Fig. 1

a Image of the custom-developed hardware for bio-signal acquisition. The ECG electrodes are boxed in green; SCG accelerometer, light-blue; and PPG LED-PD pairs, orange. b Image of a subject performing the two hemodynamic interventions; static squatting on the left and cold pressor test on the right. c A sample data of ECG (green), SCG (light-blue), and PPG (orange) with PEP labeled in between ECG R-peak and SCG AO-peak and PTT labeled between SCG AO-peak and PPG waveform minimum. ECG electrocardiogram, PPG photoplethysmogram, SCG seismocardiogram, LED light-emitting diode, PD photodiode, AO aortic opening, PEP pre-ejection period, PTT pulse transit time