Abstract / Summary
Abstract The growing demand in professional sports for precise and continuous performance assessment, has highlighted respiratory rate (RR) as a critical indicator of exertion, fatigue, and training adaptation. However,existing RR monitoring systems face limitations both in dynamic and static conditions due to reduced wearability, signal artifacts during motion, limited individual adaptability, and challenges in extracting reliable self referential and feedback oriented output. To address these limitations, a wearable interdigital capacitor (IDC) based smart belt is developed for the real time RR monitoring and longitudinal performance evaluation. The flexible IDC sensor is fabricated by a cost effective, screen printing technique on a Polyethylene terephthalate (PET) substrate using carbon conductive ink, The sensing mechanism captures capacitance variations induced by diaphragmatic motion through modulation of fringing electric fields. A robust signal conditioning strategy based on adaptive thresholding is employed to isolate true respiratory cycles from motion induced disturbances, ensuring reliable operation during dynamic activities.The proposed system includes an embedded acquisition unit and a custom designed software for real time visualization, detecting the RR pattern, and providing user friendly feedback. Experimental evaluation of the proposed sensor demonstrates a sensitivity of 1.1846 pF/N, corresponding to an estimated pressure sensitivity of ~1.036 pF/kPa, along with high linearity (R² = 0.98561), low hysteresis, and excellent repeatability, validated through a 500-second continuous respiratory signal showing stable and consistent breathing patterns, which means that the sensors work reliably. The system accurately monitors breathing patterns at different exercise intensities and implements a referential system that can obtain data in real time and generate a weekly assessment framework to measure respiratory adaptation through both endpoint and averaged metrics. The proposed platform provides a non-invasive, user specific, and feedback driven solution for continuous respiratory monitoring, offering practical utility in sports performance optimization. Clinical Trial Registration Not applicable. This study was not a clinical trial and no clinical trial registration was conducted.