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Influences of Trunk Muscles on Lumbar Lordosis and Sacral Angle

Tuesday, June 6, 2023 - 1 Likes

Brent Brookbush

Brent Brookbush


Research Review: Influences of Trunk Muscles on Lumbar Lordosis and Sacral Angle

By Corbin Henault MEd, ATC

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

Original Citation: Kim, H. J., Chung, S., Kim, S., Shin, H., Lee, J., Kim, S., & Song, M. Y. (2006). Influences of trunk muscles on lumbar lordosis and sacral angle. European Spine Journal, 15(4), 409. ABSTRACT

Why the Study is Relevant: Low back pain (LBP) is the most common cause of reduced activity in individuals under 45 (1). Trunk muscle strength ratios and lumbar angle appear to play a key role in the development and persistence of chronic LBP (4 - 11). This 2006 study by Korean and U.S. researchers examined whether a relationship exists between trunk muscle strength and lumbosacral spine angles in individuals with chronic LBP. The findings demonstrate that trunk flexor to extensor muscle strength is correlated with lordotic angle. Human movement professionals may be able to improve evaluation, treatment and rehabilitation by assessing and addressing this issues.

Note how deep the Quadratus Lumborum is in reference to other muscles inserting into the lumbar spine. In this diagram we see the Quadratus Lumborum peering out from behind the iliocostalis and the serratus posterior inferior, and the internal obliques, transverse abdominis and latissimus dorsi have been cut away. Illustration courtesy of - http://fscomps.fotosearch.com/online-courses/online-courses/bigcomps/LIF/LIF156/MM201022.jpg
Caption: Note how deep the Quadratus Lumborum is in reference to other muscles inserting into the lumbar spine. In this diagram we see the Quadratus Lumborum peering out from behind the iliocostalis and the serratus posterior inferior, and the internal obliques, transverse abdominis and latissimus dorsi have been cut away. Illustration courtesy of - http://fscomps.fotosearch.com/online-courses/online-courses/bigcomps/LIF/LIF156/MM201022.jpg

Illustration courtesy of - http://fscomps.fotosearch.com/online-courses/online-courses/bigcomps/LIF/LIF156/MM201022.jpg

Study Summary

Study DesignDescriptive cross-sectional
Level of EvidenceIII evidence from non-experimental descriptive studies, such as comparative studies, correlation studies and case-control studies
Participant Characteristics



  • Age: 35 +/- 26 yrs.
  • Gender: 20 female, 11 male
  • Number of participants: 31

Inclusion Criteria:

  • Pain reported between L1 and gluteal folds
  • Pain within the last three months
  • Outpatients of East-West Spine Center, Kyunghee Medical Center from May-Sept. 2001 receiving care for low back pain (LBP)

Exclusion Criteria:

  • Acute back pain (within one week)
  • Scoliosis greater than 15 degrees
  • Severe lumbar rigidity (sacral angle less than 10 degrees)
  • Radicular signs or symptoms
MethodologyTrunk Muscle Strength Measurement
  • Participants were placed in a B-200 Isostation in an upright neutral position
  • Participants performed maximal isometric trunk lateral flexion, flexion-extension and rotation contractions twice in all directions for 5 seconds
  • The higher range of motion (ROM) measurement was selected to calculate extension to flexion (E/F), right to left lateral flexion, and right to left rotational strength ratios

Measurement of lordosis and sacral angle

  • Radiograph films of the lumbar spine and sacrum were taken from the lateral perspective with the x-ray focused on L3 while participants stood upright with arms folded across the chest
  • Lordosis was measured using twice manually using the goniometer on the horizontal light box. The mean was accepted
  • The sacral angle was measured as the angle between the horizontal line parallel to the bottom end of the film and the superior endplate of sacrum
  • The lordotic angle was determined by altering Cobb's method. The angle was obtained between the inferior endplate of L5 and the superior endplate of L1 in the lateral view using Polly's method
  • Some of the radiographs were measured by using the Picture Achieving and Communication System (PACS) computerized goniometer
Data Collection and Analysis
  • The B-200 Isostation was used to measure trunk strength
  • The Siemens OPTITOP was used to obtain radiographs
  • PACS software measured some goniometry
  • SPSS for Windows 8.0 was used to calculate Pearson's correlation coefficients between lumbar lordosis, sacral angle and ratio of maximal torques, and muscle strength
Outcome Measures
  • Lateral flexion and rotation maximum torque values
  • Lumbar lordosis and lumbosacral angle measurement
  • Lumbar flexor and extensor muscle strength
  • E/F ratio
  • Lumbar lordosis: 27.19 (8.53)
  • Lumbosacral angle: 31.77 (6.02)
  • Lumbar Extension/Flexion strength (E/F) ratio showed significant moderate relationship with the lordotic angle (R=0.491, p<0.01), but not the sacral angle
  • Ratio of right to left rotation or lateral flexion was not significantly correlated with the lordotic or sacral angle
  • Extension maximum torque was significantly correlated with the sacral angle in men but not women (p<0.01). Other maximum torques were not significantly correlated with the sacral angle in men or women.
Our ConclusionsThe researchers' findings support the inclusion of E/F ratio assessment when working with individuals with chronic LBP. Further, the reduction in flexion strength relative to extension strength may be further evidence of the relative changes in activity described in the Lumbo Pelvic Hip Complex Dysfunction model (LPHCD).
Researchers' Conclusions

