Mechanical contraction in the human heart. Temporal evolution of apical lift δ characterizing the vertical movement of the apex along the heart's long axis towards the fixed base, left. Temporal evolution of ventricular torsion ϑ characterizing the rotation of two locations in the lateral left ventricular wall around the heart's long axis, right. Shortly after the onset of excitation, the apex lifts rapidly towards the base moving upward by approximately 8mm. Simultaneously, the heart twists rapidly about its long axis rotating clockwise by approximately 6° and 13°, with the amount of torsion increasing from the fixed base to the free apex. Both apical lift and ventricular torsion then decrease gradually as the heart returns smoothly to its resting state.