Features are extracted from seismocardiogram data to correlate with two indexes of myocardial contractility: dP/dt(max) (maximum first derivative of left ventricular pressure) and stroke volume. In the first study on three pigs, it is shown that the time period between the R peak of the ECG and the first peak of the SCG (R-AO period or pre-ejection period, PEP) correlated (r= -0.86) with dP/dt(max). In the second study, stroke volume is gradually reduced in five human subjects using lower body negative pressure. The same feature as the pigs (R-AO) is correlated the most with stroke volume (r= -0.90).