Memristor-Based Dynamic Modeling of Muscle Fatigue

We introduce a novel dynamic modeling paradigm to represent fatigue and recovery processes in muscles by dynamic extension of the classical 3-element Hill model. A memristor and a capacitor are used in a series circuit arrangement, with a voltage source representing muscle activation. This model is shown to capture the fundamental features of fatigue accumulation and recovery in response to arbitrary motion, load and activation profiles, in contrast with other work assuming specific input shapes such as constants or periodic functions. Further, the basic model is shown to capture the gradual increase in activation spectral amplitudes with fatigue progression, which is an experimental fact. The paper shows how the fatigue modeling element is integrated into larger musculoskeletal dynamic models. Possible modifications and extensions aimed at more flexibility are also suggested.