I have studied and practiced the martial arts for years and am well aware of what both the mind and body can do. I am an engineer, so I know something about various energy fields and their interactions, and have been formulating several hypothesis on such events with the help of a biologist and a physicist. If you're interested in hearing, drop me a line. I am NOT a skeptic, but I do believe that, at some point in the future, it is possible to understand these things in their proper context.
This particular event happened when I was 10, while exploring the forest behind my home in Tennessee. We had gone back about half a mile (direct line - longer as the feet wander) and we came upon a cemetary. An OLD cemetary. The most recent markings were from the turn of the century. A brief setting note - the place was on the border of two farms (judging from the barbed wire fencing). >From where we came, the only way in was through a 3' wide section, and being the size we were, we could only go in by crawling under the lower line. Of course, this presents an excellent view of the ground at that spot. What did we see? Lots of moss and leaves (it was autumn). We explored, and in the center is a metal-picket fence around a large family monolith (looks like a 8' version of the Washington monument made out of dark marble set in a granite block). The fence of course was rusted and falling, but the gate on it was slightly ajar. The handle of the gate, however, was brand new and coated lightly with oil. Needless to say, my friend and I were mildly disturbed at this. BTW, I mean new, not weathered, silver steel printed with a hardness rating.
Amazingly enough, we did not flee. We tried to make out the writing on the pillar, but it was too weathered. There were some symbols reminiscent of heraldry, but I can no longer remember them precisely. We decided to go home. This is when we got spooked. As we approached the fence, about 3' inside (where, incidentally, you'd be at your longest point crawling under) was a clean, white skull. It stood out nicely on the dark moss and leaves. As a team, we did what any rational 10-year-olds would do: he froze and I beat feet. In tribute to me, I actually dived through the lower and middle strands of barbed wire (not bad for a chubby computer geek). He did eventually catch up.
About a week later we went back. We never made it inside the fence. Where the human skull had been sitting, was a bull's skull (no, you cannot mistake a bull's skull with horns for a smooth, round human skull). We bolted again. We told my grandmother, who suggested we be sure. So, the next day we went back. You guessed it, the human skull was there waiting for us. We took it back home and my grandmother burned it. Soon after it was winter, and that winter my friend moved away, so we never went back.
It doesn't end there. Some years later, when I was 17 and dabbling with the occult, I decided to revisit the cemetary. I went with me then-girlfriend, and got permission from the folks living in my old house to pass through. The cemetary was pretty much like I remembered it. Even the handle was still shiny and oily. I plan on making a trip back soon, just to see how the place is. The last time I was there, I didn't feel at all frightened, so I have no apprehensions about returning.