Knee joint angle affects EMG-force relationship in the vastus intermedius muscle

Akira Saito, Hiroshi Akima

Research output: Contribution to journalArticle

21 Citations (Scopus)


It is not understood how the knee joint angle affects the relationship between electromyography (EMG) and force of four individual quadriceps femoris (QF) muscles. The purpose of this study was to examine the effect of the knee joint angle on the EMG-force relationship of the four individual QF muscles, particularly the vastus intermedius (VI), during isometric knee extensions. Eleven healthy men performed 20-100% of maximal voluntary contraction (MVC) at knee joint angles of 90°, 120° and 150°. Surface EMG of the four QF synergists was recorded and normalized by the root mean square during MVC. The normalized EMG of the four QF synergists at a knee joint angle of 150° was significantly lower than that at 90° and 120° (P<0.05). Comparing the normalized EMG among the four QF synergists, a significantly lower normalized EMG was observed in the VI at 150° as compared with the other three QF muscles (P<0.05). These results suggest that the EMG-force relationship of the four QF synergists shifted downward at an extended knee joint angle of 150°. Furthermore, the neuromuscular activation of the VI was the most sensitive to change in muscle length among the four QF synergistic muscles.

Original languageEnglish
Pages (from-to)1406-1412
Number of pages7
JournalJournal of Electromyography and Kinesiology
Issue number6
Publication statusPublished - 2013 Dec
Externally publishedYes



  • Isometric contraction
  • Knee extension
  • Knee joint angle
  • Muscle length
  • Quadriceps femoris

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Biophysics
  • Clinical Neurology

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