Morphological changes of the triceps surae muscle-tendon unit during passive extension: An in vivo rabbit model

Jui Sheng Sun, Yi Shiong Hang, Yang Hwei Tsuang, Cheng Kung Cheng, King Yaw Tsao, Shang Hwa Hsu

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Objective. To elucidate the morphological and biomechanical manifestation of the triceps surae muscle-tendon unit during passive extension. Design. The instantaneous changes within the load-deformation curve of muscle-tendon unit were analyzed by an in vivo rabbit model. Background. Although muscle strains occur more frequently than complete failures, the failure mechanism of these sub-failure injuries is rarely investigated. Monitoring of the instantaneous changes in the load-deformation curve allows correlation with the morphological changes that occur during passive extension. Methods. After anesthesia, the triceps surae muscle of rabbit was dissected and then stretched to failure by a MTS Bionix 858 machine. The morphological changes in failure patterns were recorded by photographs. Results. The morphological and biomechanical manifestations of the triceps surae muscle-tendon unit was divided into five different portions: first, the viscoelastic portion with minimal morphologic change; second, the portion of micro-failure with local ecchymosis; third and fourth, the portions of macrofailure with sequential rupture of the muscle fibers; and fifth, the portion of rupture and separation of muscle parenchyma. Conclusions. A threshold for stretch-induced injury does exist. The threshold of the initiation of micro-failure in this model was 16.5% of the strain, which corresponded to 16.6% of the maximal sustainable force.

Original languageEnglish
Pages (from-to)634-640
Number of pages7
JournalClinical Biomechanics
Issue number8
Publication statusPublished - Dec 1998
Externally publishedYes


  • Macrofailure
  • Micro-failure
  • Passive extension
  • Triceps surae muscle

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine


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