 Subjects in all study phases will participate in each of three visit types. Initially, subjects will participate in a screening and PD-AFO tuning visit that contains a neuromuscular screening examination, a preferred walking speed test, and measurement for a custom fitting PD-AFO. Following the manufacturing of the custom PD-AFO, subjects will return for their PD-AFO receipt and accommodation training visit. During this visit, the PD-AFO will be further customized and evaluated for comfort and performance and the subject will undergo supervised gait training in PD-AFO use. Following successful accommodation to PD-AFO use, subjects will return for their third visit and undergo instrumented gait analyses under three conditions targeted walking velocity without the PD-AFO, self selected walking velocity with the PD-AFO, and targeted walking velocity with the PD-AFO and finally, objective plantarflexor strength testing. 