[no_mind_golfer]

***First a correction***

In my last post I said that during the optimization part of the study Nesbit/McGinnis studied a "circular delivery path" and found it to be better than the scratch golfer's original hand path. That's not true ... what they found was that to get the same clubhead speed using a "circular delivery path" would require 10% MORE power (a lot more torque). (See table 7 http://www.jssm.org/vol8/n2/11/T7.htm ) . Looks like "circular delivery" is out.

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Now as to your question bucket...

It takes three points to define a plane (any plane). So if we were to take the coordinates of the hands at the top of the swing, in the middle of the downswing and at impact we can define a plane... lets call it the hand (hub) plane. That's what we're looking at in that graphic I overlayed the spiral on. Its not a front view, side view etc. ... is a view perpendicular to that hand plane.
X and Y are just cartesian coordinates on a plane. The curves are the path the hands trace on that plane. BTW Nesbit does not tell us how much the hands actually deviate from said plane. That would be nice to know.

I hear the question: How do you teach it?

Our problem statement is: how do we to maximize CHS given fixed kinetic (muscle power) limitations?

To solve any problem we must get to root cause; and a jouney of 1000 miles begins with the first step.. That what Nesbit and McGinnis have done here... They have shown definitively that hand path is THE KEY FACTOR involved in maximizing the kinetic transfer (from body to club) i.e. root cause. Furthermore the computer has told us that the optimal hand path for the blended second and third phases of the downswing should resemble a spiral (at least for this scratch golfer). Now biomechanics must tell us how that hand path goal is best achieved... what muscle groups need developing to improve the kinetic limitations and what areas of flexibility are needed... sequencing etc.

Today the latest rage is radar reports of what is happening at impact. That's all well and good but I can envision a day in the not too distant future when Instruction will begin by setting up camera(s) (or sensors of some type), plugging in computer having a validated biomechanics model of student (not unlike Nesbit's). Swing is captured and within seconds optimized improvement suggested (including animations showing how to move differently in order to achieve).

I can see it now... in the not too distant future Kostis will be expounding on a golfer's screwed up hand path seconds after the mis-hit. Gone are the days when golf was a pastime of the pipe-smoking leisure class dressed in stiff suits and bowtie swinging hickory sticks. We're on the the verge of maximizing human potential now.