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), work, energy (kinetic and potential), impulse, pressure, levers and leverage, springs, and collisions.
The very name Ukemi is often mistranslated as falling. A more correct translation takes into account the etymology of the root word Uke, or receiver. In Judo ( The Art or Way of Gentleness ) techniques are generally executed by Tori or the Giver and taken by the receiver, Uke. In that sense, a person who receives a technique must accept, and protect themselves from any attack or incident. The fundamental precept of Judo is: Maximum efficiency with minimum effort, for the mutual welfare and benefit of all. So the techniques surrounding the receipt of any technique is never to meet force with a directly opposing force, but rather to go with the incoming force, accept its energy to move in concert with it, and then deflect it in a more useful direction without harm to either party. By extension, Ukemi extends these same principles to protect a person physically from even brutal impacts with the ground. The basic goal, of course, is to be able to fall without injury, even under extreme conditions otherwise out of a person’s control.
The efficacy of these techniques is truly awesome. They are, by far, the most useful and often-used aspects derived from my many years of martial arts training, and have helped me survive some potentially serious injuries. One particular incident comes to mind from when I was about 12 or 13 years old, with around 6 years of Judo training behind me at that point, when I was pushed off of a 3-meter diving board head first onto the concrete pool deck. You know, one of those “saved your life” kind of jokes gone bad. Net result was a slight road rash on one shoulder, but the look on the guy’s face when I just dove of the board and rolled to my feet was priceless. Other examples in sports, and on Ithaca, NY ice are just too numerous to count. I just have absolutely no fear of falling anymore, and that is a very empowering thing.
The basic principals that can be used to describe the minute refinements that give Judo Ukemi its incredible protective power turn out to cover a very wide range of mechanisms.
The area of the body impacting the ground in the instant when sensitive body parts strike is maximized in order to minimize the absolute force felt by any one part of the body.
Part 2 will begin by describing how each of these principals is applied to Mai Mawari Ukemi, or the receipt of Forward-rolling-falls.
If you would like to see some excellent examples of all types of Ukemi in action, check out this video.
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An excellent analysis. It would be wonderful if you could extend it to the effects of physics in throws and maybe in ne-waza or shime-waza techniques too.
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