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Tuesday, June 6, 2023

EMG Activity and Force During Prone Hip Extension in Individuals with Lumbar Segmental Instability

Brent Brookbush

Brent Brookbush


EMG Activity and Force During Prone Hip Extension in Individuals with Lumbar Segmental Instability

By Alex Howard PT, DPT, CSCS

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Jung, H., Kang, S., Park, J., Cynn, H., & Jeon, H., (2015). EMG activity and force during prone hip extension in individuals with lumbar segmental instability. Manual Therapy, 20(3), 440-444. ABSTRACT

Why is this relevant?:

Lumbar segment instability (LSI), due to mechanical and functional impairment, is a common source of low back pain (LBP). Optimal activity and coordination between lumbar extensor and hip extensor muscles is necessary for lumbo pelvic stabilization and optimal motion during hip extension. This study compares hip extension force, lumbar erector and posterior hip muscle activity during prone hip extension (PHE), in individuals with and without LSI.

Dr. Brent Brookbush instructs Personal Trainer, Laura DeAngelis on proper form for the Quadruped Opposite Arm Leg Raise (Transverse Abdominis Activation)
Caption: Dr. Brent Brookbush instructs Personal Trainer, Laura DeAngelis on proper form for the Quadruped Opposite Arm Leg Raise (Transverse Abdominis Activation)

Quadruped Opposite Arm and Leg Raise - Transverse Abdominis Activation (TVA)

Study Summary

Study Design Cross Sectional Study
Level of Evidence IV - Evidence from well-designed case control or cohort study
Subject Demographics

Characteristics: matched control subjects

    • Gender: female
    • Age: 26 (+ 5 years)
    • Weight (+ 3 kg)
    • height (+ 3 kg)

LSI Individuals (120 recruited from orthopedic clinic)

  • Inclusion Criteria: non radicular central low back pain (LBP) > 3 months, combination of >3cm slip and translation on plain radiograph, degenerative disc disease on MRI, (+) for both clinical tests
  • Exclusion Criteria: negative concordant pain with discography, slip < 3 cm, translation < 3 cm, (-) both clinical tests, inability to perform hip extension, (+) Thomas test, history of fracture or surgery at lumbar spine or hip joint, structural deformities or neurological disorders, significant weakness in hip muscles
  • Final Inclusion: 36 individuals

Asymptotic individuals (54 recruited from orthopedic clinic)

  • Inclusion Criteria: no history of LBP in previous 12 months
  • Exclusion Criteria: failed radiographic screening, (+) clinical tests
  • Final Inclusion: 26 individuals

Clinical Tests - for lumbar segmental instability:

  • Passive lumbar extension test (PLET): (+) LBP with leg lifted passively to 30 cm off table in prone
  • Lumbar extension load test (LELT): Pressure applied to lumbar spine with patient in prone, in posterior to anterior direction in neutral and extended position. (+) LBP in neutral position that decreases in extended position


Outcome MeasuresIndividuals positioned prone with the dominant leg used for all measurements.  Subjects asked to lift leg to 10 deg of hip extension to a target bar and hold position for 5 sec. Following data was collected.

Each subject performed 3 trials with 1 min rest between repetitions. Surface electrodes were used for all muscles.

ResultsLSI individuals had significantly greater muscle activity (%RVC) in all muscle groups compared to the asymptomatic group
  • Erector Spinae: LSI 71.2 + 17.8 vs 35.4 + 10.6
  • Gluteus Maxiumus: LSI 35.3 + 23.9 vs 24.6 + 10.1
  • Biceps Femoris: LSI 96.3 + 12.4 vs 64.3 + 23.1

LSI individuals had significantly less hip extension force (N) compared to the asymptomatic group

  • LSI 121.2 + 4.0 vs 175 + 6.4

Visual analogue scale (VAS) measured at 5.31 + 8 versus no pain reported

ConclusionsThis study provides evidence that individuals with LSI cannot produce as much extension force, despite an increase in muscle activity. This may imply that patients with LSI have reduced movement efficiency, and impose greater demands on joints and soft tissues.
Conclusions of the ResearchersThis study demonstrates differences in muscle activity between asymptomatic individuals and individuals with LSI during PHE. Individuals with LSI have developed significantly greater muscle activity during PHE at their back and hip extensors and significantly less hip extension force.


