Gait Initiation and Dynamic Balance Control in Parkinson’s Disease

Hass CJ, Waddell DE, Fleming RP, Juncos JL, Gregor RJ. Gait initiation and dynamic balance control in Parkinson’s disease.ObjectiveTo determine whether the magnitude of the separation between the center of pressure (COP) and the whole-body center of mass (COM) during gait initiation can differentiate patients with varying severity of Parkinson’s disease (PD) disability.DesignCross-sectional, intact groups research design.SettingBiomechanics research laboratory.ParticipantsForty-three patients were stratified into 2 groups based on the Hoehn and Yahr (H&Y) disability score, which heavily favors balance in determining disability. The 2 groups were: H&Y score of 2.0 or less (n=23; age, 61±10y) or H&Y score of 2.5 or higher (n=20; age, 70±9y).InterventionsNot applicable.Main Outcome MeasuresThe peak COP-COM distance represents the maximum separation between the location of the whole-body COM and the ground reaction force’s COP, and thus is an indicator of dynamic balance control. The peak COP-COM was evaluated during 3 phases of the COP trajectory during a gait initiation task.ResultsThe peak magnitude of the COP-COM distance was significantly greater during the end of the single-support phase in the less disabled patients (H&Y score ≤2.0) than in more balance disabled patients (H&Y score ≥2.5) (P=.004).ConclusionsThe differences in COP-COM distances between these H&Y groups suggest that patients with PD who have impaired postural control produce shorter COM-COP distances than do persons without clinically detectable balance impairment. This method of evaluation could prove a useful quantitative index to examine the impact of interventions designed to improve ambulation and balance in PD.