Inclusion Criteria:  50 patients with survived COVID-19-infection (25 with a severe course requiring mechanical ventilation in the intensive care unit, 25 with a moderate-severe course requiring administration of supplemental oxygen only, respectively) Patients aged at least 18 years, who are mentally and physically able to consent and participate into the study  Exclusion Criteria:  Diagnosis of another disease, which causes a permanent increase in carbon dioxide level in the blood (chronic hypercapnia) or a permanent combined lung weakness (particularly a neuromuscular disease) Body-mass-index (BMI) >40 Expected absence of active participation of the patient in study-related measurements Alcohol or drug abuse Metal implant in the body that is not MRI compatible (NON MRI compatible pacemaker, implantable defibrillator, cervical implants, e.g. brain pacemakers etc.) Slipped disc Epilepsy Bound to a wheel chair Patients who are mentally and physically unable to consent and participate into the study Patients in an interdependence or with an employment contract with the principal investigator, Co-PI or his deputy. Emergency hospital stay in the last 4 weeks preceding the day of the measurements