System for activity-aware fatigue evaluation (SAFE) framework: Predictive fatigue modelling for occupational tasks

The SAFE (System for Activity-aware Fatigue Evaluation) framework integrates wearable sensing, biomechanical modelling, and task detection to enable monitoring of operator endurance and ergonomic risk. In this feasibility study, the framework was evaluated offline in a laboratory environment with 10 participants performing industry-type tasks, combining inertial measurement units (IMUs), pressure insoles, a torque-based endurance model, task classification, and a custom application. Validation against motion capture confirmed that IMU-derived joint angles were within acceptable error ranges for endurance estimation. The framework produced endurance metrics that distinguished between ergonomically high- and low-risk tasks (P < .05) and correlated strongly with subjective fatigue ratings (rmm≥.878, P < .001). IMUs captured arm movement variability across dynamic tasks and task classification via pressure insole data enabled the application of task-specific endurance coefficients. These results demonstrate that the SAFE framework is a feasible predictive method for online operator monitoring and ergonomic risk assessment, providing a foundation for future real-time deployment.