Post by dubiousgolfer on Apr 1, 2022 20:49:37 GMT -5
Dr Kwon mentioned this in his instruction video with Ben Crane so I emailed Dr Sasho MacKenzie:
Here is the exchange:
-----------------------------
Dear Sasho
Dr Kwon has mentioned that active wrist torque in the golf downswing can cause the body rotation to slow down?
But when I try and rationalise this I get the opposite , that body rotation would actually speed up.
If the golfer does use the kinematic sequence from proximal to distal then I'm assuming the below:
1. If the lead arm speeds up , the body slows down
2. If the club speeds up, the lead arm slows down
But if I work this backwards from distal to proximal I get the following:
3. If the club is made to speed up with active wrist torque using the forearm muscles, the lead arm slows down (same as point 2 above).
4. If the arm slows down, the body speeds up (ie. the opposite of point 1 above).
Have I made an error somewhere?
--------------------------------
Reply from SMK
I agree with Dr. Kwon.
I believe you made an error.
The arms slowing down does NOT mean the body will speed up. Is there a reason you believe this.
Sasho
-----------------------------
My reply which I understand has no evidence to back it up and didn't deserve a reply from SMK (and he hasn't done so).
Hi Sasho
I was looking at a biomechanics video by Dr Veronica Foster and saw this diagram below showing all the equal and opposite torques created.
Therefore I thought the following :
1. An anti-clockwise torque applied by my left my wrist from radial to ulnar deviation.
2. There will be an equal and opposite clockwise reaction torque on my left forearm (applied just above the wrist joint)
3. There will be an equal and opposite anti-clockwise reaction torque on my left humerus (applied just above my elbow joint)
5. There will be an equal and opposite clockwise reaction torque on my shoulder girdle (applied just above the shoulder joint)
6. There will be an equal and opposite anti-clockwise reaction torque on my ribcage (I don't know whether these torques act around the clavicle and the connecting AC and SC joints).
***NOTE - this was not in my email : There is something called the 'Scapulathoracic Joint' which is basically connection between the scapula and ribcage by fascia - see video below. *****
7. I am assuming that there is no joint between 'ribcage/spine/pelvis' other than the range of rotational motion offered by the facet joints in the different regions of the spine. Therefore 'ribcage/spine/pelvis' will turn anti-clockwise (ie. increase in body rotational speed in anti-clockwise direction not a decrease).
Have I made an error in my logic somewhere?
Now it gets complicated because I know the ribcage and spine are almost rigidly connected but can any regions of the spine be assumed to be joint? If not and it is rigid , the 'ribcage/spine (especially lumbar section) /pelvis' will all end up rotating anti-clockwise. I can imagine if a person has got a very flexible spine maybe there will be an extra 'joint' (maybe in the thoracic region) and the pelvis will end up rotating clockwise a slight amount until the facet joints in the spine prevent any further range of motion
------------------------------
No response from SMK (I wasn't surprised) so I spent several hours looking at the very large research article by Brady C Anderson 'An Analysis Of Angular Kinematics, Kinetic Energy and Angular Momentum In Player Body Segments' . This article is very technical and difficult to 'see the wood for the trees' as I imagine its a thesis for peer review and not supposed to be made easy for a non-academic in physics/maths to understand. But I was able to understand some of the graphs on angular momentum and submitted a more evidence based follow-up email to SMK (awaiting his reply).
My follow-up email
Dear Dr MacKenzie
Further to my previous email, I found this from 'Brady C Anderson' 2007 research article showing how the 'Absolute Angular Momentum' and the 'In Plane Angular Momentum' of the 'Hips/Torso/Arms/Club' segments vary in the golf swing. As the arms angular momentum peaks and decreases there is a large increase in the 'Torso' angular momentum up to impact.
It seems to suggest that there is a transfer of angular momentum from the arms to the torso happening at about 60% of the downswing time.
Maybe my idea about equal and opposite joint torques is not feasible and too far-fetched (without any supporting evidence) but the research article seems to imply that increasing the angular momentum of the club by active wrist torque (which will slow the arms down) may not slow the upper body down but increase its angular velocity in the mid-late downswing.
It does seem for the 500 golfers used in the research that proximal-distal sequencing is not (on average) happening therefore we cannot assume that the torso will peak and slow down as the downswing progresses to impact.
Does this make sense ?
DG
PS. Just noticed something that may 'muddy the waters' and that is Brady Anderson's definition of Hips/Torso/Arms/Club
Why is Anderson graph showing an increase in angular momentum for the Torso (which would probably mean an increase in angular velocity) when the 'arms' slow but yet the kinematic sequence graphs show a decrease in ribcage angular velocity (when the lead arm slows down)?
They cannot be compared because the body segments are being defined and measured differently. That is why Anderson research is saying Proximal-Distal sequencing is not happening from a kinetic energy and angular momentum perspective while Cheetham/Rose are saying the opposite by just using angular velocity (for different constitution of segments using different reference points of rotation for their measurements).
Note: In 'Dr Phil Cheetham/Dr Greg Rose' research article :Comparison of Kinematic Sequence Parameters between Amateur and Professional Golfers
"The arm and club rotate about an end point rather than a centre point; hence the angular velocity component around a normal to the instantaneous swing plane was used for these two segments."
The total angular momentum measured by Brady Anderson used the COM of the golfer as the point of rotation, so again, one cannot do a comparison between the Anderson and Cheetham/Rose graphs.
