Electromyographic amplitude and frequency changes in the iliocostalis lumborum and multifidus muscles during a trunk holding test

Joseph Kim Fai Ng, Carolyn A. Richardson, Gwendolen A. Jull

Research output: Journal article publicationJournal articleAcademic researchpeer-review

86 Citations (Scopus)


Background and Purpose. Muscle endurance is an important variable to measure in the assessment of back muscle function. This study investigated the electromyographic (EMG) activity and fatigue patterns of iliocostalis lumborum and multifidus muscles during a trunk holding test. Subjects. Sixteen male subjects (mean age=24.2 years, SD=4.2, range=20.6-31.9) without low back pain or known pathology were recruited in the study. Methods. Surface EMG electrodes were used to record the activity of iliocostalis lumborum and mutifidus muscles during a 60-second isometric contraction. To reflect the activity level and fatigue rate of the muscles, EMG amplitude (root mean square [RMS] values) and a frequency variable (median frequency [MF]) were measured. Results. The multifidus muscle displayed a higher level of activity, initial MF, and normalized MF slope than did the iliocostalis lumborum muscle. There was no difference, however, in the normalized RMS slope between the two muscles. The correlations between the normalized MF slope and the RMS slope of the two muscles were nonsignificant. Conclusion and Discussion. This study shows that monitoring frequency changes of the EMG signals may enable therapists to quantify the fatigue changes of individual muscles during the trunk holding test. The higher fatigue rate shown in the multifidus muscle compared with the iliocostalis lumborum muscle may be due to the higher activity level of the multifidus muscle during the trunk holding contraction. This greater activity of the multifidus muscle during the contraction might be explained by the functional differences between these two muscles.
Original languageEnglish
Pages (from-to)954-961
Number of pages8
JournalPhysical Therapy
Issue number9
Publication statusPublished - 1 Jan 1997


  • Back
  • Electromyography
  • Fourier analysis
  • Isometric contraction
  • Muscle fatigue

ASJC Scopus subject areas

  • Physical Therapy, Sports Therapy and Rehabilitation

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