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Post by dubiousgolfer on Jun 30, 2023 7:37:39 GMT -5
Dr Mann In my opinion, I think Logan Aldridge is using passive tissue interaction from around P4- P4.5-4.7 triggering the release of PA#4 . I think he is using similar biomechanics to the forward dynamics model that Dr Sasho Mackenzie used where he optimised his model for maximum clubhead speed. Look at the SMK's model graph for optimisation of clubhead speed. From P4 to around P4.5-4.7 the lead arm is basically attached to the rotating torso (ie. passive tissue interaction) and assisting in triggering the release of PA#4, moving the lead hand linearly in 3D space from P4. Only around P4.5-P4.7 will the lead shoulder torque generator be activated (ie. which would be similar to using the shoulder girdle muscles). Can we therefore assume that this type of kinetics, where the body is 'levering' the lead arm around in the early downswing, is the same as a body driven TGM lead arm swinging action? DG
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Post by imperfectgolfer on Jun 30, 2023 15:20:30 GMT -5
Dr Mann In my opinion, I think Logan Aldridge is using passive tissue interaction from around P4- P4.5-4.7 triggering the release of PA#4 . I think he is using similar biomechanics to the forward dynamics model that Dr Sasho Mackenzie used where he optimised his model for maximum clubhead speed. Look at the SMK's model graph for optimisation of clubhead speed. From P4 to around P4.5-4.7 the lead arm is basically attached to the rotating torso (ie. passive tissue interaction) and assisting in triggering the release of PA#4, moving the lead hand linearly in 3D space from P4. Only around P4.5-P4.7 will the lead shoulder torque generator be activated (ie. which would be similar to using the shoulder girdle muscles). Can we therefore assume that this type of kinetics, where the body is 'levering' the lead arm around in the early downswing, is the same as a body driven TGM lead arm swinging action? DG I can easily accept that fact that the lead upper arm may be adducted to the same degree at P4.5 as it was at P4 while the upper torso, and therefore the lead shoulder socket, is in an early state of counterclockwise motion. However, that does not mean that any soft tissue compression that happens between the lead upper arm and the lead chest's pectoral area during that time period is causally responsible for the release of PA#4 in a pivot-driven TGM swinging action. It just means that the lead upper humerus is temporarily moving at roughly the same speed as the lead shoulder socket in the initial phase of the PA#4 release action. That time period when the lead upper arm remains well adducted can be very short (eg. between P4 => P4.25) or slightly longer (eg. between P4 => P4.5). You stated-: " In my opinion, I think Logan Aldridge is using passive tissue interaction from around P4- P4.5-4.7 triggering the release of PA#4." How does a passive soft tissue interaction between the soft tissue of the lead pectoral area and the soft tissue of the lead upper arm trigger the release of PA#4? Jeff.
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Post by dubiousgolfer on Jun 30, 2023 19:52:46 GMT -5
Dr Mann I will try and explain using my diagram further below which is basically a simplified version of Dave Tutelman's image (below) where I have added an imaginary yellow triangle which will act as fulcrum (ie. representing the passive tissue interaction between chest and upper arm) I know my drawing is just amateurish but it should show the general physics involved which Dave Tutelman did not detail in his article (he just assumed readers would understand what he meant). The upper torso torque will apply a force F at the lead shoulder socket which will lever the lead arm about the fulcrum. The forces are distributed about the lever (ie. the lead arm) as shown and can result in a force F2 generated at the hand which will act on the grip of the club. That force F2 will trigger the release of PA#4 and move the club from P4 in 3D space. DG
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Post by imperfectgolfer on Jun 30, 2023 21:09:25 GMT -5
Dr Mann I will try and explain using my diagram further below which is basically a simplified version of Dave Tutelman's image (below) where I have added an imaginary yellow triangle which will act as fulcrum (ie. representing the passive tissue interaction between chest and upper arm) I know my drawing is just amateurish but it should show the general physics involved which Dave Tutelman did not detail in his article (he just assumed readers would understand what he meant). The upper torso torque will apply a force F at the lead shoulder socket which will lever the lead arm about the fulcrum. The forces are distributed about the lever (ie. the lead arm) as shown and can result in a force F2 generated at the hand which will act on the grip of the club. That force F2 will trigger the release of PA#4 and move the club from P4 in 3D space. DG I totally reject your "idea" that there is fulcrum point at the yellow triangle that allows the anterior chest wall to apply pressure against the upper lead arm. Most pro golfers do not get their upper lead arm close enough to their lead pectoral area between P4 => P4.5 for that "chest pressure" phenomenon to happen. Also, your F2 black arrow shows the reputed direction of the PA#4 release force as moving the lead arm from adduction towards abduction. However, during the early phase of the release of PA#4 between P4 => P5.5, the lead arm mainly moves from being elevated to becoming lowered with very little change in the degree of lead arm adduction => abduction. Review again this AMG video. In particular, consider these capture images. Note how much the lead arm has lowered due to the release of PA#4 with very little change in the degree of lead arm adduction => abduction.
