Ankle stiffness modulation during different gait speeds in individuals post-stroke.
Clin Biomech (Bristol, Avon) 2022;
99:105761. [PMID:
36099707 DOI:
10.1016/j.clinbiomech.2022.105761]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 09/01/2022] [Accepted: 09/05/2022] [Indexed: 02/07/2023]
Abstract
BACKGROUND
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.
METHODS
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.
FINDINGS
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).
INTERPRETATION
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.
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