Inclusion Criteria:  adults aged ≥18 years stable cardiovascular disease ; acute coronary syndrome; coronary artery bypass grafting within the previous six months ability to perform physical exercise, to speak, read and write Greek possession of a mobile phone/smartphone internet access at home  Exclusion Criteria:  ventricular arrhythmia or myocardial ischemia during low to moderate exercise intensity as assessed by symptom limited exercise testing at baseline heart failure New York Heart Association (NYHA) class IV comorbidity precluding exercise training (e.g. orthopaedic, neurological or cognitive conditions) acute myocardial infarction (within two days) stenosis unstable angina uncontrolled atrial or ventricular arrhythmia aortic uncontrolled congestive heart failure acute pulmonary embolism acute myocarditis or pericardial effusion uncontrolled diabetes mellitus (Type I, II) hemodynamic instability or exercise-induced arrhythmia in baseline (initial) assessment severe obstructive respiratory disease