Inclusion Criteria:  All participants must meet the following inclusion criteria:  Between the ages of 18-60 years Safe to be scanned using MRI Able to communicate in English Ability to sign informed consent  In addition, the participants recruited with SCI must meet the following criteria:  History of a traumatic spinal cord injury, inclusive of levels C2-T1 At least 6 months since onset of spinal cord injury Cause of the spinal cord injury was non-progressive Ability to complete and comply with information within the informed consent Ability to close and open at least one hand without assistance  Exclusion Criteria:  MRI contraindications as indicated on MRI safety screening form Subjects with pacemakers, cochlear (in the ear) implants, or aneurysm clips or subjects who have worked with metal Women who are currently pregnant, nursing, or planning on becoming pregnant Individuals with severe claustrophobia Subjects unwilling or unable to give written informed consent in English Prisoners Frequent smokers (greater than 5 cigarettes per day) Blood pressure greater than 160/110 or less than 85/55. Individuals who report headaches, feeling dizzy or light-headed, or have heart palpitations on the day of the study. Diagnosis of any of the following comorbid conditions: congestive heart failure, cardiac arrhythmias, uncontrolled diabetes mellitus, chronic obstructive pulmonary disease, emphysema, severe asthma, previous myocardial infraction or known carotid/intracerebral artery stenosis, presence of active deep venous thrombosis, or cancer. Individuals who utilize mechanical ventilation or have a tracheostomy Individuals who utilize an intrathecal baclofen pump Orthopedic injury affecting upper extremities Currently participating in any other hypoxia related study.