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Post by dubiousgolfer on Dec 2, 2019 18:47:21 GMT -5
Dr Mann I think that is a more pragmatic way to define PA#4. DG PS. So doesn't this mean there is no 'out-of-line' or 'in-line' conditions for the loading and unloading of PA#4 ? I remember we touched on this subject awhile ago in a previous thread where I mentioned an additional accumulator for the pivot. But as you've already mentioned , the pivot could also be providing some of the downward component of PA#4 (so it isn't really feasible). newtongolfinstitute.proboards.com/thread/681/why-pivot-classified-power-accumulator
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Post by utahgolfer on Dec 6, 2019 2:41:56 GMT -5
This dialogue is delightfully interesting. Comparing RF and JR side by side is very helpful in understanding the two different ways of releasing PA#4. RF may be able to articulate that his primary power source is via torso rotation, and JR may be able to sense his release of PA#4 is more through shoulder girdle muscle activation, but they may both simply do their "thing" without any conscious thought or understanding. Regardless, it is an interesting discussion about the underpinnings of how a golfer might release PA#4.
I have always thought that any shoulder girdle muscle activity at P4 would in some way promote an OTT swing pattern, but this obviously depends on which shoulder girdle muscles are activated. JR certainly is activating the correct muscles. I would think activating the right serratus anterior at P4 leading to right scapular protraction (abduction) would promote an OTT swing path, as would activation of the right shoulder internal rotator muscles leading to an active punched right elbow. Whereas, activating the right latissimus dorsi, the right scapula downward rotator muscles, and the right shoulder external rotator muscles leading to an active pitched right elbow would promote a proper swing path and accelerate the release of PA#4.
On the left side, I would think JR is activating his left latissimus dorsi, his left posterior deltoid, and his left scapula retractor (adductor) muscles to actively release PA#4.
JR still benefits from his torso CCW rotation to contribute to the speedy release of PA#4, but it doesn't appear to be his dominant power source as is the case of RF.
I assume both players maintain a relaxed and passive right triceps muscle to avoid any active straightening of the right elbow; to remain swingers and not hitters.
It is clear that players like JR and Tony Finau generate an enormous swing speed using a relatively short backswing. It seems logical and exciting to presume that an important source of this power is generated from the proper activation of the right and left shoulder girdle muscles. Since many golfers don't have the flexibility of a RF, and can only rotate the spine about half as far, understanding the potential role of proper shoulder girdle muscle activation may be an essential topic of modern golf instruction.
ug
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Post by dubiousgolfer on Dec 8, 2019 10:06:57 GMT -5
This dialogue is delightfully interesting. Comparing RF and JR side by side is very helpful in understanding the two different ways of releasing PA#4. RF may be able to articulate that his primary power source is via torso rotation, and JR may be able to sense his release of PA#4 is more through shoulder girdle muscle activation, but they may both simply do their "thing" without any conscious thought or understanding. Regardless, it is an interesting discussion about the underpinnings of how a golfer might release PA#4. I have always thought that any shoulder girdle muscle activity at P4 would in some way promote an OTT swing pattern, but this obviously depends on which shoulder girdle muscles are activated. JR certainly is activating the correct muscles. I would think activating the right serratus anterior at P4 leading to right scapular protraction (abduction) would promote an OTT swing path, as would activation of the right shoulder internal rotator muscles leading to an active punched right elbow. Whereas, activating the right latissimus dorsi, the right scapula downward rotator muscles, and the right shoulder external rotator muscles leading to an active pitched right elbow would promote a proper swing path and accelerate the release of PA#4. On the left side, I would think JR is activating his left latissimus dorsi, his left posterior deltoid, and his