The long-term objective of this project is to improve the walking speed and stability Veterans disabled by incomplete SCI (iSCI) sufficiently to safely participate in community activities outside of the home, and thereby enhance their independence and daily function. We will advance this goal by developing and implementing new, practical, and readily customizable control systems for peripheral nerve stimulation to augment the actions of selected weak or paralyzed muscles based on real-time feedback of voluntary body movements. Ten subjects representing a cross section of individuals with difficulty walking due to iSCI will undergo conventional gait training prior to serving as their own controls in a series of single-subject research studies with and without our stimulation controllers active. The proposed controller will process inputs from a small set of body-mounted sensors to guarantee that stimulated assistance works together with intact movements to automatically advance the body forward, intuitively vary walking speed, and take corrective forward or sideways steps to recover from unexpected and potentially destabilizing disturbances. By the end of the study, six of the participants will have received such gait assist systems consisting of our current implanted stimulators and externally worn sensors. The resulting knowledge with prepare for clinical translation via surface-based or completely implanted stimulation and sensing systems, such as the soon to be available Networked Neural Prosthesis System currently undergoing pivotal trials for marketing approval. Our aims are: 1) Develop and implement a stimulation control system based on estimates of movements of body Center of Mass during walking from a small set of wearable sensors. Transitions between patterns of stimulated assistance to the specific set of weak or paralyzed muscles most responsible for the individual gait difficulties of each subject will be made automatically to keep the body moving forward dynamically. 2) Adapt the timing and intensity of stimulation automatically alter walking speed from those sufficient for household ambulation (<0.4m/s) to those required to function in the community (>0.8m/s). A control algorithm will facilitate intuitive modulation of gait speed by adjusting stimulation during the next step to match the movements of the body generated by the volitional actions of the intact muscles sensed during the current and immediately previous steps. 3) Finally, we will counteract large and potentially destabilizing perturbations to the Center of Mass by interrupting continuous walking and a generating a forward or sideways protective step to prevent losses of balance and maintain standing posture. Inputs from the same wearable sensors sensitive to the Center of Mass will be interrogated to detect sudden disturbances to trigger the reactive steps in the appropriate direction and facilitate recovery. This represents the first time such mechanisms wil...