Jeff.
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Post by syllogist on Jul 1, 2023 5:33:20 GMT -5
Hi DG,
I believe that the passive lead arm will release from adduction when there is no longer acceleration of shoulder (torso) rotation. Also, there is a secondary, shorter, lever - the bent trail arm, which is not addressed in models. I think that if that arm is left passive, it will gradually straighten due to the rotational speed of the club - and, doesn't the straightening of that arm cause motion (or travel) of the lead arm? I'll leave it to you to work out.
S
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Post by dubiousgolfer on Jul 1, 2023 6:31:35 GMT -5
The interaction between upper arm and pectoral area is similar to the interaction between clubface and ball. If you look at the slow motion impact , the ball deforms and is squashed against the clubface while both travel attached together for a small amount of time (the impact period). In this case both the chest and lead upper arm are being squashed together and also rotating together for a small amount of time, which means the hand will also have to rotate in 3D space.
This rotation of chest/arm will form a component of the rotational torque in the plane of upper thorax rotation, while the shoulder girdle muscles will be applying the downward component motion of the lead arm.
The fulcrum that I drew will not be in a constant position but will shift as the lead arm gradually abducts and the point of tissue chest/arm interaction moves further in the direction towards the shoulder socket.
I cannot see any other feasible way for the upper body to drive the lead arm around in space in a TGM body driven swinging action (ie. to trigger the release of PA#4).
For example, here is a top view of Shawn Clement's swing .
In my opinion he is not using any passive tissue interaction with his chest but can still, even in his late fifties, drive the ball 300 yds playing left or right handed. He cannot be using his upper body to drive his lead arm to release PA#4 but more likely his shoulder girdle muscles.
DG
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Post by imperfectgolfer on Jul 1, 2023 9:17:24 GMT -5
The interaction between upper arm and pectoral area is similar to the interaction between clubface and ball. If you look at the slow motion impact , the ball deforms and is squashed against the clubface while both travel attached together for a small amount of time (the impact period). In this case both the chest and lead upper arm are being squashed together and also rotating together for a small amount of time, which means the hand will also have to rotate in 3D space. This rotation of chest/arm will form a component of the rotational torque in the plane of upper thorax rotation, while the shoulder girdle muscles will be applying the downward component motion of the lead arm. The fulcrum that I drew will not be in a constant position but will shift as the lead arm gradually abducts and the point of tissue chest/arm interaction moves further in the direction towards the shoulder socket. I cannot see any other feasible way for the upper body to drive the lead arm around in space in a TGM body driven swinging action (ie. to trigger the release of PA#4). For example, here is a top view of Shawn Clement's swing . In my opinion he is not using any passive tissue interaction with his chest but can still, even in his late fifties, still drive the ball 300 yds playing left or right handed. He cannot be using his upper body to drive his lead arm to release PA#4 but more likely his shoulder girdle muscles. DG We have totally opposite opinions regarding this issue. I posted an AMG capture image of Sergio Garcia, Rory McIlroy and Dustin Johnson at P4 and their measured degree of lead shoulder abduction at P4 is too large to allow for any significant tissue compression-interaction between the pectoral area of the lead chest and the lead upper arm. Mike Granato also shows that the lead upper arm is moving towards a greater degree of abduction (and at a faster speed compared to upper torso rotation) within 23 - 61 msecs of the start of the transition - watch the AMG video between the 4:20 - 5:06 minute time points. I think that any soft tissue interaction between the lead upper arm and the lead anterior chest wall plays no role in the release of PA#4. I think that the lead arm moves mainly downwards between P4 => P5.5 due to the pulling force exerted by the lead shoulder socket on the lead humeral head assisted by the contraction of some of the shoulder girdle muscles and the lead latissimus dorsi muscle. I think that Shawn Clement is using the same pivot-driven TGM swinging technique. Jeff.
