Studying Fatigue and Movement After Stroke

Exploring Neuromuscular Fatigue in Stroke Survivors: Understanding Central-Peripheral Interaction

The goal of this observational study is to learn how neuromuscular fatigue develops after stroke and how changes in brain activity, muscle activity, and their interaction contribute to reduced motor performance in stroke survivors compared to healthy individuals. The study will include adults with a first-ever stroke in the subacute phase and age-matched healthy volunteers.

The main questions it aims to answer are:

• How does neuromuscular fatigue develop during repeated muscle contractions after stroke compared to healthy individuals?
• How do brain activity, muscle activity, and brain-muscle interaction change during fatigue after stroke?

Researchers will compare stroke participants and healthy control participants to determine whether fatigue-related changes are more strongly associated with altered brain activity, altered muscle activity, or disrupted brain-muscle communication after stroke.

Participants will:

• Perform repeated leg muscle contractions until fatigue while seated in an experimental setup
• Wear non-invasive sensors to record brain activity (EEG) and muscle activity (EMG) during the task
• Complete the study during a single experimental session in which fatigue-related changes will be measured throughout the task

Stroke is a leading cause of long-term disability worldwide. Although many stroke survivors can initiate movement, sustaining motor performance during everyday activities often becomes progressively difficult, suggesting abnormal development of neuromuscular fatigue. Neuromuscular fatigue, defined as an exercise-induced reduction in force-generating capacity, arises through interactions between central neural and peripheral muscular mechanisms. However, despite extensive investigation in healthy populations, the neurophysiological mechanisms underlying neuromuscular fatigue after stroke remain poorly understood. Existing studies have focused predominantly on peripheral manifestations of fatigue, with limited investigation of cortical oscillatory dynamics and brain-muscle communication. Here, we propose a multimodal neurophysiological study combining electroencephalography (EEG), electromyography (EMG), and corticomuscular coherence analyses to determine whether fatigability after stroke is driven predominantly by altered central neural processes rather than peripheral muscle failure. Stroke survivors and age-matched healthy controls will perform sustained isometric contractions while neural and muscular activity are recorded across progressive fatigue stages. We hypothesize that stroke survivors will exhibit earlier and greater fatigability, accompanied by altered cortical oscillatory activity, peripheral muscular changes, and disrupted corticomuscular coherence, consistent with a predominant contribution of central oscillatory dysfunction.

Inclusion Criteria:

Stroke survivors will be recruited from Brussels University Hospital (Brussels, Belgium). Patients who have a first-ever stroke, ≥18 years, subacute phase: 1 week to 6 months post-stroke, quadriceps (hemiplegic side) strength ≤3/5 (Medical Research Council (MRC)), and Montreal Cognitive Assessment (MoCA) ≥21 will be included.

Exclusion Criteria:

Exclusion criteria include a history of a previous stroke, severe spasticity (Modified Ashworth Scale (MAS) 3-4 in quadriceps/hamstrings), other neurological, motor, musculoskeletal, or orthopedic conditions affecting trunk stability and lower limb mobility, non-cerebral strokes (e.g., brainstem, cerebellar), or dementia (MoCA ≤20), and current or former athletes. Athletes are defined as individuals who participated in organized competitive sports and engaged in structured training ≥3 sessions per week for ≥1 year within the 5 years preceding stroke. Control participants will be excluded if they meet the same exclusion criteria.