|
Post by dubiousgolfer on Dec 29, 2021 12:18:38 GMT -5
Dr Mann Definitely not useful from a golf instructional perspective but I was more interested in comparing its results with whatever Dr Kwon publishes regarding GRFs and any relationship with clubhead speed. Dr Kwon measures moments (about the COM) in the frontal plane, sagittal, transverse planes but, as far as I am aware, has never computed the moments in the functional plane during the downswing. I'm still waiting to see if there are more videos that provide an explanation as to how Dr Kwon devised these step drills. I am assuming that its all related to the ground reaction force 3D data that he seems to specialise in. DG PS. The most interesting aspect of that article is the graph below and it shows that the 'In Plane component' of the 'Horizontal GRF moment' is positive , while the 'In Plane component ' of the 'Vertical GRF moment' is negative during the downswing about 0.08 secs from impact (ie. around P5.5). It demonstrates the importance of the 'HGRF moments' to get positive angular momentum 'In Plane' while the negative 'VGRF In Plane Moment' diminishes angular momentum. These findings contradict Dr Kwon's statement below: The 'GRF Moment' in the 'Transverse Plane' is very small , maximises at P5 where he states "This component is fairly small and has minimal importance".
|
|
|
Post by dubiousgolfer on Dec 30, 2021 19:32:05 GMT -5
Here is another Dr Kwon coaching session (similar to Brendon De Vore but 1 hour session) but he does stress the use of oblique muscles in the downswing but not the shoulder girdle muscles.
Looks like Dr Kwon has now created his own you-tube account.
DG
|
|
|
Post by imperfectgolfer on Dec 31, 2021 14:31:37 GMT -5
Here is another Dr Kwon coaching session (similar to Brendon De Vore but 1 hour session) but he does stress the use of oblique muscles in the downswing but not the shoulder girdle muscles. Looks like Dr Kwon has now created his own you-tube account. DG I like Kwon's overall teaching a lot because it echoes my approach - a pivot-induced release of the lead arm (PA#4) using the lower body to activate the pivot action. We both teach a body-driven golf swing approach that is the antithesis of the golf instructional teaching of Tony Luczak and Mike Malaska, who both teach an arm-driven golf swing technique combined with a reactive pivot motion.
There are some significant differences between Kwon's approach and mine - as described below.
Kwon accentuates an active pelvic motion in the backswing where he wants to get the trail leg pressure-loaded by P4 and he also talks about getting the body over a straightened trail leg with a large negative O factor. I prefer that the trail knee remain slightly flexed, which means that the negative O factor may be less in magnitude. I also want to see the trail hip joint driven into internal rotation so as to maximise the pre-loading of the trail side's lateral pelvic rotator muscles, while Kwon never discusses that biomechanical element.
Kwon talks about a "mature backswing" which means that while one is physically preparing to transitionally shift-rotate the pelvis starting at P3.5+, that one should allow the upper torso to continue to rotate clockwise and the club should still be moving back. That allows one to maximise one's dynamic X-factor and torso-pelvic separation. I agree with that approach, but I find it acceptable to start the pelvic rotation closer to P4 with less upper torso windup if a golfer does not have the flexibility to generate a large degree of torso-pelvic separation between P3.5 => P4.
Kwon finds it acceptable to have a "reverse-C look" (reverse pivoting look) at P4. I don't agree with that technique if the "reverse-C look" means that the lower thoracic spine and lumbar spine become tilted towards the target. I find it acceptable to have a "reverse-C look" where the mid-upper thoracic spine become slightly tilted towards the target secondary to the fact that the upper torso is capable of rotating >90 degrees (eg. 120+ degrees); but I do not want the lumbar spine/lower thoracic spine to become tilted towards the target at P4.
Kwon talks about keeping the pelvis and upper torso closed during the re-centering phenomenon that must happen if the golfer uses a right-loading pelvic motion technique. I partially agree, but that only applies to the upper torso and I believe that it is biomechanically natural for the pelvis to start rotating counterclockwise during the re-centering phase if a golfer activates the trail side lateral pelvic rotator muscles between P3.5 => P5.
Kwon talked about using the "wrists" to add swing power, but his details were totally lacking because he never discussed any details on how a golfer should use the "wrists". He also prefers that a golfer have a larger accumulator #3 angle at impact, but he did not describe the factors that affect the accumulator #3 angle at impact. He also incorrectly asserted that this student-golfer did not have a strong grip, but I think that he does have a very strong lead hand grip.
