This proposal investigates the hypothesis that progressive aerobic exercise with Lokomat is feasible in motor incomplete SCI, and three months of training will improve cardiovascular fitness and gait functionality when compared to physical therapy controls. We propose a two-phase study to examine the feasibility, reliability and utility of aerobic exercise metabolic testing and training during robotically assisted partial weight support treadmill walking in individuals with chronic motor incomplete spinal cord injury (CMISCI). During the first phase of the study we will manipulate Lokomat training parameters of treadmill speed and percent of partial weight support to assess the effect of these changes on heart rate, perceived exertion, and oxygen consumption in untrained chronic motor incomplete spinal cord injured subjects. Subjects will be asked to maintain cardiovascular or muscular effort during testing and will be monitored in this regard by the force biofeedback system built into the Lokomat. After determining threshold levels for initial cardiovascular response, submaximal and then peak exercise testing will be attempted. These studies will be repeated on a separate day to determine the reliability of the testing results. Thirty-six subjects with varying levels of injury between C4 and L2 and ASIA (American Spinal Injury) Impairment Scales of C and D will be recruited. We anticipate that subjects with greater ASIA motor scores will require either a faster initial treadmill speed or less partial weight support to produce an initial cardiovascular response. It is also anticipated that peak exercise testing using open circuit spirometry with subjects on the Lokomat will be a feasible, reliable and valid measurement. This phase of the study will be aimed at establishing guidelines for determining initial training parameters for use in an aerobic exercise protocol using the Lokomat.