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Post by utahgolfer on Jun 15, 2020 23:29:57 GMT -5
Jeff,
You asked how the trailing arm is applying a positive "force-across-the-shaft" between P4 and P5.5, while simultaneously applying a negative "force-along-the-shaft" (that pulls the grip onto the shaft)? How is that combination biomechanically possible?
My guess is that it is related to the dorsiflexed position of the right wrist. A right wrist that is bent back from p4 to p5.5, with a rearward hand path arc, could pull the grip onto the shaft (similar to extensor action), while simultaneously produce force across the shaft to increase the club's angular velocity.
Here is a video from Be a Better Golf, highlighting Milo Lines concept of lag tension. It is clear that Milo does not feel his hand couple from p4 to p7, but to hit the ball so well, he must be doing it correctly. As illustrated in his drill, he places a high premium on keeping the right wrist dorsiflexed through impact.
UG
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Post by imperfectgolfer on Jun 16, 2020 7:08:24 GMT -5
I disagree with your suggestion that increasingly bending back the right wrist during the early downswing will allow a golfer to "pull the grip onto the club" while simultaneously increasing "force-across-the-shaft". If the degree of right wrist extension increases during the P4 => P5.5 time period, then it will increase the former phenomenon, but decrease the latter phenomenon because it is working upwards (in a direction that increases lag) and not downwards-and-outwards in a way that can increase "force-across-the-shaft".
Jeff.
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Post by dubiousgolfer on Jun 16, 2020 7:11:43 GMT -5
Dr Mann/UG
Could the pitch elbow move make the right hand grip apply a negative force along the shaft? When I do the right arm adduction and pitch elbow move, my forearm and dorsiflexed wrist seems to move clockwise (from my own eyeline perspective). My elbow moves forward leading my forearm/dorsiflexed wrist , but I do feel some sudden clockwise impetus of forearm/wrist (almost like its the inertia of my forearm/wrist dragging behind).
DG
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Post by imperfectgolfer on Jun 16, 2020 13:44:33 GMT -5
Dr Mann/UG Could the pitch elbow move make the right hand grip apply a negative force along the shaft? When I do the right arm adduction and pitch elbow move, my forearm and dorsiflexed wrist seems to move clockwise (from my own eyeline perspective). My elbow moves forward leading my forearm/dorsiflexed wrist , but I do feel some sudden clockwise impetus of forearm/wrist (almost like its the inertia of my forearm/wrist dragging behind). DG An assertive pitch elbow move can make the right forearm and right wrist move clockwise, which can then cause the "force-along-the-shaft" to move upwards, but then it should decrease one's ability to simultaneously produce a positive "force-across-the-shaft" action with the right hand, which requires an anti-clockwise move. I personally think that it makes no sense from a biomechanical perspective to imagine that one can produce a "force-along-the-shaft" move with the right hand that is directed upwards while the right hand is supposed to simultaneously produce a "force-across-the-shaft" that is directed partially downwards. Jeff.
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Post by imperfectgolfer on Jun 16, 2020 14:01:08 GMT -5
I played with Jim today and tried to produce a positive hand couple torque using both hands, but I found that it is extremely difficult to get my two hands working together in perfect symmetry. I found it much easier to apply a positive hand couple action with the left hand alone while simultaneously releasing PA#4 and I found that I could increase my speed of release of PA#2 more smoothly and efficiently using only the lead hand to produce the hand couple torque.
It is interesting to note that neither Sasho or Dr. Kwon actually measure the hand couple torque directly using an instrumented grip and they only estimate its torque value using inverse dynamic calculations. It is therefore possible to produce the same magnitude of hand couple torque with one hand (lead hand) rather than with two hands, and we have no way of clearly distinguishing the two different hand couple actions by simply looking at a golfer's swing action.
Jeff.
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Post by dubiousgolfer on Jun 16, 2020 19:25:35 GMT -5
Dr Mann Considering the vast difference in the graphs that Dr Kwon has produced before and after he 'normalises' them with the mass of the golfer, I would really like to see these graphs below before he 'normalised' them. DG PS. The graphs are very unclear but I can just see the y-axis showing Nm/kg whereas Torques are measured in Nm.
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Post by dubiousgolfer on Jun 16, 2020 20:09:50 GMT -5
Looks like Dr Kwon's graph are reasonably correct because look at SMK's 'non-normalised' graph below. The hand couple was still positive from P5.5 to P6 (during the release phase) and the Net Force has only just started to lead the club (and apply minimal MOF). DG PS. The value of the hand torque at around P5.5 in his video (from which that image above was copied from) is 17 Nm . Lets assume the couple was applied over distance 'arm' of 4 inches (2 inches either side of the Mid Hand Point ). 4 inches is about 0.1 metres The formula for hand couple is shown further below, therefore : T = 17 Nm d = 0.1 metres T= F X d Therefore 17 = F x 0.1 Force 'F' being exerted theoretically by each hand around the Mid-Hands point = 17/0.1 = 170 N Each hand is exerting a Force of 170N !!!! That is equivalent to approx 38 lbs force and drops to zero in about 0.02 secs. It seems that any releasing couple is just like a 'quick twist' (as Dr Mann said in a previous post - 'kick start' ) but obviously timed to perfection by the pro golfers.
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Post by dubiousgolfer on Jun 16, 2020 21:40:40 GMT -5
The above sort of makes sense why I felt an easier manageable release with a 10 finger grip than with a Vardon one. I am better able to 'release' the club when the hand couple moment arm distance 'd' is made larger (especially if I have small hands and weak wrists).