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Post by imperfectgolfer on Jul 1, 2023 9:31:31 GMT -5
Hi DG, I believe that the passive lead arm will release from adduction when there is no longer acceleration of shoulder (torso) rotation. Also, there is a secondary, shorter, lever - the bent trail arm, which is not addressed in models. I think that if that arm is left passive, it will gradually straighten due to the rotational speed of the club - and, doesn't the straightening of that arm cause motion (or travel) of the lead arm? I'll leave it to you to work out. S Watch this AMG video between the 4:20 - 5:05 minute time points. Note that the lead arm is moving faster than the upper torso/lead shoulder socket within 23 - 61 msecs of the start of the downswing in those 3 pro golfers, and that happens well before the upper torso (lead shoulder socket) is no longer accelerating. I do not understand why you believe that the trail elbow straightens in response to the rotational speed of the club. I think that it straightens in response to the speed of lead hand motion along the hand arc path between ~P5.2 => P7 when the lead elbow slows down its downplane/targetwards motion (which mainly happens after the trail upper arm adduction maneuver is fully completed and the trail elbow is situated near its pitch location alongside the trail hip joint area).
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Post by dubiousgolfer on Jul 1, 2023 11:41:19 GMT -5
The interaction between upper arm and pectoral area is similar to the interaction between clubface and ball. If you look at the slow motion impact , the ball deforms and is squashed against the clubface while both travel attached together for a small amount of time (the impact period). In this case both the chest and lead upper arm are being squashed together and also rotating together for a small amount of time, which means the hand will also have to rotate in 3D space. This rotation of chest/arm will form a component of the rotational torque in the plane of upper thorax rotation, while the shoulder girdle muscles will be applying the downward component motion of the lead arm. The fulcrum that I drew will not be in a constant position but will shift as the lead arm gradually abducts and the point of tissue chest/arm interaction moves further in the direction towards the shoulder socket. I cannot see any other feasible way for the upper body to drive the lead arm around in space in a TGM body driven swinging action (ie. to trigger the release of PA#4). For example, here is a top view of Shawn Clement's swing . In my opinion he is not using any passive tissue interaction with his chest but can still, even in his late fifties, still drive the ball 300 yds playing left or right handed. He cannot be using his upper body to drive his lead arm to release PA#4 but more likely his shoulder girdle muscles. DG We have totally opposite opinions regarding this issue. I posted an AMG capture image of Sergio Garcia, Rory McIlroy and Dustin Johnson at P4 and their measured degree of lead shoulder abduction at P4 is too large to allow for any significant tissue compression-interaction between the pectoral area of the lead chest and the lead upper arm. Mike Granato also shows that the lead upper arm is moving towards a greater degree of abduction (and at a faster speed compared to upper torso rotation) within 23 - 61 msecs of the start of the transition - watch the AMG video between the 4:20 - 5:06 minute time points. I think that any soft tissue interaction between the lead upper arm and the lead anterior chest wall plays no role in the release of PA#4. I think that the lead arm moves mainly downwards between P4 => P5.5 due to the pulling force exerted by the lead shoulder socket on the lead humeral head assisted by the contraction of some of the shoulder girdle muscles and the lead latissimus dorsi muscle. I think that Shawn Clement is using the same pivot-driven TGM swinging technique. Jeff. Dr Mann I think you could be correct as I've now reviewed that SMK article and I think DT has interpreted that optimised graph incorrectly. The part of the graph showing all positive torso torque is relating to the backswing, not the downswing. There is no passive tissue interaction in the downswing!.Look at the top 2 graphs for the model's optimised swing where the angular displacement of the torso is negative (as well as the angular velocity) and that's because the model was given some angular velocity in the backswing as per SMK's article excerpt shown below. What a waste of time!!! SMK states : "An initial angular velocity of 5 rad/s, in the backswing direction, about the Tz axis was also given to all segments of the model, so as to simulate the dynamic transition from the backswing into the downswing".
