Ramakrishnan Swaminathan

Models of surface electromyography (sEMG) signals are extensively used in muscle biomechanics to analyze and validate clinical investigation in healthy and pathological muscles of adult and elderly populations. sEMG is a noninvasive technique to measure electrical activity of skeletal muscles. In this work, an attempt has been made to analyze biceps brachii muscle in normal and pathological conditions for elderly people using modified sEMG model. Age associated changes such as reduction in number of motor units and ratio of type II fibers are already reported in the earlier model proposed by Arjunan et al. However, experimentally it was found that there is an increase in motor unit action potential duration (MUAPD) due to aging. This effect is incorporated in this present work to model sEMG signal. Influence of physiological changes such as loss of muscle fibers, increased fiber diameter variation and decreased MUAPD are also included in this sEMG model in myopathyic conditions. Features namely, root mean square (RMS), median frequency (MDF), entropy and fractal dimension (FD) is extracted from the signal in normal and pathological conditions. Results show that the modified sEMG model gives distinct values for both normal aging muscles and myopathic muscles. The corresponding variations in feature values are significant (p<0.05). The values of RMS, MDF and FD are found to be higher in myopathic conditions compared to normal aging. The description of the sEMG model, the method of analysis and the observations are presented in this work. It appears that this sEMG model can be used to analyze myopathic conditions in elderly populations.