Downswing

[Brian Manzella]

Good post, Jerr



But I am looking for the interaction between the Combined GRF Vector and the center of mass.




The answer to the 1st question, "WHY DOES AN EARLY SHIFT WITHOUT MUCH TURN AT ALL, MAKE IT EASIER TO TURN A BUNCH GOING BACK?"


IS.....Because if you shift your center of pressure—the origin point of the Combined Ground Reaction Force Vector—well to the right early in the backswing, while limiting how far the Center of Mass shifts, you can create a large moment arm to assist the golfer with orienting his body and rotation on an angle.


Like Jamie above.....


The distance from that blue line and the com is the MOMENT ARM.

 

[Brian Manzella]

Now....think about a golf on one leg....

 

[Brian Manzella]

And I should add....STANDING ON YOUR FRONT LEG....standing on your rear leg will produce more a completely different result body-wise for the same reasons:

<iframe width="854" height="510" src="//www.youtube.com/embed/mFVabP433TA" frameborder="0" allowfullscreen></iframe>

 

[cnadon]

The answer is in what happens if you stand on one leg (like your left) and make a backswing...or a whole swing.

I don't know what happens to others, but when I do this there is no head movement. Where and when the head moves would seem to have some effect on GVF, esp. given axis tilt, no?

 

[wulsy]

Talkin about a right handed golfer:

If you want to turn clockwise you have to get/have the COP right of the COM.

If you want to turn anti-clockwise you have to get/have the COP left of the COM.

This is because it creates a moment arm, right?

And when they line up, it's difficult to turn in any direction, right?

 

[joep]

WOW, when I stay on my left foot and swing I fall backwards and when I stand on my right foot and swing I fall forward...

 

[Brian Manzella]

Talkin about a right handed golfer:

If you want to turn clockwise you have to get/have the COP right of the COM.

If you want to turn anti-clockwise you have to get/have the COP left of the COM.

This is because it creates a moment arm, right?

And when they line up, it's difficult to turn in any direction, right?

Very good, Wulsy....!



Now....instead of IF YOU TURN clockwise you have to get/have the COP right of the COM, you could just swing the COM to the left—which is what every left foot—right swing does.

The right handed golfer standing on his right leg can just shift some mass to the right and he is slick.

 

[Brian Manzella]

WOW, when I stay on my left foot and swing I fall backwards and when I stand on my right foot and swing I fall forward...

Because you are coordinated enough to swing that left leg around to get your COM left of the COP going back, when you throw that com back to the right to turn through, you over do it and probably don't shift the cop left enough under your foot to balance it all off.


In the left legged swing you fall because the mass is easily to the left and the cop has to be further left to keep you from falling—requiring you to shift the cop a bit under your foot and lean back and tilt a bunch to move the m=com over to the right enough.



Priceless info.

 

[Brian Manzella]

Never forget, the golfer is TILTed over.....

 

[Jurr80]

Because you are coordinated enough to swing that left leg around to get your COM left of the COP going back, when you throw that com back to the right to turn through, you over do it and probably don't shift the cop left enough under your foot to balance it all off.


In the left legged swing you fall because the mass is easily to the left and the cop has to be further left to keep you from falling—requiring you to shift the cop a bit under your foot and lean back and tilt a bunch to move the m=com over to the right enough.



Priceless info.

So this is what explains the "backing out" look of a Stack and Tilter?

 

[Brian Manzella]

At what point in the swing, Jurr?

 

[Mike Richardson]

He moves his head quite a lot to the right, you can see it against the 2 trees in the background. Is that why the vector is going thro' his left ear when at this stage you'd be expecting it to be still going past his right ear? Or has he already started the move left?

 

[Brian Manzella]

Not by that point.

But that vector will do what forces tend to do—LINE THINGS UP...UP that VECTOR.

 

[wulsy]

Is the purpose of this specific displacement of the COP and the COM to produce a mechanical advantage? In other words, it would still be possible to make a golf swing of sorts (ie less effective) without it?

 

[Brian Manzella]

Is the purpose of this specific displacement of the COP and the COM to produce a mechanical advantage? In other words, it would still be possible to make a golf swing of sorts (ie less effective) without it?

Yes.

No.


This is just how it is. This interaction is something that happens in ever swing.

In fact, it may be the first things an infant learns—how to manipulate the ground's interaction with their COM.

 

[joep]

Is that why Hogan added an extra spike on his shoe?

 

[wulsy]

Yes.

No.


This is just how it is. This interaction is something that happens in ever swing.

In fact, it may be the first things an infant learns—how to manipulate the ground's interaction with their COM.

But there are some folks who get it fundamentally wrong, right? eg. victims of keep your head still instruction

 

[Jurr80]

I'd say that the "head still" business causes so many problems, and this instruction is so enlightening.
I was instructed for TWO YEARS to focus on nothing but turning my rear butt cheek towards the midline to start the backswing.

I had this "teeter totter" feeling in my pivot, and had to back out of every shot to put my body into appropriate impact angles. It was a nightmare. Pressuring the back leg PRIOR to initiating the pivot move was a new concept, and it has recently been introduced to me (by one of Brian's colleagues). It's funny how such a small change can alter the entire dynamics of the golf swing. It feels natural, like throwing a baseball or swinging a bat. You pressure the back foot, wind up, then pressure the forward foot, unwind, and throw a ball. Understanding the concepts of GRF makes this all seem obvious. It's amazing that scores of teachers are still obsessed with video-based positions (line drawing programs) over the real science of athletic motion. It's hilarious and sad at the same time.

 

[wulsy]

After watching Kaymer blow a ten, yes 10, that's zehn, dix, diez, tio...., shot lead today I went and hit a few eggs on the range, the result of which is this question:

Is it even desirable to finish standing on the left leg in a balanced position? I doubt it.

 

[coophitter]

The study of athletic motion is not a hard science. I believe its considered a gray science like psychology at most, and more likely just a subject matter like philosophy. Sport psychologists, biomechanists, exercise scientists, etc. know that they don't exactly know how humans and other organisms initiate voluntary muscular movements except to agree that the brain or motor control division of the central nervous system does it.

There isn't a scientist alive who can tell you what starts a downswing except to say that whatever a particular golfer commands himself to do is what starts it, and it is that particular command that determines whether it is arguably a good or not so good downswing compared to every downswing that's ever been made.

Umpires often have to determine whether a batter swung, checked his swing, started to swing but stopped it with no intent to swing, or intended to swing, and did swing, but tried to act as if he didn't.

When Tiger awes us with his ability to check his downswing, did he start it and stop it?, or did he not even start it? What starts a downswing in my opinion is the individual golfer's intent to make the ball do what he wants it to do given the situation at hand. Ideally that intent is not really in English, or the native tongue of the golfer, as human language is probably too slow to expect the best results.

But maybe regular language is good enough! Who knows? Whatever the language that is used however, it is human thought that starts the downswing and thebody obeys in accordance with its capacity to carry out or perform the thought.