The long-term goal of this project is to develop rehabilitation strategies that facilitate optimal restoration of skilled hand use in individuals with spinal cord injury (SCI). The objective of the studies proposed in this application is to determine whether a protocol of massed practice + somatosensory stimulation (MP+SS) is more effective for improving skilled hand use compared to a somatosensory stimulation (SS) alone, and to determine whether these approaches are each more effective than traditional therapy (consisting of conventional resistance training; CRT).

Specific Aim I: In individuals with chronic incomplete tetraplegia, quantify changes in skilled hand use and sensory function associated with either: massed practice training combined with somatosensory stimulation (MP+SS), somatosensory stimulation (SS), or control (conventional resistance training [CRT]), and compare differences among groups. The investigators hypothesize that:

H1.1: At the end of 4 weeks, gains in scores on standardized tests of skilled hand motor function (Jebsen-Taylor Hand Function Test and Chedoke-McMaster Arm and Hand Activity Inventory) and sensory function (quantitative sensory tests; QST) will be greater in individuals who are trained using MP+SS compared to the SS and RT groups.

H1.2: At the end of 4 weeks, gains in scores on standardized tests of skilled hand motor function and sensory function tests will be greater in individuals who are trained using SS compared to CRT.

H1.3: At 6 months post training, motor and sensory gains will be retained by the MP+SS and SS groups.

Specific Aim 2: In individuals with chronic incomplete tetraplegia, quantify changes in cortical and spinal neurophysiology associated with either: massed practice combined with somatosensory stimulation (MP+SS), somatosensory stimulation (SS), or control (conventional resistance training [CRT]), and compare differences among groups. The investigators hypothesize that, after 4 weeks:

H2.1: Measures representing cortical neurophysiologic function (i.e., motor-evoked potential amplitude and location of cortical map) will show greater change in the direction of more normal values in individuals who are trained using MP+SS compared to the SS and the CRT groups.

H2.2: Measures representing spinal neurophysiologic function (i.e., F-wave and H-reflex amplitude) will show greater change in the direction of more normal values in individuals who are trained using SS compared to the MP+SS and the CRT groups.

H2.3: There will be a positive relationship between change scores associated with functional outcome measures and cortical neurophysiologic outcome measures in the MP+SS group; there will be a positive relationship between change scores associated with the functional outcome measures and spinal neurophysiologic outcome measures in the SS group.

Specific Aim 3: In individuals with chronic incomplete tetraplegia, quantify changes in self-assessment of quality of life and societal participation associated with massed practice combined with somatosensory stimulation (MP+SS), somatosensory stimulation (SS) or control (conventional resistance training [CRT]), and compare difference among groups. The investigators hypothesize that:

H3.1: Gains in scores on standardized measures of quality of life (Medical Outcomes Study Short Form 36 [SF-36]) and societal participation (Impact on Participation and Autonomy Questionnaire [IPAQ]) will be greater in individuals who are trained using MP+SS compared to both the SS and the CRT groups.

H3.2: Gains in scores on standardized measures of quality of life and societal participation will be greater in individuals who are trained using SS compared to the CRT group.

H3.3: At 6 months post training, gains in the quality of life and the societal participation measures will be retained by the MP+SS and SS groups.

Risks: This is a low risk study that investigates the effects of standard rehabilitation and exercise interventions on hand/arm function in individuals with SCI. All devices are considered minimal risk devices by the FDA.

Evidence suggests that both intensive, skill-based practice training combined with somatosensory stimulation (MP+SS) and somatosensory stimulation alone (SS) may be associated with functional changes that are greater than those associated with skill-based training alone (MP). These studies are significant in that they advance the field of rehabilitation science as it relates to the goal of improving skilled hand use in individuals with SCI; there are few goals that have more important implications for function, independence and quality of life in these individuals.

Inclusion Criteria:

• traumatic spinal cord injury of at least one-year duration
• injury to cervical spinal cord at C7 or higher
• sufficient strength of thenar muscles to generate, at minimum, a visible twitch contraction in at least one thumb

Exclusion Criteria:

• history of head trauma and/or cognitive deficit
• subject history of stroke, seizures or other intracranial disease
• family history of seizures
• inability to provide informed consent