The proposed study includes a between groups comparison (for Aim 1) and a fully repeated crossover design (for Aim 2). It will be conducted in the Military Performance Lab (MPL) at the Center for the Intrepid (CFI), Brooke Army Medical Center, Joint Base San Antonio (JBSA)Fort Sam Houston, Texas. Subjects who use IDEOs will come to the Military Performance Lab for one test session during which they will walk in standardized shoes with six different heel wedges in random order. Control data will also be collected on able-bodied individuals. Control subjects will also come to the MPL for one test session in which they will walk using the same standardized shoes. For all subjects, biomechanical gait data will be collected as the subjects walk along a walkway in the MPL. This data will be used to calculate roll-over shape, instantaneous radius of curvature, Center of Pressure (COP) velocity, and ankle moment.