A new optimization criterion introducing the muscle stretch velocity in the muscular redundancy problem: A first step into the modeling of spastic muscle

Abstract

Over the past few decades, musculo-skeletal modeling has been proposed as an in silico alternative to the invasive in vivo measurement of internal forces (e.g., musculo-tendon and joint reaction forces). However, even if great efforts have been made to improve the models, they remain partially validated and not adapted to pathologic subjects with orthopeadic and/or neurologic disorders. Indeed, even if a geometric scaling can be done using medical imaging techniques, the personalization of motor control specificities remains problematic. Consequently, when optimization techniques are used to solve the muscular redundancy problem, the selected criteria, that should reflect the motor control strategies, are not adapted to the gait disorders, such as muscle spasticity. The goal of this study was to introduce the muscle stretch velocity in the objective function, since muscle spasticity is linked to this parameter. We show that the maximization of the squared muscle stretch velocity provide more physiologic results during the stance phase and could be a way to introduce a spasticity criterion.