An active, non-linear, model of the leg drop pendulum test: assessing changes in spastic cerebral palsy

Reports on the use of a second order nonlinear system with active force input to model the leg drop pendulum test in spastic cerebral palsy. The model is used as a means of gaining insight into a therapeutic intervention with this population. Optimization techniques are used to adjust model parameters, such that model data fit actual data. Actual data is taken from a set of triplets, two of which have varying degrees of spastic: cerebral palsy and one is without disability. The author compares five sets of data, one from the normal triplet and two each from the subjects with spasticity. Data from the subjects with spasticity is taken before and after vertical stimulation similar to that which one would receive while on horseback. The model parameters show several trends. First, the amplitude of the active forces are reduced to more normal values after vestibular stimulation. Second, the duration of these forces is longer after stimulation than before.