Soft Wearable Robot that Provides Anti-Gravity Arm Support Improves Upper Limb Movement Quality in Individuals Post-Stroke

Post-stroke motor impairments limit the ability to functionally move the arm against gravity which leads to a reduction in upper limb movement quality. Hence, providing anti-gravity arm support is widely adopted as an effective strategy in motor rehabilitation to enable functional upper limb movement. Recently, we developed a soft wearable shoulder robot that lifts the arm against gravity using a pneumatic actuator attached underneath the arm on a custom-made shirt. This study aims to evaluate the effectiveness of the soft wearable robot in improving upper limb movement quality for individuals post-stroke. We recruited four individuals post-stroke (age = 60.5±18.3 years, UE-FMA scores = 45.5±11) and asked them to lift their arm against gravity to 90° flexion and abduction, three times each with the robot turned on and off. We used an optical motion capture system to record and evaluate upper limb movement by calculating 1) shoulder elevation/depression range of motion (ROM), 2) end-effector movement quality (hand-path-ratio of the three-dimensional (3D) hand center of mass (COM) trajectory), and 3) trunk compensation (displacement of 3D trunk COM). We found that the soft wearable robot increased shoulder elevation/depression ROM, on average, by 6.1±1.7°, for the four participants. Additionally, the robot improved end-effector movement quality and reduced trunk compensation by decreasing hand-path-ratio and trunk displacement, on average, by 50.9±7.7% and 15.3±6.7%, respectively. The demonstrated improvement in movement quality highlights the potential utility of our device for upper limb motor rehabilitation.