Research Review: The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia
By Erik Korzen DC, NASM-CES, Acupuncturist
Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS
Original Citation: Vleeming, A., Schuenke, M.D., Danneels,Willard, F.H. The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia. Journal of Anatomy, 2014. 225, 447-462. Article Abstract.
Why is this relevant?: The thoracolumbar fascia (T/L fascia) is a complex network of myofascial structures that aids in stabilization of the lumbopelvic complex and connects muscles of the extremities to the trunk. This study provides insight into the coupling of these myofascial structures during contractions. The researchers utilized fluoroscopic images to determine changes in size, shape and tension of the paraspinal musclar compartment (PMC) (the space labeled "A" in the image below) due to inflation, with and without tension in the common tendon of the transversus abdominis and internal oblique muscle. The findings of this study imply that the deep abdominal and lumbar spinal muscles demonstrate a co-dependent mechanism linked through the posterior layer of the thoracolumbar fascia (PLF). Additionally, the findings indicate that robust paraspinal muscle contractions are required within the paraspinal muscular compartment (PMC) to enable pressure increases sufficient to alter the geometric shape of this fascial structure.
A schematic and simplified view of the bifurcation of the TA and IO aponeurosis and the paraspinal retinacular sheath (PRS), creating the lumbar interfascial triangle (LIFT). A represents the empty space normally occupied by the paraspinal muscles and enclosed by the PRS. The aponeurosis of the transversus abdominis (TA) and internal oblique (IO) bifurcates into anterior and posterior laminae. The anterior lamina contributes to the middle layer of the thoracolumbar fascia (MLF). The posterior lamina contributes to the deep lamina of the posterior layer of the thoracolumbar fascia (PLF). The lateral raphe (LR) represents a thickened complex of dense connective tissue at the lateral border of the PRS, from the iliac crest caudally to the 12th rib cranially. The junction of the TA aponeuroses with the PRS creates the LIFT, which is at the core of the LR. Thus, the raphe is formed at the location where abdominal myofascial structures join the PRS surrounding the paraspinal muscles. sPLF, superficial lamina of PLF.
Study Summary
| Study Design | Experimental Case Study |
| Level of Evidence | Level of Evidence IV - Observational Study with Controls |
| Subject Demographics | 7 embalmed human specimens
14 axial slabs (Left and Right paraspinal muscular compartments of each of the 7 cadavers) were prepared using a saw at the L2-L3 levels |
| Outcome Measures |
Method 1: Loading the CTrA 1a: Left and Right CTrA pulled anterolaterally, generating bilateral forces of 8.5N (cadaveric strain has been demonstrated to occur at approximately 10N (2). 1b: Each CTrA was loaded with 8.5N tension anterolaterally, simulating function of CTrA. Method 2: Simulation of paraspinal muscle contraction Paraspinal muscles removed from the slab and custom-made inflatable tubes were inserted into the PMC (2.54cm uninflated diameter, 10cm length). Subsequent inflations were set at 1.5cm increments above the tube circumference. Respectively, these inflation increments are referred to as Inf1, Inf2, Inf3 throughout the study. *due to inter- and intra-specimen variability, standard initial pressure could not be obtained; instead, a first inflation measurement was used which is the minimum pressure to hold the inflatable tube in place Average intra-tube circumferential measurements were taken using a tailor's tape measure. Average intra-tube pressure was also measured using Vernier LabPro. The average intra-tube pressures for Inf1, Inf2 and Inf3 were 79.1, 99.8 and 106.5 mmHg respectively. Method 3: Measuring perimeter of Thoracolumbar Fascia (TLF) Neutral position of copper beads imaged using a C-arm fluoroscope. While CTrA was being put under 8.5N of tension, a 2nd image was captured. The 2nd image was then superimposed on the initial (neutral position) image to compare movement of the copper beads. Method 4: Analyzing posterior and lateral displacement of the PMC The straight-line perpendicular distance from the lateral tip of the transverse process to the posterior portion of the posterior layer of the thoracolumbar fascia (PLF). Measurements were then taken under the same incremental changes described in Method 2. Method 5: Differentiating MLF/PLF force transfer resulting from CTrA tension Tension load cells attached to anterior and posterior laminae of CTrA. A reading of each load cell in neutral (without tension on the CTrA) and a reading of each load cell with 8.5N applied anterolaterally was performed. Calculation of the MLF and PLF force transfer was perfomred using the following: PLF (tension)= PLF (tensed) - PLF (neutral) MLF (tension)= MLF (tensed) - MLF (neutral) Method 6: Analyzing the effect of inflation on PLF force transfer 2 axial slabs tested utilizing 2 load cells attached to the posteromedial and anterolateral portions of the PLF. The same 8.5N tension and incremental inflations described in Method 2 were used. Alphabetical Abbreviations used throughout the article:
|
