Source: American Physiological Society (APS)
New Orleans, LA — Fibromyalgia (FM) is a syndrome characterized by chronic widespread musculoskeletal pain, with maladaptive responses to food and the environment. The underlying cause is still unknown for this disorder that affects approximately four million Americans.
Recent research has examined the altered function of the sympathetic nervous system (SNS) as part of the cause for this disorder. However, conflicting opinions of the SNS role exists because studies have found SNS hyperactivity and reduced activity in these patients. What is consistent in these studies is that the SNS responses of subjects with fibromyalgia undertaken during exercise indicated a blunted response.
It is known that healthy subjects, exercise induces activation of muscle sympathetic nervous activity, as well as more general SNS activity, especially when the exercise exceeds a certain level or duration. The SNS activity during exercise is important for performance of exercise and also closely related to the regulation of muscle blood flow and metabolic processes during exercise.
To find out if the same postulate applies to FM patients, a Norwegian research group aimed to determine whether the metabolic responses (including catecholamine, an organic compound affecting the sympathetic nervous system) induced by bicycle exercise, differed between the FM patients and controls matched for self-reported fitness-level, age and smoking. The second objective of her research was to assess whether the maximal oxygen uptake, being an objective measure of fitness, differed between matched groups.
The principle investigator of "Metabolic And Hormonal Responses During Dynamic Exercise in Female Fibromyalgia Patients and Matched Healthy Controls" is Nina K. Vjllestad, Professor, Section for Health Science, University of Oslo, Norway. She will present her findings in detail during the American Physiological Society (APS) annual meeting, which is being held as part of the Experimental Biology (EB '02) meeting. More than 12,000 scientific investigators are attending the conference, which begins April 20-24, 2002 at the Ernest N. Morial Convention Center, New Orleans, LA.
Methodology Fifteen women with fibromyalgia and 15 healthy women were individually matched with respect to age, smoking and frequency of physical activity. All subjects had at least a half-time job. One physician performed a standardized and detailed physical examination, and blood tests for rheumatic and thyroid diseases were taken.
Subjects with coexisting diseases were excluded, and so were controls on sick leave because of musculoskeletal disorders during the last three months. Anti-depressive medication was abandoned three weeks before the experiment, and all other medication was abandoned one week before.
The test subjects' ages ranged from 21 to 45 years, and the difference in each matched pair was below six years. Five subjects in each group smoked, and five in each group trained at least once a week. A slightly higher body mass index (BMI) was observed in the FM group compared to the control group, but no differences were found in height and weight.
All subjects answered a pain questionnaire; pain; fatigue and morning tiredness were registered on 100 mm visual analogue scales (VAS). The end points for pain were "no pain" and "worst possible pain", for fatigue "no fatigue" and "completely exhausted" and for morning tiredness the end points were "waking up completely refreshed" and "waking up completely exhausted".
The FM patients reported widespread and intense pain. Thirteen out of 14 patients reported daily pain and continuous pain. The control group reported no pain and minimal fatigue and sleeping problems. Blood samples were taken three times at rest; during exercise, blood samples were taken at every workload twice after exhaustion. At each workload the expired air was collected to determine the oxygen uptake.
Result The peak oxygen uptake in the FM patients in this study was markedly reduced compared to the control subjects, even though they were matched on self-reported activity level. The hormonal and metabolic responses were comparable in the two groups, indicating normal muscle physiology and normal responses from the sympathetic nervous system during dynamic exercise and a patient group.
Neither the control subjects nor the FM patients reported augmented pain in the post-exercise days.
Conclusion Many FM patients experience continuous pain both at work and at home, and if this condition is linked to altered physiological processes, one should organize their occupational work and tasks at home accordingly. However, the results from this research indicate that no adverse responses to exercise in FM patients was noted, suggesting that physical tasks by themselves do not create possible the responses that would exacerbate the disorder.
The American Physiological Society (APS) is one of the world's most prestigious organizations for physiological scientists. These researchers specialize in understanding the processes and functions underlying human health and disease. Founded in 1887 the Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals each year.