Modeling and identification of pendular motion of the lower leg in normal and stroke subjects

Pendulum test is a common clinical technique for assessing spasticity in stroke patients. In this study a new biomechanical model was built to describe the trajectory of knee joint angle during the pendulum test. In the model the torques contributed by muscles with stretch reflexes, passive tissue and gravity were all considered. By using a constrained optimization method, parameters of the model were obtained by minimizing the squared errors between the experimental data and simulated data. Three normal subjects and one stroke patient were recruited in this study. The preliminary results indicated that, for normal subjects in the relaxed state, the torque acting on the knee was mainly contributed by the soft tissue and gravity. The torque contributed by muscles with stretch reflexes was almost negligible. On the other hand, in the stroke patient, the torque contributed by muscles with stretch reflexes was significant.