the angular velocity of the club. If it does , it will twist against the platform of the arm and slow its angular velocity. But the predominant increase in the angular acceleration of the club (and release of PA#2) is caused by the linear forces transmitted via arms/hands across the grip of the club . The net force across the grip will cause an 'In Plane Mof' which will apply torque/twist to the club but (because of Newtons 3rd Law) means the grip will also apply an 'equal and opposite' torque/twist to the lead arm which will predominantly slow it down (completely separate to any SSC wrist contraction). There is no active slowing down of the body pivot to make the club move faster , the body segments optimally only slow down after they've first transferred some of their energy to other segments and club. The proximal segments are further slowed down when the more peripheral segments contract to speed up their motion. DG I agree with your criticism of Kwon's statement that the slowing of the body rotation that happens naturally in the late downswing can itself be causally responsible for an increase in clubhead speed at impact. Kwon performs a ridiculously wrongheaded demo when he pulls another person between the 14:56 - 15:08 minute time point of the video. He seems to imply that by slowing his body's motion, it allows him to move that person (conceptually equivalent to a golf club) faster. However, when you watch what he is actually doing when he makes that person move faster - he is actively using his arm and shoulder girdle muscles to supply the pulling power independent of his body motion. I cannot conceive how a slowing of the lead shoulder socket motion (secondary to a slowing of the body pivot motion) during the later downswing can make the lead hand move faster down the hand arc path - because the slowing of the torso motion does not make the lead arm pull the lead hand faster down the hand arc path. What it can do is increase the speed of release of PA#2 - not by increasing the speed of lead hand motion down the hand arc path, but by increasing the centripetal component of the MoF being generated by the lead hand moving down the hand arc path if the lead hand's hub path radius becomes shortened by elevation of the lead shoulder socket. DG - you wrote-: "There is no active slowing down of the body pivot to make the club move faster, the body segments optimally only slow down after they've first transferred some of their energy to other segments and club. The proximal segments are further slowed down when the more peripheral segments contract to speed up their motion." I cannot understand how the upper torso rotation (proximal segment) can be slowed down if the peripheral segment (lead arm) speeds up due to a contraction of the lead shoulder girdle/arm muscles. First of all, any speeding up of the motion of the lead arm (= release of PA#4) happens when the upper torso is also rotating fast between P4 => P5.5, and it does not primarily happen after the upper torso rotation slows down after P5.5. So, when you wrote-: "The shoulder girdle muscles will then contract to accelerate the 'arms/club' unit. To do this they have to twist against a platform (ie. the ribcage) which will decelerate the ribcage" you are surely getting the kinematic sequence wrong because the upper torso is being actively rotated between P4 => P5.5 and the lead shoulder girdle muscles are also actively pulling the lead arm down at the same time, and it does not happen subsequently while the upper torso rotation slows down. Jeff.
