Force production capacity and acute neuromuscular responses to fatiguing loading in women with fibromyalgia are not different from those of healthy women.

OBJECTIVE: To compare the maximal and explosive strength characteristics of the leg muscles in premenopausal women with fibromyalgia (FM) with those of healthy female controls (HC) and to examine acute neuromuscular fatigue during heavy resistance loading and short term recovery from fatigue in these 2 groups.
METHODS: Subjects were 11 women with FM, 38.6 (5.8) years old, and 12 healthy female controls, 37.3 (6.1) years old. The following were recorded before, during, and after a fatiguing loading session: maximal bilateral concentric and isometric force, isometric force-time curves and relaxation-time curves with agonist-antagonist neural activation (by EMG) of the leg muscles, muscle pain, and blood lactate concentrations.
RESULTS: At baseline all the measured muscle strength characteristics were comparable between the study groups. The heavy fatiguing loading led to considerable and comparable acute fatigue found in both muscle strength characteristics and agonist-antagonist electromyography in both groups. The respective changes in blood lactate concentration and subjectively perceived muscular pain in the loaded muscles during strenuous resistance loading and recovery from fatigue were similar in both groups.
CONCLUSION: Premenopausal women with FM do not demonstrate lower dynamic or isometric muscle strength characteristics compared to matched healthy controls. Second, the similar neuromuscular responses recorded during and after the fatiguing loading strongly support the hypothesis of normal muscle structure and neuromuscular function in patients with FM.