Timeframe for patients after cardiac surgery: Screening day0; baseline/start of the training day0 +(0-2days); training period one week with the Lokomat® with three training sessions; end of study visit after one week, telephone follow up twelve weeks after hospital discharge to evaluate possible deep sterna wound infection. Due to the character as a pilot trial, there are no statistical end points, but stress test (spiroergometry), blood sample (interleukin 6, CRP, BNP) , strength measurement of the Musc. quadriceps and a quality of life questionnaire (SF 36) are taken at baseline (day0) and after the 4 week training period at end of study visit. Patients after cardiac surgery are trained with another strategy. There the safety aspect is the most important in this pilot trial. Patients after cardiac surgery are trained with the Lokomat® during initial hospitalization for one week with three sessions. A six minute walk test and measurement of quadriceps peak force is done at at baseline/start of the training day0, expected at day 3 to 14 after surgery, and after one week of training at end of study visit day seven. A telephone follow up of this patients three months after hospital discharge is done for possible deep sternal wound infection.