Lumbar lordosis is moderately correlated with trunk E/F strength ratio. This ratio can be applied as an indicator of strength imbalance during trunk muscle assessment.  Though not the focus of the study, low E/F ratio was found to correlate with LBP. The researchers suggest that several other factors be examined before concluding that an abnormal lordotic angle can be directly associated with LBP.

Low back muscle static manual release by Dr. Brent Brookbush
Caption: Low back muscle static manual release by Dr. Brent Brookbush

Erector spinae and multifidus static manual release by Dr. Brent Brookbush

Review & Commentary: This study adds to the body of research investigating correlations between anthropometric variables and chronic lower back pain (LBP). This research is unique in its use of computerized goniometer software to maximize inter-rater reliability of the lumbosacral angles. A relationship between trunk muscle strength ratios, lordotic and lumbosacral angles was observed in both men and women with LBP.

  • The study had many methodological strengths:
    • The researchers used validated methods - the B200 Isostation, a well-established means of measuring both isometric and isodynamic trunk strength (2), and the Cobb method, used to measure scoliosis curvature and was adapted in this study to measure lordotic angle.
    • PACS software was used to measure the sacral angle, which increased inter-rater reliability over other studies that used manual measures.
    • This study filled a gap in the body of research through its demonstration of a relationship between trunk muscle strength and spine angle in both men and women with LBP.
  • Weaknesses that should be noted prior to clinical integration include:
    • Participants were not selected randomly but rather chosen from a specific location after clinical evaluation, which limits the generalizability of the study. Drawing participants from the general population would provide a clearer comparison of variables in healthy and injured populations.
    • This study had no intervention by design and was purely descriptive/observational. An intervention will be needed in future studies to build a stronger case for clinical integration.
    • The B200 Isostation is not a device accessible to most human movement professionals, which limits the ability of clinicians and researchers to accurately replicate the study.

How This Study is Important:

The relationships between lumbosacral position, muscle strength and low back pain may highlight common compensatory patterns that influence assessment and intervention selection. This study compared changes in trunk muscle strength with lordotic curve and sacral slope angles, in those with low back pain and asymptomatic individuals. Prior studies have investigated lumbosacral position and muscle strength individually in those exhibiting signs low back pain; however, few studies have examined both in the same study (4-11). The inclusion of both outcome measures in this one study allows lumbosacral position and muscle strength to be correlated to one another. The correlation between low back pain, increased lumbar lordosis and sacral slope angle and a decrease in lumbar flexor endurance imply these issues should be considered collectively.

How the Findings Apply to Practice:

Human movement professionals should attempt to identify imbalances between trunk flexor and extensor strength, perhaps by identifying an “excessive lordotic curve ” during static and dynamic postures (example, Overhead Squat Assessment ) in those with low back pain. If an increased lordotic curve or muscle imbalance is identified, consideration should be given to rectifying this imbalance as part of a treatment/corrective program.

How does it relate to Brookbush Institute Content?

The findings of this study indicate that the ratio between trunk flexion and extension strength are correlated with chronic LBP. This is consistent with changes in muscle activity and interventions proposed in the Brookbush Institute's predictive models of Lumbo Pelvic Hip Complex Dysfunction (LPHCD) , Lumbosacral Dysfunction (LSD) , and Lower Extremity Dysfunction (LED) . Although this study did not employ an intervention, it establishes a relationship between E/F strength ratio and LBP. Human movement professionals should consider going beyond the generally recommended "core strengthening" to addressing the specific muscle weakness/movement impairments identified during assessment. Relative to this study, low back pain correlated with increased lumbar lordosis, may imply a need for greater focus on trunk flexor strength.

The following videos present a refresher on spine anatomy and trunk muscles, illustrate a common trunk flexor exercise and demonstrate a taping technique for low back decompression:

Muscles of the Core:

Quadruped Crawl


Low Back Decompression Tape:


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© 2017 Brent Brookbush

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