All right - actually, twisting of any limb is a very viable and proven fighting technique, taught not only in the martial arts, but also wrestling and police academies, militaries, etc. It's a lot easier to do without boxing gloves on. While bones are strong, they tend to only be strong in certain directions. Muscles too. Also, the bones are connected by connective tissues which are not nearly as strong, and are in fact very easily torn. This is especially true of wrists, elbows, and shoulder joints. The limbs of the body are designed to move in very specific directions. They are strong only in highly limited ways. I bid you right now, just hold out your right arm, now rotate it to the right until it stops, then rotate it back to the left until it stops. That is your limit right there. 20% past that will rip tendons and muscle, tear ligaments and cartilage, and shatter bones. In fact, I can move your entire body pretty much wherever I like if I have your arm already twisted. The pain from having your arm torn up like that often leads to a loss of consciousness. It will render your arm just as useless as that guy who was shot in the arm by Kyle. In other words, if I get a hold of your arm, you are entirely fucked. I don't really need anything else after that. You'll be screaming in pain if you can even remain awake. This is basic ass martial arts. It works perfectly well both inside and outside of the dojo. Remember, cops twist people's arms behind their backs when arresting them, frequently breaking arms in the process.