Survivorship after critical illness is an increasingly important health care concern as intensive unit care (ICU) utilization continues to increase while ICU mortality is decreasing. Critical illness survivors experience marked disability and impairments in physical and cognitive function that persist for years after their initial ICU stay1-7. Newfound impairment is associated with increased healthcare costs and utilization, reductions in health related quality of life and prolonged unemployment5,8,9. Weakness, critical illness neuropathy and/or myopathy, and muscle atrophy are common in critically ill patients with up to 80% of patients admitted to the ICU developing some form of neuromuscular dysunction1,10,11. ICU acquired weakness (ICUAW) is associated with longer durations of mechanical ventilation and hospitalization along with greater functional impairment for survivors. Although there is increasing recognition of ICUAW as a clinical entity, significant knowledge gaps exist around identifying high risk patients for its development and understanding its role in long-term outcomes after critical illness. This review addresses the epidemiology and pathophysiology of ICUAW, highlights the diagnostic challenges associated with its diagnosis in critically ill patients and proposes a novel strategy for identifying ICUAW.