DG
PS. I am also assuming that the 170N individual hand couple torque at P5.5 is mostly composed of pressure forces transmitted to the hands/club via the more proximal body movements of the golfer. That's because I cannot imagine that the muscular torque via the wrists alone can create such a large force via each hand . But there 'may' also be some independent muscular wrist torque happening to 'release' the club from P5.5-P6 but impossible to confirm.
Dr Mann : This 'inverse dynamics' used by the golf scientists that resolve the motion of the club into a net force and hand couple is causing me great confusion.
For example take this scenario:
I can hold the club with straight arms in front of me with both wrists cocked to their maximum, then just bend my left arm slightly while forcefully keeping my right arm straight, which will cause my wrists to uncock slightly and the club to rotate away from me . Does that action constitute a 'Hand Couple' ? Reaction forces via my wrists have done the uncocking but it was really due to my left elbow bending and right arm being kept firmly straight.
So when the golf scientists use the term 'Hand Couple' does that actually mean a torque applied by muscular wrist torque or also wrist/hand 'reaction' torque forces that are secondary to other body movements?
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Post by imperfectgolfer on Jun 17, 2020 9:11:15 GMT -5
DG,
Surely, any force that produces an uncocking action of the left wrist that works at the level of the hands would constitute a couple torque and it does not mandate contraction of specific muscles.
I strongly suspect that the magnitude of the left wrist uncocking torque produced by a hand couple phenomenon is very small.
This one-armed golfer is obviously applying the necessary torque - using just one hand.
Jeff.
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Post by dubiousgolfer on Jun 17, 2020 9:26:25 GMT -5
Dr Mann
So how does one know whether some of that 17Nm 'Hand Couple' in SMK's video (related to the frame image I posted in previous post) has any active independent wrist uncocking happening? The 'couple ' could indirectly be caused by the active pivot , shoulder girdle actions, right elbow adduction movement , lateral flexion.
Maybe this is the reason why SMK, Dr Kwon and the other scientists have not put forward any conceptual ideas on the practical biomechanics that could create that 'Hand Couple'.
DG
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Post by imperfectgolfer on Jun 17, 2020 11:11:41 GMT -5
Dr Mann So how does one know whether some of that 17Nm 'Hand Couple' in SMK's video (related to the frame image I posted in previous post) has any active independent wrist uncocking happening? The 'couple ' could indirectly be caused by the active pivot , shoulder girdle actions, right elbow adduction movement , lateral flexion. Maybe this is the reason why SMK, Dr Kwon and the other scientists have not put forward any conceptual ideas on the practical biomechanics that could create that 'Hand Couple'. DG The left wrist uncocking torque produced by the left hand couple is likely produced purely by the left forearm muscles causing left wrist uncocking combined with the speed/direction of the downplane motion of the left hand along its circular path, and no further torque is required if the golfer is a left arm-only swinger. The torque applied by the right hand couple is going to be affected by many more biomechanical factors eg. punch versus pitch elbow motion, degree of right arm adduction, degree of right lateral bend, and degree of any right wrist straightening or right elbow straightening happening between P4 => P5.5. I am therefore not surprised that Kwon/Sasho are not putting any ideas forward on the actual biomechanical factors producing the hand couple torque. Another complicating factor is the position of the right hand on the grip. If the golfer uses a baseball grip, then any right hand push-force is applied below the mid-hand point. If the golfer places his right hand higher up the grip with two fingers overlapping the left hand in a Vardon pattern (like Jim Furyk), then most of the push-force could be applied over the left thumb. Jeff.
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Post by dubiousgolfer on Jun 17, 2020 12:20:10 GMT -5
Many thanks Dr Mann - I think my brain is starting to make sense of it all.
So for example, if SMK/Dr Kwon did an 'inverse dynamics' simplification of PINGMAN's swing , it would still show a net force and hand couple , but the whole of the hand couple would just be the 'Net Force MOF' . That's because PINGMAN doesn't have any other biomechanical means to provide indirect 'hand couples' to effect release. there would be no hand couple just a net force and a MOF.
DG
PS. I think I've got the above wrong so corrected
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Post by dubiousgolfer on Jun 18, 2020 18:18:02 GMT -5
Just to confirm that Sasho Mackenzie has confirmed:
"The hand couple is not just wrist torque"
I've also just re-read his most recent article '"How Amateur Golfers Deliver Energy To The Driver' and he only suggests the following regarding the biomechanics of the hand couple.
"The ability of a golfer to apply wrist joint torques and trail elbow extension torque would be key to maintaining a positive couple"
DG
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Post by imperfectgolfer on Jun 18, 2020 18:24:46 GMT -5
Just to confirm that Sasho Mackenzie has confirmed: "The hand couple is not just wrist torque" I've also just re-read his most recent article '"How Amateur Golfers Deliver Energy To The Driver' and he only suggests the following regarding the biomechanics of the hand couple. "The ability of a golfer to apply wrist joint torques and trail elbow extension torque would be key to maintaining a positive couple" DG What is trail elbow extension torque? Jeff.
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Post by dubiousgolfer on Jun 18, 2020 19:58:32 GMT -5
I haven't got a clue but the word extension seems to imply the straightening of the right arm. So wondering if he is inferring that the trail hand forces are providing its own couple.
DG
PS. On reflection , I don't think I'm correct and he must mean something else (only known to himself)
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