Effects of High-intensity Gait Training on Fatigue, Gait, and Neuroplasticity in People With Multiple Sclerosis

Inclusion Criteria: * Age ≥21 years * Multiple sclerosis diagnosis * Stable disease-modifying therapy (DMT) over the past 6 months * Walking dysfunction (i.e., abnormal gait pattern, Expanded Disability Status Scale (EDSS) score of 4-6.5, and/or Patient-determined disease steps (PDDS) score of 3-6) * Able to walk for 6 minutes at self-paced speed. Handheld assistive device is acceptable. * Symptomatic fatigue (Fatigue Severity Score ≥ 4) Exclusion Criteria: * Adults unable to consent * Pregnant women * Prisoners * Multiple sclerosis relapse within the last 30 days * Other neurological disorders besides multiple sclerosis * Cardiorespiratory or metabolic diseases (e.g., cardiac arrhythmia, uncontrolled hypertension or diabetes, chronic emphysema) * Significant cognitive or communication impairment (Mini-Mental State Examination (MMSE)\<21), which could impede the understanding of the purpose of procedures of the study or prevent the patient from performing the ankle-tracking task. * Severe osteoporosis * Failure to pass the graded exercise stress test * Implanted cardiac pacemaker * Metal implants in the head or face * Unexplained, recurring headaches * History of seizures or epilepsy * Currently under medication that could increase motor excitability and lower seizure threshold * Skull abnormalities or fractures * Concussion within the last 6 months