Electrical impedance of relaxed and contracted skeletal muscle.

A feasibility of bioimpedance measurement for the evaluation of skeletal muscle contractile state was examined. The 4-electrode impedance spectra of relaxed, moderately contracted and geometrically changed muscle biceps brachii were compared in a human subject over the frequency range from 300 Hz to 75 kHz. The frequency response was parameterized and a simple neural network was used to determine contractile state of a muscle. The parameters that could indicate skeletal muscle contractile state were found to be a frequency of the phase angle minimum and the rate of phase angle change with the frequency. The impedance spectra data set was further examined by a principal component analysis. The score plots show a data grouping of geometrically changed, relaxed and contracted muscle. [ABSTRACT FROM AUTHOR]