Double-Fishtail-Shaped FBG Wearable Device for Sitting Posture Recognition and Real-Time Respiratory Monitoring

Musculoskeletal issues frequently affect individuals who sit for prolonged periods, particularly in work settings. Addressing and preventing these upper body musculoskeletal disorders (UBMDs) requires close monitoring of seated behavior among employees. This study introduces a solution—an adaptable wearable device incorporating three distinct modular devices using fiber Bragg grating (FBG) technology. The FBG array, integrated into a polydimethylsiloxane (PDMS)-based double fishtail (DF) design, significantly enhances curvature sensitivity and durability. By fine-tuning the length of DF silicone, we further optimized curvature sensitivity. Our wearable device demonstrates prompt correlation with thoracic spine patterns, validated against a motion capture (MoCap) system using ten volunteers as a benchmark. Furthermore, it successfully identifies common sitting postures—normal, breast-bearing, and hunchbacked—with exceptional accuracy exceeding 96.30%, employing the random forest machine learning methodology. Additionally, this device facilitates timely and accurate monitoring of respiratory rate (RR) by time–frequency domain analysis. This innovative optical solution showcases its potential for a variety of wearable device applications.