Structural and passive mechanical properties of the medial gastrocnemius muscle in ambulatory individuals with chronic stroke

Meizhen Huang, Tiev Miller, Siu Ngor Fu, Michael T.C. Ying, Marco Y.C. Pang (Corresponding Author)

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

Background: This study aimed to investigate the structural, morphological and passive mechanical properties of the medial gastrocnemius muscle among ambulating chronic stroke survivors using a computational model previously established in healthy individuals without stroke. Methods: Individuals with chronic stroke (n = 14, age = 63.4 ± 6.0 years) and healthy controls (n = 15, age = 59.6 ± 8.4 years) participated in the study. The mechanical properties of the medial gastrocnemius were measured during continuous passive ankle motion using ultrasound elastography and a corresponding muscle mechanical property-angle curve was estimated where slack angle and elasticity were determined. Muscle thickness, fascicle length, pennation angle, and echo intensity were also assessed using B-mode ultrasound. Findings: No significant differences in slack angle (paretic: −16.2° ± 6.13°, non-paretic: −16.93° ± 6.80°, p = 0.82), or slack elasticity (paretic: 4.36 ± 1.94 kPa, non-paretic: 4.54 ± 1.24 kPa, p = 0.64) were found between sides or groups. Lower muscle pennation angle (paretic: 13.6 ± 2.9°, non-paretic: 15.9 ± 2.0°, p = 0.019) and higher echo intensity (paretic: 80.5 ± 13.6, non-paretic: 63.4 ± 17.1, p = 0.003) were observed for paretic muscles. No significant between-sides differences were found for muscle thickness (paretic: 1.5 ± 0.3 cm, non-paretic: 1.6 ± 0.2 cm, p = 0.255) or fascicle length (paretic: 6.6 ± 1.9 cm, non-paretic: 7.1 ± 2.2 cm, p = 0.216). Significant between-groups difference was also observed for fascicle length [non-dominant side (control): 6.2 ± 0.8 cm, paretic side (stroke): 6.6 ± 1.9 cm, p = 0.017]. Interpretation: Although muscle mechanical properties increased exponentially over the slack ankle, measures between paretic and non-paretic sides were similar in ambulating participants with chronic stroke. Side-to-side differences in structural and morphological measures suggest the impact of stroke was relatively more pronounced for these muscle parameters than for passive mechanical properties.

Original languageEnglish
Article number105672
JournalClinical Biomechanics
Volume96
DOIs
Publication statusPublished - Jun 2022

Keywords

  • Gastrocnemius muscle
  • Muscle stiffness
  • Slack angle
  • Stroke
  • Ultrasound elastography

ASJC Scopus subject areas

  • Biophysics
  • Orthopedics and Sports Medicine

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