Electrical muscle stimulation (EMS) is the therapy used to passively activate muscles using electrodes on the surface of the skin. EMS may be helpful in preserving muscle function in people who are on bedrest due to critical illness in the intensive care unit. The purpose of this study is to determine the safety and feasibility of implementing EMS in critically ill patients who are on mechanical ventilation for greater than 7 days, and examine the effects of 4 weeks of EMS on leg muscle size, muscle strength and functional outcomes in these patients. The investigators hypothesize that EMS will be safe and feasible and that critically ill patients receiving EMS will show a smaller loss of muscle size and strength than those in the control group, who do not receive EMS.

Inclusion Criteria:

• admitted to the medical-surgical ICU or cardiovascular ICU
• walking independently prior to admission
• mechanically ventilated for more than 7 days (i.e. prolonged ventilation)
• receiving enteral or parenteral nutrition.

Exclusion Criteria:

• history of neurological or psychiatric disease
• primary muscle disease (e.g. muscular dystrophy, polymyositis)
• catastrophic neurological event
• receiving palliative care
• contraindications to EMS (e.g. cardiac pacemaker/defibrillator, pregnancy, infected or cancerous lesions in proximity of electrode sites)
• inadequate access to electrode sites due to medical devices
• lower extremity edema affecting the thighs or buttocks
• BMI > 35 kg/m2
• allergies to adhesives or latex