Extending a Dynamic Muscle Model for Usage with Amputees

When muscles are used during ordinary work, the fibers of a particular muscle are recruited by the corresponding motor-neurons of the spine. From the total number of fibers in the muscle, only parts are recruited to be active for work according to the required force which the cortical system has estimated. Thus, using the activated fibers by applying force over a period of time, the fibers get more and more fatigued and are replaced by newly activated ones. J. Z. Liu et al. developed a technically sound theoretical model for muscle activation, fatigue and recovery which describes how many motor units are in the states of rest, activation and fatigue. In this work, Liu’s theoretical model is adopted and extended in order to simulate and investigate fatigue. The actual state of a muscle is estimated by the measurement of surface Electro-Myo-Graphy (sEMG), force and torque. In the model, using the input parameters sEMG, or force and torque, with amputees the number of Motor Units (MU) are estimated in the states: rest, activation and fatigue. A method for muscle state estimation at amputees is presented in this work.