Using Localized Impedance Measurements to Study Muscle Changes in Injury and Disease

A bstract : We measured localized impedance on the surface of the thigh to determine the properties of underlying muscle; these include ρ 1 , the resistivity for current flowing parallel to the fibers, and θ avg , the average phase along the thigh (normalized to a standard length). The results for a modest sampling of nominally healthy subjects show that the θ avg values are substantially higher than the whole body phases encountered in standard bioimpedance analysis. When the sample is augmented to include subjects undergoing hemodialysis and/or recovering from serious illness or leg injury, the behavior of the position dependence of the phase θ( z ) and the ρ 1 vs. θ avg average distribution both strongly indicate a correlation between very low phase angles and injury or disease. Furthermore, measurements on a subject in a weight training program after injury provide evidence of a monotone increase in ρ 1 with increasing strength. Measurements on dialysis patients during treatment show a nonlinear response of thigh muscle to the degree of fluid removal and wide disparities between individuals.