24 October 2013


Some recent readings have me musing once again on the notion, "there's many a slip twixt the cup and the lip."

After finishing school, I set out into the world of work, at a time when the USofA was contracting. Not quite so bad as The Great Recession, but pretty close. I ended up mostly in my chosen profession, and got exposed to systems' building and stats-in-the-wild (SPSS). I also found that not all jobs are as time consuming as graduate school, and thus leaving significant number of hours in the day to fill; more or less meaningfully. I sought out forms of physical activity, a welcome change from six years of sitting in class, library, and impromptu study hall.

Off to the Boston Y, next to the Green Line as was my abode at North Station. How about karate? Dave Edwards was teaching a class, so I talked with him about taking his class. He advised me to study with his teacher, George Gonis over in East Boston. George taught (near as I can tell, he's no longer teaching) his branded version of Gojo Ryu, which he first learned from a man in New York City, and later continued with the man's father in the mountains of India. I don't recall ever knowing their names. As fanciful as it sounds, my all too brief (soon after I was off to DC, and Dr. McElhone) tutelage covered the time of one of his trips to India, so I was around when he returned from promotion (a higher level of black belt, but I've long since forgotten what number). Not having a hair on one's body is kind of striking. Unlike olympic swimmers, this process was part of ritual cleansing, not a mode of faster movement.

To complicate matters further, I also found an arts/meditation/foobar workshop in Cambridge, where I found a tai chi teacher, Julian Miller. His brother, Don would be there occasionally. Julian learned from William C.C. Chen, while Don with T.T. Liang, who has since passed on, although I did get to see him perform a double sword form in Boston when he was about 74.

Karate is considered a hard style, while tai chi is the ultimate soft style of eastern martial arts. Kung fu is generally considered in between. Never did do a kung fu, although I've toyed with the idea of aikido. They all teach in two parts: forms and free fighting. In most karates, the latter is called kumite'.

Now, what you see in 99.44% of mixed martial arts, kung fu movies, and the like has little to do with what is taught. More interestingly, the same is true in the kumite' section of tournaments put on by legitimate practitioners. This is particularly true of kicks. And most particularly true of the signature kick of karate (not so much in tai chi), the roundhouse.

Much to my surprise the Wiki has a description, and pretty accurate from my history anyway:
The original method involved bringing up the knee, and then swiftly turning the hip over and snapping the leg outwards from the knee to deliver a strike...

What part of the foot is used varies. When first taught, the instep. But the preceding quote is farther down the page. This is what the opening paragraph says:
A roundhouse kick (also known as swinging kick or a power angle kick but often confused with the round kick) is a kick in which the attacker swings his or her leg around in a semicircular motion, striking with the front of the leg or foot.

The difference in wording is critical. What passes, today, for a roundhouse kick is merely a leg swing. It isn't of much use, as it telegraphs it's intentions like a horny sailor on shore leave. The true roundhouse begins with the knee thrust upward. If you've studied with a veteran, you've been taught that from the knee elevated position, at least two kicks can be completed: a front snap or a roundhouse. Yes, a true roundhouse is a front snap on its side. The front snap extends the energy of the moving glute and thigh through the lower leg to the foot, and thus the target. Whichever part of the body the opponent has left least protected determines how to finish the kick; either the head or the kidneys. Take your choice. If you've studied well enough and long enough, both kicks take the same time to complete. There's no speed advantage to the simpler front snap.

What the hell has this got to do with databases and stats, I can hear from the peanut gallery!!!???

Just this. Folks who should know better de/un-normalize the schema because everybody else says it's for performance. Folks who should know better abuse the assumption of normality (not to mention homoscedasticity) in data without even thinking a second about it. There was a time when "thou shalt not estimate beyond the data" was the First Commandment. Not so much these days. The trigger for this stroll down memory lane were some recent posts.

This on the problem with backtests.
This on joy of honest data analysis.
This on backtests.
(all links posted on R-bloggers; you do spend time there as I suggested?)

It's easier to do a leg swing and call it a roundhouse, but that doesn't mean you should.

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