MXene hydrogel sensor enables heart and breathing monitoring in endurance sports Stretchable MXene hydrogel sensor tracks heart rate and respiration during intense exercise, staying stable under heat, humidity, motion, and sweat. This study presents a stretchable, skin-like hydrogel sensor designed to maintain stable electrical and mechanical performance in hot and humid environments. Schematic illustration of the dual-network MXene hydrogel sensor with multifunctional properties for wearable cardiorespiratory monitoring under hot and humid conditions. Researchers from Xi’an Jiaotong-Liverpool University and collaborating institutions report a new MXene-based hydrogel sensor capable of stable physiological monitoring under extreme exercise conditions. The recorded heart rate and breathing patterns closely matched reference measurements, capturing both linear cardiovascular responses and nonlinear respiratory changes as exercise intensity increased.