Jeff.
|
|
janik
Full Member
Posts: 143
Member is Online
|
Post by janik on Dec 31, 2021 16:42:39 GMT -5
Personally I am finding Dr. Kwon’s instructional videos very informative. It is good to see students make common mistakes (like we all do) and how he picks up on them.
Just by trying his step staged drills, I have achieved a PB driver swing speed of 115 mph (vs previous of 109mph) with little physical effort, so there is something in it! Still won’t fix my 60 yard slice into the trees!
Dr. Mann, can you summarise how a lower body pivot driven swing actually works? We all would agree that to make the club head go faster then the arm unit must travel faster through impact. So how does a relatively slow moving pelvis cause such a chain reaction in the shoulders? Also, I believe ladies are faster rotators than men, so why aren’t they generating higher club speeds if a pivot driven swing is so beneficial?
Thanks Janik
|
|
|
Post by imperfectgolfer on Dec 31, 2021 16:54:34 GMT -5
Personally I am finding Dr. Kwon’s instructional videos very informative. It is good to see students make common mistakes (like we all do) and how he picks up on them. Just by trying his step staged drills, I have achieved a PB driver swing speed of 115 mph (vs previous of 109mph) with little physical effort, so there is something in it! Still won’t fix my 60 yard slice into the trees! Dr. Mann, can you summarise how a lower body pivot driven swing actually works? We all would agree that to make the club head go faster then the arm unit must travel faster through impact. So how does a relatively slow moving pelvis cause such a chain reaction in the shoulders? Also, I believe ladies are faster rotators than men, so why aren’t they generating higher club speeds if a pivot driven swing is so beneficial? Thanks Janik
A female LPGA golfer may indeed have a faster pelvic rotation than a male PGA golfer even though they do not hit the ball as far. The reason is that having a fast pelvic rotation is only one part of the swing power equation and the upper torso must also rotate faster with an avoidance of excessive torso-pelvic separation. Most importantly, by having a very efficient right upper arm adduction maneuver combined with a pitch elbow motion, one can potentially have a faster release of PA#4 (lead arm) with a greater amount of retained clubhead lag between P4 => P6, and then subsequently a faster release of PA#2 - and I suspect that this is the major reason why male PGA tour golfers drive the ball farther than female LPGA tour golfers. It would be interested to know what Kwon thinks is the main reason for the difference in driving distance between male and female pro tour golfers.
Jeff.
|
|
|
Post by dubiousgolfer on Dec 31, 2021 20:07:37 GMT -5
It might be worthwhile listening to this podcast by Phil Cheetham which might explain why PGA men can generate more power in the downswing than LPGA women (ie. even with similar core and shoulder 'stretch shorten' capabilities). Apparently PGA men have more stretch shorten capability in their wrists and are able to retain the PA2 angle until later in the downswing. Listen to podcast clip from 18:44- 19:24 soundcloud.com/golf-science-lab/what-the-research-says-about-x-factor-w-dr-phil-cheetham?utm_source=golfsciencelab.com&utm_campaign=wtshare&utm_medium=widget&utm_content=https%253A%252F%252Fsoundcloud.com%252Fgolf-science-lab%252Fwhat-the-research-says-about-x-factor-w-dr-phil-cheethamI have previously posted some extracts from a research article that compared PGA vs LPGA kinematic data which showed PGA rate of uncocking the lead wrist and rate of trail arm extension were significantly greater than LPGA women. Further , there were 50% more wrist injuries in LPGA women than PGA men which suggest that the weak link in the golf swing kinematic sequence could be their wrist actions. I'm assuming the rate of trail arm extension in the mid-late downswing is due to a more energetic right upper arm adduction by PGA men (ie. like its own double-pendulum effect) rather than some active PP#1 release (see .gif below ) ------------------ cloud2.golfloopy.com/wp-content/uploads/2013/02/TW-Downswing-Combo-sm1.gif-------------- DG PS. I'm confused by Phil Cheetham saying PGA men have 6 degrees wrist stretch while LPGA have 2 degrees . What exactly does that mean? Does it mean that their backswing is more energetic and this promotes a greater eccentric stretch of their wrist muscles to stop the club and therefore generate a greater starting contractual force on the grip during the early downswing? Will this greater eccentric stretch create a smaller PA2 angle which they can use to optimise release around P5.5? I'm not wholly convinced yet. Dr Kwon has just published another you-tube video for a golfer who is more stocky than previous pupils and less flexible.
