Understanding the Effects of Quantitatively-Prescribing Passive-Dynamic Ankle-Foot Orthosis Bending Stiffness for Individuals Post-Stroke

When people walk, their ankle joints help to hold them upright and move them forward. Ankle braces are often given to people who have had a stroke to help their ankle joints work properly. The investigators have developed a method to design and make a special type of ankle brace that allows the investigators to control every characteristic of the ankle brace, allowing the investigators to customize the ankle brace to fit and function just the way the investigators want it to. The investigators think that ankle braces customized to meet the needs of each individual person will help the participants walk better. The investigators have also developed a prescription model that tells the investigators how to customize these ankle braces to address different levels of two common impairments experienced by people post stroke -decreased ability to move the ankle joint and weakened calf muscles. The purpose of this study is to test the prescription model to see if wearing the ankle brace customized based on the prescription model improves people's ability to walk. To accomplish this goal, the investigators will first measure each person's ability to move his/her ankle joint and the strength of his/her calf muscles. The investigators will put this information in to the prescription model to determine how to customize the ankle brace for each person. The investigators will then use the method developed to make the customized ankle brace. Finally, the investigators will measure how each person walks in the ankle brace customized just for the participants. This study will allow the investigators to validate and/or refine the prescription model and teach the investigators how persons post-stroke adapt to walking in ankle braces with different characteristics.


Eligibility Criteria:
Inclusion Criteria:

* 21-85 years of age
* chronic hemiparesis stroke (\> 6 months post stroke)
* prescribed an AFO by a clinician
* able to walk for at least two minutes without assistance from another person
* adequate paretic dorsiflexion range-of-motion (RoM ≥ 12°)
* plantar flexor strength deficits (peak paretic plantar flexion moment in gait at least 0.15 Nm/kg lower than the mean speed-matched, height normalized value from our normative database)

Exclusion Criteria:

* cerebellar signs (ataxic ("drunken") gait or decreased coordination during rapid alternating hand or foot movements)
* neurologic conditions other than stroke
* more than one stroke
* sensorimotor neglect
* intermittent claudication
* inability to walk outside the home prior to the stroke
* total joint replacement and orthopedic problems in the lower limbs or spine that limit walking
* coronary artery bypass graft or myocardial infarction within past 3 months
* unexplained dizziness in last 6 months
* cannot understand spoken instruction, communicate with the investigators
* walk for 2 minutes at a self-selected speed without assistance from another person (assistive device allowed)
* must have a resting heart rate between 40-100 beats per minute and a resting blood pressure between 90/60 to 170/90.