Skeletal Muscle Regeneration in Survivors of Critical Illness: How to Prevent Satellite Cell Failure?

Eligibility Criteria for group of Critically ill patients: Inclusion Criteria: * Critically ill patients receiving mechanical ventilation, to be enrolled within 72 hours of admission, who are likely to need 7 days or more of ICU stay * Sudden onset of disease, which can be determined in time (such as trauma, stroke, sudden cardiac arrest etc.) * Informed consent signed by patient or patient's representative Exclusion Criteria: * Unlikely to survive 6 months * Premorbid downslope functional trajectory or poor performance status (ECOG Gr. 3 or worse) or baseline functional status unknown * Bleeding disorder (INR≥1.5 or PLT\< that would preclude muscle biopsies) * Known mitochondrial disease * Endocrine crisis as a reason for admission * Pregnant women Eligibility Criteria for a control group: Elective hip surgery patients with a very good to excellent performance status, only limited to joint pain (ECOG 0)