DT says: For the first part of the downswing, the muscular torque is all torso. There is no shoulder torque, the torque that separates the left arm from the chest. That means that the left arm is being driven by what MacKenzie calls "passive tissue interaction" with the chest; the chest is pushing the left arm around. That is further confirmation that this does in fact increase clubhead speed, because a computer optimization of one of the better swing models recommends it.DG
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Post by syllogist on Jul 2, 2023 1:38:53 GMT -5
Dr. Mann said: "Note that the lead arm is moving faster than the upper torso/lead shoulder socket within 23 - 61 msecs of the start of the downswing in those 3 pro golfers, and that happens well before the upper torso (lead shoulder socket) is no longer accelerating.
I do not understand why you believe that the trail elbow straightens in response to the rotational speed of the club. I think that it straightens in response to the speed of lead hand motion along the hand arc path between ~P5.2 => P7 when the lead elbow slows down its downplane/targetwards motion (which mainly happens after the trail upper arm adduction maneuver is fully completed and the trail elbow is situated near its pitch location alongside the trail hip joint area)."
Dr. Mann, The small amount of loss of the adduction angle very early in the downswing is not worth investigating since acceleration of the torso is just starting and the arm is passive in that one need not try to muscularly maintain that adduction angle. Could it also be due to the trail scapula becoming less retracted?
Of course as a small degree of the adduction angle is lost early, so too can there be a small degree of an early loss of trail arm bend. However, after P4 when the elbow nears the hip, such location represents something of an anatomical limit to elbow travel. At the same time, the speed of the hands slows because the clubhead is moving in the opposite direction of the travel of hands (what DT refers to as the onset of wrist release). Hands decelerating = clubhead gaining rotational speed which releases the trail elbow at the point where it has virtually stopped traveling.
S
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Post by dubiousgolfer on Jul 11, 2023 16:01:57 GMT -5
JB Holmes has a bent lead elbow at P4 and straightens it by P5.5 which means the angular velocity of his forearm increased more than his upper arm before PA2# release. DG I think that the amount of lead elbow bend is small and not significant. It would be significant if one used the Jack Kuykendall technique - where be bends his lead elbow to ~90 degrees at P4. Jeff. Dr Mann Here is a slide I found, which was created by Dr Phil Cheetham from AMM 3D data for JB Holms. It looks like JB's forearm angular velocity is significantly higher than his upper arm before PA#2 release. DG PS. The pga driving stats show Rory driver clubhead speed is 123 mph (2023) while JB is 115.21 mph (2023 ) . But in the 2015/16 season Rory had 120 mph while JB 121 mph. Unsure of the dates of these kinematic sequence graphs, but I'm assuming it was several years ago and that their driver clubhead speeds must have been very similar.
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Post by imperfectgolfer on Jul 12, 2023 9:44:37 GMT -5
I think that the amount of lead elbow bend is small and not significant. It would be significant if one used the Jack Kuykendall technique - where be bends his lead elbow to ~90 degrees at P4. Jeff. Dr Mann Here is a slide I found, which was created by Dr Phil Cheetham from AMM 3D data for JB Holms. It looks like JB's forearm angular velocity is significantly higher than his upper arm before PA#2 release. DG PS. The pga driving stats show Rory driver clubhead speed is 123 mph (2023) while JB is 115.21 mph (2023 ) . But in the 2015/16 season Rory had 120 mph while JB 121 mph. Unsure of the dates of these kinematic sequence graphs, but I'm assuming it was several years ago and that their driver clubhead speeds must have been very similar. That Cheetham graph showing that JB Holmes' lead forearm's angular velocity is much greater than his lead upper arm's angular velocity is very interesting. The difference is much greater than I anticipated. Note that when his lead upper arm slows down, the lead forearm's angular velocity does not increase and it follows the same slope-steepness of the lead upper's arm early downswing time period. In other words, if you look at his lead forearm's red graph, it would look similar to Rory McIlroy's lead arm angular velocity graph. Here is a comparison between Rory McIlroy and JB Holmes. It always puzzled me how JB Holmes could generate the same clubhead speed at impact as Rory McIlroy even though his maximum lead arm speed (reflecting the speed of PA#4 release) is much lower. I now suspect that the blue graph reflects the angular speed of JB Holmes' lead upper arm. If they measured the speed of his lead forearm (and not his lead humerus) to produce the blue graph, then his blue graph would probably look very similar to Rory's blue graph where the lead hand speed at P5.5 would be closely similar. In other words, the speed of lead hand motion at P5.5 is a reflection of the speed of release of PA#4, and that JB Holmes uses a slightly different PA#4 release technique involving a triple pendulum swing model where the release of the lead forearm relative to the lead upper arm can be considered to be an additional PA-release phenomenon, which we can arbitrarily label it as being a PA#6 release phenomenon. Then, there is no evidence that JB Holmes, who uses a PA#6 release action in his PA-release action sequence, can generate a faster hand speed at P5.5 than Rory Mcilroy, who keeps his lead arm straight.
