Minimal-calibration multimodal wearable sensing for long-duration three-dimensional shoulder kinematics

Shoulder motion is essential for daily activities, yet accurate quantification outside laboratory settings remains challenging. Existing wearable systems either accumulate drift over extended recordings or rely on elaborate calibration protocols that limit real-world deployment. Here we report a wearable platform for long-duration tracking of three-dimensional shoulder kinematics with minimal calibration. The system combines a sensing shirt instrumented with inertial measurement units and soft strain sensors with a lightweight learning-based fusion framework to estimate joint orientation. Using only a few minutes of unconstrained arm movements and no laboratory equipment, the approach achieves tracking errors below 5° across all degrees of freedom during more than 1 h of continuous functional activity. Sensitivity analyses indicate robust performance with shortened calibration and reduced sensor configurations. This strategy establishes a practical route towards reliable, long-duration shoulder kinematics in unconstrained environments, supporting applications in movement science, clinical monitoring and assistive technologies.