 Ankle-Foot Orthoses are a common form of ankle joint bracing prescribed for patients with impaired joint function. Passive Dynamic Ankle-Foot Orthoses PD-AFOs constitute a special class of ankle braces designed to enhance gait function by providing natural support to the lower limb as it progresses over the stance foot. However, a fundamental design characteristic of all PD-AFOs is that they are not capable of replicating all dynamic characteristics of the natural ankle complex. As a result, the efficient use of PD-AFOs during gait requires the wearer to develop an adapted, lower limb movement control strategy that effectively optimizes positive PD-AFO characteristics while compensating for characteristics detrimental to gait function. The long term goal of this research effort is to predict a patients ability to adapt to PD-AFO use and to customize PD-AFO characteristics to optimize that adaptation. The purpose of this series of studies is to further refine our existing methods of constructing custom PD-AFOs and to document the movement control adaptations produced by normal and healthy strength impaired subjects in response to PD-AFO use. 