Shear Waves Reveal Viscoelastic Changes in Skeletal Muscles after Hemispheric Stroke

Ghulam Rasool*, Allison B. Wang, William Z Rymer, Sabrina Sien Man Lee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


We investigated alterations in material properties such as elasticity and viscoelasticity of stroke-affected muscles using ultrasound induced shear waves and mechanical models. We used acoustic radiation force to generate shear waves along fascicles of biceps muscles and measured their propagation velocity. The shear wave data were collected in muscles of 13 hemiplegic stroke survivors under passive conditions at 90°, 120°, and 150° elbow flexion angles. In a viscoelastic medium, as opposed to a purely elastic medium, the shear wave propagation velocity depends on the frequency content of the induced wave. Therefore, in addition to the shear wave group velocity (GpV), we also estimated a frequency-dependent phase velocity (PhV). We found significantly higher GpVs and PhVs in stroke-affected muscles (p < 0.05). The velocity data were used to estimate shear elasticity and viscosity using an elastic and viscoelastic material models. A pure elastic model showed increased shear elasticity in stroke-affected muscles (p < 0.05). The Voigt model estimates of viscoelastic properties were also significantly different between the stroke-impaired and non-impaired muscles. We observed significantly larger model-estimated viscosity values on the stroke-affected side at elbow flexion angles of 120° and 150°. Furthermore, the creep behavior (tissue strain resulting from the application of sudden constant stress) of the model was also different between muscles of the paretic and non-paretic side. We speculate that these changes are associated with the structural disruption of muscles after stroke and may potentially affect force generation from muscle fibers as well as transmission of force to tendons.

Original languageEnglish (US)
Article number8466608
Pages (from-to)2006-2014
Number of pages9
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number10
StatePublished - Oct 2018


  • Stroke
  • Voigt model
  • muscle
  • viscoelasticity

ASJC Scopus subject areas

  • Rehabilitation
  • General Neuroscience
  • Internal Medicine
  • Biomedical Engineering


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