Objectives: To quantify the prevalence and coexistence of these two forms of ICU- acquired weakness and their impact on outcome.

Background: Intensive care unit- acquired weakness is a frequent complication of critical illness because of patients' immobility and prolonged use of mechanical ventilation.

Objectives: To describe daily measurements of peripheral muscle strength in patients receiving mechanical ventilation and explore relationships among factors that influence intensive care unit- acquired weakness.

Intensive care unit- acquired weakness, a syndrome characterized by acute symmetrical limb muscle weakness after ICU admission, belongs to physical impairments in three domains of PICS.