Muscle ischemia has been postulated as a causative factor in pain and disability in patients with primary fibromyalgia syndrome (PFS) and previous studies have demonstrated that patients with PFS have reduced maximum oxygen uptake (VO2). Our objective was to examine the level and pattern of VO2 in response to graded exercise and defined levels of constant work rate exercise in patients with PFS.
Unmedicated patients fulfilling modified Yunus' criteria for the diagnosis of PFS and healthy control subjects performed upright cycle ergometry exercise with measurements of respiratory gas exchange and grading of pain using visual analog scores.
Patients, but not controls, had significantly higher levels of pain after graded exercise than before exercise. Although peak VO2 did not differ between the 2 groups, effort dependent variables of exercise function were more variable in the patients than in control subjects. The onset of muscle anaerobiosis as reflected in respiratory gas exchange, the relationship between VO2 and work rate throughout the range of exercise work rates, and the mean response time for the increase in VO2 to the exercise level in response to a constant work rate of exercise were not different for patients compared to controls.
Despite the subjective reports of pain, our studies demonstrate no abnormality in the overall rate and pattern of utilization of oxygen during muscular exercise in patients with PFS.