Questions at the summit

[wulsy]

Were any of the forum questions put to the panel?

My question was whether we should be trying to create shear forces on the ground or trying to avoid them.

http://www.brianmanzella.com/golfin...ummit-ii-questions-right-here.html#post211547

 

[SteveT]

That's a stopid question... of course there are "shear" forces between the shoes and the ground, otherwise you wouldn't have rotation and shifts in the body-club centers of mass...!!!

Every force and torque generated by the golfswing are countered by Ground Reaction Forces... that's unavoidable..

 

[wulsy]

Steve, you may be an engineer, but you sure ain't a Professor of English. Read the question bud.

 

[SteveT]

Steve, you may be an engineer, but you sure ain't a Professor of English. Read the question bud.

Okay... Your question was whether we should be trying to (a)create shear forces on the ground or trying to (b)avoid them.

Since it's impossible to (b)avoid them, you are only left with option (a)... and I think I rationally responded to that.

So where does the confusion lay... with me or you? I still think your's is still a stopid question.... oh, is there a "u" in stopid?!

 

[wulsy]

It all about intention baby!

Trying to create = active trying to create them ie maximising the friction.

Trying to avoid = passively accepting them but actually trying to minimise them.

Kapish? Ya gerrit? Comprends? Verstehst?

 

[SteveT]

It all about intention baby!

Trying to create = active trying to create them ie maximising the friction.

Trying to avoid = passively accepting them but actually trying to minimise them.

Baby intention..???!!!!!

If you're trying to get somebody pregnant, I would say maximise.... but if your trying to play golf keep it all under control .... or as Brian says: "going normal" ... and staying normal too.

Hope that helps (stopid is as stopid does).....

 

[wulsy]

Thanks Steve, I'll bear that in mind. Man, you know a lota stuff...

 

[SteveT]

Thanks Steve, I'll bear that in mind. Man, you know a lota stuff...

"Ask and ye shall learn... seek and ye shall find... swing and ye shall suffer immense pain and confusion forevermore ..." - SteveT

 

[wulsy]

Thank you great one, you are not only wise, but you are a kind and generous man also.

But did you understand my question?

 

[wulsy]

Maybe this question cannot be answered at the moment because nobody knows. Could it be that it may be answered in part II of Project 1.68 as it would seem that influences from the body are now under observation in more detail...

 

[SteveT]

Maybe this question cannot be answered at the moment because nobody knows. Could it be that it may be answered in part II of Project 1.68 as it would seem that influences from the body are now under observation in more detail...

Oday, let's parse your questions with these questions:

(a) how do you create shear forces on the ground, and,

(b) how can you "avoid" them?

I thot I answered your question, and now you think your question cannot be answered because you incorrectly assume "nobody knows". So let's backtrack and have you clarify your questions by answering my questions... so we know what you are talking about and if you know what you are talking about.

I too look forward to some answers to forum questions by the ASII scientific team, particularly my cogent questions on body kinetics/kinematics such as this one:

Since ASII will be examining the role of the body in the golfswing, could the scientific team please comment on this recent study that also has examined the role of the body in the golfswing and in particular the downswing?:

J Appl Biomech. 2011 Aug;27(3):242-51.

Rotational biomechanics of the elite golf swing: benchmarks for amateurs.

Meister DW, Ladd AL, Butler EE, Zhao B, Rogers AP, Ray CJ, Rose J.
Stanford University School of Medicine, Stanford, CA, USA.

Abstract

The purpose of this study was to determine biomechanical factors that may influence golf swing power generation. Three-dimensional kinematics and kinetics were examined in 10 professional and 5 amateur male golfers. Upper-torso rotation, pelvic rotation, X-factor (relative hip-shoulder rotation), O-factor (pelvic obliquity), S-factor (shoulder obliquity), and normalized free moment were assessed in relation to clubhead speed at impact (CSI). Among professional golfers, results revealed that peak free moment per kilogram, peak X-factor, and peak S-factor were highly consistent, with coefficients of variation of 6.8%, 7.4%, and 8.4%, respectively. Downswing was initiated by reversal of pelvic rotation, followed by reversal of upper-torso rotation. Peak X-factor preceded peak free moment in all swings for all golfers, and occurred during initial downswing. Peak free moment per kilogram, X-factor at impact, peak X-factor, and peak upper-torso rotation were highly correlated to CSI (median correlation coefficients of 0.943, 0.943, 0.900, and 0.900, respectively). Benchmark curves revealed kinematic and kinetic temporal and spatial differences of amateurs compared with professional golfers. For amateurs, the number of factors that fell outside 1-2 standard deviations of professional means increased with handicap. This study identified biomechanical factors highly correlated to golf swing power generation and may provide a basis for strategic training and injury prevention.

Thank you.... SteveT

 

[footwedge]

I beat you to that Steveo, posted that a long time ago and ......crickets!

 

[bryan@nobackswing.com]

Since ASII will be examining the role of the body in the golfswing, could the scientific team please comment on this recent study that also has examined the role of the body in the golfswing and in particular the downswing?:

J Appl Biomech. 2011 Aug;27(3):242-51.

Rotational biomechanics of the elite golf swing: benchmarks for amateurs.

Meister DW, Ladd AL, Butler EE, Zhao B, Rogers AP, Ray CJ, Rose J.
Stanford University School of Medicine, Stanford, CA, USA.

