RecruitingDevice studyA Neuroprosthesis for Seated Posture and BalanceThe purpose of this study is to evaluate a surgically implanted functional electrical stimulation (FES) system to facilitate stability of the trunk and hips. FES involves applying small electric currents to the nerves, which cause the muscles to contract. This study evaluates how stabilizing and stiffening the trunk with FES can change the way spinal cord injured volunteers sit, breathe, reach, push a wheelchair, or roll in bed.