I'll admit to being a bit confused by some alleged aspects of martial arts. Ch'i in particular.
My first instructor was an ex-street rumbler. He taught us two styles, in a sense. We learned the traditional Japanese techniques/style (the "Formal" way of doing things) and also what he would often refer to as what works on the street.
One of the things that was stressed to us was that timing was a major factor in delivery. We were taught to, basically, get all the associated body movements working together to use the full effect of the momentums involved, concentrated at the point of contact. Nothing mystical there. Just getting the most "body" behind a punch as possible, while using stances that attempted to get the best compromise between speed and power ("if it's all power and no speed it won't land, if it's all speed and no power, it won't do any good if it does land").
When I first found Randi's weekly tidbits, I was a bit put off, while going through past issues, by some comments he made negative toward martial arts. I haven't had a formal lesson since the 80's. My first was in the early 70's. I have never been told about any mystical powers. Everything we were taught relied on using our bodies to the best of our abilities. Heavy drilling on timing and reflexes. Lots of drills on combinations. I never realized that the field seems to have been invaded by Woo. A little research eased my feelings about Randi's comments, but caused me some concern about where the martial arts were headed.
Now, all that being said, I've never heard the Internal/External thing. My opinion is that true martial arts are nothing more than learning how to use your body to it's maximum potential. I believe (based on the schools I was trained in) that a 4 part training regime -
1. Physical exercise/stretching
2. Formal technique training, solo and with partners, and reflex training *
3. Kata practice
4. Free style sparing
gives a good balanced way of learning any martial art. Done properly, you end up in good general physical condition. Have a large range of "tools" available to use, should the need arise (note that we were told to avoid conflict when possible). Have a good degree of self confidence, and (IMHO) no need to "Prove" that you are tough. Case in point, I was about 16 when I started my training. I'm about 52 now. There has been one time that I had no choice but to fight (I was grabbed by the arms by two guys that were walking past me). That is the only time I used (the pure basic fighting aspects of) my training in self defense. But over the years, I believe the general benefits of the training have served me many times and very well, from my general health, to my ability to think well under pressure, along with what I believe would be a long list of other benefits. Again, nothing mystical, just good physical and mental training.
OK, I rambled a bit. Sorry. But in summary, I think to deliver a good punch boils down to getting your body moving in the proper direction(s) at the proper time, and bringing it all together on your opponent. Now, whether that's External or Internal or what, I don't know. I think it boils down to using the right muscles. in the right way, at the right time
I will add that sometimes speed is more important than power. In the case I briefly described above, it was a quick snap kick to the groan that took the fight from 2 on 1, to 1 on 1, and allowed me to walk away, while the 2 thought things over
* We had a few methods of working on reflexes. One was to be running in place while our instructor walked around us. He would yell Drop, or Jump, and swing a plastic tube at our head, or knees (never applying more than a gentle tap, if he made contact). My favorite involved using a string of lights he had along one wall. He would line us up, one half facing the lights, and one half with backs to them. He had a long cord with a switch attached for the lights. We would practice whatever "movements" we had been working on. Those facing the lights would attack when the lights flashed on, this required those defending to react to the movement, not the command to attack.