Review & Commentary:

The authors of this study examined muscle activity at the lumbar spine (erector spinae and multifidus ) and the posterior hip (gluteus maximus and biceps femoris ). This muscle activity was recorded while comparing force production in prone hip extension to 10 degrees in individuals with and without lumbar segment instability (LSI).

There were many strengths to the methodology of this study including selection of subjects and establishing percent reference voluntary contraction (%RVC) of testing muscles. The authors set clear guidelines for exclusion criteria, excluding those individuals who had low back pain (LBP) but did not have LSI. The PLET clinical test used to identify LSI has very high sensitivity (84.2%) and specificity (90.4%) . The author describes the EMG recording procedures in detail, including preparation of the skin, placement of the electrodes and processing of EMG data. For collection of %RVC, data was normalized over three trials using actions standard muscles test. Before testing began subjects were allowed 10 practice trials of prone hip extension (PHE).

There were limitations to this study. The subjects recruited were a homogeneous group - young, otherwise healthy females. This may limit the transferability of findings to other groups. Also LBP may have been a confounding factor for EMG measurements, as perceived pain may affect force production (although we may expect this to reduce force output and EMG, rather than increase EMG). The authors reported; however, that subjects in the LSI group did not report increased pain during testing. Future research should investigate the effects of activation and strengthening of the intrinsic core musculature and glute complex , and its affect on EMG and PHE force production in individuals with LSI.

Why is this study important?

This research provides evidence that lumbar segmental instability (LSI) results in altered back and hip extensor muscle activity and a reduction hip extension force when compared to asymptomatic individuals. This may imply that patients with LSI have reduced movement efficiency, and impose greater demands on joints and soft tissues.

How does it affect practice?

These findings support previous studies that lumbar pain and pathology results in altered muscle activity and a decrease in force production at the hip. It is theorized that the increase in muscle activity in individuals with LSI, may be due to the pathomechanical changes that have resulted in a loss of passive tissue stability. Unfortunately, it is also theorized that the increase in activity may also increase stress on joints and soft tissues (for example, increased compression in the lumbar spine due to increased erector spinae and multifidus activity. Some of these tissues may be the same tissues compromised in those exhibiting LSI, creating a feed-forward mechanism contributing to further and potentially worsening LBP. Further, the decreased hip extension force noted by the authors, may suggest inhibition and weakness in the intrinsic core musculature and glute complex , reducing movement efficiency and performance in an athletic population. Although it is recommended that over-active muscles should be release (erector spinae ), special attention should be paid to intrinsic core musculature activation and glute complex activation in this patient population.

How does it relate to Brookbush Institute Content?

Relative to the Brookbush Institute predictive models of postural dysfunction, lumbar segmental instability is a commonly noted result of Lumbo Pelvic Hip Complex Dysfunction (LPHCD) . Although, many texts have recommended "strengthening the lumbar erectors" in the treatment of low back pain and/or LSI, this study and the LPHCD model suggest that these muscles should be released and potentially lengthened in an attempt to normalize tone. Further, this study notes a considerable increase in biceps femoris activity in those with LSI (when compared to the increase noted in the gluteus maximus ), which may also suggest that biceps femoris release prior to gluteus medius and gluteus maximus activation would be prudent. As those with individuals exhibiting symptoms of LSI do have a "stability" issue, more emphasis should likely be placed on activation , stabilization and conditioning exercises (especially those that incorporate hip extension) than mobility techniques .

Below you will find a few sample exercises used by the Brookbush Institute for individuals exhibiting Lumbar Segmental Instability:

Biceps Femoris Self-administered Active Release

Thoracic Spine Mobilization (and erector spinae release)

Glute Activation Circuit

Dynamic Quadruped

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