An intro with an admitted Judo bias.Several folks at work recently expressed some interest in taking a self defense class. I have to admit that the idea of teaching such a class definitely increased my pulse rate a bit. You see, I’ve noticed several withdrawal symptoms lately (though I bet my wife has noticed a few more). You know the typical sort of thing that comes up: I get to be a little twitchy late in the day, I always fiddle with a pen or marker, and the path to irritation is a little quicker than normal. Oh yes, and let’s not forget the extra spare tire that has gained a little too much ground over the last couple of years since the little ones arrived. My favorite local Aikido Dojo has class hours which I just can’t make on a regular basis, so what the heck … I guess I’ll teach a class myself and perhaps regain a little personal fitness in the process. It’s a little ironic, really, because historically I’ve tended to scoff at these “Six Week Women’s Self Defense” sort of classes as being good ...

This is some nice video of a Korean Judo team demonstrating basic Judo techniques starting with Ukemi for a warm-up. It shows a wide range of skills across the team, with some of the advanced rank-holders showing decent technique. They are probably not as crisp in terms of technique as the more anal Japanese-style practitioners (some body positioning out of place, toes not pointed so power is limited, more lifting than timing...etc.) but there are great camera angles despite the hand-held aspects to show the protective power of Ukemi.For a point of reference, judging from the relative skills demonstrated, the more advanced students in this video probably have about 10-15 years of practice under their belts (so-to-speak), while the newer students go all the way down to about 1 year or so.

After over 30 years of studying Judo with some Karate, Tae-Kwan-Do, and Aikido thrown in from time to time, I have finally come to conclude that I have never seen a decent technical description of the physical principles surrounding the very specialized and effective techniques that martial arts have evolved over the centuries to protect people from injury when falling. Many practitioners are quite expert in the practice, and can teach the techniques quite effectively, but traditionally do not speak in any real detail on the scientific aspects. Frankly, I have found that this is a good thing, as the technical descriptions, even to MIT undergrads, have little impact on student improvement. But the study of different refinements and variations across different martial arts could be instructive. So I guess I'll write it myself and invite comment.In the interest of reaching the broadest possible audience, I will restrict this discourse to fundamental physical principles without any real mathematics, though possible later posts might go into specific numerical examples. In order to understand this discussion, readers should be, or make themselves, familiar with the basic physics surrounding velocity, acceleration, linear and angular momentum (and conservation thereof), ...

The Difference Between Judo and Aikido UkemiHere is a nice demonstration of the classic Aikido form of Ukemi. Let me begin my comments with an admission that I am clearly biased, with over 30 years of Judo practice and only about 2 years of cumulative Aikido experience. That said, I have found the precise application of the Judo style to be more protective than that of Aikido. I have observed two fundamental differences, each of which is highlighted by comparing the various demo videos posted on this site.First of all, the Aikido version has Uke tuck the off-direction leg under the other closer to the buttocks. This has the effect of somewhat facilitating a roll to a standing position, but it fails to protect either the ankle bone, or one leg from impacting the other upon significant impacts. This leg tuck also has the effect of decreasing the angular moment of inertia, and can do nothing to slow the rate of rotation and thus better control the landing position.The other fundamental difference is that the Aikido style seems to rely on being relatively in control of the fall from the beginning with more ...