Effect of Parkinson's Disease on the Step Response to a Backwards Pull

Abstract

This study was designed to identify parameters of balance recovery that are sensitive to postural instability early in the progression of Parkinson's disease. The response to a backwards pull was analyzed in a group of healthy controls and a group of adults diagnosed with mild Parkinson's disease (H&Y 2). Video, motion, EMG, and force plate data were analyzed to determine differences in strategy, temporal, kinematic, kinetic, and center of pressure parameters for the first step in the response. In the PD group, subjects were less consistent in their choice of stepping limb over multiple trials, had a longer weight shift time, and showed different motion at the ankle joint prior to liftoff. In addition, the center of pressure was further posterior at landing in the PD group. These results suggest that further investigation focused on the movement preparation stage may be able to identify early markers of postural instability.