In fifteen patients recovering from a myocardial infarction dating of at least three months, examined at rest or during a submaximal exercise, various circulatory (cardiac rate, blood pressure, cardiac output...) and ventricular parameters (oxygen consumption, ventilation per minute) both before and after a program of physical training for a period of six to eight weeks. The benefit of readaptation was judged on the increased work capacity (VO2max increase of 24.6%) and the improvement of cardio-circulatory adaptation during a submaximal exercise: reduction of the cardiac rate by 11%, of Katz's index by 12.6%, of the cardiac output by 5.8% and of the left ventricular work by 8.8%. This cardiac thrift at the origin of the increase of physical aptitude is essentially due to a better peripheral circulation adaptation to exercise, as indicated by the increased oxygen arterio-ventout difference by 11.4%.