A positive feed-back mechanism enhancing the heart beat

The dynamic equilibrium between cardiothoracic system oscillations and those of the whole body mass in humans is studied in a noninvasive way and compared with direct body ballistocardiography. During progressive physical effort the body lying in the supine position starts to oscillate and supports the movement of the plane of the valves. From these observations it follows that the heart rate equal to one-half of the natural frequency of the body has an optimal enhancing effect on the pumping activity of the heart.