Fibromyalgia (FM) is a world widely common syndrome, characterized by widespread pain, often accompanied by general fatigue, soreness, and abnormal sensations (like "pins and needles"). The reasons and the mechanisms (pathogenesis) of FM are still poorly understood. Efficacious therapies cannot be developed without understanding the pathophysiological mechanisms of the disease or syndrome.

FM patients suffer from pain and sense of weakness and fatigue in the muscles, and often report difficulty in relaxing their muscles. So far, the studies on muscle activation in fibromyalgia (mostly using surface electromyography) have shown some unusual functioning, a kind of overuse, but the results have been somewhat contradictory.

FM symptoms share some features with small fibre neuropathy, which is a disease or abnormality of small nerve fibres with a diverse aetiology. Recently, several research groups have shown (studying both the electrical function of superficial nerves and nerve endings of skin samples) that up to 50% of the FM patients with severe symptoms have small fibre neuropathy: their small nerves do not function properly and small nerve fibre density in their skin is reduced. However, as this phenomenon is common but not a rule, it might be rather a consequence of some underlying mechanisms of the syndrome, creating even more symptoms.

The aim is to investigate whether there would exist metabolic changes in FM patients that would create pain and lead to functional changes and damage in small nerve fibres. The investigators also aim to explore the muscle function particularly in distressed situations and at rest. The hypothesis is that a towards-overuse-altered function would create unfavourable metabolic changes. Third, the aim is to investigate some psychological factors (such as tendency to get anxious or distressed) to find out, if there is any association between them and muscle function.

The FM patients as well as healthy control subjects will be recruited at Helsinki University Hospital Pain Clinic and from primary care at Vantaa Health Care Centre. The voluntary test subjects will attend

1. A muscle function examination of 30 minutes with electromyography using surface electrodes, including mentally distressing tasks and relaxing periods. At the same session, the subject will reply to some questionnaires regarding their symptoms and measuring some psychological factors. Actual pain level will be assessed.
2. A glucose tolerance test, with other blood samples
3. A bicycle ergometer exercise test of 20 - 30 minutes, with both physiological and chemical (blood samples) recordings. Actual pain level will be assessed as well.

At this stage, 40 patients and 20 healthy control subjects will be recruited.

Inclusion Criteria:

• fibromyalgia diagnosed by the researchers RM or TZ, based on the ACR criteria from 1990
• Finnish as native language

Exclusion Criteria:

• male sex
• muscular or neuromuscular diseases
• diabetes
• heart disease
• generalised atherosclerosis
• untreated hypertension
• neurological or other disease that systematically affects muscles
• a severe psychiatric disorder
• regular consumption of beta-blockers, bronchodilators, or statins

The Finnish personal ID system includes identification of gender. As most of clinical FM patients are women, we exclude men to create as much homogenity as possible in our sample.

Individual participant data are available for only two of the researchers, Ritva Markkula and Teemu Zetterman, who are recruiting the subjects and collecting and coding their personal data to an unidentified mode.