Lack of association between fibromyalgia syndrome and abnormalities in muscle energy metabolism

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Abstract
Objective. To compare parameters of muscle energy metabolism in patients with fibromyalgia syndrome (FMS) and sedentary controls. Methods. Thirteen female FMS patients and 13 female sedentary controls underwent a standardized clinical assessment (including dolorimeter measurements of the upper trapezius and tibialis anterior muscles) and a standardized aerobic fitness test including measurement of maximum oxygen uptake (VO2max). Phosphorus (31P) magnetic resonance spectroscopy studies of the upper trapezius and tibialis anterior muscles were then performed in FMS patients and controls, at rest and during and following a musclefatiguing exercise protocol. Results. FMS patients and controls had similar levels of VO2max and of maximum voluntary contraction (MVC) of the upper trapezius and tibialis anterior muscles. After controlling for VO2max and MVC, measurements of phosphocreatine (PCr), inorganic phosphate (Pi), and intracellular pH in these muscles were not significantly different in FMS patients versus sedentary controls either at rest, during exercise, or during recovery. In the patients with FMS, no correlation was found between overall or local pain severity and the principal muscle metabolic parameter, PCr/Pi. Inverse correlations between dolorimeter scores at 2 muscle sites and tibialis anterior PCr/Pi were found both in patients and in controls. Conclusion. This study demonstrates that under the conditions studied, muscle energy metabolism in FMS is no different than that in sedentary controls. These findings do not support the hypothesis that detectable defects in muscle energy metabolism occur in FMS.