By means of noninvasive transthoracic impedance cardiography, the cardiovascular profile of two groups of male asymptomatic and glycometabolic‐compensated insulin‐dependent diabetics (IDD), one composed of five untrained patients (UD) and the other of five athletes trained for aerobic‐anaerobic sports (TD), was studied during a cycle ergometer progressive exercise up to a submaximal work rate corresponding to a heart rate (HR) of 130 beats/ min (W 130). At rest, although HR and arterial blood pressure were similar in the two groups, values for TD were higher than for UD in stroke volume (SI, +14%) and cardiac output (CI, +26%) index expressed per m2of body surface area, impedance‐derived cardiac work indicator (CWI, +24%), impedance‐derived heart mechanical efficiency indicator (HEI, +16%), impedance‐derived ventricle preload indicator (PLI, +12%), and those for TD were lower than for UD in impedance‐derived total peripheral resistance indicator (TPRI,‐24%) and impedance‐derived myocardial contractility indicator (MCI,‐25%). With respect to rest, at W 130 TD showed the following changes: SI, +9%; CI, +82%; CWI, +122%; HEI,‐3%; PLI, +5%; TPRI,‐65%; and MCI, +27%. UD showed: SI,‐6%; CI, +59%; CWI, +82%; HEI,‐20%; PLI,‐3%; TPRI,‐29%; and MCI,‐5%. It was concluded that in the asymptomatic IDD patient a sedentary habit may lead to subclinical left ventricle dysfunction. On the contrary, participation in competitive sports led to an increase in the physical capacity of the subjects and also reduced the risk of cardiomyopathy.