Can We Redesign a Shoulder Exosuit to Enhance Comfort and Usability Without Reducing Assistance?

: Reduced shoulder mobility limits upper-limb function and daily activities across a wide range of conditions. Wearable exosuits have shown promise in assisting arm movements and reducing muscle effort; however, comfort has rarely been prioritized as an explicit design objective, despite it strongly affects mass-adoption and long-term usage. This study presents a redesigned soft shoulder exosuit developed to address comfort-related limitations identified in our previous version. In parallel, the actuator-harness configuration has been redesigned to bias assistance preferentially toward shoulder flexion, to enhance functionally relevant hand positioning. A comparison between the previous (v1) and redesigned (v2) versions was conducted in eight healthy participants, who performed static, dynamic, and functional tasks, with muscle activity, kinematics, and user-reported feedback as main outcomes. Both versions increased endurance time and reduced deltoid activation when assistance was active, without hindering movement freedom when unpowered. However, the difference emerged most clearly during functional tasks and comfort evaluation. Version 2 was associated with forward-directed arm elevation and larger transverse-plane mobility by up to 30°, without a detected increase in deltoid activation. User-reported outcomes further suggested improved wearability, with lower perceived pressure across the harness and higher ratings in effectiveness (+23%), ease of use (+20%), and comfort (+17%) compared to the previous version. Taken together, these findings suggest that redesign strategies focused on wearability and task-oriented assistance can improve comfort and functional interaction without compromising assistive performance.