I doubt Dr Sasho MacKenzie will be able to provide an answer for me because the Brady Anderson vs Cheetham/Rose research is like comparing apples and pears.
Here is the exchange:
-----------------------------
Dear Sasho
Dr Kwon has mentioned that active wrist torque in the golf downswing can cause the body rotation to slow down?
But when I try and rationalise this I get the opposite , that body rotation would actually speed up.
If the golfer does use the kinematic sequence from proximal to distal then I'm assuming the below:
1. If the lead arm speeds up , the body slows down
2. If the club speeds up, the lead arm slows down
But if I work this backwards from distal to proximal I get the following:
3. If the club is made to speed up with active wrist torque using the forearm muscles, the lead arm slows down (same as point 2 above).
4. If the arm slows down, the body speeds up (ie. the opposite of point 1 above).
Have I made an error somewhere?
--------------------------------
Reply from SMK
I agree with Dr. Kwon.
I believe you made an error.
The arms slowing down does NOT mean the body will speed up. Is there a reason you believe this.
Sasho
-----------------------------
My reply which I understand has no evidence to back it up and didn't deserve a reply from SMK (and he hasn't done so).
Hi Sasho
I was looking at a biomechanics video by Dr Veronica Foster and saw this diagram below showing all the equal and opposite torques created.
Therefore I thought the following :
1. An anti-clockwise torque applied by my left my wrist from radial to ulnar deviation.
2. There will be an equal and opposite clockwise reaction torque on my left forearm (applied just above the wrist joint)
3. There will be an equal and opposite anti-clockwise reaction torque on my left humerus (applied just above my elbow joint)
5. There will be an equal and opposite clockwise reaction torque on my shoulder girdle (applied just above the shoulder joint)
6. There will be an equal and opposite anti-clockwise reaction torque on my ribcage (I don't know whether these torques act around the clavicle and the connecting AC and SC joints).
***NOTE - this was not in my email : There is something called the 'Scapulathoracic Joint' which is basically connection between the scapula and ribcage by fascia - see video below. *****
7. I am assuming that there is no joint between 'ribcage/spine/pelvis' other than the range of rotational motion offered by the facet joints in the different regions of the spine. Therefore 'ribcage/spine/pelvis' will turn anti-clockwise (ie. increase in body rotational speed in anti-clockwise direction not a decrease).
Have I made an error in my logic somewhere?
Now it gets complicated because I know the ribcage and spine are almost rigidly connected but can any regions of the spine be assumed to be joint? If not and it is rigid , the 'ribcage/spine (especially lumbar section) /pelvis' will all end up rotating anti-clockwise. I can imagine if a person has got a very flexible spine maybe there will be an extra 'joint' (maybe in the thoracic region) and the pelvis will end up rotating clockwise a slight amount until the facet joints in the spine prevent any further range of motion
------------------------------
No response from SMK (I wasn't surprised) so I spent several hours looking at the very large research article by Brady C Anderson 'An Analysis Of Angular Kinematics, Kinetic Energy and Angular Momentum In Player Body Segments' . This article is very technical and difficult to 'see the wood for the trees' as I imagine its a thesis for peer review and not supposed to be made easy for a non-academic in physics/maths to understand. But I was able to understand some of the graphs on angular momentum and submitted a more evidence based follow-up email to SMK (awaiting his reply).
My follow-up email
Dear Dr MacKenzie
Further to my previous email, I found this from 'Brady C Anderson' 2007 research article showing how the 'Absolute Angular Momentum' and the 'In Plane Angular Momentum' of the 'Hips/Torso/Arms/Club' segments vary in the golf swing. As the arms angular momentum peaks and decreases there is a large increase in the 'Torso' angular momentum up to impact.
It seems to suggest that there is a transfer of angular momentum from the arms to the torso happening at about 60% of the downswing time.
Maybe my idea about equal and opposite joint torques is not feasible and too far-fetched (without any supporting evidence) but the research article seems to imply that increasing the angular momentum of the club by active wrist torque (which will slow the arms down) may not slow the upper body down but increase its angular velocity in the mid-late downswing.
It does seem for the 500 golfers used in the research that proximal-distal sequencing is not (on average) happening therefore we cannot assume that the torso will peak and slow down as the downswing progresses to impact.
Does this make sense ?
DG
PS. Just noticed something that may 'muddy the waters' and that is Brady Anderson's definition of Hips/Torso/Arms/Club
Why is Anderson graph showing an increase in angular momentum for the Torso (which would probably mean an increase in angular velocity) when the 'arms' slow but yet the kinematic sequence graphs show a decrease in ribcage angular velocity (when the lead arm slows down)?
They cannot be compared because the body segments are being defined and measured differently. That is why Anderson research is saying Proximal-Distal sequencing is not happening from a kinetic energy and angular momentum perspective while Cheetham/Rose are saying the opposite by just using angular velocity (for different constitution of segments using different reference points of rotation for their measurements).
Note: In 'Dr Phil Cheetham/Dr Greg Rose' research article :Comparison of Kinematic Sequence Parameters between Amateur and Professional Golfers
"The arm and club rotate about an end point rather than a centre point; hence the angular velocity component around a normal to the instantaneous swing plane was used for these two segments."
The total angular momentum measured by Brady Anderson used the COM of the golfer as the point of rotation, so again, one cannot do a comparison between the Anderson and Cheetham/Rose graphs.
I doubt Dr Sasho MacKenzie will be able to provide an answer for me because the Brady Anderson vs Cheetham/Rose research is like comparing apples and pears.