This study is being done to measure the differences between the electrical activity of muscles and /single muscle fibers in individuals with long-term spinal cord injury and neurologically intact individuals without spinal cord injury. This study is also being done to find out if muscle and /single muscle fiber electrical activity, voluntary strength, reflex measurements, and/or spasms are changed after a single, oral dose of three commonly prescribed drugs, Rilutek®, isradipine, and Namenda®. These medications are approved by the FDA for treatment of disorders other than the control of spasms and strength. In this study, they are being used in an experimental manner. Finally, this study is also being done to find out whether or not a brief stretching exercise influences reflex measurements.