Continuation of power

July 13, 2009

Every art I’m familiar with talks about “efficiency” or “economy of motion” or some synonymous principle. The idea is, let the other guy do as much work as possible while you do as little as possible, so he gets tired and you don’t. Often, this principle is expressed as “keep your motions small” or “don’t move unless you have a reason” or some such, and those are all good ideas. Clearly, if you can get the other guy to move more than you do, he’ll expend more energy than you will. Right? Well, probably, but not necessarily.

So, here’s the deal: movement, as such, is irrelevant. If I jump out of a plane, I can go several miles (very quickly!) without expending any energy at all. The important thing is to conserve energy. Obviously, moving less will require less energy, all else being equal. Unfortunately, moving less can also hamper your fighting ability; if nothing else, movement makes you a harder target. So, the trick is to move without expending energy (and by “move”, I mean “move and attack”; movement alone is not very useful unless you want to play shooting gallery).

At this point, lots of armchair physicists are starting to talk about F=ma and ½mv^2 and so forth, but that’s an oversimplification. You can work out energy expended over distance with those simple equations only if you assume that a person moves like a rolling sphere or some such, and that’s just not true. A person is an extremely complex structure, with lots of joints and muscles working with varying amounts of leverage, and under the constant force of gravity. By properly employing the principles of biomechanics, it’s possible to move quite a lot with minimum expenditure of energy.

Certainly, from a standing start, you need to expend some muscular energy to start moving (unless you’re willing to lose your balance and just topple over, which we’re generally not). However, and here’s the trick, it’s possible to keep using that same energy for quite a long time with only minimal additional expenditures.

Let’s look at a simple example: imagine that you take a strong step forward. At this point, your body is in motion, and, per Newton’s first law, it would take energy to stop it. So, if you keep moving forward at a constant speed, the only energy you’re using (to a first approximation) is that needed to move your legs and hold yourself up off the ground. With proper body structure, the latter can be minimized (by making your bones and connective tissues take most of the load), so we’re down to just what’s needed to move your legs, which is pretty minimal.

Obviously, that analysis is simplistic. For one thing, thermodynamics tells us that any system will lose energy over time (roughly, I know this statement isn’t strictly true, but it works in this case), so there’s a constant trickle of energy needed to overcome factors like friction in your joints, air resistance, etc. Also, and more important, walking forward in a straight line isn’t usually what we want to do – we want to move side to side, and we want to extend energy into a strike or a weapon.

The good news is, kinetic energy can easily be transferred around the body if you know how, so the motion of a step can become an attack, and vice versa. It’s entirely possible to execute a series of movements (say, a kata) while performing powerful attacks with a weapon, while expending minimal energy. All you need to do (don’t you love it when people say that?) is to make sure that the energy you’re using for each movement transfers smoothly to the next movement, with minimal loss at each step. The first movement in the sequence thus requires energy to start, but successive movements are almost free unless you stop.

This, of course, is much easier said than done. Actually performing this trick requires many, many hours of careful observation of your body movement in every possible situation, and detailed analysis of where the power is going and how it can be redirected at each step. However, the payoff is worth it – it’s economy of motion without having to be economical at all.


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