The organization of stepping in patients with Parkinson's disease: bradykinesia or discoordination?

The purpose of this experiment was to quantify and analyse multijoint coordination of patients with Parkinson's disease (N = 5) and control subjects (N = 5) during forward and backward stepping motions executed at different cadences. Coordinates of reflective markers placed on the shoulder, hip, knee, ankle and metatarsal joints were recorded in the sagittal plane using a video motion analysis system. Kinematic and kinetic analyses provided angular displacements and velocities as well as joint moments of force and powers. Results suggest the presence of two types of discoordination: one type is velocity-dependent, hence related to bradykinesia, whereas the other type appears to reflect qualitatively different coordination patterns.