The purpose of this study is to quantify changes in ankle and knee motion and force resulting from five progressive modifications to the anterior-posterior trim lines of thermoformed ankle-foot orthoses (AFO). It is hypothesized that the AFO with the most anterior trim line will prevent the most plantar flexion during loading response (the first 10% of the gait cycle)and prevent the most dorsiflexion at terminal stance (from 30 to 50% of the gait cycle) as compared to the non-device condition. This will be evidenced by the sagittal plane ankle motion and ground reaction force magnitude and location during loading response and terminal stance. Additionally, the angular velocity of knee flexion will increase during these same periods. By contrast, as the trim lines are moved more posterior this will result in lowering the effective stiffness of the device which will result in progressive increases in dorsiflexion and allow increasing amounts of knee flexion during terminal stance.

Inclusion Criteria:

• Participants must have no known pathology that would affect their ambulatory ability.
• Age greater than or equal to 18 years, but less than 40 years.
• Ability to tolerate walking for a minimum of 100 yards over the course of a three and a half hour time period.
• No current skin breakdown or sores on either lower extremity.

Exclusion Criteria:

• Use of ambulatory aids such as canes or crutches.
• Any medical or psychological condition that could jeopardize the subject's participation and compliance with the study protocol.

This study seeks to recruit younger, healthy (non-pathological) individuals over 18 years of age.