ответить на вопрос ... Some people can overcome pain - some of them can walk across burning coals or sleep on beds of nails. How do you think this can be?

I think they are a kind of people, who train their body from the childhood or have some unknown energy. Also it can happen just as subconscious level of body and soul, as in yoga. Because people can feel their thoughts, and often these thoughts become material. That's why they experience their energy and body in such way.