Inclusion Criteria:  Patients in a stable condition on the same disease specific medication >4 weeks. Signed informed consent. Precapillary pulmonary hypertension (PH) diagnosed according to international guidelines: mean pulmonary artery pressure (mPAP) ≥25 mmHg and pulmonary artery wedge pressure (PAWP) ≤15 mmHg, pulmonary vascular resistance >2 WU, measured by right heart catherization and clinically diagnosed as Pulmonary arterial and chronic thromboembolic pulmonary hypertension, class 1 or class 4  Exclusion Criteria:  Severe daytime hypoxemia (pO2 ≤7.3 kPa or <55 mmHg) Other clinically significant concomitant disease states (e.g., renal, hepatic dysfunction, etc.). Inability to follow the procedures of the study, e.g. due to language problems, psychological disorder, dementia or confusional state of the subject, neurological or orthopedic problems with inability to ride a bicycle. Woman with known pregnancy. Enrolment into another clinical trial with active treatment.