Rehabilitation in heart failure medicine is limited due to many comorbidities and reduced exercise capacity in this patient group. In patients after cardiac surgery rehabilitation is sometimes difficult especially due to ICU- acquired weakness following a prolonged intensive care course. To tackle these problems and enable recovery and rehabilitation many of the conventional methods are lacking feasibility. During the next decades increasing numbers of older and more frail patients in the field of advanced heart failure are expected. To establish a new method for rehabilitation we use technology well established in other divisions of medicine. Robotic assisted gait therapy is well established in neurology in paraplegic and tetraplegic patients, patients after stroke and traumatic injured patients. Gait therapy is used to re-establish the normal course of motion. The Lokomat ® (Hocoma AG) is therefore used in over 25 countries worldwide. The combination of different training modes (interval training, endurance training and resistance training) is one of the advantages. The most important benefit is the possibility to extend or relieve the robotic assistance up to a point without support on the one hand and full support from the Lokomat ® on the other hand and relieve the patient partly or complete from his bodyweight. This enables the therapist to plan the most possible individual training almost independent from his exercise capacity for each patient. Up to now heart failure is a contraindication for training with the Lokomat ® and no trial was performed after cardiac surgery. Therefore a clinical trial is necessary to establish this method in the field of heart failure medicine and after cardiac surgery. In our prospective trial we investigate two points after a feasibility trial first, were healthy persons and patients with NYHA 1 or less are trained for safety reasons, to establish possible protocols and get familiar with the robotic assisted gait therapy. In the prospective trial we train patients with stable heart failure (NYHA 2 or NYHA 3) and a left ventricular ejection fraction less than 45% for 4 weeks with 3 trainings per week.