Jeff.
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Post by dubiousgolfer on Jul 12, 2023 16:26:19 GMT -5
Dr Mann
When you said "the lead forearm's angular velocity does not increase and it follows the same slope-steepness of the lead upper's arm early downswing time period" I think you meant to say 'angular acceleration'.
Yes, it seems like PA#6 might be a nice way to describe the release of the forearm relative to the humerus and it will have to be timed properly in the downswing so that the whole arm is relatively straight approaching impact (I think JB's elbow extension is about 175 degrees at P7).
JB's elbow extension angle from P4-P5 (ie. humerus is horizontal at P5) is relatively unchanged and then he releases the forearm from P5-P7 . Therefore his release of PA#2 must be happening while his lead elbow still has some bend.
I am confused how a non-optimal lead elbow bend could start after P5. Wouldn't that mean the right 'arm/hand' is somehow dragging back the lead hand/forearm , while the upper torso pivot & lead shoulder girdle is pulling around the lead humerus? Could this also be caused by an inadequate right arm adduction to support the lead arm swinging motion?
DG
PS. This is what Dr Phil Cheetham said about those graphs:
"Yes, bending the lead elbow and releasing the angle in the downswing can increase club head speed.
Using the AMM3D system we can graph the angular speed of both the upper arm and the forearm for some golfers we found an increase in angular speed from the lead upper arm to the lead forearm. In others, we didn't. So our conclusion was that if correctly timed, as in all other joints in the kinematic sequence, an extra link in the sequence can increase club head speed. The example I show of an effective link is JB Holmes. On the left of the top set of graphs, you see the graphs of angular velocities for the pelvis (red), chest (thorax) (green), upper arm (blue), forearm (dark red), and shaft (brown) in the downswing. Notice the sequential peaking then decelerations, and that there is a substantial increase in angular velocity from one curve to the next. This demonstrates an effective extra link in the kinematic sequence showing substantial speed gain from one body segment to the next. The graphs on the right show the joint angle when they reach their minimum values (max negative value for spine) also that this happens sequentially (the frame number of each minimum is shown on the graphs). So each joint releases sequentially in the downswing. The second example shows an ineffective use of the elbow link in the kinematic sequence. The forearm's max angular speed is actually lower than the upper arm's speed. So yes a bent lead elbow can help increase the club head speed but only if its release is timed correctly. If the elbow bend is released at the wrong time, it can actually slow the speed of the forearm and hence the speed transmitted to the club."
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Post by imperfectgolfer on Jul 12, 2023 17:42:56 GMT -5
Dr Mann When you said "the lead forearm's angular velocity does not increase and it follows the same slope-steepness of the lead upper's arm early downswing time period" I think you meant to say 'angular acceleration'. Yes, it seems like PA#6 might be a nice way to describe the release of the forearm relative to the humerus and it will have to be timed properly in the downswing so that the whole arm is relatively straight approaching impact (I think JB's elbow extension is about 175 degrees at P7). JB's elbow extension angle from P4-P5 (ie. humerus is horizontal at P5) is relatively unchanged and then he releases the forearm from P5-P7 . Therefore his release of PA#2 must be happening while his lead elbow still has some bend. I am confused how a non-optimal lead elbow bend could start after P5. Wouldn't that mean the right 'arm/hand' is somehow dragging back the lead hand/forearm , while the upper torso pivot & lead shoulder girdle is pulling around the lead humerus? Could this also be caused by an inadequate right arm adduction to support the lead arm swinging motion? DG PS. This is what Dr Phil Cheetham said about those graphs: "Yes, bending the lead elbow and releasing the angle in the downswing can increase club head speed.
