 Walking velocity will be statistically compared between with and without PD-AFO conditions to determine the accommodation effect for self selected conditions and to test for differences between targeted walking conditions. The magnitude of peak natural ankle plantarflexion moments will be statistically compared to determine the efficacy of the strength substitution and strength enhancement paradigms. The nature and extent of movement control adaptations will be explored by contrasting the various biomechanical kinematic and kinetic variables between with and without PD-AFO conditions having congruent walking speeds. Results of the neurological examination and objective strength testing will be used to rationalize the existence of different movement control adaptations between subjects and form the basis for developing an initial predictive model. 