Mechanically ventilated patients in the ICU are commonly immobilized for prolonged time periods due to factors that include the underlying illness, encephalopathy, or sedation. In this setting, severe ICU-acquired weakness is common and may represent both a cause and consequence of immobilization. Physical and occupational therapy is feasible in ICU patients, even very early during mechanical ventilation. This intervention requires a coordinated effort between physicians, nurses, respiratory therapists, and the physical/occupational therapy team. Early physical and occupational therapy can lead to improved strength and functional status, reduced ventilator days and length of stay, and fewer days of ICU delirium.