Truth is, no one really knows exactly what brings on the aches and pains of fibromyalgia. What we do know about fibro pain is that it involves a complex interplay of highly sensitive nerve fibers known as C-fibers and the rest of the central nervous system.

Everyone has small C-fibers in the skin. These slow-moving nerve fibers are highly sensitive to chemical, mechanical, and thermal energy. Your tongue for instance, may react to both the chemical and thermal energy of hot chili peppers. Overstretching a muscle, on the other hand, is a mechanical stimulus for pain.

When these stimuli are strong enough, they activate the C-fibers. The C-fibers send their information to pain-processing nerve cells in the spinal cord, which then pass their information up to the brain. If stimulation of the pain fibers is too intense or goes on for too long, a condition known as central sensitization occurs.

Central sensitization is a condition in which neurons in the central nervous system become overexcited and normal sensations become abnormally painful. Sensations that come from C-fibers in the muscles are more likely to trigger central sensitization than input from the skin.

Central sensitization results in wind-up phenomenon, in which your response to pain is significantly increased. In essence, the computer that processes pain in your spinal cord becomes hyperactive. You become overly sensitive to heat. A tap on the arm feels like a punch. The soft texture of a cotton blanket makes you ache.

When the wind-up phenomenon occurs, other nerve fibers that don't normally carry pain start to get involved in the transmission of pain signals in order to handle the overload of stimulation. Now more nerves are charged up.

In this excited state, the body becomes hypersensitive to pain. For some people with fibromyalgia, even a warm bath is enough to cause bodily distress. When mildly painful events become very painful, you are said to have hyperalgesia. When a person feels pain due to a stimulus that would normally not cause pain, it is called allodynia.

Pain Without Stimulus

In some cases, people experience pain without any input or stimulus. This seemingly bizarre phenomenon occurs when people feel pain in the absence of any external factor, such as injury. It's caused by spontaneous discharging of the nerves that normally carry or process pain, often due to some type of irritation or injury. The classic example is phantom limb pain. A patient whose left leg has been amputated, for instance, might still complain that his left ankle hurts. Phantom limb pain may seem impossible, but it lends further proof to the fact that people can feel pain even if they haven't suffered any obvious trauma, just as fibro patients do.