| Results | Incremental inflation of the PMC, without tension on the CTrA produced a minimal but significant increase in length of the PLF accompanied by a posterior displacement. In contrast, the MLF length was not altered with incremental inflation. Without PMC inflation, increasing CTrA tension resulted in anterior and lateral movement of the borders of the compartment. However, when CTrA tension is coupled with inflation, the net displacement of the borders of the compartment is posterior and slightly medial. Tension created in the CTrA is mostly passed through the PLF with little impact on the MLF, regardless of the pressure in the PMC. The results of this study imply that an adequate paraspinal muscle contraction can oppose the tension and lateral displacement generated by the TrA and IO muscles and vice versa. "Further, it implies the existence of a point of equal tension between the paraspinal muscles and the transverse abdominus and internal oblique muscles acting through the CTrA resulting increased force closure and self-bracing of the spine" (Vleeming et al. 1990a,b). |
| Conclusions | In the absence of PMC inflation (mimicking the lack of muscle contraction), CTrA tension results in anterior and lateral movement of the PLF. Additionally, the combination of PMC inflation (mimicking muscle contraction via increased pressure) with increased CTrA tension substantially displaces the PLF in a posterior and slightly medial direction. This indicates that with increasing PMC inflation, the angle of load transfer between the anterolateral pull of CTrA to the PLF is further optimized, creating an increasingly linear pull to the PLF. For each 1 cm of expansion in the posterior direction there was a 0.18 cm movement medially. This indicates that the lateral border of the TLF is not expanding and is even slightly displaced medially, compared with a much larger posterior displacement of the PLF. |
| Conclusions of the Researchers | The findings of this research are rather intriguing as this is the first study of it's kind. The above results show that increasing tension on the CTrA (mimicking deep abdominal muscle contraction), combined with PMC inflation, transfers significantly more load to the PLF in comparison to the MLF thereby girdling the spine posteriorly. The present study shows an average posterior displacement of the PLF of 1.56 cm, when the PMC is submaximally inflated. This rep- resents a substantial increase of the extensor moment arm of the PLF. This study shows a critical co-dependent mechanism between deep abdominal and lumbar spinal muscles linked to each other, especially through the PLF. |
Cadeveric analysis of thoracolumbar fascia - horizontal cross-section. Image from study.
Commentary:
Why is this study important?
Comparing this study to previously conducted research, similar methods have been used to simulate muscle contraction and force transfer. In the present study, custom-made butyl inflatable tubes were inserted, in order to simulate three stages of contraction/inflation (inf), with and without CTrA tension. This study confirms that by mimicking activation of the paraspinal muscles , combined with CTrA pull, the PLF becomes preferentially tensed while the MLF is barely influenced. The CTrA tension combined with PMC inflation restrains the lateral border and even results in a small amount of medial displacement. This restraint of the lateral border matches well with a reported four times stronger lateral strength of the PLF, compared with longitudinal strength (3).
There is an average posterior displacement of the PLF of 1.56cm during Inf3 of the PMC, which represents a substantial increase in the moment arm of the PLF. This is an important finding when one considers that there the fibers of the PLF are approximately 40 degrees from horizontal and appear cross-hatched below T12. Due to the fiber orientation and myofascial attachments, the tension transferred to the PLF is a result of longitudinal and horizontal pulling.
Deconditioning, fatty involution, size and shape changes and alterations in motor control for the abdominal and paraspinal muscles , particularly the deep lumbar multifidus , have been identified in patients with low back pain (Parkkola et al. 1993; Hides et al. 1994, 1995; Mooney et al. 1997; Danneels et al. 2000; Kader et al. 2000; Mengiardi et al. 2006; Dickx et al. 2008, 2010; Chan et al. 2012).
All of these conditions have the potential to alter the effective load transfer characteristics of the T/L fascia. The present study shows that in the absence of sufficient PMC inflation, CTrA tension results in anterior and lateral movement of the PLF. This suggests that decreased cross-sectional area (CSA) of the paraspinal muscles , with less volume load to fill the PMC, combined with or without CTrA tension, will displace the T/L fascia anteriorly and laterally, thereby reducing the extension moment of the PLF.
A weakness of this current research is that the biomechanical properties of the PLF were studied exclusively in the axial plane. Future studies should include multi-axial analysis as well as the inclusion of extremity muscles such as the latissimus dorsi and/or gluteus maximus which have direct and strong attachments to the PLF. Another limitation of the current study is that elderly cadaveric specimens were utilized for all methods. Therefore, generalizing the findings to a younger population may require support from additional research on a younger population.
How does it affect practice?