|
|
|
Post by imperfectgolfer on Dec 31, 2021 23:10:55 GMT -5
It might be worthwhile listening to this podcast by Phil Cheetham which might explain why PGA men can generate more power in the downswing than LPGA women (ie. even with similar core and shoulder 'stretch shorten' capabilities). Apparently PGA men have more stretch shorten capability in their wrists and are able to retain the PA2 angle until later in the downswing. Listen to clip from 18:44- 19:24 soundcloud.com/golf-science-lab/what-the-research-says-about-x-factor-w-dr-phil-cheetham?utm_source=golfsciencelab.com&utm_campaign=wtshare&utm_medium=widget&utm_content=https%253A%252F%252Fsoundcloud.com%252Fgolf-science-lab%252Fwhat-the-research-says-about-x-factor-w-dr-phil-cheethamI have previously posted some extracts from a research article that compared PGA vs LPGA kinematic data which showed PGA rate of uncocking the lead wrist and rate of trail arm extension were significantly greater than LPGA women. Further , there were 50% more wrist injuries in LPGA women than PGA men which suggest that the weak link in the golf swing kinematic sequence could be their wrist actions. I'm assuming the rate of trail arm extension in the mid-late downswing is due to a more energetic right upper arm adduction by PGA men (ie. like its own double-pendulum effect) rather than some active PP#1 release (see .gif below ) ------------------ cloud2.golfloopy.com/wp-content/uploads/2013/02/TW-Downswing-Combo-sm1.gif-------------- DG PS. I'm confused by Phil Cheetham saying PGA men have 6 degrees wrist stretch while LPGA have 2 degrees . What exactly does that mean? Does it mean that their backswing is more energetic and this promotes a greater eccentric stretch of their wrist muscles to stop the club and therefore generate a greater starting contractual force on the grip during the early downswing? Will this greater eccentric stretch create a smaller PA2 angle which they can use to optimise release around P5.5? I'm not wholly convinced yet. I do not believe in the possibility of a stretch-shorten cycle happening with respect to the lead wrist in the plane of radial => ulnar deviation because I do not believe that the extensor carpi ulnaris muscle is actively causing the release of PA#2. I believe that the speed of release of PA#2 is primarily due to the interplay between the speed-of-decreasing of the trail hand's hand couple torque and the speed-of-increasing of the lead hand's MoF happening simultaneously around P5 => P5.5. Also, I do not believe that an extra 4 degrees of wrist deviation in a radial direction could account for the fact that male pro golfers can release PA#2 faster than female pro golfers.
I think that the rate of trail arm extension in the later downswing in a pro golfer (who uses a pivot-induced lead arm swinging action) is simply due to the interplay of two factors - i) the speed of lead hand motion down the hand arc path after P5.5 and ii) the relative position of the trail shoulder where a trail shoulder that moves downplane slower will cause a faster "running-out-of-trail arm" scenario and therefore a faster trail arm extension phenomenon.
Jeff.
|
|
|
Post by dubiousgolfer on Dec 31, 2021 23:52:45 GMT -5
I asked Dr Kwon this question in a comment on his you-tube video:
"Dr Kwon - if the lower body is mainly responsible for generating clubhead speed , why can't LPGA players drive the ball as far as PGA men? From what I've read LPGA players have faster pelvic rotation and almost equivalent ribcage speed rotation."
Dr Kwon reply: "I believe it is because they just turn the pelvis. They don't use the legs much."
DG
|
|
|
Post by imperfectgolfer on Jan 1, 2022 1:30:47 GMT -5
I asked Dr Kwon this question in a comment on his you-tube video: "Dr Kwon - if the lower body is mainly responsible for generating clubhead speed , why can't LPGA players drive the ball as far as PGA men? From what I've read LPGA players have faster pelvic rotation and almost equivalent ribcage speed rotation." Dr Kwon reply: "I believe it is because they just turn the pelvis. They don't use the legs much." DG That's an unbelievably woeful reply that doesn't make any biomechanical sense to me! Jeff.
|
|
|
Post by dubiousgolfer on Jan 1, 2022 10:20:35 GMT -5
Dr Sasho MacKenzie intimated the same in this video below (see 28:10 -31:17)
If I've interpreted this correctly , LPGA women must be using horizontal ground reaction forces more than vertical ground reaction forces.
