So, all you really need to be called a hacker is a love of knowing how things tick. The specialty doesn't need to be programming and circuits. The very authoritative Jargon file says that a person could be an astronomy hacker, for example.
So, a martial artist is a hacker of sorts--let's say, a biomechanical hacker. Some martial artists even create their own weapons or adapt them from everyday objects, which makes them hackers in a very traditional sense: "one who enjoys creatively overcoming or circumventing limitations," again in the words of the Jargon File.
As a martial artist and programmer myself, I can say that there are big similarities between those fields. It takes finesse. It takes knowledge. It takes an instinctive feel of the playing ground. It's engineering. And I love it.
My favorite way to hack the body involves controlling something that Aikidoists call the "center", or "ki". In the dojo, I've learned that when two people make contact, they become a single physical system, and the point of contact becomes the "center" of that system. Whoever controls that "center" controls all the movement of the system. This idea is common to all martial arts, but is especially important in Judo, karate, wrestling, and Aikido.
In general, there are a few ways to control movement:
- Change the location of the Center.
- Change the direction of your pressure on the Center.
- Overpower opposing forces on the Center.
In a more usual sense of "hacking," the adaptation of common items as weapons is a classic idea in martial arts. The kama, for instance, started out as a sickle for farming before it was adopted into Okinawan Karate as a practical weapon. The famous nunchaku, commonly called "nunchucks," were originally tools for threshing grain. The jo staff was just a walking stick. And the list goes on. Martial artists have been hacking from the beginning of time.
I think this might be why many computer hackers are also martial artists. It appeals to the hacker aesthetic of using things in unusual ways to solve problems in a beautiful, functionally perfect, or clever way.