Hey Readers! I am so glad you are here! In this blog series, I am taking a deep dive into the world of chronic low back pain (CLBP). Unfortunately, CLBP is very common among adults, and it is sadly becoming more and more common among adolescents and children as well. CLBP can be caused by a variety of factors, including muscle imbalances, disc pathologies, muscle strains, and more. Ask anyone with CLBP, and they will likely tell you that CLBP is highly debilitating. And it is – CLBP is one of the most common reasons people miss work in the U.S. CLBP is usually accompanied by many other issues, such as injury elsewhere in the body, lack of sleep, depression, anxiety, irritability, and a reduced quality of life. Often, surgery and/or pain-alleviating medications (e.g. opiods, NSAIDs) are prescribed to patients with CLBP, with little abatement in the symptoms.
But, there is some light at the end of this “back pain tunnel.” Many research studies have shown that yoga is actually quite effective at mitigating, and preventing, CLBP symptoms. Double bonus – yoga appears to be safe for people with CLBP, especially when completed from a trained and knowledgeable yoga teacher. Triple bonus – practicing yoga may be a more affordable option compared to surgery and some medications. And, quadruple bonus – practicing yoga does way more good for the body than just alleviating CLBP, such as improving balance, strength, and mobility in the entire body.
Over the course of this blog series, I will go over the following information, released in weekly installments:
Part I – Anatomy of the low back area
Part II – General information about CLBP
Part III – Research supporting yoga for CLBP
Part IV – Yoga practice guidelines and suggestions for CLBP
In this part of the series (part I), I will go over the anatomy of the low back area. Just a heads up - this post is a little long because there are so many muscles that attach in some way to, or near, the lumbar spine. I have simplified this information significantly, so if you feel like you need more thorough descriptions, please refer to my reference list at the end of each post. So… without further ado, let’s talk some low-back anatomy!
Vertebral Column
The vertebral column, or spine, is a bony column on the back of the trunk that is designed for stability, force transmission between the upper body and lower body, and protection of the delicate spinal cord.
The spine is made up of 34 bones called vertebrae. All but 10 of these vertebrae are movable. The movable vertebrae are divided into three groups - seven cervical vertebrae in the neck, 12 thoracic vertebrae that attach to the ribs in the thorax, and five lumbar vertebrae in the low back. The remaining ten vertebrae are located at the base of the spine. Five of these vertebrae are fused together to form a triangular-shaped bone known as the sacrum, which sits between your hip bones to form your pelvis. Below the sacrum are three to five (most people have four) fused or partially mobile segments that form the coccyx, which is really a rudimentary “tail” inherited from early human ancestors.
Each vertebrae in your spinal column meets up with the neighboring vertebrae at a facet joint. The spaces between the vertebrae contain round, rubbery pads called intervertebral discs that act like shock absorbers throughout the spinal column. Bands of tissue known as ligaments hold the vertebrae in place, and tendons attach muscles to the spinal column. Thirty-one pairs of nerves are rooted to the spinal cord, transmitting signals from the body to the brain and vice versa.
When viewed from the side, the vertebral column has four natural curvatures, forming a repeating “S” shape. The cervical and lumbar regions bend anteriorly (i.e. towards the front of the body) to form lordotic curves, while the thoracic and sacral sections bend posteriorly (i.e. towards the back of the body), creating kyphotic curves. The purpose of the lumbar lordosis is to allow humans to stand and walk upright on two feet (i.e. bipedalism). Lumbar lordosis also allows humans to bring shoulders over the hips when standing upright, without having to flex the knees or extend the hips. Indeed, the curve of our lumbar spine is what differentiates our species from other apes and animals. No other animals have a lordotic curve in their lumbar spine. Rather, their spines are kyphotic (like the thoracic spine in humans) for the entire length.
