Changes in passive ankle stiffness and its effects on gait function in people with chronic stroke

Area of Science:

• Neurorehabilitation
• Biomechanics
• Robotics

Background:

• Ankle mechanical impedance significantly impacts motor function.
• Chronic stroke often results in impaired ankle function and gait abnormalities.

Purpose of the Study:

• To investigate the effects of robot-assisted ankle training on passive ankle stiffness (PAS) in individuals with chronic stroke.
• To examine the relationship between changes in PAS and overground gait function.

Main Methods:

• Eight participants with chronic stroke underwent 6 weeks of seated, visuomotor ankle training using an ankle robot.
• Passive ankle stiffness was measured in the sagittal (dorsiflexion/plantar flexion) and frontal planes before and after training.
• Gait parameters including step length, stride length, and single-support stance duration were assessed during independent floor walking.

Main Results:

• Robot-assisted training significantly decreased passive ankle stiffness in both dorsiflexion and plantar flexion.
• Post-training PAS in dorsiflexion fell within the range of age-matched controls.
• Reduced plantar flexion stiffness correlated with increased paretic step and stride lengths.
• Baseline stiffness measures predicted improvements in gait parameters like step length, stride length, stance duration, and cadence.

Conclusions:

• Robot-assisted, visuomotor ankle training effectively reduces passive ankle stiffness in individuals with chronic stroke.
• Improved ankle stiffness is strongly associated with enhanced gait function, particularly step and stride length.
• This training approach offers a promising avenue for improving mobility in post-stroke populations.