left scapula retractor (adductor) muscles to actively release PA#4. JR still benefits from his torso CCW rotation to contribute to the speedy release of PA#4, but it doesn't appear to be his dominant power source as is the case of RF. I assume both players maintain a relaxed and passive right triceps muscle to avoid any active straightening of the right elbow; to remain swingers and not hitters. It is clear that players like JR and Tony Finau generate an enormous swing speed using a relatively short backswing. It seems logical and exciting to presume that an important source of this power is generated from the proper activation of the right and left shoulder girdle muscles. Since many golfers don't have the flexibility of a RF, and can only rotate the spine about half as far, understanding the potential role of proper shoulder girdle muscle activation may be an essential topic of modern golf instruction. ug Hi UG With regards which muscles are being activated , doesn't this study by 'Jobe' provide an insight ? I've copied it from Dr Manns Tyler Ferrell review (see further below) There is also a review paper that analysed 19 EMG Golf research articles and tried to summarise the findings (see link below) www.academia.edu/11252977/Electromyography_variables_during_the_golf_swing_A_literature_reviewI've not read it in any detail (yet) but here is their conclusion: This literature review found 19 papers that matched the defined search criteria: six on the trunk, four on the shoulder muscles, two on the forearm, one on the lower limbs and six literature reviews.There is only one literature review, which centered on EMG patterns in the golf swing (McHardy and Pollard, 2005a). The review performed provides a basis of knowledge about the neuromuscular patterns in the golf swing, but a number of limitations must be considered regarding comparisons of studies performed in different laboratories. These limitations are related to the heterogeneity in the golfers studied and differences in, or lack of information on the EMG methods used. For example, the local placement of the surface electrodes is different in the studies found. There is an absence of specific information on the methodology used to determine the maximal voluntary contraction to normalize the EMG signals. In the few studies that analyzed timing parameters there is also no clear information about the criteria used to define timing parameters, e.g. times of EMG onset and offset. One of the most important questions is the influence of different types of golf clubs on neuromuscular patterns because some differences in the kinematics and club head speed were found.There is also a need to characterize the muscular participation during the swing in more distal regions of the limbs, i.e. the muscles acting on the ankle, elbow and wrist, since those regions have a considerable potential for injury. In the future would be important to perform EMG in less skilled golfers, since they are the majority of the population playing golf.
Additionally, particular interest should be attributed to the female golfer. Finally, most studies evaluated only EMG amplitude parameters. Only two studies that evaluated timing parameters on trunk muscles were found. This dimension to understand how the central nervous system controls the coordination patterns between the different muscles and adapts to different constraints such as the type of golf club or different game strategies
--------------------------------------------- Copied from Dr Manns website: To further elaborate on his conviction that the golf swing is powered by the right arm, Tony Luczak provides "evidence" based on EMG (electromyography) studies, and he makes the following statements in his paper-: "The use of electromyography (EMG) may offer additional insight into the neuromotor mechanisms that drive the golf swing. EMG evidence that the arms are a main contributor to forward and acceleration phase control has been reported by Jobe, Perry, & Pink (1989) study of 6 men and 7 women professional golfers in that both male and female golfers reported combined right pectoralis major (PM) activation of 64% and left PM 18% during the forward swing and increasing to 93% PM bilaterally during the acceleration phase as a percentage of their manual muscle test. Evidence that the right arm plays a key role in delivering the golf club is that the pectoralis major is the most active than any other muscle tested by Pink, Jobe, & Perry (1990), which provides power