The amount of lumbar lordosis varies greatly, with values of the curvature ranging from 29 – 69 degrees (the average being around 49 degrees), resulting in great variation in people’s ability to move their spines. Women typically have a little more lordosis than men due to their ability to bear children. A deeper lordotic curve moves the upper body’s center of gravity further backward, which is helpful when a woman has a growing belly during pregnancy. Lumbar lordosis can decrease with age secondary to muscle weakening and/or tightening and/or disc shape changes. Too little lumbar lordosis can reduce the efficiency of standing and walking, possibly leading to low back pain (LBP). Too much lordosis can restrict the lumbar spine’s total range of motion (ROM), potentially causing LBP. Thus, too much, or too little, lordosis is not a good thing.
The lumbar spine, or low back, includes five vertebrae, referred to as L1-L5, and they support much of the weight of the upper body. Interestingly, a small percentage of people (about 3.4%) actually have four or six lumbar vertebrae. Unlike the sacral and thoracic spine, the lumbar spine is a pretty flexible stack of bones. The ROM in the sacral spine is more limited since it is grounded into the hip bones, and the thoracic spine is connected to your ribs and breastbone, so it too is relatively limited in its options for movement. Second only to the neck, the lumbar spine is a very mobile segment of the spine, providing mobility for everyday motions such as bending forward and backward (flexion and extension, respectively), bending to the side (i.e. lateral flexion), and twisting or rotating (i.e. rotation).
The lumbar vertebrae are much fatter and thicker than the other vertebrae since they must bear the full weight of the upper body. However, the lumbar vertebrae closer to the thoracic spine (L1 and L2) more closely resemble the thoracic vertebrae, with most differences appearing in the lower lumbar vertebrae (L3-L5), and L5 having the thickest vertebral body. The lowest lumbar vertebrae, L5, sits in between your back hip bones, where it connects with S1 (the top sacral vertebrae). The joint between L5 and S1 allows for the rotation of your hips when you walk and run. This joint, along with the one above it, between lumbar L4 and L5, are the most weight-bearing joints of the lower back. Consequently, they are the most prone to injury.
Anatomic Organization of the Low Back Muscles
The lumbar spine is heavily influenced by many muscles and their surrounding tissues (i.e. myofascia), as quite a lot of muscles attach to, or near, the lumbar spine region. The high number of muscles attaching in, or near, the lumbar region coupled with the fact that the lumbar spine is very mobile AND bears the weight of the entire upper body makes this region of the body super susceptible to injury and/or pain.
The muscles of the lumbar region are responsible for much of the movement that occurs in the low back, hips, and trunk. Nerves in the low back supply sensation and motor control to the muscles in the pelvis, legs, and feet. Some low back injuries can compress these nerves, resulting in pain that radiates down the leg. The lumbar muscles are often imbalanced, where one side may be thicker than the other side, or where one side may be longer, or shorter, than the other side. These imbalances are typically the result of chronic sitting, a high number of repetitive movements (e.g. always carrying your purse on one shoulder), or faulty static or dynamic posture.
The lumbar myofascia are generally organized into five main categories: superficial low back myofascia, intermediate low back myofascia, deep low back myofascia, abdominal myofascia, and additional myofascia. Each one of these categories will be discussed further in the following sections. With the exception of the diaphragm, all other lumbar region muscles have bilateral symmetry, meaning they are found on both sides of the body. Through fascial connections and movements of the pelvis, the leg (e.g. quadriceps, hamstrings, etc.) and gluteal muscles can also affect the lumbar spine; however, these muscles will not be discussed in depth in this series. For more information on the gluteal muscles, please refer to my earlier blog post on that topic (click here).
Superficial Low Back Myofascia
The superficial low back myofascia are located closest to the surface of the skin. The primary muscle that influences the low back from this category is the latissimus dorsi, also known as the “lats.” The latissimus dorsi is the broadest muscle of the back, and it sort of resembles the wings of a flying animal. The muscle fibers of the latissimus dorsi are relatively thin, and they originate in the low back area and insert into the humerus (or upper arm bone).
