In vivo determination of fascicle curvature in contracting human skeletal muscles

Tadashi Muramatsu*, Tetsuro Muraoka, Yasuo Kawakami, Akira Shibayamaand, Tetsuo Fukunaga

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

100 Citations (Scopus)


Fascicle curvature of human medial gastrocnemius muscle (MG) was determined in vivo by ultrasonography during isometric contractions at three (distal, central, and proximal) locations (n = 7) and at three ankle angles (n = 7). The curvature significantly (P < 0.05) increased from rest to maximum voluntary contraction (MVC) (0.4-5.2 m-1). In addition, the curvature at MVC became larger in the order dorsiflexed, neutral, plantar flexed (P < 0.05). Thus both contraction levels and muscle length affected the curvature. Intramuscular differences in neither the curvature nor the fascicle length were found. The direction of curving was consistent along the muscle: fascicles were concave in the proximal side. Fascicle length estimated from the pennation angle and muscle thickness, under the assumption that the fascicle was straight, was underestimated by ∼6%. In addition, the curvature was significantly correlated to pennation angle and muscle thickness. These findings are particularly important for understanding the mechanical functions of human skeletal muscle in vivo.

Original languageEnglish
Pages (from-to)129-134
Number of pages6
JournalJournal of Applied Physiology
Issue number1
Publication statusPublished - 2002
Externally publishedYes


  • Intramuscular variability
  • Medial gastrocnemius muscle

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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