Animals, as well as humans, may be taught to perform unnatural actions, such as elephants standing on their front legs, dogs “shaking hands,” or martial artists using unnatural body positions. If a person trains enough in any style of fighting, he or she will become proficient in fighting in that style, but that does not mean that style of fighting is the most effective or the most efficient. A good high school wrestler could win a fight with any average person, but that does not mean high school wrestling is an effective and efficient fighting system. I wouldn’t want to get punched by a tennis pro who has used his arm to swing tennis racket for hours a day for years. In TKDTutor, I criticize many of the techniques taught in Taekwondo as being archaic and useless other than for their historical value.
Anecdotal evidence of the effectiveness of vertical punching does not mean that it is indeed effective. For every story about how it works, a story may be found about how it does not work. I don’t know of any reputable scientific study that has looked into the differences in effectiveness between the two punching methods. Barring that, all that is left is to use science, logic, and reasoning to judge their effectiveness. Knuckles will break if the fist is not closed tightly and its hits an non peneratable object with too much force, no matter whether the fist is held vertical or horizontal. While punching, either vertical or horizontal, if the wrist is not locked, it may buckle even when the striking force of the punch is relatively light.