Effect of the "Sitting Out of Bed in an Arm-chair Position" in ICU on Functional Recovery Among Ventilated Patients

Inclusion Criteria: 1. Patient \> 18 years old 2. Patient on invasive mechanical ventilation for more than 24 hours 3. Patient in recovery phase with a RASS score greater than "-3" for more than 12 hours 4. Stay expected to last 48 hours 5. Patient has never been placed in a chair during this hospitalization in intensive care. 6. Fragility score \< 6, during the month preceding admission to intensive care 7. Patient (or support person/relative if patient is unable to participate) who has agreed to take part in the study. Exclusion Criteria: 1. Patient with an absolute and non-resolving contraindication to chair positioning 1. Fracture or orthopedic disorder contraindicating mobilization out of bed 2. Obesity with body mass index greater than 45 kg/cm2 3. Sacral eschar stage greater than 2 2. Patient using a wheelchair for mobility (i.e. paraplegic patient or patient with progressive neurological pathology). 3. Patient treated with veno-venous or veno-arterial ECMO at the time of screening. 4. Moribund patient 5. Encephalic death 6. Acute polyradiculoneuritis (Guillain-Barré syndrome) 7. Myasthenia 8. Patient treated by continuous hemodialysis or hemofiltration for more than 72 hours following the onset of awakening. 9. Complete transmetatarsal or higher amputation of one or both lower limbs. 10. Protected person (under guardianship or curatorship) 11. Person under court protection 12. Person not affiliated to a social security scheme 13. Pregnant or breast-feeding woman 14. Patient already included in the study 15. Patient taking part in an interventional clinical study, the aim of which is to show an improvement in functional level on discharge from the intensive care unit or which focuses on the theme of early rehabilitation in the intensive care unit.