The mind is a powerful thing.
I once had a bout of Post Concussion Syndrome (PCS) after banging my head pretty hard. It lasted about 8 weeks. It was a nightmare.
I had difficulty eating during that time. Everytime I would try to eat, I would lose my appetite.
I experienced my head injury by passing out due to illness caused by eating bad food.
I had read that sufferers of PCS who had suffered head injuries in car accidents would get bad PCS "attacks" when they got into cars after their accidents. Their minds reacted because they believed they were in danger. My doc said my mind may have been reacting to my bad experience with food (i.e. in some way, my mind believed food was going to hurt me!).
While suffering a bad bout of PCS, I got up and did the small part of a Taiji Form I knew. I repeated it 8 times. By the end of the session, I felt as right as rain. Now maybe it was due to getting out of a chair and helping my posture, circulation and nervous system, which helped my brain. Or maybe it was the placebo effect i.e. I thought doing Taiji would help my health, so it did.
The point I am making is that the belief mechanism is incredibly powerful. If your mind believes something, especially subconsciously, it can have very real impacts on your body.
Here is a great example from a TV show "Is it Real?", where they bust some popular myths. In this part, two scientists confront a senior student of George Dillman. Dillman is a karate teacher who is a master of the "No touch KO" apparently:
http://www.youtube.com/watch?v=5HXyJTXGTOkHere is the outcome of the test (from about 4:00 on):
http://www.youtube.com/watch?v=QoQE5DOL ... re=relatedI found it interesting that it compared things such as "No touch Knock out" to a form of hypnotism/suggestion.
P.S. I like Dillmans explanation! It's worth watching if just for that