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

• Published in: Clinical biomechanics (Bristol) Vol. 99; p. 105761
• Main Authors: Hinton, Erica H, Likens, Aaron, Hsiao, Hao-Yuan, Binder-Markey, Benjamin I, Binder-Macleod, Stuart A, Knarr, Brian A
• Format: Journal Article
• Language: English
• Published: England 01.10.2022
• Subjects: Ankle; Ankle Joint; Biomechanical Phenomena - physiology; Gait - physiology; Humans; Paresis - etiology; Stroke - complications; Stroke Rehabilitation; Walking - physiology; Walking Speed - physiology; Propulsion; Quasi-stiffness; Walking speed; Ankle moment; Paresis
• ISSN: 0268-0033; 1879-1271; 1879-1271
• DOI: 10.1016/j.clinbiomech.2022.105761

Neurotypical individuals alter their ankle joint quasi-stiffness in response to changing walking speed; however, for individuals post-stroke, the ability to alter their ankle quasi-stiffness is unknown. Individuals post-stroke commonly have weak plantarflexor muscles, which may limit their ability to alter ankle quasi-stiffness. The objective was to investigate the relationship between ankle quasi-stiffness and propulsion, at two walking speeds. We hypothesized that in individuals post-stroke, there would be no difference in their paretic ankle quasi-stiffness between walking at a self-selected versus a fast speed. However, we hypothesized that ankle quasi-stiffness would correlate with gait speed and propulsion across individuals. Twenty-eight participants with chronic stroke walked on an instrumented treadmill at their self-selected and fast-walking speeds. Multilevel models were used to determine the relationships between ankle quasi-stiffness, speed, and propulsion. Overall, ankle quasi-stiffness did not increase within individuals from a self-selected to a fast gait speed (p = 0.69). A 1 m/s increase in speed across participants predicted an increase in overall ankle quasi-stiffness of 0.02 Nm/deg./kg (p = 0.03) and a 1 N/BW change in overall propulsion across participants predicted a 0.265 Nm/deg./kg increase in overall ankle quasi-stiffness (p < 0.0001). Individuals post-stroke did not modulate their ankle quasi-stiffness with increased speed, but across individuals there was a positive relationship between ankle quasi-stiffness and both speed and peak propulsion. Walking speed and propulsion are limited in individuals post-stroke, therefore, improving either could lead to a higher functional status. Understanding post-stroke ankle stiffness may be important in the design of therapeutic interventions and exoskeletons, where these devices augment the biological ankle quasi-stiffness to improve walking performance.