Date of Graduation
School of Medicine
A stroke often damages the neural structures responsible for movement. Stroke is a heterogeneous disease, affecting each survivor differently. There are common motor features of a stroke, but even these features vary across time as an individual proceeds through different stages of recovery. The different ways in which stroke motor impairment can present itself are often overlooked, but these differences are fundamental to the understanding of the disease and its recovery. When motor assessments are capable of acquiring information necessary to parse out a detailed profile of each stroke case, this will lead to an improved neuromechanical understanding of the disease and an improved application of personalized rehabilitative techniques and assistive devices.
In my research, the key approach was to understand the stroke-related neuromechanical disruption at the level of joint torques and then selectively restore function using a wearable assistive device. In my first aim, I investigated post-stroke upper-limb motor deficits in terms of muscle torques related to movement and gravity compensation. Using biomechanical simulations of detailed kinematic data from the upper limbs, I was able to separate active muscle torques into profiles of activity that stabilize the limb against gravity from those that are used to control multi-joint movement. The results of this work found that elements of active muscle torque provide a more sensitive measure of impairment than angular kinematic measures. In my second aim, I designed a Functional Electrical Stimulation (FES) protocol using concepts of neuromechanics to improve coordination and promote neuroplasticity. I hypothesized that FES used to support the weight of the arm against gravity in upper-limb motor impaired stroke subjects will not interfere with the execution of reaching movements and will improve grasping performance. The goal of this aim was to design and test a biomechanical model-driven FES intervention to reduce shoulder abduction and flexion loads due to gravity and assist with a reaching movement. Rather than use an exoskeleton to offer support, we used profiles of gravity-compensation torque, identified in Aim 1, as the design for the FES stimulation to support the weight of the arm during unrestrained center-out and return movements.. This improved movement speed, grasping performance, and distal muscle coordination while not interfering with reaching trajectory in our sample of 4 stroke survivors. Following this application, we investigated the effect of extended use of assistive FES on the induced movement and on the glenohumeral joint of the shoulder. Movement induced by FES decreased did not decrease over time and the stimulation-induced effect on the glenohumeral joint was still present after a 1-1.5 hour session in controls, or in a 30 minute session in stroke participants. This supports the effectiveness of this technique used for movement assistance. Although this data is preliminary, the results in our last aim also suggest that this application of FES may strengthen muscles associated with the glenohumeral joint, which in turn prevents subluxation injury. We believe this application has potential for the improvement of assistive technology after stroke.
Thomas, Ariel, "Biomechanically Inspired Assistive Technology to Restore Movement of the Upper Limbs After Stroke" (2021). Graduate Theses, Dissertations, and Problem Reports. 8217.