New Scientist Magazine recently published an article "Pain be gone" by Clare Wilson (22 Jan 2011, No 2796, pg 34-37) which noted research that while scientists would like to find a pain (P1) area of the brain as there is a vision area, auditory area, etc., it is more likely that pain is a product of many parts. As an endurance athlete and the mother of three children, each born via natural, drug-free childbirth, this notion resounds with me. To me, pain is often actually fear. The amygdala is the part of the brain associated with emotions including fear which is undoubtably a huge factor. I would go further in also including the pre-frontal cortex known for controlling cognitive thought.
I've always found that when the cause of the pain is known and you know that no further damage is being done, the pain is much more bearable. When the pain has a known endpoint such as the birth of the child or the end of the race, I would actually expect that the pain would be rated as less painful (i.e. a "5" rather than a "7" on a scale from 0 to 10).
Whether my thinking applies as well to chronic pain as to acute pain is debatable. What does pain have to do with "training with your jogging stroller"? Do you need to ask? Burning quads never seem to hurt as much as a pulled muscle. I would venture to say that is because you 1. know what is causing the pain and 2. know that it is not causing further damage. The burning in your lungs you may feel when you are breathing hard is not painful or stressful as compared to an asthma attack.