Biomechanical analysis of arm reaching in individual with stroke and non-disabled adults

Abstract

Upper extremity (UE) tasks such as arm reaching involve a variety of movement control strategies and unique specialization of function and lateralization in motor performance, namely handedness. UE dysfunction from stroke results in impairment in routine daily activities, including dressing, bathing, and writing. After stroke, movement patterns change to accommodate altered constraints; this is termed compensatory movement control strategy. The aim of this dissertation was to quantify the movement control strategies of arm reaching and identify the contributing biomechanical factors in motor lateralization and stroke. Better understanding of the control strategy of arm reaching could provide important insights for developing new interventions and promoting neural motor functional recovery. Early research findings on quantifying arm movement control strategies are limited to kinematic analysis or use a traditional inverse dynamics approach. The approach used in my research employs a newer quantification method called induced position analysis (IPA) that links both kinematic and kinetic domains. In the first study we developed and validated an IPA to address multijoint coordination of arm reaching in nondisabled individuals. We found that the shoulder and elbow act together in "overshoot" and "undershoot" patterns to move the arm forward to the final position. We termed this pattern as a directional control principle. In the second study we applied IPA to analyze lateralization and to test the current "hand dynamic dominance hypothesis" of arm reaching in nondisabled subjects. Both arms had similar multijoint dynamic patterns that showed movement asymmetry only at a fast speed, where the contribution of the shoulder and elbow was greater in the dominant vs. the nondominant arm. In the third study we did a post-hoc analysis of a bilateral arm training study and explored compensatory movement strategies in stroke survivors. We found that there were two different types of compensatory movement strategies associated with impairment levels ("mild to moderate" vs. "severe") and functional outcomes ("poor" vs. "good" outcomes). Shoulder moment contribution was a strong predictor of arm function change after bilateral arm training. In summary, using IPA provided new information about arm reaching in non-disabled adults and stroke survivors.