Inclusion Criteria:

• Spinal cord injury due to trauma located between the seventh cervical and tenth thoracic vertebrae.
• American Spinal Injury Association grading scale of A or B (at least 4 each of A and B) below the level of SCI.
• Intact spinal reflexes below the level of SCI.
• At least 1-year post-SCI.
• At least 22 years of age.
• Willing to use medically acceptable methods of contraception, if female and of child-bearing potential.

Exclusion Criteria:

• Currently a prison inmate, or awaiting trial, related to criminal activity.
• Pregnancy at the time of enrollment.
• DEXA t score <-3.5 at spine and femur head.
• History of chronic and/or treatment resistant urinary tract infection.
• Unhealed decubitus ulcer.
• Unhealed skeletal fracture.
• Untreated clinical diagnosis of depression.
• Presence of joint contractures or an Ashworth spasticity score of 4.
• Active anti-spasticity medication regimen within 3 months prior to study enrollment.
• Presence of transcranial magnetic stimulation-evoked potentials in leg muscles.
• Non MRI-compatible implanted medical devices.
• Undergoing, or planning to undergo, diathermy treatment.
• Active participation in another interventionalclinical trial.
• Presence of conditions or disorders which require MRI monitoring.
• For EES cohort subjects, a history of coagulopathy or other significant cardiac or medical risk factors for surgery.
• Current use of a ventilator.
• Clinically diagnosed cardiopulmonary complications such as chronic obstructive pulmonary disease, cardiac failure, or heart arrhythmia that contraindicate changes in body position such as supine-to-sit-to-stand activities, prolonged standing, or stepping.
• Mass > 113 kg (250 pounds).
• History of frequent hypotension characterized by light headedness, or loss of consciousness.
• History of frequent hypertension characterized by headache, or bradycardia.
• History of frequent, severe, autonomic dysreflexia.
• Any illness or condition which, based on the research team’s assessment, will compromise with the patient’s ability to comply with the protocol, patient safety, or the validity of the data collected during this study.