Deficient Muscle Coordination Patterns of Reactive Stepping Responses in People With Chronic Stroke

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomechanics

Background:

• Stroke survivors frequently experience persistent balance impairments affecting mobility and independence.
• Existing research on neuromuscular responses to balance perturbations often uses low-intensity stimuli, unlike high-intensity events where stepping is crucial for recovery.
• Understanding deficits in reactive stepping is vital for improving post-stroke balance and reducing fall risk.

Purpose of the Study:

• To identify specific deficits in muscle coordination patterns during reactive stepping in individuals with supratentorial stroke.
• To analyze muscle synergy structure and activation during multidirectional stepping responses.

Main Methods:

• 32 individuals with supratentorial stroke performed multidirectional stepping tasks.
• Evaluated step quality and analyzed muscle coordination patterns using muscle synergy analysis for both paretic and non-paretic legs.
• Quantified muscle synergies for stance and swing legs, assessing variance explained (VAF).

Main Results:

• Individuals with stroke demonstrated reduced leg angles in lateral, posterolateral, and posterior directions, especially with the paretic leg.
• Muscle synergy analysis identified 5 consistent synergies for swing and stance legs (VAFs ranging from 0.84-0.85).
• Three specific muscle synergies were underrepresented during paretic leg stepping, and one gluteus medius-dominant synergy's underrepresentation correlated with lower Fugl-Meyer lower-extremity scores.

Conclusions:

• Deficits in muscle synergy structure and activation during reactive stepping provide deeper understanding of post-stroke balance impairments.
• The presented methodology can assess if rehabilitation improves reactive stepping by optimizing existing coordination or restoring 'normal' patterns.
• This research highlights potential targets for interventions aimed at enhancing reactive balance and mobility in stroke survivors.