Fig. 2.
(a) Functional block diagram of signal processing and feature extraction procedure: Wearable ECG, SCG and AP signals were synchronized with breath-by-breath (BxB) data from COSMED K5 system. Wearable ECG and SCG signals were filtered and sections corrupted with motion artifacts were removed from the signals. The ECG signal was normalized and the R-peaks of the ECG signal were detected, and the SCG and AP signals were segmented into heartbeats using corresponding R-peaks. SCG and AP heartbeats were averaged to get ensemble averaged heartbeats and features were extracted from the averaged beats. The wearable features were fed into regressor as estimators. VO2 from the BxB data corresponding to each averaged heartbeats were computed and fed into regressor as target variables. (b) Visual representation of ECG artifact removal (with legends showing different lines for the figure in the middle). (c) Visual representation of heartbeat segmentation, ensemble averaging and feature extraction of SCGDV signal.