For all aims, participants will complete a first testing session where biomechanical variables will be assessed pre- and post-training with the hip extension device. A second testing session will be completed 24-hours following the first session where retention of training will be assessed. Biomechanical assessments, control sessions and training sessions are described as follows:

Biomechanical Assessments: Biomechanical Assessments will be performed to assess variables including walking speed, hip extension angle, and propulsion. Retro-reflective markers will be placed over anatomical landmarks using a lower-body marker set. Participants will be instructed to walk in a straight line over a set of embedded force platforms (AMTI) while a 17-camera motion capture system (Motion Analysis Corp.) records lower-body kinematics and kinetics. Participants will complete a total of three successful walking trials for each assessment with a successful trial being defined as having at least one clean foot strike in a force platform for each foot. No biofeedback will be provided during biomechanical assessments. During the biomechanical assessments, subjects may wear a harness suspended from the ceiling (no body-weight support) for safety. Control Session: Prior to training, participants will undergo assessments without biofeedback. This session will be used as a comparison for the effects of a single training session. Training: Participants will complete three training bouts in a session. For these training bouts, participants will be instructed to walk around the perimeter of the 9m x 15m laboratory while wearing the custom gait biofeedback device and visual display glasses. The training bouts will each be 6 minutes in duration with a 5-minute break in between bouts. The same training structure was successfully used in a previous study10. The biofeedback will be intermittent, with one minute on and one minute off, in order for the individual to not become dependent on the feedback and to promote motor learning. Participants will be told that the device measures the angle their paretic leg is at, and as they move their leg, the line on the screen will move. They will be shown as they move their leg farther back, the line moves up, closer to the target. Participants will not be given specific feedback on what walking strategies to use to increase hip extension angle, to not bias the results. If the participant surpasses the target hip extension angle, the target will blink green, indicating a successful trial. The target hip extension angle is the average of the four greatest peak hip extension angles the individual has achieves within the current training bout. Once the participant exceeds the current target angle, a new target will be created at the new average value. This novel feedback paradigm encourages the individual to progressively increase their peak hip extension by providing a high, but previously achieved target goal that adapts to improved performance in real-time. During training bouts, research personnel will follow the participant for safety.

Clinical Assessment: Participants will complete a clinical assessment prior to biomechanical assessments and training. Measurements from this assessment will include hip flexion and extension range of motion, hip flexion and extension strength, plantarflexion strength, and spasticity and will be used as covariates in analysis if significant effects are demonstrated within a factor. Hip flexion and extension range of motion will be measured with a goniometer while the participant is positioned on a patient table supine for flexion and prone for extension. Research personnel will guide the limb being measured to end range of motion while also bracing the pelvis to prevent extra motion not coming from the hip. Hip flexion and extension and plantarflexion strength will be measured using an isokinetic dynamometer (Biodex Medical Systems) where participants will complete three maximal voluntary contractions in each direction for each limb with the maximum torque being recorded and used for analysis. Spasticity will be assessed by asking participants to rate the frequency of their spasms on a 5-point scale ranging from no spasms to spasms occurring more than 10 times per hour, then severity of spasms will be assessed by a researcher using a 3-point scale ranging from mild to severe.