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Post by dubiousgolfer on Jan 26, 2022 18:50:24 GMT -5
Dr Mann I should rephrase what I wrote as per below: "There is no active slowing down of the body pivot to make the club move faster, the body segments transfer some of their energy to other segments and club. The proximal segments will experience a negative torque when the peripheral segments contract to speed up their motion." Look at this Dr Phil Cheetham 2005 article on the Kinematic sequence: www.mytpi.com/articles/biomechanics/kinematic_sequence_revisited?search=SequenceHe said the following (note my bolded section): During the forward swing, the larger, core segments such as the pelvis and trunk, move slower with the speed building as the energy progresses to the smaller distal segments such as the arms and club. Note that the pelvis does not continue accelerating through impact, but decelerates before impact. Whether the deceleration of the previous segment is caused by the acceleration of the next segment or, whether the previous segment is actively decelerated by muscular action is still a matter of debate within the biomechanics community. Further research is needed on this point.This is Dr Greg Rose's 2013 article on the Kinematic Sequence www.mytpi.com/articles/biomechanics/kinematic_sequence_basics?search=SequenceHe said the following (note my bolded section) Each segment of the chain slows down once the next segment begins to accelerate. This is due to the distal segment pushing off the proximal segment. Imagine a child jumping off their dad's shoulders in a swimming pool. As the child jumps, the force rapidly slows down the dad's energy. This causes a sequential deceleration or stabilization of the segments. Here is Dr Phil Cheetham's 2014 article relating to the 'Linear Kinematic Sequence' (but I think in principle it also applies to the 'Rotational Kinematic Sequence ') www.mytpi.com/articles/biomechanics/the_linear_kinematic_sequenceHe said the following (note the part I bolded). In fact, it is not as important what the speeds of the joints are at impact but what their maximum speeds are earlier in the downswing. We expect their speeds at impact to be lower because of the deceleration phase of each joint as it passes energy to the next segment - each joint is slowed down by the interaction force of the next segment accelerating against it. Take for example the mid-hands curve. You see that its highest speed is 22.6 mph and its speed at impact is 19 mph. For the mid-hands curve, the deceleration is related to the explosiveness of the release. The faster the release of the wrists the more the deceleration and the slower the hands will be at impact. It is a nice example of the action-reaction law of motion; the force of the club releasing causes and opposite force on the hands causing the lead arm to slow down. This is the email Dr Phil Cheetham sent me on the 23rd May 2020 regarding the kinematic sequence including the shoulders: -------------------- "I do not have specific data at my fingertips. I am not involved with My Swing anymore. I do suspect though, that if you were to measure the shoulders separately to the ribcage you would see them fall into the kinematic sequence. On transition I think you would see, pelvis, ribcage, shoulders, arm, club in that order. Thanks for asking." ---------------------- If I am understanding the above correctly , the contraction of the shoulder girdle muscles will act against the ribcage and will apply a negative torque to try and slow it down using Newtons 3rd Law.However, if the shoulder girdle muscles are actively pulling the lead arm down while the upper torso is actively being rotated between P4-P5.5 and not being slowed down (by the contraction of the shoulder girdle muscles) then that must mean there is still enough positive torque being applied to the ribcage (via the more proximal segments) to counter that deceleration. DG
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Post by imperfectgolfer on Jan 26, 2022 21:50:15 GMT -5
DG, You wrote-: " If I am understanding the above correctly , the contraction of the shoulder girdle muscles will act against the ribcage and will apply a negative torque to try and slow it down using Newtons 3rd Law.
However, if the shoulder girdle muscles are actively pulling the lead arm down while the upper torso is actively being rotated between P4-P5.5 and not being slowed down (by the contraction of the shoulder girdle muscles) then that must mean there is still enough positive torque being applied to the ribcage (via the more proximal segments) to counter that deceleration."
I don't know why you believe that the shoulder girdle's muscular action of pulling the lead arm down should slow down the rotation of the upper torso if the operant force is comparatively small in magnitude and acting roughly perpendicular to the more horizontal motion of the upper torso. In that example of a child jumping up from the shoulders of his father swimming in a pool, the force will push his father down into the water (according to Newton's 3rd law) if the child jumps vertically upwards. However, if the child jumps sideways it will produce a reactive force (according to Newton's 3rd law) that is angled more sideways, and it will move his father more sideways in the water. Also, if the child is very small and only weights 20lbs, then then the reactive force would be far less than if the child weighed 100lbs. Using that analogy, the shoulder girdle muscle pulling force (eg. from the lead side lats) is very small in magnitude relative to the forces causing torso rotation in a more horizontal plane of motion. Finally, as you stated the golfer can potentially increase the force exerted by his torso's core muscles to overcome any impedance caused by the contraction of the shoulder girdle muscles.
Jeff.
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Post by dubiousgolfer on Jan 27, 2022 10:03:43 GMT -5
DG, You wrote-: " If I am understanding the above correctly , the contraction of the shoulder girdle muscles will act against the ribcage and will apply a negative torque to try and slow it down using Newtons 3rd Law.
