Pain perception is not as simple as everyday experience suggests. Some people experience great pain without any apparent cause. Others experience little or no pain despite great injury. Cognitive and emotional factors seem to be important. A belief that one has control over the pain seems to reduce the level of pain experienced.
Fear seems to increase it.
Firewalking is usually done in a religious or spiritual context. This would tend to reduce the level of pain experienced by firewalkers without affecting the amount of physical damage done to the feet. Some firewalkers put forward mystical explanations of why firewalking is possible without serious physical harm. A few skeptics have challenged these firewalkers to stand on hot metal plates instead of coals. Others have pointed out that making such a challenge in the belief that the firewalker would be seriously hurt is of dubious morality.