The seems like the best place to ask this question...
I have been thinking hard about the vertical versus the horizontal karate punch lately - especially since doing a seminar with Kris Wilder.
As we know, the technique of punching is best performed starting from hikite with the wrist facing up, and finishing with the elbow pointing down, having passed as close to the body as possible. In traditional karate the wrist twist occurs at the very end, but for some people, myself included, twisting the wrist all the way over to horizontal engages the deltoid, something that Kris Wilder advised strongly against, and for good reason.
I have found, or suspect, that the horizontal punch is slightly less powerful, and in my case a tiny bit shorter. Certainly I find it impossible not to pronate my elbow sightly in order to make the punch horizontal. The way Kris Wilder described is that the deltoid should feel like "over-ripe fruit", at the end of the punch - meaning completely relaxed. This was in the context of a seminar almost exclusively on power generation and especially Sanchin kata. We were adivsed to focus on engaging the lats to pull the shoulder joint down, locking into place at the end of punch so that no energy could escape through the recoil of the shoulder joint on impact. His advice was "don't look for bunkai in Sanchin kata, look for sanchin kata in your bunkai". It was one of those major light bulb moments that furnish the karate path.
I note that Goju pracitioners often use the vertical punch as well as Wing Chun. Are there any other styles that use it? Do they use it exclusively? What are peoples thoughts on the vertical versus horizontal punch?
I have heard one theory regarding the benefit of the horizontal punch, which is that the twist on impact, can impart energy, and cause damage. I am not convinced...yet...I would love to hear peoples thoughts. It is, after all, a mainstay in traditional karate.
One other point to make about the vertical punch is that if you are punching head level, you are much less likely to damage your fingers should you strike the chin or the jaw, since they are aligned in the same direction. If you punch the chin with a horizontal fist, you may end up striking with the delicate finger bones rather than the knuckles. Obviously, palm heel strikes are ideal for striking that area, but they are a good 2 inches shorter than a fist.
So lets have it. Dying to know what others think about this question.