Chair positioning is one of a series of early mobilization techniques. At present, this technique, which involves moving a patient out of the resuscitation bed, can be performed passively or actively. It does not constitute a rehabilitative act as such, but it is considered in common paradigms as a technique to improve "the patient's breathing and strength".

However, recommendations issued in 2013 by the Society of intensive care physiotherapy and the society "Société de réanimation de langue française (SRLF)", reveal that this chair position cannot be recommended with a high grade.

The aim of the investigators is therefore to break down this early mobilization process in intensive care, to find out whether the armchair is an indispensable tool for improving functional and muscular processes.

The research hypothesis is therefore as follows:

"Early armchairing of the resuscitation patient, improves functional recovery compared to a conservative positioning strategy (sitting in bed)."

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.