A growing body of knowledge has documented that the diaphragm, the primary muscle of breathing, atrophies and weakens within days of instituting mechanical ventilation support. Diaphragm weakness has been implicated as a major contributor to difficulty with weaning, or breathing without ventilator support. This study will test whether instituting a diaphragm strength training rehabilitation program will reduce the time patients require mechanical ventilation in a surgical intensive care setting.

Inclusion Criteria:

1. Admission to general surgical intensive care unit with respiratory failure and expected to require mechanical ventilation support for more than 72 hours.

Exclusion Criteria:

1. inability to follow simple, one step commands such as "inspire forcefully",
2. patients with prior arrangements to be transferred to other facilities when stabilized,
3. any contraindications to disconnecting pt from ventilator for SHAM or IMST treatment,
4. unstable or difficult airway upon ICU admission and predicted to last for more than 72 hours,
5. use of more than minimal vasopressor or vasodilatatory agents as a continuous infusion,
6. severe dysrhythmias,
7. acute coronary syndrome
8. pulmonary contraindications (pneumon/hemothorax, flail chest),
9. acute surgical problems arising in the immediate post operative period (serious postoperative bleeding, wound dehiscence, etc). When and if these problems resolve and the patient meets other entry criteria, they will be eligible to be recruited for participation.
10. active neuromuscular diseases that would prevent or interfere with responding to strength training (e.g., amyotrophic lateral sclerosis, multiple sclerosis, myasthenia gravis, polymyositis, muscular dystrophy or other dystrophies and myopathies)
11. spinal cord injuries.