Work program: 80 patients at the beginning of phase II cardiac rehabilitation will be randomly assigned to an interval group or to a control group. In both groups, patients will exercise 4x / week for 12 weeks. At the beginning, after 6 weeks and at the end an exercise test will be carried out. Blood will be taken before (platelet function at rest) and immediately after each exercise test (platelet function after acute, strenuous exercise). Basal platelet activation as well as platelet responsiveness towards a platelet agonist (platelet reactivity) will be analyzed.