The Body's Load-Sharing Hub: The Thoracolumbar Fascia
December 3, 2014
The Body's Load-Sharing Hub: The Thoracolumbar Fascia
December 3, 2014
Have you ever wondered why you swing your arms when walking? It's largely due to kinetic energy being stored and released in the thoracolumbar fascia (TLF), as forces from the lower body transfer upwards - and vice-versa.
Consider, for example, direct mechanical force-transmission from the lower extremity to the pelvis and the trunk, as load (tension) is transferred between the hamstrings, the sacro-tuberous ligament and gluteus maximus, and on to the contralateral latissimus dorsi, by means of forces transmitted via the superficial and deep layers of the TLF.
Because of their direct connections to the TLF, this transferred load also directly influences the behavior of the erector spinae muscles, as well as external and internal obliques, transversus abdominis and serratus posterior inferior ... and more. Any dysfunctional situations, in any of these (or anything they connect to and with), has the ability to alter the function of all the other listed muscles, with unpredictable symptoms emerging relating to either restriction, pain or motor control, or all of these.
The "load-transfer" process involves a virtual spring-loading of the amazing TLF junctional area, the hub, where forces from the lower body, upper body, abdominal area and the trunk are spread and shared. This virtual hub contains some remarkable features where distribution of load is even more concentrated – such as the Lumbar Interfascial Triangle (LIFT) - which is discussed later in this article.
Therapists Need To Know About The TLF
How might awareness of these links help your work to be more effective? Quite simply - manual therapists (and those working with movement/exercise methods) who understand the multiple connections formed, via the TLF, can focus their methods more appropriately.
For example, a painful knee can - in many cases - be shown to be connected to gluteus maximus dysfunction, which may itself be being negatively influenced by inappropriate load reaching it from the contralateral latissimus dorsi – which is itself being influenced by myofascial events in pectoral and cervical structures.
Stecco et al (2014) describe their findings following 12 successive dissections: "In all (12) subjects gluteus maximus presented a major insertion into the fascia lata, so large that the iliotibial tract could be considered a tendon of insertion of the gluteus maximus ... [explaining] ... transmission of the forces from the thoraco-lumbar fascia to the knee ... possibly explaining why hypertonicity of gluteus maximus could cause an iliotibial band friction syndrome (IBFS) or, more generally, knee pain."
Sliding And Gliding Between Fascial Layers
Each layer of dense fascia is separated from the layers above and below by a thin layer of loose connective tissue that permits the different deeper layers to slide on each other. This allows the multiple directions of force, generated by different muscular orientations, to be transmitted smoothly.
Where unexplained musculoskeletal dysfunction exists (restriction, or pain for example) it is possible that reduction in the sliding/gliding function between the different fascial layers that make up the TLF, might be causing it to fail in its efficient transmission of load/force.
When it is healthy and operating normally, this remarkable structure, (the TLF) structurally and functionally connects the legs to the arms, the abdominal muscles to the low back muscles, the hamstrings to the neck, the gluteal muscles to the arms – simultaneously transferring forces in multiple directions, while also allowing sliding and gliding functions between its various layers of deep and superficial fascia and muscle. It therefore deserves the focused attention of all manual therapists – for when it is not functioning well due to trauma, inflammation, overuse, misuse, disuse and or age - a variety of symptoms can emerge – ranging from back pain to poor motor-control and balance problems.
Helene Langevin and her colleagues (2011) have shown that reduction of fascia's gliding potential in the thoracolumbar area (described technically as "reduced thoracolumbar shear strain"),is strongly associated with increased thickness of some fascial layers in the TLF, and in males in particular, this seems to predispose to low back pain. This gender-bias between a free sliding motion of fascia in the TLF, the thickness (or "densification") of some connective tissue layers, and low back pain, remains unexplained. Note: Some of the main reasons for fascial dysfunction are discussed later in this article.
As previously mentioned, the thoracolumbar fascia (TLF) integrates forces deriving from connective tissues, as well as numerous active muscular structures that attach to the fascial layers, including aponeurotic and fascial structures that separate paraspinal muscles from the muscles of the posterior abdominal wall.
