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Fibromyalgia patients also displayed greater muscle fiber conduction velocity at nontender points
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Higher muscle fiber conduction velocity in nonpainful and nontender point-related muscles occurred among women with fibromyalgia than in women without the disorder, according to study results.
“There are clear functional disturbances in the muscles of patients with fibromyalgia,” researcher Ewa G. Klaver-Król, MD, PhD, of the department of neurology and clinical neurophysiology, Hospital Group Twente ZGT, Hengelo, Netherlands, told Healio.com. “These factors may be an underlying factor in producing pain.”
Ewa G. Klaver-Krol
Klaver-Król and colleagues performed surface electromyography on the biceps brachii of 13 women (mean age, 43 years) with fibromyalgia (FM) and 13 matched healthy controls. Exclusion factors for FM patients — who in earlier studies displayed higher conduction velocity (CV) in tender point muscles than observed in healthy controls — included disease severity requiring a wheelchair, orthoses use; shoulder, elbow or wrist pain in the dominant arm; obesity (BMI greater than 30); comorbidity with diabetes mellitus, and use of medicines, drugs or tobacco.
Static contractions were exerted on the arm while in an unloaded state, then loaded at 5% and 10% of maximum voluntary force. Muscle fiber CV was measured through cross-correlation (CV-cc) and inter-peak latency (CV-ipl). Tender point (TP) score and Fibromyalgia Impact Questionnaire (FIQ) were conducted for study participants, and correlations between CV, TP score and FIQ items were calculated.
Patients with FM displayed less voluntary maximum strength than controls (P=.011). TPs were greater in the FM cohort vs. controls (P<.001), and they also had significantly poorer scores on relevant FIQ items. CV was greater in the FM patients compared with controls (CV-cc, P=.005; CV-ipl, P=.022). TPs in the FM cohort were correlated with CV (r=0.642, CV-cc; r=0.672, CV-ipl), while CV and FIQ health aspects showed no correlations.
“The present-day paradigm of fibromyalgia mostly embraces disturbances in the central pain regulation and in the patients’ behavior,” Klaver-Król said. “Most surprising in our study is that, in fibromyalgia, the disturbances were also found in the peripheral tissue.”
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