Spasticity Mathematical Modelling in Compliance with Modified Ashworth Scale and Modified Tardieu Scales

The aim of this work is to formulate a spasticity symptoms-oriented model, in terms of its capability to consistently emulate unidirectional and velocity-dependent spasticity symptoms, based on a Modified Tardieu Scale (MTS). Spasticity stiffness can be simulated using two dynamic equations expressing 1) muscle tone catch during passive stretching at different velocities and 2) resistance through Range Of Motion (ROM). Muscle tone is proportionate to velocity; where muscle resistance is constant until reaching a certain angular velocity. Following different Modified Ashworth Scale (MAS) levels, muscle resistance can occur at varying degrees through the ROM. The simulated spasticity of MAS 1+, based on the developed model, shows a strong positive linear correlation coefficient with average r = 0.7414 for fast forearm extension. The derived model will be used to develop new principles of variable stiffness actuation in an upper limb part-task trainer that is able to emulate upper limb spasticity symptoms.