The T/L fascia is an often discussed structure by human movement professionals; however, it's function is a somewhat convoluted topic. After careful review, the T/L fascia seems to provide a myofascial connection between the torso and the extremities, and transmits the force of muscular contractions aiding in stabilization of the lumbar spine and sacroiliac joints. Based on the findings of the current study a co-contraction of the paraspinal muscles , the transverse abdominus and the internal oblique muscles, acting through the CTrA, results in more force transmitted through the PLF which is posteriorly shifted by the co-contraction. This may alter T/L fascia fiber direction and resistance to axial load/flexion of the spine; however, further research is needed. Human movement professionals should consider how co-contraction of these muscles (as well as other muscles investing in the T/L fascia) may aid in lumbar stability, moving away from interventions that address a single muscle, joint, nerve or connective tissue structure. The authors of this review, do find it interesting that the muscles discussed relative to co-contraction match those discussed as the "Intrinsic Stabilizers" by Richardson et al, implying that the "Motor Control Model" may also be a myofascial model (4).
How does it relate to Brookbush Institute Content?
Because of the extensive nature of the T/L fascia, the predictive models of lumbopelvic-hip complex dysfunction (LPHCD) , lumbosacral dysfunction (SIJD) , upper body dysfunction (UBD) and lower body dysfunction (LLD) may be affected by or potentially cause abnormalities in the function of this tissue. Comprehensive analysis of the T/L fascia would include dynamic posture/movement assessment (Overhead Squat Assessment) , as well as assessment of the hip , sacroiliac joint, lumbar and thoracic spine. A conceptual framework for integrating the findings of this study into practice may be found in the Brookbush Institute's discussion on core subsystems, specifically the posterior oblique subsystem (POS) and intrinsic stabilization subsystem (ISS) .
The videos below address the T/L fascia as part of assessment, activation and integration techniques.
Overhead Squat Assessment Sign Cluster: Lumbo Pelvic Hip Complex Dysfunction
Static Standing Chop Pattern:
Static Lunge to Unilateral Row:
Power Squat to Row
Bibliography
- Vleeming, A., Schuenke, M.D., Danneels,Willard, F.H. The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia. Journal of Anatomy, 2014. 225, 447-462.
- Barker, P. J., C. A. Briggs, and G. Bogeski. "Tensile transmission across the lumbar fasciae in unembalmed cadavers: effects of tension to various muscular attachments." Spine 29.2 (2004): 129.
- KM Tesh, J Shaw Dunn, JH Evans. Abdominal muscles and vertebral stability. Spine, 12 (1987), pp. 501–508
- Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition (c) Elsevier Limited, 2004
- Vleeming A, Stoeckart R, Volkers AC, et al. (1990a) Relation between form and function in the sacroiliac joint. Part I: clini- cal anatomical aspects. Spine 15, 130–132.
- Vleeming A, Volkers AC, Snijders CJ, et al. (1990b) Relation between form and function in the sacroiliac joint. Part II: bio- mechanical aspects. Spine 15, 133–136.
- Parkkola R, Ryto€koski U, Kormano M (1993) Magnetic resonance imaging of the discs and trunk muscles in patients with chronic low back pain and healthy control subjects. Spine 18, 830–836.
- Hides JA, Stokes MJ, Saide M, et al. (1994) Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back pain. Spine 19, 165–172.
- Hides JA, Richardson CA, Jull GA (1995) Magnetic resonance imaging and ultrasonography of the lumbar multifidus mus- cle. Comparison of two different modalities. Spine 20, 54–58.
- Mooney V, Gulick J, Perlman M, et al. (1997) Relationships between myoelectric activity, strength, and MRI of lumbar extensor muscles in back pain patients and normal subjects. J Spinal Disord 10, 348–356.
- Danneels LA, Vanderstraeten GG, Cambier DC, et al. (2000) CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects. Eur Spine J 9, 266–272.
- Kader DF, Wardlaw D, Smith FW (2000) Correlation between the MRI changes in the lumbar multifidus muscles and leg pain. Clin Radiol 55, 145–149.
- Mengiardi B, Schmid MR, Boos N, et al. (2006) Fat content of lumbar paraspinal muscles in patients with chronic low back pain and in asymptomatic volunteers: quantification with MR spectroscopy. Radiology 240, 786–792.
- Dickx N, Cagnie B, Achten E, et al. (2008) Changes in lumbar muscle activity because of induced muscle pain evaluated by muscle functional magnetic resonance imaging. Spine 33, E983–E989.
- Dickx N, Cagnie B, Parlevliet T, et al. (2010) The effect of unilat- eral muscle pain on recruitment of the lumbar multifidus dur- ing automatic contraction. An experimental pain study. Man Ther 15, 364–369.
- Chan ST, Fung PK, Ng NY, et al. (2012) Dynamic changes of elas- ticity, cross-sectional area, and fat infiltration of multifidus at different postures in men with chronic low back pain. Spine J 12, 381–388.
© 2016 Brent Brookbush
Questions, comments, and criticisms are welcomed and encouraged -