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

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Abstract
Abstract: We measured localized impedance on the surface of the thigh to determine the properties of underlying muscle; these include ρ1, the resistivity for current flowing parallel to the fibers, and θavg, the average phase along the thigh (normalized to a standard length). The results for a modest sampling of nominally healthy subjects show that the θavg 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 ρ1 vs. θavg 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 ρ1 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.