Inhomogeneous architectural changes of the quadriceps femoris induced by resistance training

Ryoichi Ema, Taku Wakahara, Naokazu Miyamoto, Hiroaki Kanehisa, Yasuo Kawakami*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

115 Citations (Scopus)


Purpose: This study aimed to clarify whether resistance training-induced changes in muscle architecture are homogeneous among the quadriceps and over different regions within each muscle. Methods: Eleven recreationally active men (27 ± 2 years) completed a 12-week resistance training program for knee extensors. Before and after the intervention, muscle thicknesses, fascicle lengths, and pennation angles of the four muscles (vastus lateralis, vastus medialis, vastus intermedius, rectus femoris) in several regions (2-4 regions per each muscle) were measured using ultrasonography. Anatomical cross-sectional areas (ACSAs) at the same positions as the ultrasound measurements were determined from magnetic resonance images. Results: Relative increases in the ACSA, muscle thickness, and pennation angle of the rectus femoris were significantly greater than those of the vasti. Relative increases in the ACSAs of the vastus lateralis and rectus femoris were significantly greater in the distal than in the proximal region, and those in the muscle thickness and pennation angle of the vastus intermedius were significantly greater in the medial than in the lateral region. Fascicle lengths did not change in any muscles. The interrelations between muscle thickness and pennation angle remained unchanged after the intervention, with a significant association between the relative changes of the two variables. Conclusion: The current results indicate that (1) hypertrophy of the quadriceps femoris is associated with a proportional increase in pennation angle but not necessarily in fascicle length, and (2) training-induced changes in muscle size and pennation do not evenly occur among the quadriceps, along or across a muscle.

Original languageEnglish
Pages (from-to)2691-2703
Number of pages13
JournalEuropean Journal of Applied Physiology
Issue number11
Publication statusPublished - 2013 Nov


  • Cross-sectional area
  • Fascicle length
  • Muscle thickness
  • Pennation angle
  • Regional difference

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Public Health, Environmental and Occupational Health
  • Physiology (medical)


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