So I am tentatively assuming that LPGA are predominantly using HGRFs that spin their pelvis body segment (ie. lower body) faster because it is more 'disconnected' with the upper torso because of their superior pelvic-torso separability. That PGA men are more 'connected' between their lower and upper bodies, which means they have to use the ground reaction forces more (that means larger HGRFs and VGRFs) to assist in the rotation of their whole body mass ,especially their upper torso, to help propel the lead arm and club in the downswing.
But what I've said above seems to contradict what Dr Phil Cheetham said on that podcast (listen from 18:50-19:08) where he says they found that men and women have the same core and shoulder stretch. That suggests to me that men and women are just as 'connected' as the men at the top of the backswing or during the transition in terms of 'stretch-shorten'.
Again, I am not wholly convinced by the suggested explanations because no-one has proved anatomically how ground reaction forces can permeate through the body segments and ultimately generate forces via the hands to increase clubhead speed. I can appreciate how SSC can contribute to greater contractual muscle force with less effort but a 4 degree difference at the wrist doesn't explain why PGA men can generate significantly greater clubhead speed than LPGA women.
DG
PS. I'm becoming more inclined to believe that the difference in clubhead speed is simply because of superior PGA shoulder girdle strength.
|
|
|
Post by imperfectgolfer on Jan 1, 2022 10:38:34 GMT -5
I posted the following reply to Dr. Kwon in his comments section of that video-"How can using the legs cause male pro golfers to generate a faster clubhead speed at impact than female pro golfers if it does not increase the speed of pelvic rotation? I could imagine that a male pro golfer can generate a greater magnitude of vertical GRF than a female pro golfer and that theoretically could produce a greater counterclockwise rotation of the torso around the body's COM and possibly increase the speed of upper torso rotation during the downswing. However, studies have shown that female pro golfers have similar rates of upper torso rotation than male pro golfers, so that explanation would make no sense. Studies have also shown that male pro golfers have higher speeds of release of the club (called the release of PA#2 in TGM terminology) than female pro golfers and that is the only significant difference between PGA male golfers and LPGA female golfers. What is causing that difference that is operating at the level of the lead wrist? I imagine that it could be due to differences i) in the rate of decrease of the positive trail hand couple torque that starts to decrease between P5 => P5.5 and/or differences ii) in the rate of increase of the MoF that is secondary to the lead hand moving down the hand arc path that is happening at the same time. What are your thoughts on this issue? "
Is my reply viewable by the public or has my post been blocked?
Jeff.
|
|
|
Post by imperfectgolfer on Jan 1, 2022 10:52:23 GMT -5
Dr Sasho MacKenzie intimated the same in this video below (see 28:10 -31:17) If I've interpreted this correctly , LPGA women must be using horizontal ground reaction forces more than vertical ground reaction forces. So I am tentatively assuming that LPGA are predominantly using HGRFs that spin their pelvis body segment (ie. lower body) faster because it is more 'disconnected' with the upper torso because of their superior pelvic-torso separability. That PGA men are more 'connected' between their lower and upper bodies, which means they have to use the ground reaction forces more (that means larger HGRFs and VGRFs) to assist in the rotation of their whole body mass ,especially their upper torso, to help propel the lead arm and club in the downswing. But what I've said above seems to contradict what Dr Phil Cheetham said on that podcast (listen from 18:50-19:08) where he says they found that men and women have the same core and shoulder stretch. That suggests to me that men and women are just as 'connected' as the men at the top of the backswing or during the transition in terms of 'stretch-shorten'. Again, I am not wholly convinced by the suggested explanations because no-one has proved anatomically how ground reaction forces can permeate through the body segments and ultimately generate forces via the hands to increase clubhead speed. I can appreciate how SSC can contribute to greater contractual muscle force with less effort but a 4 degree difference at the wrist doesn't explain why PGA men can generate significantly greater clubhead speed than LPGA women. DG PS. I'm becoming more inclined to believe that the difference in clubhead speed is simply because of superior PGA shoulder girdle strength. Sasho's explanation makes no sense to me because even if female pro golfers cannot generate as large vertical GRFs as male golfers, they can still rotate their upper torso as fast as men. The only major difference between LPGA female golfers and PGA male golfers is their speed of release of PA#2.