Using the AMM3D system we can graph the angular speed of both the upper arm and the forearm for some golfers we found an increase in angular speed from the lead upper arm to the lead forearm. In others, we didn't. So our conclusion was that if correctly timed, as in all other joints in the kinematic sequence, an extra link in the sequence can increase club head speed. The example I show of an effective link is JB Holmes. On the left of the top set of graphs, you see the graphs of angular velocities for the pelvis (red), chest (thorax) (green), upper arm (blue), forearm (dark red), and shaft (brown) in the downswing. Notice the sequential peaking then decelerations, and that there is a substantial increase in angular velocity from one curve to the next. This demonstrates an effective extra link in the kinematic sequence showing substantial speed gain from one body segment to the next. The graphs on the right show the joint angle when they reach their minimum values (max negative value for spine) also that this happens sequentially (the frame number of each minimum is shown on the graphs). So each joint releases sequentially in the downswing. The second example shows an ineffective use of the elbow link in the kinematic sequence. The forearm's max angular speed is actually lower than the upper arm's speed. So yes a bent lead elbow can help increase the club head speed but only if its release is timed correctly. If the elbow bend is released at the wrong time, it can actually slow the speed of the forearm and hence the speed transmitted to the club."Yes - I meant angular acceleration when I referred to the slope of the curve. You wrote-: "I am confused how a non-optimal lead elbow bend could start after P5. Wouldn't that mean the right 'arm/hand' is somehow dragging back the lead hand/forearm , while the upper torso pivot & lead shoulder girdle is pulling around the lead humerus? Could this also be caused by an inadequate right arm adduction to support the lead arm swinging motion?" I agree with your bold-highlighted statement. If a golfer has a relaxed lead elbow that allows for bending between P4 => P5.5, then it could bend more if the trail hand cannot keep up with the speed of the lead hand due to a too sluggish trail arm adduction maneuver that holds the lead hand back despite an efficient release of PA#4. You quoted Phil Cheetham as follows-: "So our conclusion was that if correctly timed, as in all other joints in the kinematic sequence, an extra link in the sequence can increase club head speed. The example I show of an effective link is JB Holmes. On the left of the top set of graphs, you see the graphs of angular velocities for the pelvis (red), chest (thorax) (green), upper arm (blue), forearm (dark red), and shaft (brown) in the downswing. Notice the sequential peaking then decelerations, and that there is a substantial increase in angular velocity from one curve to the next. This demonstrates an effective extra link in the kinematic sequence showing substantial speed gain from one body segment to the next." He has not shown that an extra link in the kinematic sequence can increase clubhead speed. JB Holmes' lead forearm travels faster than his lead humerus at a certain time point in the early-mid downswing, but he has not shown that his lead hand speed at P5.5 is faster than it would otherwise have been - compared to a scenario where he maintains a straight left arm. His bold-highlighted statement is totally unscientific because there is no evidence that any of the body/arm kinematic curves build-up clubhead speed on top of the sequence of a previous curve - and they may be happening concurrently, and not sequentially, from a clubhead speed generation perspective.
Jeff.
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Post by dubiousgolfer on Jul 12, 2023 19:09:07 GMT -5
Dr Mann
What if JB was using his lead triceps muscle to actively extend his elbow in the downswing? Wouldn't that increase clubhead speed over a straighter arm if the extension was timed perfectly?
Phil Cheetham didn't mention how the forearm is released , whether due to a mechanism like the 'in plane MOF' that releases PA#2 or by musculature triceps contraction or a bit of both.
We do know that active wrist torque in the downswing can be detrimental to clubhead speed unless the timing is perfect , so does the same apply to an active triceps release of the lead forearm?
If we look at the kinematic sequence graphs again for Rory vs JB , JB's maximum pelvis/thorax angular velocities are inferior but his max forearm angular velocity is similar to Rory's straight arm angular speed. How can that be?
Somehow, JB is able to do similar linear work on the club as Rory but with a bent lead elbow, where his hands traverse over a smaller downswing path. Rory's straighter lead arm means he has more width in his downswing and his hands travel over a longer hand path.
Therefore, for JB to do similar linear work (via his hands on the grip) as Rory, he will have to apply, on average, a greater linear force along a smaller hand path. How can he generate a larger average linear force in the downswing if has an inferior upper/lower pivot angular velocity than Rory? I suspect he could be using his shoulder girdles more actively to generate larger hand forces on the grip or actively using his lead triceps to help release his forearm, or a bit of both.
DG
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