However, if the shoulder girdle muscles are actively pulling the lead arm down while the upper torso is actively being rotated between P4-P5.5 and not being slowed down (by the contraction of the shoulder girdle muscles) then that must mean there is still enough positive torque being applied to the ribcage (via the more proximal segments) to counter that deceleration."
I don't know why you believe that the shoulder girdle's muscular action of pulling the lead arm down should slow down the rotation of the upper torso if the operant force is comparatively small in magnitude and acting roughly perpendicular to the more horizontal motion of the upper torso. In that example of a child jumping up from the shoulders of his father swimming in a pool, the force will push his father down into the water (according to Newton's 3rd law) if the child jumps vertically upwards. However, if the child jumps sideways it will produce a reactive force (according to Newton's 3rd law) that is angled more sideways, and it will move his father more sideways in the water. Also, if the child is very small and only weights 20lbs, then then the reactive force would be far less than if the child weighed 100lbs. Using that analogy, the shoulder girdle muscle pulling force (eg. from the lead side lats) is very small in magnitude relative to the forces causing torso rotation in a more horizontal plane of motion. Finally, as you stated the golfer can potentially increase the force exerted by his torso's core muscles to overcome any impedance caused by the contraction of the shoulder girdle muscles.
Jeff. Dr Mann Yes , that makes sense . If the shoulder girdle contraction rotation is more on a vertical plane its reactive 'torque component' acting against the ribcage (which is turning on a more horizontal plane compared to the shoulder plane) , will be small. DG PS. If the above is the case, then how does one explain the rotation of the pelvis and torso (which is turning on a more horizontal plane ) can contribute power to the lead arm rotation which is happening on a more vertical plane in the early downswing? The golfers spine can have secondary axis tilt and right lateral flexion which can change its orientation to a more vertical rotational plane but doesn't that happen later in the downswing? If you look at the image below , I cannot understand how the rotation of the hips/ribcage which is applying a body driven torque in a more horizontal plane can contribute torque to the lead arm in a more vertical plane. Further , if you look at that Dr Scott Lynn video "Winter Education: Ground Reaction Forces on Swing Catalyst with Dr. Scott Lynn" at frame 48:18 , it says that the maximum torque ground reaction forces happens at near P5 . That seems to imply that most of the body driven torque is quite early in the downswing on a more horizontal plane compared to the lead arm rotational plane. If the lower body is being used to drive the lead arm , then it must be applying torque in a more vertical plane which seems to correlate with what Dr Kwon is implying (ie. GRF torques happening in the frontal plane), but I still cannot understand anatomically how that can be possible.
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Post by imperfectgolfer on Jan 27, 2022 11:06:45 GMT -5
DG,
You asked-: "If you look at the image below , I cannot understand how the rotation of the hips/ribcage which is applying a body driven torque in a more horizontal plane can contribute torque to the lead arm in a more vertical plane."
The motion of the lead arm during a PA#4 release action between P4 => P6 is not vertical, but angled and reasonably close to being parallel to the angle of the swingplane. So, it has two component planes of motion - a horizontal and a vertical. The torso rotation provides most of the power for the horizontal component via the targetwards motion of the lead shoulder socket and the shoulder girdle muscles can provide much of the power for the vertical component.
Jeff.
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Post by dubiousgolfer on Jan 27, 2022 19:50:32 GMT -5
Dr Mann
I can easily perceive a body driven swing by Logan Aldridge in the video below.
Jim Furyk is a bit more difficult to visualise from P4-P5 but I noted some label on his shirt in his chest area that also moves on a steep incline which does seem to suggest that he is using his upper body pivot to help pull his lead arm down and out. He also seems to have greater spine tilt at address which I suspect make it easier for him to use his upper body pivot to drive his lead arm on a more vertical plane from P4-P5
DG
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Post by dubiousgolfer on Jan 31, 2022 20:06:54 GMT -5
Here is BBG Dr Kwon video for the LPGA golfer , concerning the right elbow movement.
Why isn't Dr Kwon looking at the right hip spinning for the possible cause of the right elbow getting stuck by the side of the torso?
DG
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