Inclusion Criteria:  tested positive for SARS-nCOV-2 using antigen- or PCR tests within the last 24 months previous hospitalization due to COVID-19 fully vaccinated (only for controls)  Exclusion Criteria:  inability to follow the study procedures (e.g. due to language barriers, psychological disorders, dementia, etc.), known pregnancy or lactating women, presence of any contraindications for exercising until maximum exhaustion, including insufficient blood pressure control (systolic >170 mmHg, diastolic >100 mmHg), ongoing cancer treatment, unstable angina pectoris, uncontrolled bradyarrhythmia or tachyarrhythmia, severe uncorrected valvular heart disease, clinically relevant acute infection, any form of musculoskeletal injury, participating in any interventional clinical trial within the last four weeks, previous participation in the current study history of COVID-19 (only for controls)