Inclusion Criteria:  ⋧18 years old, subjects diagnosed with COVID-19 confirmed by positive SARS-CoV-2 PCR testing who require admission to ICU for invasive mechanical ventilation invasive ventilation > 24 hours.  Exclusion Criteria:  pre-existing cognitive impairment, communication/language barrier any concurrent physical or mental health condition/ impairment that prevents subjects from taking part in evaluations or providing informed consent loss of independent walking ability (with or without walking aids) prior to hospitalisation defined by a score of ≤2 on the mobility item of the modified Barthel Index, pregnancy, any injuries/surgery that requires medical bed rest.