The superficial posterior layer of the TLF is mainly an aponeuroses of latissimus dorsi and serratus posterior inferior, while deep to this is sheath that encapsulates the paraspinal muscles that support the lumbosacral spine.
Where this sheath meets the aponeurosis of transversus abdominus, it forms a seam-like ridge (known as as a raphe [pronounced "rafe" – see illustration of the TLF]. This dense septum is the junction of the structures anterior and posterior to the spine - where the Lumbar Interfascial Triangle (LIFT) is formed.
The LIFT is a remarkable structure (a "roundhouse" in Tom Myers terminology) that helps to distribute load from the abdominal and extremity muscles into, across, and from, the TLF.
Inferiorly, all the layers of the TLF fuse, to merge with the posterior superior iliac spine, and the sacrotuberous ligament, (which links directly to the hamstring group) - assisting in support of the lower lumbar spine and sacroiliac joint, and sharing load with the lower extremity.
Load reaching the LIFT from the abdominal muscles, latissimus dorsi, the lower extremity and pelvic muscles, are therefore appropriately distributed, in order to assist in stabilizing the spine, trunk and pelvis.
Strain Transmission During Stretching
Research has now explained more about how muscular forces are transferred – largely via fascia – to surrounding and distant tissues. For example, Franlklyn-Miller and colleagues (2009) have shown that when the hamstring group of muscles are stretched – as in straight-leg raising – whatever the degree of force being used in that stretch is multiplied greatly – so that 240% of that load reaches the iliotibial band, and 145% of the load transfers to the same-side low back, via the TLF.
The evidence is quite clear therefore – that the use of the word isolated in conjunction with the word stretching is difficult to justify. We need to learn more about which tissues are affected when stretching or compression is used – where load transfers to – and from - and where dysfunction might be coming from when we identify it!
The clinical relevance emerging from awareness of the TFL and LIFT and their multiple attachments, relates to their junctional coordinating functions, as pathways of force transmission, to and from different areas of the body, meet.
The transfer of load from knee to hamstring to gluteus maximus to hip to TLF and on to latissimus dorsi etc etc - example, described above, suggests that influences at a distance need to be considered when seeking the causes and maintaining features of any pain or restriction – and that therapeutic attention to these areas may have multiple effects.
The TLF As a Sensory Center
The thoracolumbar fascia is a richly innervated, with marked differences in the distribution of the nerve endings, over various fascial layers: The superficial fascia contains a dense presence of sensory mechanoreceptors (such as Pacini receptors and Ruffini endings). Substance P-positive free nerve endings—assumed to be nociceptive—are exclusively found in these layers. "The finding that most sensory fibers are located in the outer layer of the fascia, and the subcutaneous tissue, may explain why some manual therapies that are directed at the fascia and the subcutaneous tissue (e.g. fascial release) are often painful."
How Fascial Problems Start
Fascial dysfunction may result from slowly evolving trauma (disuse, overuse and misuse), or sudden injury (abuse) leading to inflammation and inadequate remodeling (such as excessive scarring or development of fibrosis):
- Densification may occur involving distortion of myofascial relationships, reducing sliding facilities and altering muscle balance and proprioception.
- As a result of such changes, chronic tissue loading forms global soft tissue holding patterns.
- When fascia is excessively mechanically stressed, inflamed or immobile, collagen and matrix deposition becomes disorganized, resulting in fibrosis and adhesions.
- Fascia is also greatly affected by the aging process – as well as by inactivity, possibly related to illness or concurrent pain.
The more manual therapists know about and understand structures such as the TLF the more they will be able to understand their patient's symptoms, and be able to help them towards recovery from pain and restriction.
New Book on Fascial Dysfunction
In my new book, Fascial Dysfunction: Manual Therapy Approaches, I have explored and explained fascia's multiple roles in the body, as well as the ways fascial dysfunction starts and develops – based on translation of the avalanche of scientific research that is emerging.
In addition, the book contains guides to assessment protocols (including a chapter by Tom Myers), as well as chapters that examine a wide range of fascia-focused treatment approaches - involving contributions from approximately 20 leading experts.
In a future article, I will focus attention on which manual approaches have demonstrated evidence of efficacy.
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