Kinematics of Pointing Movements Made in a Virtual Versus a Physical 3-Dimensional Environment in Healthy and Stroke Subjects

Knaut LA, Subramanian SK, McFadyen BJ, Bourbonnais D, Levin MF. Kinematics of pointing movements made in a virtual versus a physical 3-dimensional environment in healthy and stroke subjects. Objective: To compare kinematics of 3-dimensional pointing movements performed in a virtual environment (VE) displayed through a head-mounted display with those made in a physical environment. Design: Observational study of movement in poststroke and healthy subjects. Setting: Motion analysis laboratory. Participants: Adults (n=15; 4 women; 59±15.4y) with chronic poststroke hemiparesis were recruited. Participants had moderate upper-limb impairment with Chedoke-McMaster Arm Scores ranging from 3 to 6 out of 7. Twelve healthy subjects (6 women; 53.3±17.1y) were recruited from the community. Interventions: Not applicable. Main Outcome Measures: Arm and trunk kinematics were recorded in similar virtual and physical environments with an Optotrak System (6 markers; 100Hz; 5s). Subjects pointed as quickly and as accurately as possible to 6 targets (12 trials/target in a randomized sequence) placed in arm workspace areas requiring different arm movement patterns and levels of difficulty. Movements were analyzed in terms of performance outcome measures (endpoint precision, trajectory, peak velocity) and arm and trunk movement patterns (elbow and shoulder ranges of motion, elbow/shoulder coordination, trunk displacement, rotation). Results: For healthy subjects, precision and trajectory straightness were higher in VE when pointing to contralateral targets, and movements were slower for all targets in VE. Stroke participants made less accurate and more curved movements in VE and used less trunk displacement. Elbow/shoulder coordination differed when pointing to the lower ipsilateral target. There were no group-by-environment interactions. Conclusions: Movements in both environments were sufficiently similar to consider VE a valid environment for clinical interventions and motor control studies.