Dose of Early Therapeutic Mobility: Does Type or Frequency Matter?

This study will examine the effects of once and twice daily activity performed with patients who are breathing with the aid of a machine in an intensive care unit. Activity can occur in bed. Activity can include transfer to a chair and even walking once the patient\'s condition allows safe, out-of-bed activity. The investigators hypothesize that early, progressive activity will reduce inflammatory molecules in the blood, promote muscle and physical health and help patients to recover more quickly from critical illness.