The latissimus dorsi (pictured below) has three primary jobs at the shoulder joint – extension (i.e. reaching the arm behind you), adduction (i.e. bringing your arm closer to your body), and internal rotation (i.e. turning your entire arm into your body). But, the lats do not only affect movement at the shoulder joint. Because of its origin in the low back, the latissimus dorsi can also influence movements occurring in the low back. Indeed, unilateral contraction of the latissimus dorsi can assist with lateral flexion of the trunk (i.e. side bending), and bilateral contraction of the lats can assist with extending the spine (i.e. backbend shapes). Thus, mobility AND strength of the lats can have a direct impact on the low back. And many people actually have chronically shortened, but also weakened, lats, which can affect alignment in the low back area, potentially causing LBP.
The lumbar region also contains a large sheath of fascia, or connective tissue, known as the thoracolumbar fascia (TLF), sometimes called the thoracolumbar aponeurosis. The TLF spans from the sacrum to the lower thoracic spine. The lats technically originate from this fascial sheath. The TLF is important in maintaining some stability in the low back while also transferring stress from the trunk to the limbs. It is hypothesized that the TLF acts as a motherboard, where mechanical information from the musculoskeletal system converges and is communicated to the nervous system to help coordinate the synergistic action of muscles.
Intermediate Low Back Myofascia
The intermediate low back muscles are slightly deeper than the superficial myofascia. The main muscle in the category is the serratus posterior inferior. While this muscle does attach to the lumbar vertebrae, this muscle is primarily used for respiration and will not be discussed in detail in this blog post. Please refer to my reference list for more detailed information on this muscle.
Deep Low Back Myofascia
There are three groups of the deep, low-back myofascia – the erector spinae group, the transversospinal group, and the short segmental group.
The bilateral erector spinae group (pictured below) is the most superficial of the deep, low-back muscles, and these muscles run from the sacrum to the base of the skull, along the posterior (or back) vertebral column. There are three major branches of the erector spinae group – the spinalis, longissimus, and iliocostalis. The erector spinae are large, dense, layered muscles, and they are more suited for gross motor movements (i.e. movements with large ranges of motion) of the spine, rather than finer movements at selected intervertebral junctions. Bilateral contraction of the erector spinae extends the spine, creating backbend shapes, such as locust pose in yoga. The erector spinae can actually generate large extension torque across the spine, which is needed for lifting and carrying heavy objects. Unilaterally, the erector spinae group laterally flexes the vertebral column to the same side, making it a synergist (or helper) to the oblique abdominal muscles. Since the erector spinae attach to the sacrum and pelvis, they can tilt the pelvis anteriorly, creating a deeper lumbar lordosis. Overactivity in the erector spinae, resulting in hyperlordosis of the low back, is relatively common and can lead to LBP.
The transversospinalis group (pictured below) also has three branches – multifidi, rotatores, and semispinalis capitis. This group of muscles lie deep to the erector spinae. The transversospinalis group also run the entire length of the vertebral column. But, unlike the long and large erector spinae muscles, the transversospinalis muscles consist of many short and small fibers that form an intricate stitchlike design that links the vertebrae together. The shorter, smaller rotatores lie deep to the multifidi. The semispinalis capitis is found along the thoracic and cervical vertebrae, so these will not be discussed in any depth in this post. Unlike the erector spinae which are involved in gross motor movements, the transversospinalis muscles favor fine motor movements and stabilization of the spine against various forces. Bilaterally, these muscles assist with extending the vertebral column, AND they contribute to stabilizing and controlling movements of the lumbar spine. While the multifidi and rotatores can assist with lateral flexion and rotation of the spine, their leverage for these actions are limited because of their close proximity to the vertebral column. The multifidi are the thickest and most developed in the lumbosacral region of the spine, and this architectural design provides excellent stability to the base of the spine. In fact, the multifidi account for two-thirds of the muscular stability in the lumbosacral spine. Some studies have shown that people with LBP have weak multifidi and may be unable to engage them sufficiently to stabilize the spine during movement.
The short segmental muscles are deepest of the low back muscles (not pictured), and they consist of two groups – interspinalis and intertransversarius. These muscles are thought to be involved with proprioception of the spine (i.e. where the spine is in space) as well as stabilization of the spine among a few intervertebral junctions at a time. The short segmental muscles are most developed in the cervical spine where fine control of head movements is required, and then they are next developed in the lumbar spine. They seem to be mostly absent from the thoracic spine.
