Nonisometric behavior of fascicles during isometric contractions of a human muscle

Masamitsu Ito*, Yasuo Kawakami, Yoshiho Ichinose, Senshi Fukashiro, Tetsuo Fukunaga

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

192 Citations (Scopus)


Fascicle length, pennation angle, and tendon elongation of the human tibialis anterior were measured in vivo by ultrasonography. Subjects (n = 9) were requested to develop isometric dorsiflexion torque gradually up to maximal at the ankle joint angle of 20°plantarflexion from the anatomic position. Fascicle length shortened from 90 ± 7 to 76 ± 7 (SE) mm, pennation angle increased from 10 ± 1 to 12 ± 1°, and tendon elongation increased up to 15 ± 2 mm with graded force development up to maximum. The tendon stiffness increased with increasing tendon force from 10 N/mm at 0-20 N to 32 N/mm at 240-260 N. Young's modulus increased from 157 MPa at 0-20 N to 530 MPa at 240-260 N. It can be concluded that, in isometric contractions of a human muscle, mechanical work, some of which is absorbed by the tendinous tissue, is generated by the shortening of muscle fibers and that ultrasonography can be used to determine the stiffness and Young's modulus for human tendons.

Original languageEnglish
Pages (from-to)1230-1235
Number of pages6
JournalJournal of Applied Physiology
Issue number4
Publication statusPublished - 1998 Oct
Externally publishedYes


  • Stiffness
  • Tendon
  • Ultrasound
  • Young's modulus

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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