ABSTRACT
The combined effect of stepwise intermittent hypoxia and physical training was investigated with ultrasonic cardiography on 12 bikers who were permanent inhabitants at 1895 meters above sea level and were subjecting to physical training under hypoxic condition in a hypobaric chamber. It was found that the internal diameters of the right ventricle and right pulmonary artery of the bikers increased proportionally with the increase of both the altitude and the duration of the physical training. At a simulated altitude of 4000 meters, the cardiac stroke volume and cardiac cutput, the internal diameter of the left ventricle and the left ventricular mass increased markedly as compared with those at sea level. The thickness of the interventricular septum and the posterior wall of the left ventricle also increased. The stroke volume and cardiac output of the bikers increased more significantly at the simulated altitude of 4000m., that at the altitude of 3000m. All these change are still within the physiologic ranges and can be considered as adaptation changes to highaltitude training. NO case of acute mountain sickness occurred in any of the trained bikers.These findings suggest that this intermittent stepwise hypoxic physical training can improve the cardiac function and increase its adaptibility towards hypo-xic conditions.