to the swing through adduction and internal rotation. These findings seem to indicate that golf instructional methodologies need to be reassessed and possibly be based on learning strategies that mimic proper muscle activation patterns not just kinematic observation." Note that Tony Luczak justifies his conclusion that the right arm powers the golf swing by stating that EGM studies show that the right pectoralis muscle is the most active of any of the muscles tested by Pink, Jobe and Perry, and that it provides power to the swing motion through right arm adduction and internal rotation. Do Tony Luczak's observations and conclusions make any sense? First of all, let's look at the results of Jobe's EMG study on shoulder girdle area muscles. Note that Jobe uses the term "forward swing" for the P4 => P6 time period of the downswing and the term "acceleration" for the P6 => impact time period of the downswing. Note that the right pectoralis muscle reaches its peak EMG activity between P6 and impact. That is fully expected in both right arm swingers and TGM swingers (like Dustin Johnson) because that is when the right upper arm is being maximally adducted across the front of the rotating torso. However, swing power is actually being generated between P4 and P6 in both right arm swingers and left arm swingers. Note that the most active right shoulder girdle muscles during that P4 => P6 time period are the right subscapularis muscle (which pulls the right arm downwards), the right latissimus dorsi muscle (which pulls the right arm downwards and also adducts the right arm towards the right side of the torso) and the right pectoralis muscle (which adducts the right arm towards the right side of the torso). What does this EMG data suggest? The data only suggest that the right arm is being actively adducted towards the right side of the torso between P4 and P6 in most professional golfers who efficiently get their right elbow down to a pitch location alongside the right hip area by P6. However, that doesn't prove that a professional golfer is solely using a right arm swinging action because TGM swingers (lead arm swingers) are also going to be actively adducting their right arm between P4 and P6 in order to i) more efficiently shape their hand arc path by increasing the efficiency/speed of the downward-component of their PA#4 release action (as I demonstrated when I analysed the hand arc path of the driver swings of Jamie Sadlowski, Dustin Johnson, Cameron Champ and Jon Rahm) and ii) to optionally shallow the clubshaft (as described in topic number 3). Therefore, I believe it is impossible to conclude that EMG data of the right-sided shoulder girdle muscle can differentiate the difference between right arm swingers and TGM swingers who use an active right arm adduction maneuver during their early-mid downswing. ---------------------------------- So it seems that more research study is required before we can understand in more detail what is actually happening in different golf swings. DG
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Post by utahgolfer on Dec 8, 2019 16:20:28 GMT -5
DG, thanks for your insightful post.
This particular thread was so apropos because my swing thought has been to only accelerate my left arm with my torso rotation, with no active muscle activation of the shoulder girdle muscles. This approach works for those like RF, but I have limited torso rotation, so this topic is of particular interest to me.
It is helpful to research and document the exact shoulder girdle muscle activation from p4 to p6, the left arm acceleration phase, however, if a golfer moves correctly then it implies the correct muscles are activated. Thus, if you move correctly, then you must be activating the correct combination of muscles.
The discussion of this thread implies that JR activates these same muscles more actively and with more force than does RF. The kinematic sequence data suggest this, as does JR's ability to hit long drives with minimal upper torso rotation. RF has to be activating these same shoulder muscles to get his arms to move along a correct path, but may need to lower and spread out their force of contraction because he has a much greater CCW upper torso rotational distance from p4 to p6.
I hope the research continues to clarify this topic. In the mean time, golfers with a limited upper torso rotation might be well advised to train and activate their shoulder girdle muscles using correct movement golf swing patterns similar to JR.
