Body Position Impact on Ballistocardiographic Waveforms and Heart Rate Detection

Body posture alters bed-based ballistocardiogram (BCG) signals, yet its impact on cardiac monitoring remains insufficiently understood. We systematically evaluated posture-induced changes recorded with an EmFit bed sensor across five body positions: supine, prone, left lateral, right lateral, and Semi-Fowler. Fifteen healthy participants were measured in each posture for three minutes, repeated three times, with synchronized electrocardiography (ECG) as reference. Waveform morphology, heart rate (HR), and heart rate variability (HRV) were evaluated using manual annotation and two automated algorithms. Hand-annotated HR showed excellent agreement with ECG across all postures (Pearson r>0.99). Automated methods showed posture-dependent performance, with left lateral and prone postures yielding the best results. HRV estimation remained challenging across all postures due to the broad BCG S1 peak morphology. These findings support the development of posture-robust bed-based cardiovascular monitoring.