Investigating Central Contributions to Fatigue Using Non-invasive Brain Stimulation

Investigating the Causal Contribution of Neural Oscillations to Neuromuscular Fatigue After Stroke Using tACS

The goal of this interventional study is to understand the contribution of the central components to the manifestation of neuromuscular fatigue in stroke survivors. The study will include adults with a first-ever stroke in the subacute phase.

The main question it aims to answer:

• How does the brain activity contribute to the manifestation of neuromuscular fatigue in stroke survivors?

Researchers will compare stroke participants receiving active vs sham tACS in a single session before the fatiguing contractions to determine whether central changes can influence fatigue onset/progression.

Participants will:

• Perform repeated leg muscle contractions until fatigue while seated in an experimental setup
• Receive either active or sham tACS for 20 minutes before the fatiguing contractions.
• 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

Inclusion Criteria:

First-ever stroke

≥18 years Subacute phase: 1 week to 6 months post-stroke Quadriceps (hemiplegic side) strength ≤3/5 (Medical Research Council (MRC)) Montreal Cognitive Assessment (MoCA) ≥21

Exclusion Criteria:

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) 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 Contraindications for tACS (e.g., presence of a deep brain stimulator, pacemaker, head wound, etc.).