ug
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Post by dubiousgolfer on Dec 14, 2019 10:06:29 GMT -5
DG, thanks for your insightful post. This particular thread was so apropos because my swing thought has been to only accelerate my left arm with my torso rotation, with no active muscle activation of the shoulder girdle muscles. This approach works for those like RF, but I have limited torso rotation, so this topic is of particular interest to me. It is helpful to research and document the exact shoulder girdle muscle activation from p4 to p6, the left arm acceleration phase, however, if a golfer moves correctly then it implies the correct muscles are activated. Thus, if you move correctly, then you must be activating the correct combination of muscles. The discussion of this thread implies that JR activates these same muscles more actively and with more force than does RF. The kinematic sequence data suggest this, as does JR's ability to hit long drives with minimal upper torso rotation. RF has to be activating these same shoulder muscles to get his arms to move along a correct path, but may need to lower and spread out their force of contraction because he has a much greater CCW upper torso rotational distance from p4 to p6. I hope the research continues to clarify this topic. In the mean time, golfers with a limited upper torso rotation might be well advised to train and activate their shoulder girdle muscles using correct movement golf swing patterns similar to JR. ug Hi UG Have found another article ( I think I may have used this before in a previous thread ) . The problem with EMG is that it cannot differentiate between ISOTONIC and ISOMETRIC contractions so still not completely reliable in explaining what is actually happening in the muscle groups. Further , there is no monitoring of the EMG activity in the pelvic girdle rotary muscles for the hip-squaring phase of the golf swing. They are also missing monitoring of the 'internal/external' obliques and latissimus dorsi. * Just found a 'Table 2' in the article which shows all the muscle groups monitored and they do include the obliques and latissumus dorsi* bjsm.bmj.com/content/39/11/799They summarise the EMG activity as per below: ------------------------------ Figure 1 Phases of the golf swing. (A) Address position; (B) early back swing; (C) late back swing; (D) top of swing; (E) down swing; (F) acceleration; (G) early follow through; (H) late follow through. Forward swing
The forward swing starts at the top of swing and ends when the club is horizontal to the ground (early part of down swing). The most active muscle in the upper body during this phase in the upper body on the left side is the rhomboid (68% MMT) and middle trapezuis (51% MMT). On the right side, the most active muscles are the pectoralis major (64% MMT) and upper serratus (58% MMT). The most active muscle during the forward swing phase in the lower body are the upper and lower gluteus maximus (100% MMT and 98% MM) on the right side along with the biceps femoris (78% MMT). On the left side, the most active muscles are the vastus lateralis (88% MMT) and the adductor magnus (63% MMT). Acceleration
The acceleration phase starts from the horizontal club to the impact of the ball (late part of down swing). This phase of the swing sees the pectoralis major muscle bilaterally being the most active muscle (93% MMT bilaterally) in the upper body. On the right side, the second most active muscle is the upper serratus anterior (69% MMT). On the left side, the levator scapulae is the second most active muscle (62% MMT). In the lower body, the acceleration phase sees the left biceps femoris (83% MMT) being the most active muscle with the left upper and lower gluteus maximus, along with the vastus lateralis being the second most active muscles (58% MMT). On the right side, the abdominal oblique (59% MMT) is the most active muscle, followed by the gluteus medius (51% MMT). Early follow through
The early follow through starts at impact to when the club is horizontal to the ground. In the upper body, the most active muscle during the early follow through is the pectoralis major bilaterally (74% MMT), followed by the right subscapularis (64% MMT) and the infraspinatus on the left (61% MMT). The most active muscle in the lower body during the early follow through is the left long head of biceps femoris (79% MMT), and left vastus lateralis (59% MMT). The right gluteus medius (59% MMT) is the most active right sided muscle, followed by the abdominal oblique (51% MMT). Late follow through
The late follow through starts when the club is horizontal to the ground and ends at the completion of the swing. The most active muscles in the upper body during the late follow through on the left are the infraspinatus (40% MMT) and the pectoralis major (39% MMT). On the right side, the most active muscles are the subscapularis (56% MMT), followed by the upper and lower serratus anterior (40% MMT). In the lower body, the most active left sided muscles are the semimembranosus and vastus lateralis (42% MMT each), followed by the adductor magnus (35% MMT). On the right, the vastus lateralis muscle (40% MMT) is the most active muscle followed by the gluteus medius (22% MMT). ------------------ DG PS. Doesn't seem to be much correlation between Jobe's findings and the above article for the 'Forward Swing' in the upper body from P4-P5 (apart from the EMG activity in the right pectoralis major)
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Post by dubiousgolfer on Jan 13, 2020 10:16:44 GMT -5
I am increasingly inclined to modify my personal (non-TGM) definition of a PA#4 release action where I define the start of the release of PA#4 as happening when the hands first start to move from its P4 position. Here is Jamie Sadlowski's PA# 4 release action.
