The primary goal of the proposed study is to identify the contributions of the amount of task-specific practice on locomotor (i.e., walking) recovery in patients with chronic (> 1 yr) motor incomplete spinal cord injury (iSCI). The investigators will do this by building on previous work directed towards identifying the essential exercise training parameters that maximize locomotor recovery. Consistent with principles of motor learning and exercise physiology, the investigators contend that certain training (i.e., dosage) parameters of physical rehabilitation, including the type (specificity) and amount of task practice, are critical to mobility outcomes following neurological injury. Previous work suggests these training parameters may influence locomotor recovery in patients with other neurological disorders (i.e., stroke), although few studies have attempted to delineate similar contributions of amount of task-specific practice in iSCI. Indeed, no studies have carefully controlled these training parameters during physical rehabilitation of patients with iSCI, and such interventions are rarely utilized in the clinical setting.