First, general exercise capacity will be assessed by spiroergometry (maximal oxygen uptake, respiratory efficiency, oxygen pulse, etc.). The scientists will investigate potential abnormalities between the reported NYHA class and the recorded physical exercise capacity. In a second step, the potential influencing factors are analyzed. Right ventricular pump function and inferior vena cava respiratory variability will be worked up using echocardiographic data and assessed as possible determinants of better or worse endurance capacity. Questionnaires on quality of life, mental health, and personality factors will be analyzed with respect to exercise capacity. In the project, an analysis will be performed affiliated to the multicenter cohort study Transition CHF-DZHK2 (congestive heart failure) of the DZHK. The aim is to collect data from NYHA I patients to build a biobank of this underrepresented cohort.