Inclusion Criteria:

• * ≥ 18 years old
• * ≥ 12 months post-SCI and medically/neurologically stable
• * Cervical spinal cord injury (C1-C8); any etiology except neurodegenerative conditions
• * Unable to grasp objects independently with both hands (tetraplegia)
• * Manual muscle testing (MMT) scores ≥4/5 for elbow flexion and ≥2/5 for wrist extension
• * Willing to participate in sessions at home or able to travel to alternate site for study sessions

Exclusion Criteria:

• * Ventilator-dependent (dependent upon mechanical life support due to inability to breathe effectively)
• * Poorly controlled autonomic dysreflexia (more than one episode in 3 months prior to enrollment)
• * Moderate to severe spasticity (Modified Ashworth Scale (MAS) \>1+) in the hand, wrist, or forearm
• * Received a localized injection (e.g. Botox) to hand, wrist, or forearm muscles within past 12 months
• * Currently participating in physical rehabilitation for upper extremity impairments
• * Individuals having or requiring any of the following: implanted pacemaker, life supporting/sustaining equipment, or critical non-removable implantable electronic devices such as an insulin pump or neurostimulator.
• * Presence of any other clinically significant medical comorbidity and/or neurological condition for which participation in the study may pose a safety risk and/or influence results
• * Presence of the following medical conditions: uncontrolled seizure disorder, active malignancy in the upper extremities, or open wounds/infections in the upper extremities
• * Individuals whose forearm is determined to be too small or too large to fit the electrode sleeve being investigated
• * Individuals who are pregnant or plan to get pregnant during the course of the study