[Yoda]

Yoda - the yellow lines represent the spinal tilt angle.

The yellow line in photo 2 is only an approximation because I believe that it is impossible to accurately represent the spine position when the golfer is at the end-backswing position - when viewing the golfer from a face-on view. At the end-backswing, the pelvis has rotated about 45 degrees and the shoulders about 90 degrees. That causes the spine to twist in a spiral manner, so it is impossible to draw a single line as being accurately representative of the degree of spinal tilt (of a spiral structure).

I draw my "approximate spine line" as follows. I know that the pelvis rotates 45 degrees in the backswing which shifts the lowest lumbar vertebra to the left. I then start the bottom of my line just left of center (approximately where I think the L5 vertebra is located). I then look for a point at the base of the neck where I imagine the C7 vertebra is located (which is near the blue dot = upper swing center between the shoulder blades), and I draw a straight line between those two points.

Jeff,

I respect your scientific and biomechanically-based methodolgy, but . . .

I also trust you and your innate sense of movement!

Please gimme a Jeff's freehand approximation of the "spiraled" -- I agree with and love this description! -- spine angle. With all due respect to any perceived straight-line relationship between L5 and C7, just let it go, and let's see what we get. [Can we use the color red? I like red!] Then, let's compare that rendering to the yellow line.

FWIW, it appears to me that the Head has remained within its 'box' during the Backstroke and that the Hips have Shifted decidedly to the right (we now can see a pine tree!). And that means -- according to my own theoretical 'grandfather clock' model expressed above -- that the lower spine tilts ever so slightly 'away' from the target on the Backstroke, not 'toward' it.

Whatever it is, is, of course . . .

So, let's figure out just what is, is.

Sounds like I ought to be running for office!