Study of muscular tissue in different physiological conditions using electrical impedance spectroscopy measurements

While performing physiological functions, muscles modify their intrinsic characteristics. As has already successfully done in various clinical fields, the technique of electrical impedance spectroscopy (EIS) measurement can be applied in order to study tissue changes. The aim of this study was to study changes in the electrical properties of muscular tissues due to an isometric contraction and successive relaxation.For this work, the electrodes lay out and trials protocol were carefully designed, also according to studies concerning muscle fatigue. A device previously tested and employed for in vivo EIS measurements was used. Impedance measurements were carried out on the forearm flexor muscles in a group of sixteen healthy adult subjects. In order to have a quantitative index of spectral impedance variation, the relative variation of the area under curve of Nyquist plots was computed to study the different muscle states under consideration (rest, contraction and 4 min after contraction).The index introduced showed itself to be sensitive to different muscular conditions. Results from healthy subjects showed statistically significant differences in the impedance data in the various muscle conditions under examination.