Abstract

Measurement by impedance cardiography (ZCG) of cardiac output and contractility indices during exercise is a recent addition to exercise testing of the cardiac patient. To provide a needed standard of normal responses to exercise at integrals of resting oxygen consumption (METS), 10 healthy men were tested.Basal oxygen consumption (1 MET) under standardized conditions was measured bymass spectrometry. Over several days the subjects were exercised on a treadmill at 2 METS through 6 METS with monitoring of heart rate, electrocardiogram, oxygen consumption per minute (VO2) and ZCG. The exercise routine was then repeated to look for test-retest effect. Values closely approximating presently accepted basal oxygen consumptions were achieved under these standardized but practical conditions. Cardiac output during sitting, fully supported rest was slightly higher than that at 2 METS on treadmill owing to higher stroke volume. From 2 METHS through 6 METS the curvilinear mean heart rate and stroke volume were mirror images, producing a linear increase in meancardiac output which at 6 METS was 145 of basal and 160 of the 2 MET value, while the contractilty index increased to 217 of basal. Comparison ofthe 2 trials revealed no significant test-retest effect. Verf.-Referat