 Subjects with an unsafe or highly variable gait pattern upon visual observation will be excluded. Subjects who are unable to repeatedly walk through the data collection volume without the use of assistive devices will be excluded. In addition, subjects with pain related to walking or impaired skin sensation touch and pressure will be excluded. Subjects with lower extremity muscle spasticity of 3 or greater on the Ashworth Scale will be excluded. Subjects with a history of injury, surgery, or disease affecting the function of the lower extremity will be excluded from the normal study. Subjects will be excluded from participation in the normal study if muscle strength and joint range of motion measures are outside normal limits. 