Spreading of Pain: Women vs. Men

by Kristin Thorson, Fibromyalgia Network Editor
Posted: August 28, 2008

Fibromyalgia occurs more often in women, although men get this painful condition too. While many reports have documented that healthy women have a lower pain threshold than healthy men, this does not explain why more than twice as many women develop fibromyalgia.

Quite often, fibromyalgia is triggered by muscle pain in one area (due to an injury or fall) that eventually spreads, or refers, to the whole body. In addition, once symptoms of fibromyalgia are present, it is common for the regional pain caused by myofascial trigger points to produce a referral of pain. Myofascial trigger points (MTPs) are regions in a muscle with tense, ropey bands that feel like firm knots. Pressing on an MTP hurts, and it also refers pain to other muscle areas. This spreading pain is a common phenomenon, but it is not known if it varies between men and women.

A research study presented at the 2008 American Pain Society meeting investigated whether local and referred pain is different between women and men.* A University of Iowa research team recruited 69 healthy volunteers (35 female, 34 male) and injected a painful acidic solution into the mid-belly of their back calf muscle to determine if the spread or referral of pain was different between the sexes.

The average pain ratings at the site of the acidic injection was the same for the two groups (women and men) … an important observation because it means that women do not simply complain more about their pain. Of the participants, 62 percent experienced a referral or spreading of pain from the middle of the calf down to the back ankle region. Looking specifically at the group of volunteers who referred pain, women outnumbered the men two to one. Ironically, this is the same distribution ratio of reported widespread pain in the general population.

The study authors state that the referral or spread of pain likely occurs by a central nervous system mechanism when the pain at a regional muscle site exceeds a certain threshold. Given that women do have lower pain thresholds, this could partially explain why women are more likely to experience the spreading of pain and may be why more women develop fibromyalgia. And although a smaller portion of male volunteers in this study developed referred pain, these findings also support the fact that there is a subgroup of men that may be more susceptible to getting fibromyalgia.

Aside from helping to explain the higher prevalence of fibromyalgia in women, this study offers insight on the importance of treating MTPs—for both women and men. Not only do MTPs refer pain to other areas (which provides a strong case to get them treated post haste), they also increase the number of pain signals going to the central nervous system. This, in turn, can cause a magnification of the “whole body” pain of fibromyalgia.

Many treatments may help relieve or reduce the pain of MTPs, such as massage, injecting the MTP with an anesthetic, ultrasound-omit, frequency specific microcurrent, low level laser therapy, application of moist heat or coolant spray and then gently stretching the affected muscles, and various hands-on physical therapy techniques. In addition, factors that may enhance the development of MTPs should be addressed. This may include getting quality sleep, improving the way you use your muscles to avoid straining them, and eating healthy so that your muscles are adequately nourished.

* Frey Law L, et al. J Pain 9(4 suppl 2):P9 Abs #134, 2008.

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