Participation in this study will consist of four visits to the Human Engineering Research Lab (HERL) for the FB, IO and CG. Visits 1-4 will be the same, except visit 4 will not include training for any of the groups. All subjects will use their own wheelchair and cushion; however researchers will attach SMART Wheels TM to the subjects' wheelchair in place of their current wheels. The SMART Wheels TM are used to record the forces and moments that occur during propulsion and will not alter the dimensions or feel of the subjects current wheelchair. During each visit, all subjects will be asked to push over a real life course that includes various grades and surfaces. Then they will be asked to push on a wheelchair dynamometer at 1 meter/sec for one minute, 2 meter/sec for one minute, and a self selected speed for one minute. During this time, data will may also be collected with use of an Optotrak kinematic measurement system that incorporates a camera 3D-motion analysis system.