Modeling of ankle angle-torque characteristic during passive dorsiflexion

Stroke often leaves with spasticity which increases muscle tone. For an accurate assessment of ankle spasticity, automatic devices that measure a resistance torque during passive dorsiflexion have been developed. However, conventional methods have not been successfully distinguishing spastic, elastic, viscous, and inertial torques around the ankle joint. The distinguish among these torques is essential to determine treatment. In this paper, therefore, we developed a novel device which dorsiflexes the ankle joint and measures the resistance torque and ankle angle. As the first step, we formulated the relationship between the elastic torque and the angle. The proposed model includes an elastic model of three muscles; tibialis anterior (TA), agastrocnemius (GC), and soleus (SL).