Coronary heart disease and beta-blocker treatment can increase the use of the Frank-Starling mechanism during exercise. The aim of the study was to assess whether this could be influenced by physical training. Male patients on beta-blocker treatment after myocardial infarction were randomised to four weeks of training (ET, n = 19) or to a control group (Ctr, n = 18). Cardiac output (CO) at rest and at identical submaximal exercise levels in each patient were determined by radionuclide ventriculography at baseline and after the intervention period. CO was calculated as end diastolic volume (EDV) x ejection fraction x heart rate, and deltaCO and deltaEDV as change in parameter from rest to exercise. The mean (SD) deltaCO decreased from 6.5 (2.1) L/min(-1) to 5.1 (2.4) in ET patients and increased from 5.0 (1.7) to 5.8 (2.7) in Ctr, p = 0.004. deltaEDV decreased from 30 (30) mL to 12 (35) in ET and increased from 11 (20) to 36 (33) in Ctr, p = 0.005. When adjusting for baseline dissimilarities between the groups in a multivariate linear regression analysis, these differences were still statistically significant, p = 0.018 and p = 0.044, respectively. Physical training reduces the CO increase needed to perform identical submaximal exercise, and this is accompanied by less left ventricular dilatation, with a potential for reducing exercise-induced ischaemia.