Abstract

The purpose of this study was to determine biomechanical factors that may influence golf swing power generation. Three-dimensional kinematics and kinetics were examined in 10 professional and 5 amateur male golfers. Upper-torso rotation, pelvic rotation, X-factor (relative hip-shoulder rotation), O-factor (pelvic obliquity), S-factor (shoulder obliquity), and normalized free moment were assessed in relation to clubhead speed at impact (CSI). Among professional golfers, results revealed that peak free moment per kilogram, peak X-factor, and peak S-factor were highly consistent, with coefficients of variation of 6.8%, 7.4%, and 8.4%, respectively. Downswing was initiated by reversal of pelvic rotation, followed by reversal of upper-torso rotation. Peak X-factor preceded peak free moment in all swings for all golfers, and occurred during initial downswing. Peak free moment per kilogram, X-factor at impact, peak X-factor, and peak upper-torso rotation were highly correlated to CSI (median correlation coefficients of 0.943, 0.943, 0.900, and 0.900, respectively). Benchmark curves revealed kinematic and kinetic temporal and spatial differences of amateurs compared with professional golfers. For amateurs, the number of factors that fell outside 1-2 standard deviations of professional means increased with handicap. This study identified biomechanical factors highly correlated to golf swing power generation and may provide a basis for strategic training and injury prevention.

Thank you.... SteveT

thanks for posting that, were you able to find a good explanation (and maybe a visual) of their "s-factor" measurement? i was having trouble picturing it exactly. i'm guessing it means that pros tend to finish with their lead shoulder higher (and probably deeper).

 

[footwedge]

Downswing was initiated by reversal of pelvic rotation, followed by reversal of upper-torso rotation. Peak X-factor preceded peak free moment in all swings for all golfers, and occurred during initial downswing.

 

[wulsy]

Oday, let's parse your questions with these questions:

(a) how do you create shear forces on the ground, and,

(b) how can you "avoid" them?

StephenTee:

Firstly, like you, I am not a scientist. Secondly, unlike you, I am a sheeat hot golfer.

You have an engineering background (big advantage for someone trying to understand the golf swing), I have a golfing one (big advantage for someone trying to use the information to play better golf). What we have in common is a desire to understand the golf swing and a recognition that there's a lot of BS information out there. Hence we are both on the Bmanz forum which is a source of great information. Sometimes there is even a good discussion.

I can, at will, make very different swings that look the same on 2D video but produce identical TM numbers. I can produce identical AND different predetermined TM numbers. THAT'S WHY I CAN DIFFERENTIATE BETWEEN MINIMISING AND MAXIMISING SHEAR FORCES ON THE GROUND.)

To answer your question in a GOLFING sense from a GOLFER who plays GOLF.

IMHO shear forces on the ground are increased by increasing the speed and range of the rotations/torques associated with those body parts closest to the ground. The closer to the ground the more this increased torque will increase the shear forces. (Obviously the reverse is valid for decreasing.)

That do ya bud?

PS: I'd be interested in Daruisz's opinion on this.

 

[Dariusz J.]

Wulsy, shear forces between feet and ground are horizontally oriented ones, therefore, created in the process of sliding/rotation (opposite to normal forces which are vertically oriented ones - e.g. when one jumps). The bigger are they the bigger can be the torque built - and it is dependent on the coefficient of friction of two objects - in our case, soles of shoes and ground as well as on dynamic mass of the object interacting with the ground.
Saying shortly - a heavy golfer with long spikes will be able to benefit from a tremendous amount of shear forces; similarily, when a golfer is able to create them dynamically thanks to a correct sequentiality of the motion in time (e.g. squating to power the downswing) he will benefit more as well.
IMO, the best and most appealing example of using shear forces in the history of golf is famous post-secret Hogan's presetting his rear foot at setup (armed with metal spikes, and not with this plastic crap of today) so that he could build enormous torques in his rear leg's joints with a goal of automating the transition:

Cheers

 

[wulsy]

Thanks Dari.

I was indeed referring to the horizontal (shear) forces. My questioning of how much shear force(s) should be present was more related to the downswing than the backswing.

Any ideas on how they change in Hogan's case for example during the down swing and into the through swing?

 

[Dariusz J.]

Thanks Dari.

I was indeed referring to the horizontal (shear) forces. My questioning of how much shear force(s) should be present was more related to the downswing than the backswing.

Any ideas on how they change in Hogan's case for example during the down swing and into the through swing?

Downswing ? You mean lead foot ?
If yes, this is another great example, this time of releasing the torques = zeroing shear forces. The earlier these are released the more pronounced extension happens and more power unleashed (vide Sadlowski and all these kids who jump so that the ball goes the farthest). The accuracy swing needs maintaining these torques until follow-through which is equal with external rotation of the ankle/knee joints till the limit and loose the foot later on. Then the foot turns out (relieving the torques) since the RoM in joints ends and torques become bigger than the friction can hold.

Cheers

 

[wulsy]

Thanks Dari. So through the impact phase the shear force in lead foot should be "minimised" to hit it far, right?

If so, should it be maximised to hit it short?

 

[Dariusz J.]

Thanks Dari. So through the impact phase the shear force in lead foot should be "minimised" to hit it far, right?

If so, should it be maximised to hit it short?

ad.1. Rather extension maximized. The bigger extension the bigger torques and, simultaneously, the smaller amount of friction.

ad.2. Rather to ensure more accuracy.

Cheers