Stroke is one of the leading causes of disability in the United States, affecting ~795,000 people annually. Among ambulatory people with chronic stroke, impaired balance is common and substantially limits mobility (those with the poorest balance walk the least). This project will explore if a novel gait training intervention using a robotic device to amplify a person's self-generated movements can improve walking balance in people with chronic stroke. The development of effective interventions to increase walking balance among people with chronic stroke will positively impact quality of life and ability to participate in walking activities.

Background: People with chronic stroke (PwCS) have substantial walking balance dysfunctions that limit independence and participation in walking activities. There is a pressing need to develop effective methods to enhance walking balance in PwCS. Interventions that amplify self-generated movements may accelerate motor learning by enhance a person's perception of movement errors. This method could potentially be applied to help PwCS improve walking balance. To this end, we have developed a cable-driven robot to create a Movement Amplification Environment (MAE) during treadmill walking. The MAE challenges walking balance by applying lateral forces to the pelvis that are proportional in magnitude to real-time lateral center of mass (COM) velocity. Our purpose is to evaluate effects of MAE training on walking balance in PwCS.

Specific Aims: Aim 1a: To quantify locomotor adaptations PwCS make to maintain walking balance in a MAE. We will evaluate the impact of the two foremost gait training variables: Gait Speed and MAE Strength. Aim 1b: To evaluate short-term changes in the ability of PwCS to control their lateral COM excursion during walking (a quantifiable walking balance measure) immediately after MAE training. Aim 2: To evaluate long-term changes in walking balance and daily walking following a 5-week high-intensity gait training intervention performed in a MAE.

Approach: Aims 1a & b: Twenty PwCS will each participate in two experiments evaluating gait biomechanics (COM dynamics and stepping patterns) during and immediately following MAE training. Aim 1a will evaluate locomotor adaptations when walking in a MAE and the effect of gait speed (slow, preferred, and fast) and MAE strength (low, medium, and high). Aim 1b will use visual feedback to challenge PwCS to control their lateral COM excursion during walking immediately before and after walking in different external conditions (No applied forces, or MAE). Outcomes will assess if short-term walking balance is enhanced immediately following MAE exposure. Aim 2: Ten PwCS will participate in 10-sessions of high intensity gait training performed in a MAE. We will assess pre- to post- changes in walking balance using clinical gait and balance measures, biomechanical assessments, and participation in daily walking (steps/day). Outcomes will assess if long-term walking balance is enhanced following MAE gait training.

Impact: Training walking balance of PwCS by amplifying their own self-generated movements is a radical departure from current practice and could substantially enhance walking balance. This study will provide a foundational understanding of how PwCS maintain walking balance in a MAE and if beneficial behaviors persist following MAE training. Successful outcomes will motivate a randomized controlled trial assessing efficacy of MAE training on walking balance in PwCS.

Inclusion Criteria:

1. 18 to 80 years of age;
2. diagnosis of hemiparetic stroke;
3. more than 6 months post-stroke;
4. ability to ambulate over ground for 10 meters with or without a single cane, and/or ankle-foot orthosis.

Exclusion Criteria:

1. cognitive impairment (score of ≤22/30 on the Montreal Cognitive Assessment scale);
2. aphasia (score of ≥71/100 on the Mississippi Aphasia Screening Test);
3. excessive spasticity in lower limbs (score of > 3 on the Modified Ashworth Scale);
4. unable to tolerate 10-min. of standing;
5. enrollment in concurrent physical therapy;
6. use of braces/orthotics crossing the knee joint;
7. known pregnancy;
8. severe cardiovascular, musculoskeletal, or other neurological conditions affecting gait and balance.
9. brainstem and/or cerebellar lesion
10. perinatal stroke

De-identified data from this study will be uploaded on the Northwestern University Research and Data repository (Arch) so that it is fully available to other parties interested in probing the data further and performing secondary analyses.

After completion of the study

Data will be publicly available.