Ankle stiffness modulation during different gait speeds in individuals post-stroke

Area of Science:

• Biomechanics
• Neurology
• Rehabilitation Science

Background:

• Neurotypical individuals adjust ankle joint quasi-stiffness with walking speed.
• Individuals post-stroke often exhibit plantarflexor weakness, potentially limiting ankle quasi-stiffness modulation.
• The relationship between ankle quasi-stiffness and propulsion in post-stroke individuals remains unclear.

Purpose of the Study:

• To investigate the relationship between ankle quasi-stiffness and propulsion at self-selected and fast walking speeds in individuals post-stroke.
• To test the hypothesis that ankle quasi-stiffness does not differ between self-selected and fast walking speeds within individuals post-stroke.
• To test the hypothesis that ankle quasi-stiffness correlates with gait speed and propulsion across individuals post-stroke.

Main Methods:

• Twenty-eight participants with chronic stroke walked on an instrumented treadmill at two speeds: self-selected and fast.
• Multilevel statistical models were employed to analyze the data.

Main Results:

• Ankle quasi-stiffness did not significantly increase within individuals when walking faster (p=0.69).
• Across participants, a 1 m/s increase in speed predicted a 0.02 Nm/deg./kg increase in ankle quasi-stiffness (p=0.03).
• Across participants, a 1 N/BW change in propulsion predicted a 0.265 Nm/deg./kg increase in ankle quasi-stiffness (p<0.0001).

Conclusions:

• Individuals post-stroke do not modulate ankle quasi-stiffness with increased walking speed.
• A positive relationship exists between ankle quasi-stiffness and both walking speed and propulsion across individuals post-stroke.
• Understanding ankle quasi-stiffness in stroke may inform the design of therapeutic interventions and assistive devices to enhance walking performance.