Thus, in summary, the large extensor muscles, such as erector spinae, are activated to cause large movements of the whole spine (e.g. extension, flexion, etc.), while the short muscles (e.g. multifidi) activate to ensure stability and small movements locally throughout the spinal column.
Abdominal Myofascia
There are four abdominal muscles (generally referred to as the “abs”) – the rectus abdominis, external obliques, internal obliques, and transverse abdominis (pictured below). Among other things, the abdominal muscles, or abs, support the lumbar spine by helping to resist hyperlordosis. If the abdominal muscles do not have sufficient tone or strength, they might not be able to support spine well enough, causing excess lumbar lordosis, and potentially leading to LBP. When you create support for your lumbar spine by strengthening your abdominal muscles, you counteract not only excessive lordosis, but also excessive thoracic kyphosis and neck contractions as well.
The rectus abdominis is the most superficial (i.e. closer to the surface of the skin) of the abdominal muscles, and this is the muscle responsible for the “6 pack” that can so often be coveted by fitness enthusiasts. But quick side note, while definition of this muscle is desired by many for aesthetic reasons, the rectus abdominis isn’t really the strongest muscle of the abs. It originates at the bottom center of the pubic bone, and it inserts onto the cartilage of ribs 5 – 7. The rectus abdominis flexes the vertebral column (i.e. bends it forward) and tilts the pelvis posteriorly (i.e. rotated backward).
The external obliques are found on the sides of the abdomen area. The external obliques originate on the external surfaces of ribs 5 – 12, and they insert onto the top of the hip bone at the front of the body. Working unilaterally, the external oblique laterally flexes the vertebral column to the same side AND rotates the vertebral column to the opposite side. Bilateral activation of the external obliques flexes the vertebral column (spinal flexion) AND posteriorly tilts the pelvis.
The internal obliques are also found on the sides of the abdomen area, but they are mostly deep to (or below) the external obliques. The internal obliques originate from the top of the hip bones at the front of the body, and they insert into the cartilage of ribs 8 – 12. Working unilaterally, the internal obliques laterally flex AND rotate the vertebral column to the same side (in contrast to the external obliques, which rotate the spine to the opposite side). Bilateral activation of the internal obliques helps to flex the vertebral column (spinal flexion), posteriorly tilt the pelvis, AND increase tension in the thoracolumbar fascia.
The transverse abdominis (sometimes referred to as “transversus abdominis”) is the deepest of the abdominal muscles. It originates from several places – the top of the hip bones at the front of the body, the thoracolumbar fascia, and the cartilage of ribs 6 – 12. The transverse abdominis inserts onto a few places as well – the bottom of the breast bone and the bottom of the pubic bone. Of all the abdominal muscles, the transverse abdominis has the most extensive and consistent attachments into the thoracolumbar fascia, followed closely by the internal oblique muscle. Thus, the functioning of the transverse abdominis, re: strength and mobility, can have pretty powerful implications for low back mechanics. The transverse abdominis essentially has two main functions. One, when it contracts it can help to compress the abdominal contents, which is important when lifting heavy objects. Two, bilateral activation can help to stabilize the attachment sites for the other abdominal muscles, helping to keep the spine stable. The transverse abdominis appears to function more as a stabilizer for the abdominal and spinal muscles rather than actually generating torque for spinal movement.
Additional Low Back Myofascia
There are three additional muscles that have attachments to the lumbar vertebrae, and thus, they can affect the mechanics of the low back. These muscles are the quadratus lumborum (known as the “QL”), the psoas major (typically referred to as the “psoas”), and the diaphragm.
