An interactive EMG-EMS system for assisted exercise monitoring: a user-centered evaluation

Surface electromyography (sEMG) and electrical muscle stimulation (EMS) are increasingly used in rehabilitation and training. However, turning EMG-EMS setups into usable end-to-end interactive experiences remains challenging due to real-time constraints, safety, and user-facing workflow complexity. We investigate an interactive EMG-EMS exercise workflow that supports exercise execution and post-session reflection, and we evaluate it from an interaction-centered perspective focusing on usability, learnability, perceived usefulness, and comfort. The system integrates real-time sEMG visualization with session history and session comparison for reflective analysis. During the study, EMS assistance was delivered in a manual, operator-mediated manner, in which the application provided real-time stimulation cues that guided manual adjustments of a commercial EMS device. A small exploratory pilot study with healthy participants ([Formula: see text]) examined the full interaction workflow in two sequential phases (sEMG-only followed by EMS-assisted), using think-aloud, task-level performance logging, and questionnaires (SUS and domain-specific). The evaluation showed positive perceived usability and user experience (SUS mean: 78.95/100), with participants particularly valuing session history and comparison as tools for post-exercise reflection. Real-time sEMG feedback was delivered with stable behavior and an effective processing delay on the order of tens of milliseconds. At the same time, the study revealed recurring challenges inherent to EMG-EMS interaction, including sensor onboarding, electrode placement, and users' interpretation of sEMG-derived feedback, which point toward important directions for future system design. Findings provide preliminary support for the feasibility of an interactive EMG-EMS exercise experience with positive perceived usability and comfort in a healthy, technologically literate pilot sample. However, the results should be interpreted as exploratory because of the small sample, sequential study design, and operator-mediated EMS delivery. These findings motivate HCI-focused iterations to improve onboarding, interpretability, and future evaluation with more reliable and automated hardware.