Image 1 is at P4 and image 2 is at P4.5. I previously thought that PA#4 is not being released between P4 and P4.5 because the left arm has not changed its degree of adduction against the chest wall during that time period. However, the hands are definitely moving away from its P4 location and hand speed is starting to be generated. I now think that it may be better to include that time period in the definition of a PA#4 release action. I also now think that when considering the forces that cause the release of PA#4 (release of the left arm) that one should include all potential biomechanical forces - i) motion of the left shoulder socket pulling the left humeral head along; ii) left shoulder girdle muscles pulling the left arm downwards; iii) right shoulder girdle muscles adducting the intact "right upper arm + RFFW" unit in a downwards direction.
Jeff.
Dr Mann Am I correct in assuming for bullet point (i) above , that you regard any left scapula retraction (in the plane of left arm adduction=>abduction) as being minimal in pulling the left humeral head along? DG
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Post by imperfectgolfer on Jan 13, 2020 11:32:14 GMT -5
I am increasingly inclined to modify my personal (non-TGM) definition of a PA#4 release action where I define the start of the release of PA#4 as happening when the hands first start to move from its P4 position. Here is Jamie Sadlowski's PA# 4 release action. Image 1 is at P4 and image 2 is at P4.5. I previously thought that PA#4 is not being released between P4 and P4.5 because the left arm has not changed its degree of adduction against the chest wall during that time period. However, the hands are definitely moving away from its P4 location and hand speed is starting to be generated. I now think that it may be better to include that time period in the definition of a PA#4 release action. I also now think that when considering the forces that cause the release of PA#4 (release of the left arm) that one should include all potential biomechanical forces - i) motion of the left shoulder socket pulling the left humeral head along; ii) left shoulder girdle muscles pulling the left arm downwards; iii) right shoulder girdle muscles adducting the intact "right upper arm + RFFW" unit in a downwards direction. Jeff.
Dr Mann Am I correct in assuming for bullet point (i) above , that you regard any left scapula retraction (in the plane of left arm adduction=>abduction) as being minimal in pulling the left humeral head along? DG Yes. I think that left scapular retraction must help pull the left shoulder targetwards between P4 and P5.5, but I think that most of the targetwards motion of the left shoulder socket is due to the counterclockwise rotation of the upper torso. Jeff.
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Post by syllogist on Mar 12, 2020 10:20:29 GMT -5
Dr. Mann,
You wrote:, "I presently (in 2019) believe that the speed of release of PA#4 can be significantly determined by the degree of contraction of the left-and-right shoulder girdle muscles - rather than the speed of upper torso rotation."
I have the opposite opinion, i.e., the speed of release of PA 4 is most significantly determined by the rotational speed of the torso. The reason for the release of PA 4 has to do with increasing inertia of the arm/club mass, as the rotation of the torso is what moves the arm in sync with the torso (which you correctly called a passive action). This is not to say that one cannot deliberately contract the shoulder girdle muscles, but such is not necessary to develop significant PA 4 release speed in the area of the downswing where it releases. In fact, a deliberate attempt to contract those muscles might be akin to deliberately uncocking the wrists to release the club.
Just food for thought.
S
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Post by utahgolfer on Mar 22, 2020 17:56:12 GMT -5
Jeff, could you provide some examples of specific shoulder girdle muscles and their exact actions to promote the early release of pa#4?
Also, isn't this example of Ben Hogan still the main description of the release of pa#4: To bring the arms down to p5.5, as the hips and shoulders turn, with no obvious release of pa#2 or 4?
Thanks, UG
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Post by imperfectgolfer on Mar 22, 2020 19:55:57 GMT -5
UG,
You asked-: "Jeff, could you provide some examples of specific shoulder girdle muscles and their exact actions to promote the early release of pa#4?"
Any left shoulder girdle muscle that contributes to depression of an elevated left arm eg. latisssimus dorsi.
You wrote-: "Also, isn't this example of Ben Hogan still the main description of the release of pa#4: To bring the arms down to p5.5, as the hips and shoulders turn, with no obvious release of pa#2 or 4?"