The bilateral QL (pictured below) is the deepest muscle of the abdomen, and it is located on the posterior (i.e. towards the back of the body) abdominal wall. The QL originates from the top of the hip bones on the back side of the body and inserts on the last (12th) rib AND the 1st – 4th lumbar vertebrae. Due to its attachment sites, the QL can absolutely affect the biomechanics of the low back. Working bilaterally, the QL can assist respiration by stabilizing the lower rib cage, particularly during forced inhalation and exhalation. Bilateral activation can also help with extending the vertebral column (i.e. bending the spine backwards) and stabilizing the spine vertically. Unilateral activation of the QL can elevate one side of the pelvis (i.e. hip hiking), such as when stepping over something during walking. Unilateral QL activation can also side-bend (or laterally flex) the vertebral column to the same side, such as when raising yourself up from a side-lying position. Spasms in the QL muscles are a common source of LBP.
The bilateral psoas (pictured below) is a long muscle located deep to (or below) the abdominal contents. The psoas muscle exerts a very powerful kinetic influence across the entire trunk, lumbar spine, and hip joints. Thus, tightness or weakness in this muscle can negatively affect the biomechanics and force transmission of the back, potentially causing LBP. The psoas originates at the lumbar spine and attaches to the top of the femur (i.e. hip bone). The psoas is primarily a hip flexor, drawing the femur toward the pelvis or the pelvis toward the femur (click here to read more about the different movements at the hip joint). The psoas can also anteriorly tilt the pelvis (i.e. rotating the pelvis forward), which increases the lordosis of the lumbar spine. Unilaterally, the psoas can help to laterally flex (i.e. side-bend) the lumbar spine. The psoas may also help to stabilize the lumbar spine. You use your psoas to hike, climb, walk up an incline, and when getting up from a reclined position.
The diaphragm (pictured below) is your primary breathing muscle (click here to read more about breathing physiology in general). You might be wondering why I would include the diaphragm in a blog series about LBP. Well, the diaphragm is important for low back functioning for three reasons. One, if the diaphragm is not working quite right (e.g. reduced mobility, endurance, etc.), it can affect breathing mechanics, which can then have far-reaching effects across the entire body, including the low back. Two, the diaphragm partly attaches to the upper two or three lumbar vertebrae. Hence, it can have a direct impact on the low back, particularly if it is tight, rigid, or weak. Third, the diaphragm also helps to control intra-abdominal pressure, which can help stabilize the spine and maintain posture. Thus, maintaining adequate ROM and strength in the diaphragm is super important for preventing, or alleviating, LBP.
Summary
Phew! That was A LOT of anatomy! Thank you for hanging on with me until the end. As you can see from this blog post, the anatomy of the low back area is incredibly complex, with many muscles attaching to, or near, the lumbar region. These muscles can directly, or indirectly, affect the biomechanics of the low back, particularly if the muscle is too short or too long (more on this in part II of this series). Some muscles have attachments to the lumbar spine, while causing movement elsewhere in the body, such as the latissimus dorsi. Other muscles attach to the lumbar spine and affect motion in the hips or pelvis, such as the psoas or QL. Still, other muscles work to stabilize the lumbar spine, rather than causing large movements, such as the multifidi. And, other muscles work to create large, gross motor movements of the spine, such as the erector spinae. The abdominal muscles help to both stabilize AND move the spine. Lastly, the diaphgram, while considered the chief breathing muscle, can also have a huge impact on the lumbar spine due to its attachment sites. In my opinion, having an understanding of your own anatomy can make you feel more empowered and help you make informed decisions that are best for your body. In part II of this series, I will go over more information about CLBP, pain itself, and some of the causes for CLBP. Thanks for reading!
As always, the information presented in this blog post is derived from my own study of neuroscience, human movement, anatomy, and yoga. If you have specific questions about your low back, please consult with your physician, physical therapist, personal trainer, or private yoga teacher. If you are interested in private yoga and/or personal training sessions with me, Jackie, email me at info@lotusyogisbyjackie.com for more information about my services. Also, please subscribe to my website so you can receive my weekly newsletters (scroll to the bottom of the page where you can submit your email address). This will help keep you "in-the-know" about my latest blog releases and other helpful yoga and wellness information. Thanks for reading!
~Namaste, Jackie Allen, M.S., M.Ed., CCC-SLP, RYT-200, RCYT, NASM-CPT
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