Obstacle crossing in Parkinson's disease: Mediolateral sway of the centre of mass during level-ground walking and obstacle crossing

•Some people with PD sway sideways abnormally far and fast when walking.•Obstacle crossing can exacerbate abnormal sideways sway in people with PD.•People with more severe PD sway faster when crossing obstacles.

BackgroundFalls are common in idiopathic Parkinson's disease (PD) and frequently occur when walking and crossing obstacles.ObjectiveTo determine whether people with mild to moderately severe PD have abnormal centre of mass (CoM) motion in response to the perturbations of level-ground walking and obstacle crossing.MethodMediolateral excursion and velocity of the CoM were measured using three-dimensional motion analysis and force platforms in 20 people with mild to moderately severe PD at the peak dose of their PD medication, and 20 age and sex matched healthy control participants.ResultsPeople with PD had greater sideways sway than healthy older adults when walking, particularly when walking over obstacles. People with PD also maintained their CoM more medial to their stance foot throughout the swing phase of gait compared to controls. The severity of motor symptoms in people with PD, measured using the UPDRS-III, was associated with faster sideways CoM motion but not increased CoM excursions.ConclusionsEnvironmental hazards, such as ground-based obstacles, may accentuate postural instability in people with PD. Increased mediolateral sway might be due to impaired postural responses or kinematic compensations to increase foot clearance. Fall prevention programs could benefit from inclusion of components educating people with PD about the risks associated with obstacle crossing when walking.