Differential activation of psoas major and rectus femoris during active straight leg raise to end range

Yu Okubo*, Koji Kaneoka, Kiyotaka Hasebe, Naoto Matsunaga, Atsushi Imai, Paul W. Hodges

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


The purpose of this study was to investigate the activation of the hip flexor and abdominal muscles during an active straight leg raise (ASLR) to end range of hip flexion. Data were recorded from nine healthy men. Fine-wire electromyography (EMG) electrodes were inserted into psoas major (PM), and surface electrodes were placed over rectus femoris (RF), rectus abdominis, obliquus externus abdominis (OE), and obliquus internus abdominis/transversus abdominis (OI/TrA). EMG and kinematic data were obtained during concentric, hold (at end range) and eccentric phases of an ASLR. Concentric and eccentric movements were divided into three phases (early, mid, and late). Onsets of EMG relative to the onset of the ALSR movement and EMG amplitudes in each phase were compared between muscles. Onsets of the PM (–33 ± 245 ms) and RF (-3 ± 119 ms) EMG prior to leg elevation were significantly earlier than those of the OE and OI/TrA. PM EMG showed highest activation in the late concentric, hold, early eccentric phase, and was significantly higher than RF EMG. OI/TrA EMG was significantly greater in mid and late concentric, hold, and early eccentric phase than other phases. During the ASLR, unlike RF, PM EMG continues to increase towards the end range of hip flexion. Activation of OI/TrA muscle may be involved in control trunk and pelvic movement.

Original languageEnglish
Article number102588
JournalJournal of Electromyography and Kinesiology
Publication statusPublished - 2021 Oct


  • Electromyography
  • Hip flexion
  • Muscle activity
  • Muscle onset
  • Psoas major

ASJC Scopus subject areas

  • Neuroscience (miscellaneous)
  • Biophysics
  • Clinical Neurology


Dive into the research topics of 'Differential activation of psoas major and rectus femoris during active straight leg raise to end range'. Together they form a unique fingerprint.

Cite this