Concurrent deficits of soleus and gastrocnemius muscle fascicles and Achilles tendon post stroke

Heng Zhao, Yupeng Ren, Elliot J. Roth, Richard L. Harvey, Li Qun Zhang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Calf muscles and Achilles tendon play important roles in functional activities. However, it is not clear how biomechanical properties of the uniarticular soleus (SOL) and biarticular gastrocnemius muscle and Achilles tendon, including the fascicle length, pennation angle, and stiffness, change concurrently post stroke. Biomechanical properties of the medial gastrocnemius (GM) and soleus muscles were evaluated bilaterally in 10 hemiparetic stroke survivors using combined ultra-sonography-biomechanical measurements. Biomechanical properties of the Achilles tendon including the length, cross-sectional area (CSA), stiffness, and Young's modulus were evaluated, together with calf muscle biomechanical properties. Gastrocnemius and SOL contributions were separated using flexed and extended knee positions. The impaired side showed decreased fascicle length (GM: 6%, P = 0.002 and SOL: 9%, P = 0.03, at full knee extension and 0° ankle dorsiflexion) and increased fascicular stiffness (GM: 64%, P = 0.005 and SOL: 19%, P = 0.012, at a common 50 N force level). In contrast, Achilles tendon on the impaired side showed changes in the opposite direction as the muscle fascicles with increased tendon length (5%, P < 0.001), decreased tendon CSA (5%, P < 0.04), decreased tendon stiffness (42%, P < 0.001) and Young's modulus (30%, P < 0.001) compared with the unimpaired side. The fascicle and tendon stiffness changes were correlated negatively to the corresponding fascicle and tendon length changes, and decrease in Achilles tendon stiffness was correlated to the increases of SOL and GM fascicular stiffness (P < 0.05). Characterizations of calf muscle fascicles and Achilles tendon biomechanical properties help us better understand concurrent changes of fascicles and tendon as part of the calf muscle-tendon unit and facilitate development of more effective treatments.

Original languageEnglish (US)
Pages (from-to)863-871
Number of pages9
JournalJournal of applied physiology
Issue number7
StatePublished - Apr 1 2015


  • Muscle fascicles
  • Stiffness
  • Stroke
  • Tendon

ASJC Scopus subject areas

  • Physiology (medical)
  • Physiology


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