A multimodal stretchable bioelectronic system for simultaneous monitoring of skeletal-muscular and metabolic biomarkers.

Physical activity involves coordinated skeletal muscle contraction and metabolic regulation, with its impact on human health determined by complex interactions between mechanical motion and biochemical processes. Monitoring these interactions requires real-time tracking of skeletal muscle activity that regulates movement and the associated metabolites produced during exercise. Here, we present iTrainer, a stand-alone, multimodal, stretchable, and wearable bioelectronic system that enables non-invasive and dynamic monitoring of skeletal-muscular and metabolic biomarkers. The device simultaneously captures physiological signals of skeletal muscle (motion frequency, skin strain, joint bending angle, and temperature) and sweat-based metabolic biomarkers (lactate and Na+) during both aerobic and anaerobic exercise. The iTrainer integrates three key components: an epidermal microfluidic module for skin-worn sweat collection and transport, a multimodal sensing array module for skin-on physicochemical biomarkers monitoring, and an integrated electronic module for data processing and wireless transmission. Human trials in aerobic (e.g., running) and anaerobic (e.g., bench press) exercise validated the system's capability to measure synchronized mechanical and biochemical signals. We also evaluate the utility of iTrainer as a partial substitute for professional coaches in the iTrainer-assisted self-exercise training management for novice individuals.