What do you mean when you state no obvious release of PA#4? If the arms get down to P5.5 as Ben Hogan demonstrates, surely PA#4 is being released.
Jeff.
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Post by utahgolfer on Mar 23, 2020 1:25:27 GMT -5
Jeff, one idea that the left arm is only released when the left humerus moves independent of the torso and releases its angle set at p4. When Hogan provides his video example he simply turns his shoulders from p4 to p5.5 and his left arm does not significantly change its orientation to his shoulder turn. To me, I don't think Hogan would have felt or agreed that he had any independent left arm motion. The only way he moved his left arm was due to his hip turn and simultaneous shoulder turn. To me, he is trying to keep the original angle attained at p4 by simply allowing the left arm to stay in sync with his shoulder turn. Only after p5.5 would Hogan agree that his left arm is outpacing his turning torso and moving independently, as he swings into impact.
So, to me, from p4 to p5.5 is when the golfer should feel no conscious independent motion of the left arm, just as Hogan demonstrates. This is the foundation of the kinematic sequence. The left arm is pulled by the turning torso; the left arm doesn't move on its own. Don't you think this is how all golfers should "feel" the release of the left arm? Not from p4, but from p5.5, as Hogan demonstrates?
Of course, the left arm moves from p4 to p5.5, and this is part of its speed increasing release, and there are other subtleties you have mentioned, but what should the golfer feel consciously from p4 to p5.5 with respect to left arm motion?
UG
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Post by syllogist on Mar 23, 2020 4:47:09 GMT -5
Hi UG,
In my opinion, this topic is probably the most important for acquiring a golf swing. It is largely the difference between "skilled" golfers and the rest or, rather, optimal vs. sub-optimal technique. I think that what you have described in terms of what one should "feel" and kinematic sequence is counterintuitive, but you're absolutely correct. The left arm needs no help except for a rotating torso causing inertia of the arm/club unit, despite what else one believes happens concurrently. Hogan could have explained it better but the old masters failed miserably in their explanations and could not relay to others what was so simple for them to perform, which, in one sense, is to do nothing. Enough rambling for me for the day ...
S
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Post by imperfectgolfer on Mar 23, 2020 9:15:57 GMT -5
UG, You wrote-: " one idea that the left arm is only released when the left humerus moves independent of the torso and releases its angle set at p4. When Hogan provides his video example he simply turns his shoulders from p4 to p5.5 and his left arm does not significantly change its orientation to his shoulder turn." What do you mean when you state that the left humerus has not changed its orientation angle relative to the torso (which is set at P4) when Hogan gets down to his P5.5 position? If the left hand moves from shoulder height to waist height, then it surely must have changed its orientation angle in the plane of left arm elevation => left arm depression - even though it has not changed its angle in the plane of left arm adduction => left arm abduction. Are you arguing that the release of PA#4 should only be considered to be present when the left arm changes its angle in the plane of adduction => abduction? Also, what about golfers (eg. Ryan Moore and Rory Sabbatinni) who have very high hands at P4 and then drop their hands to waist level? Ryan Moore downswing from P4 => P5.5. Are you inferring that he has not released PA#4 between P4 => P5.5? Jeff.
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Post by utahgolfer on Mar 23, 2020 15:46:22 GMT -5
Thanks S. Yes, this is a move I struggle with, so this topic is particularly important to me and, as you said, all golfers.
Jeff, no arguing here. Just trying to be enlightened. On page 77 of TGM, Homer outlines the four pressure points..."the force to be applied for the movement of the lever assemblies". PP#4 is described as "whenever the straight left arm contacts the left side". He illustrates this point as being where the upper left arm contacts the chest or the left pectoralis major muscle. To me, PP#4 is in play at p1, but obviously the left humerus slides independently across the chest wall from p1 to p4, depending on the player, so the hands can attain a more vertical position (the hands and shoulders usually move on different planes). But, at p4, the idea is that PP#4 represents a stable non-moving humerus on the chest wall for all players. The humerus essentially does not slide or move from that PP#4 until p5.5. The only way the humerus or hands change their position in space from p4 to p5.5 is a result of torso CCW rotation, some right scapula protraction, and some right lateral bend. There is essentially no release of the #4 pressure point and no independent sliding of the left humerus across the left chest wall until p5.5.
