Breaking things – boards, bricks, concrete, bones – is about the delivery of kinetic energy. I’m not just talking about the cheesy pine board breaks they have 6-year olds do at the kiddie martial arts class, either. I’m talking about serious breaks, with real bricks, concrete, and so forth.
First of all, the relevant physics terms are in the mass times the square of the velocity portion of the kinetic energy formulation. Mass and velocity are the user-controllable parameters that determine just how much kinetic energy will be delivered to the target. Let’s consider the fist.
Generally speaking, the mass is the fist, plus, if the wrist and elbow are held rigid, the mass of the two arm sections and even the shoulder; real experts can hold the shoulder rigid at the time of impact, and so a surprising amount of central body mass can be counted in the formula. From there, breathing (and yelling) techniques that give you a rigid structure through your chest and stomach musculature, and the locking of the hips and legs through the moment of contact. But once you get that far, you’re kind of stuck – because you don’t have any more mass.
Velocity, though, both counts more (because it’s squared) and is easier to boost as compared to your average other person, because we don’t really generally work at anywhere near our potential speed.
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