Power is a much-misused word in martial arts, and its usage has lead to quite a lot of misunderstanding about what is important in technique and training methods.
Think of a bullet.
It weighs comparatively little, but is capable of doing a huge amount of damage when it hits a person. Of course this makes sense intuitively, but you may never have understood why, from a theoretical point of view.
The secret is in an equation that you will almost certainly have learned in physics at school. (You see, it was actually useful, after all!) It’s all about…
Kinetic energy = ½mv2
m is mass (which, to the lay-person, can be thought of as weight), and
v is velocity (which, to the lay-person, can be thought of as speed).
The most significant thing about this equation, in martial arts terms, is that the energy of a technique is proportional to the velocity squared. So, if a technique moves twice as fast, the energy is four times as much. Four times as fast, the energy is sixteen times as much, and so on.
It should be clear from this that it is not actually the strength or size of a person which is important, but rather the speed at which they can move. How fast they can strike or kick.
Improving the striking velocity of a technique can make a dramatic improvement to its effectiveness – much more so than by, for example, being bigger, or having bigger muscles.
So, from a mechanics point of view, the energy transferred into your opponent on impact relies on the impact speed being as high as possible.
When training, make sure you pay attention to your striking limb arriving at full speed. Use the ball-and-chain principle with your strikes, and make sure your distancing is correct so that there is no slowing down prior to impact.
The surface area over which this energy transfers will determine how your opponent’s body is damaged. A lot of energy transferred over a small area will have a large effect and can do quite a lot of damage. The same amount of energy transferred over a large area will have a smaller effect, and will do less damage (This is why bullet-proof vests work, as the energy is dispersed over a large area).
Newton’s Third Law
Newton’s third law is important to a martial artist because it explains the effect on you when you strike someone else.
“When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.”
What this means to the martial artist is that, on impact, as all this force is transferred into your opponent, there will be an equal amount of force transferred back along your striking limb. This is where alignment and strength of the limb become important, to prevent injury to yourself in the process of trying to injure your opponent.
The third thing that is worth discussing is “force vectors”, because it will help you to understand the direction you should strike in.
Essentially, to be as efficient as possible, you should strike directly into the surface you are hitting. The striking force should meet the impact surface at right angles (or 90 degrees).
If the impact is not perpendicular to the surface, then some of the force created on impact will be wasted.
This is explained theoretically using “force vectors”, which are drawn at right-angles to the desired direction of impact, and represent a proportion of the force being directed – in this instance – in the wrong direction.
The greater the error in angle, the greater the reduction in impact force – this can even result in a skimming effect, where the fist or foot slides along the target, rather than connecting solidly with it.
This is also an important thing to understand from a defensive point of view, as quite subtle movements can dramatically reduce your opponent’s impact force.