In physiological experiments and clinical practices, the Pressure-Volume (PV) loop of left ventricle is important to evaluate the cardiac contractility and energetics. The end-systolic PV relation (ESPVR) is almost linear and its slope is well known as representing the maximum elastance (Emax) to evaluate the cardiac contractility. Furthermore, the pressure volume area (PVA) represents the total mechanical energy per beat and correlates with myocardial oxygen consumption. In order to study mechanical energetics in human cardiac myocyte, we developed a human circulation model which consisted of a preload, an afterload and a sphere heart. The pressure of the heart was converted from the tension of human ventricular myocyte model based on Kyoto Model according to Laplace's law. Our circulation model produced the PV loops with each afterload and showed a linear ESPVR. PVA was proportional to oxygen consumption like many experimental results. We calculated ATP consumptions per beat by the Na-K pump, SERCA and the cross-bridge. ATP consumptions by Na-K pump and SERCA was almost independent from PVA, while the ATP consumption by the cross-bridge was proportional to PVA. [J Physiol Sci. 2007;57 Suppl:S198]