I would suggest the same for Ryan Moore, although he may have some initial downward sliding of the left humerus from p4 to p4.5. But, at p4.5, the same applies to him and other golfers who have extremely upright swings (Jim Furyk and Matthew Wolff). They need to reconnect PP#4 as soon as possible and stop all independent humerus motion as soon as possible. I believe any independent humerus motion close to p4 would be called a micro-movement outside the consciousness of the player.
Certainly, I believe Hogan would agree and state this was the basis for his swing drill to p5.5, showing how his arms were delivered to the p5.5 position with only body rotation and no independent left arm motion. He attempted to make this point very clear.
I'm not suggesting there are absolutely no micro-movements, but these are incidental to the major concept that the left arm is delivered to p5.5, and it does not do anything on its own until p5.5.
Another issue is how to define the release of PA#4. I assume Homer defined it as happening after p5.5, when there is a clear release of the angle between the shoulders and left arm, but this may be less precise because we know the left arm gains speed from p4 to p5.5.
Finally, I don't think the left arm ever blasts off the chest wall at p5.5, at least not for most golfers. With the left arm already moving fast into p5.5 and the shoulders still moving relatively fast, the left arm doesn't get an immediate jolt of energy. But, as the left arm is released from PP#4 and begins to move independently there is definitely a sustained increase of left arm speed. However, it is momentary as the left shoulder begins to move up and around and the łeft arm begins to decelerate and transfer maximum speed to the club at impact.
UG
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Post by imperfectgolfer on Mar 23, 2020 18:38:20 GMT -5
UG, You wrote-: " On page 77 of TGM, Homer outlines the four pressure points..."the force to be applied for the movement of the lever assemblies". PP#4 is described as "whenever the straight left arm contacts the left side". He illustrates this point as being where the upper left arm contacts the chest or the left pectoralis major muscle. To me, PP#4 is in play at p1, but obviously the left humerus slides independently across the chest wall from p1 to p4, depending on the player, so the hands can attain a more vertical position (the hands and shoulders usually move on different planes). But, at p4, the idea is that PP#4 represents a stable non-moving humerus on the chest wall for all players. The humerus essentially does not slide or move from that PP#4 until p5.5. The only way the humerus or hands change their position in space from p4 to p5.5 is a result of torso CCW rotation, some right scapula retraction, and some right lateral bend. There is essentially no release of the #4 pressure point and no independent sliding of the left humerus across the left chest wall until p5.5. --- Another issue is how to define the release of PA#4. I assume Homer defined it as happening after p5.5, when there is a clear release of the angle between the shoulders and left arm." I started this thread before I am re-thinking my definition of a PA#4 release. You are quoting HK's TGM definition of a PA#4 release as happening after P5.5 when the left arm becomes less adducted against the chest wall thereby decreasing the magnitude of pressure sensed at PP#4. HK's definition makes no sense to me because it implies that swing power is only generated via the release of PA#4 after P5.5, while I now believe that PA#4 release power is generated from the very start of the downswing as soon as the left hand moves away from its position at P4. Using my new personal definition of a PA#4 release phenomenon, PA#4 is released between P4 and P5.5 and it includes the movement of the left arm in the plane of left arm elevation => depression, and not only the movement of the left arm in the plane of left arm adduction => abduction. I also now think that the concept of PP#4 does not make any sense from a practical perspective because many pro golfers (eg. Tony Finau and Jon Rahm) do not even adduct their left arm far enough back to create any pressure of the left arm against their chest wall.
Jeff.
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