Sensory Augmentation Methods in Stroke (SAM)

Many chronic stroke survivors have poor walking balance, contributing to an increased risk of falls and fear of falling. One factor contributing to these balance deficits is a reduced ability to place the feet appropriately when walking. This study investigates whether enhancing the sensory information available to chronic stroke survivors while they walk improves their foot placement accuracy and balance.

The objective of this project is to test a method of providing real-time augmentation of hip proprioceptive feedback during post-stroke walking. The sensory information available to participants will be augmented by providing vibration of the hip abductor musculature that is scaled to the near-real-time mechanical state of their body. The central hypothesis is that augmented proprioception will improve participants' perception of their body's motion, thus increasing the mechanics-dependent modulation of foot placement, an important gait stabilization strategy. This clinical trial will establish the safety, feasibility, and efficacy of a rehabilitation intervention centered on repeated exposure to sensory augmentation during gait. Specifically, participants in the experimental group will complete training sessions twice a week for four weeks in which they receive sensory augmentation during ~30 minutes of treadmill walking. Participants in the activity-matched control group will perform the same task, except the hip vibration will be randomly delivered, not linked to the body's actual mechanical state. Changes in walking balance and foot placement accuracy will be quantified over the course of the intervention.

Participants will be randomly assigned to either an Experimental (n=22) or Control (n=22) group. These groups will differ only in terms of how vibration is delivered to the hip musculature during training sessions. In the Experimental group, vibration magnitude will be controlled by the real-time mechanical state of the user's body. In the Control group, vibration magnitude will be randomly varied.

Participants will complete 8 training sessions over 4 weeks, in which they walk on a treadmill at their self-selected speed. During training sessions, the magnitude of the vibration delivered over the hip abductor musculature will scale with the mechanical state of the pelvis at the start of each step. For example, if the step begins with the pelvis far mediolaterally from the stance foot, the swing leg hip abductors will receive strong vibration. If instead the step begins with the pelvis close mediolaterally to the stance foot, the stance hip abductors will receive strong vibration.

Participants will complete 8 training sessions over 4 weeks, in which they walk on a treadmill at their self-selected speed. During training sessions, the magnitude of the vibration applied to the hip abductors will vary randomly (following a normal distribution) on a step-by-step basis.

Participants will complete 8 training sessions over 4 weeks, in which they walk on a treadmill at their self-selected speed. During training sessions, the magnitude of the vibration delivered over the hip abductor musculature will scale with the mechanical state of the pelvis at the start of each step. For example, if the step begins with the pelvis far mediolaterally from the stance foot, the swing leg hip abductors will receive strong vibration. If instead the step begins with the pelvis close mediolaterally to the stance foot, the stance hip abductors will receive strong vibration.

Participants will complete 8 training sessions over 4 weeks, in which they walk on a treadmill at their self-selected speed. During training sessions, the magnitude of the vibration applied to the hip abductors will vary randomly (following a normal distribution) on a step-by-step basis.

The investigators will monitor the safety of the intervention by quantifying the proportion of participants who experience an adverse event potentially related to the intervention (e.g. skin irritation; falls) or any serious adverse event (e.g. hospitalization; death).

The investigators will assess participant drop-out as the percentage of participants who do not attend the final Assessment Session.

The primary effectiveness measure will be the change in participants' gait stabilization strategy over the course of the 4-week intervention. This will be quantified as the partial correlation between paretic mediolateral foot placement and mediolateral pelvis displacement at the start of the step over a 2-minute period of walking. The investigators will calculate the change in this metric from initial (Week 0) assessment session to the final (Week 4) assessment session.

The investigators will quantify the total walking time across all training sessions (out of a maximum possible 312 minutes).

The investigators will assess the change in fear of falling (identified using a yes/no question of "do you have a fear of falling?") from the initial (Week 0) assessment session to the final (Week 4) assessment session.

The investigators will quantify the change in Functional Gait Assessment score from the initial (Week 0) assessment session to the final (Week 4) assessment session.

The investigators will quantify the change in Activity-specific Balance Confidence score from the initial (Week 0) assessment session to the final (Week 4) assessment session.

The investigators will quantify the change in overground self-selected gait speed from the initial (Week 0) assessment session to the final (Week 4) assessment session.

Inclusion Criteria: Experience of a stroke 6 months prior to participation Gait speed of at least 0.2 m/s Ability to walk on a treadmill without a cane or walker Provision of informed consent Exclusion Criteria: Evidence of cerebellar damage Resting blood pressure higher than 220/110 mm Hg History of congestive heart failure, unstable cardiac arrhythmias, hypertrophic cardiomyopathy, severe aortic stenosis, angina or dyspnea at rest or during activities of daily living Preexisting neurological disorders or dementia Legal blindness or severe visual impairment History of DVT or pulmonary embolism within 6 months Uncontrolled diabetes with recent weight loss, diabetic coma, or frequent insulin reactions Orthopedic injuries or conditions (e.g. joint replacements) in the lower extremities with the potential to alter the gait pattern

De-identified participant data from the assessment sessions (Week 0 and Week 4) will be shared. Specifically, this will include gait biomechanics data (e.g. the partial correlation between mediolateral foot placement and mediolateral pelvis displacement), Functional Gait Assessment scores, Activity-specific Balance Confidence scores, overground gait speeds, and self-reported fear of falling.