Inclusion Criteria:  Patient has been in ICU receiving ECMO for more than 24 hours Patient is aged 18 years or older Patient was functionally independent prior to the current admission. Patient is eligible for Medicare (Australian sites only)  Exclusion Criteria:  Patient has been receiving ECMO for more than 72 hours Patient has been in ICU for more than 5 days Patient has suspected or proven primary myopathic or neurological process associated with prolonged weakness or acute brain injury Death is deemed imminent by the treating clinician Patient has a documented medical diagnosis of cognitive impairment e.g. dementia Patient was unable to mobilise prior to this admission Patient is unable to communicate in local language Patient is known to be pregnant Patient is unlikely to stay in the country (of the recruitment site) for more than 6 months