Development of new inverse analyses of surface EMG about change of neuromuscular structure and function with ageing

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We examined the inverse analysis of surface EMG to extract anatomical and physiological information such as the position (depth),current strength, size (radius), muscle fiber density, recruitment and firing rate of active motor units. It became clear that the depth of the active motor units was 0.5-7.7mm, and the current strength of the active motor units was 0.1-230.9nAm, through the inverse analysis with surface MUAP. In addition, the radius of the motor units was 1.4-5.4mm, and the muscle fiber density of the motor units was 0.4-9.3fiber/mm2, was estimated through the relationships between depth and current strength that were clarified by the inverse analysis. Furthermore, we developed the extended electrode array for new inverse analysis to progress the accuracy of estimation. It was clarified that the number of recruitment of motor units in rapid contraction with low force was smaller than that in maximal voluntary contraction for EMG amplitude, from the simulation of surface EMG … More with the model that had anatomical and physiological parameters about motor unit. But, the simulation method including the model of motor units must be extended for information about firing statistics of the motor units. On the other hand, the effect of the inhomogenious tissue such as epidermis and dermis, and the fiber density of motor unit on the surface electromyo potential was examined through the simulation with finite element method. As the results, it was clarified that the estimate of depth of motor unit was robust and stable against the above conditions. The inverse analysis developed in this study have the advantage that this method is able to estimate the anatomical and physiological process such as the depth, current strength, size, fiber density and firing statistics of active motor units, which is not able to measure practically under the interfered condition produced by recruitment of many motor units. In order to collect more detail and effective information about neuromuscular system, we must progress the development of the inverse analysis including recording method and model for simulation, and application of those methods to aged subjects. Less