How could superior shoulder girdle muscle strength cause male pro golfers to generate a greater clubhead speed at impact? Are you suggesting that it allows them to release PA#4 faster? Where is the evidence that lead arm speed is faster in male pro golfers versus female pro golfers? Look at this comparison. Note that there is no significant differences in pelvic rotation, upper torso rotation and left arm-to-trunk speeds, and the only major difference is in left wrist uncocking speed.
Jeff.
|
|
|
Post by dubiousgolfer on Jan 1, 2022 12:22:01 GMT -5
Dr Mann
I can see your you-tube comment so it hasn't been barred.
You are also correct about the left/right arm to trunk velocities being similar for the men and women however the physics is slightly more complicated to deduce the forces that are applied via the hands on the club .
There are other factors involved other than angular velocities , such as the arm 'angular acceleration' , length of the arm moment, and its 'angular mass' (ie. moment of inertia).
DG
PS. I skimmed through that research article again and it said:
When compared with maximum angular velocities of the PGA players during downswing, the LPGA players had significantly lower wrist cocking (29% less), right elbow extension angular velocity (18% less), club shaft angular velocity (15% less), and lower club head linear speed (6% less) (> Table 2).
The timing in which maximum velocities occurred during downswing for the LPGA group was almost the same as in the PGA group (> Table 3). The maximum club head speed of the LPGA players occurred only slightly earlier (3%), although this difference was statistically significant (p = 0.005).
This means that there was little difference in the angular accelerations and I suspect there isn't a significant impact regarding the lengths of the moment arm and the angular mass . It does seem to be the LPGA women's inability to efficiently release PA#2. Also , I made an error regarding the degree of wrist injuries because LPGA experience twice as many wrist injuries as PGA men. I think I now understand what the author meant by significant lower angular velocity of the wrists due to 'Locking and braking' of the wrists and it may relate to how LPGA women safely decelerate the club in the follow-through. If their wrists are weak they may have to release PA#2 more slowly before impact so that they can safely decelerate them in the follow-through to avoid injury.
|
|
janik
Full Member
Posts: 143
Member is Online
|
Post by janik on Jan 1, 2022 14:11:26 GMT -5
Here’s a thought on what Dr Kwon may mean by using the legs:
Let’s imagine a heavy kettle bell or sledgehammer, say 10kg. Have a subject hold it with both hands. Then raise it up with an assist crane to a top of backswing position. Then with some other mechanical machine have it be forced downwards in a normal swing path.
Who would be more likely to be pulled off balance and fall forward; a man or woman?
So my hypothesis is that due to leg strength, men are ‘enabled’ to swing the mass of the club at higher speeds, as they have a stronger ability to counter balance the momentum.
|
|
|
Post by imperfectgolfer on Jan 1, 2022 17:52:12 GMT -5
Dr Mann I can see your you-tube comment so it hasn't been barred. You are also correct about the left/right arm to trunk velocities being similar for the men and women however the physics is slightly more complicated to deduce the forces that are applied via the hands on the club . There are other factors involved other than angular velocities , such as the arm 'angular acceleration' , length of the arm moment, and its 'angular mass' (ie. moment of inertia). DG PS. I skimmed through that research article again and it said: When compared with maximum angular velocities of the PGA players during downswing, the LPGA players had significantly lower wrist cocking (29% less), right elbow extension angular velocity (18% less), club shaft angular velocity (15% less), and lower club head linear speed (6% less) (> Table 2). The timing in which maximum velocities occurred during downswing for the LPGA group was almost the same as in the PGA group (> Table 3). The maximum club head speed of the LPGA players occurred only slightly earlier (3%), although this difference was statistically significant (p = 0.005). This means that there was little difference in the angular accelerations and I suspect there isn't a significant impact regarding the lengths of the moment arm and the angular mass . It does seem to be the LPGA women's inability to efficiently release PA#2. Also , I made an error regarding the degree of wrist injuries because LPGA experience twice as many wrist injuries as PGA men. I think I now understand what the author meant by significant lower angular velocity of the wrists due to 'Locking and braking' of the wrists and it may relate to how LPGA women safely decelerate the club in the follow-through. If their wrists are weak they may have to release PA#2 more slowly before impact so that they can safely decelerate them in the follow-through to avoid injury. I have very little sympathy for the idea that generating a high clubhead speed at impact predisposes to wrist injuries in female pro golfers because one assumes that they have "weak" wrists (whatever that means). Why should it predispose to wrist injuries if one uses the intact LFFW/GFLW technique combined with a DH-hand release action?
Jeff.
|
|