SwimHR: Wearable-Free Heart Rate Monitoring for Swimmers via Water-Mediated ECG Sensing

摘要

Heart rate (HR) monitoring during swimming is crucial for athlete performance optimization and physiological assessment. Yet existing solutions remain unsatisfactory. ECG chest straps require tight skin contact and are often uncomfortable during swimming, while photoplethysmography (PPG) sensors suffer severe accuracy degradation due to swimming-induced motion artifacts. We present SwimHR, the first wearable-free HR monitoring system that captures electrocardiogram (ECG) signals transmitted through pool water without any on-body device. To enable practical pool-scale underwater ECG sensing, we (1) derive and validate a physical model of ECG transmission in water and quantify environmental attenuation in swimming pools through simulation, (2) design a lane-scale sensing architecture with a bias-electrode-free acquisition circuit for reliable full-lane coverage, and (3) develop a U-Net-based pipeline for robust R-peak detection under stroke-dependent swimming artifacts. We evaluate SwimHR with 34 swimmers (12 amateur and 22 professional) across four strokes and multiple pools. SwimHR achieves a mean HR error of 1.0 bpm with a standard deviation of 0.9 bpm relative to the ECG ground truth, significantly outperforming PPG-based wearables. SwimHR demonstrates the feasibility of accurate, real-time, wearable-free HR monitoring in standard swimming pool settings while avoiding the discomfort of body-worn sensors.