Heart rate monitoring from wrist-type photoplethysmographic (PPG) signals during intensive physical exercise

Heart rate monitoring from wrist-type photoplethysmographic (PPG) signals during subjects´ intensive exercise is a difficult problem, since the PPG signals are contaminated by extremely strong motion artifacts caused by subjects´ hand movements. In this work, we formulate the heart rate estimation problem as a sparse signal recovery problem, and use a sparse signal recovery algorithm to calculate high-resolution power spectra of PPG signals, from which heart rates are estimated by selecting corresponding spectrum peaks. To facilitate the use of sparse signal recovery, we propose using bandpass filtering, singular spectrum analysis, and temporal difference operation to partially remove motion artifacts and sparsify PPG spectra. The proposed method was tested on PPG recordings from 10 subjects who were fast running at the peak speed of 15km/hour. The results showed that the averaged absolute estimation error was only 2.56 Beats/Minute, or 1.94% error compared to ground-truth heart rates from simultaneously recorded ECG.