Introduction: Fibromyalgia (FM) is a condition characterized by chronic widespread pain and generalized tenderness accompanied by fatigue, disturbed sleep and cognitive difficulties. Several types of muscle abnormalities have been reported in FM at tissue, cellular and subcellular level, which could eventually alter the passive electrical response of the muscle. Methods: We evaluated the brachial musculature of 41 women, 21 with FM and 20 without, using multi-frequency electrical impedance myography and the characteristic parameters of the Cole-Cole model were obtained (R
0, R∞, τ and α). Results: The alpha parameter of the FM group was statistically different (0.21 ± 0.05 against 0.17 ± 0.05 p = 0.008). Discussion: The higher values of alpha parameter in the FM group may suggest that the behaviour of the cell membrane in FM is more permeable to the ions than in the non FM group and, therefore, less resistive.