Hmm, as a practitioner of Aikido and also a student of Shiatsu, which both rely heavily on Ki energy, I feel I should add my 2 cents into this and give a few examples of Ki (Chi, prana) at work.
As one example:
I have asked extremely buff men (football players and weight trainers) to try to bend my arm when I simply held it out straight in front of me. When I used muscle to try and stop them, there was no chance. It bent like a bendy straw.
I then stop using muscle strength and instead channel Ki through my arm. No one has yet been able to bend it even the slightest bit.
As another:
Have you ever stood on one leg and had someone push you? You fall like a dead tree. I, on the other hand, have allowed people to try their hardest to knock me over while channeling Ki through my leg. It can’t be done!
As a third:
I, by channeling Ki, whether you choose to believe this or not, can tell exactly where you are in relation to me with my eyes closed simply by reaching my Ki energy out and finding yours. I have even tried this through walls. I can sense you from about 50 feet away - people who are exceptionally strong in Aikido can sense you from much further than that.
I’ll also mention that every human body has what are called “meridians” running through it. These meridians run through the same place on every body and carry Ki through the body. Along these meridians, and especially at end points, are points called “tsubos.” When Ki is channeled into a tsubo, it can cause either healing or extreme damage to occur, depending on the intent and skill of the practitioner who is channeling it. I have personally walked up behind people, who didn’t even know I was there, and barely touched a tsubo on them, channeling Ki into it, and watched them fall to the ground like a sack of rocks. This sort of approach has been proven to knock people unconscious, and, in some cases, can be fatal.
So, yes, Ki does exist, and even if it can’t be measured, par say, its existence has been proven for thousands of years.
Sorry if this topic’s already been left… admittedly, I didn’t read the entire thread.