I don’t doubt at all your sincerity, dedication, and skill. I appreciate hearing about your golfing biography and quest in understanding the swing. My criticisms are restricted to what is being thrown around as science. Perhaps a bit of my biography will help us understand each other.
My undergrad was at Cornell University '91, majoring in electrical engineering. Realizing late that my preference was pure mathematics, I took as many math classes as I could, including real and complex analysis, harmonic analysis, Lebesgue measure and integration, probability theory, set theory and logic, etc. My late uncle was a full professor, specializing in analytic number theory. I learned more advanced mathematics through long conversations with him throughout my twenties. Along with my mathematics and engineering background, I’ve taken and studied enough physics to hold my own. I bring this up only so you can see where I’m coming from.
As I’m sure you know on an intimate level, any human motion is complicated, and the golf swing is no exception. No simple physical model with pendulums and gears and pulleys and springs will capture fully what’s happening. Moreover, certain exceptional people have performed physically amazing feats throughout history. No sane person would say that in doing so they defy the laws of physics, even if it may seem as though they do. It may seem impossible to you that someone skilled in a certain technique can accelerate a club all the way to impact, but you wouldn’t deny a robot can be built to do so. Would you? You wouldn’t deny that by starting slowly from P3, acceleration can be maintained to impact. Would you? You still may not believe it’s possible for a human making a full swing with sufficient club head speed at impact to play serious golf can do so, but it’s not at all like claiming one can fly by flapping one’s arms. It’s certainly not clearly impossible. Citing the basic laws of physics won’t help either. As we noted, these are complicated movements. And robots can certainly perform this feat.
Since there’s no law of physics that’s being defied by the claim that accelerating to impact is possible, we must turn away from theoretical arguments and look for other means. Indeed, you have looked to data. That brings us to my next criticism.
Broadly speaking, scientists use data in two ways. One is to test a theoretical result. Calculations are made from a theory, and they are compared against data collected by measurement. But there’s no theory being tested in that video, so let’s move on to the other use of data. Scientists also use data from observations to play with. That is, to gain insights to better understand and possibly, after much effort, make a theory that can then be tested. That is the stage we’re in. And that’s where my objections lie.
You can’t draw conclusions from the same data you used to make your hypothesis. You’re looking at data from certain swings, and then using that same data to make bold assertions. “We tested all these pros who don’t accelerate to impact, therefore it’s not possible to do so.”
This is not science. It’s marketing. (The pharmaceutical industry suffers from the same diseased mentality!) It may still be useful, and it may be profitable, but it’s not science. There’s another danger inherent in using data in this way. While we should strive to measure whatever we can, there’s a pernicious tendency to overweigh the importance of what we can easily measure and undervalue what we can’t or at present haven’t.
I also know that no matter what I post its going to be excuses about how it doesn’t meet whatever standard you want it to meet and the goal post is going to be raised.
You’re making the claim that it’s science, it’s physics. It’s not. Can it lead to good science? Sure. Is it worthwhile making these observations and looking at the data? Yes. But that’s not what you’re doing. You’re claiming that it establishes scientific facts about accelerating to impact. It doesn’t. Pointing this out is not an excuse or a shifting of goalposts.
If you haven’t already done so, I recommend reading Richard Feynman’s essay/commencement address about what he called cargo cult science. It’s very well known, and quite funny. http://calteches.library.caltech.edu/51/2/CargoCult.pdf
As for pivot stalling, it means just what it implies, the rotation of the core, of the hips/torso/shoulders, is slowing down or stopping near impact. You don’t even need fancy equipment to see this. Just look at video from a down-the-line view. Step through the video frame by frame. Is the pivot of the core moving (rotating) significantly in each frame from P3 to P4? If so then there’s no pivot stall. If the pivot slows down dramatically or stops, there’s a pivot stall. Even though that video you posted was from a caddy view, you can see that the core slowed down to let the arms catch up. Indeed, that’s what you describe as “evidence” of it being impossible to accelerate to impact. Hogan clearly didn’t pivot stall. ABS teaches a very gradual speed increase from the top to P3 (which is not, as you stated, what that pro is doing) and then pouring it on after P3 using mainly a vicious torso rotation. It’s a very different technique. That’s why the observation and data from that video you posted have nothing to say on whether it’s possible for an ABS type technique to accelerate all the way to impact.
At the risk of making this already too long post even longer, I want to end it on a constructive note. What would be an interesting and useful application of the GEARS data is to see, among other things, how far into the downswing players maintain acceleration. How do different techniques effect this? Is there even a correlation? That is, we can use the proverbial lamppost for its intended purpose, illumination, rather than how the drunkard uses it, for support (of prior biases).
next. Same old same old. Nauseating 
