The human body is capable of a wide variety of types of movement. We can do everything from walking upright, to coordinating pedals, steering, and shifting to drive a car, to fancy dance movements, and yoga. Our anatomy is one important key to how we do all those things, how we move. Even seemingly straightforward movements like walking and running actually require complex coordination of many parts of our body. In this article, I want to focus on one particular part of our anatomy, the lumbar spine. Let’s take a look at how its shape, location, and other characteristics impact common yoga poses.
General anatomy of the lumbar spine
Anatomically, we divide the spine into three regions. This makes it easier to be clear about which region we’re talking about. But functionally, we still have one connected spine. The lumbar spine is the most inferior (farthest from the head) section of the spine. It is usually composed of five vertebrae, named from superior to inferior as L1-L5. However, there is some variability in the number of vertebrae in the lumbar spine throughout the human population. Although the vast majority of people have five lumbar vertebrae, the number of vertebrae in the lumbar spine can range from four to six.
The overall shape of the lumbar spine is curved in toward the body and is often referred to as a lordotic curve. But, it’s also known as a secondary curve. Before we’re born, our whole spine is in a flexed position. So it’s basically one long curve in the same direction. That is our primary curve in the spine. During various stages of our development, through actions like learning to hold our head upright, we create two curves going in the opposite direction. Those are our secondary curves. The curves in our spine add to its stability, strength, and mobility.
Lumbar vertebrae shape
Within the lumbar section of our spine, the vertebrae have a particular shape that is unique to that section. The bodies of the vertebrae (the bony area that the discs sit between) in the lumbar section are generally wider and thicker than those of the cervical and thoracic vertebrae. Additionally, the spinous processes (the bony part that sticks out on the back) of the lumbar vertebrae have a shape that is particular to that spinal section. The spinous processes are larger and more rounded in the lumbar spine than in other sections of the spine. And they have more space between them. The surfaces where one vertebra connects to the vertebrae above and below (the facet joints) are also more vertically oriented compared to other sections of the spine. This allows them to slide relative to one another very well when we flex, extend, and hyperextend the spine.
Functions of the lumbar spine
One important function of the lumbar spine is weight bearing. This section of the spine is at the bottom of the chain. All the weight of the torso is above it, so the size of the vertebrae reflects this function. Even within the five lumbar vertebrae, the size and angle of their position change as you go from inferior to superior. L5 is the largest and the vertebral body is angled down and forward more than you might expect. This angle persists, but reduces, as you make your way up the lumbar section. We even have additional ligaments that help hold the L4 and L5 to the top of the sacrum, likely because of the improbable angle of these last two vertebrae.
The thoracolumbar junction
The lumbar spine is bordered on each end by a transition section of the spine. On the superior end, the lumbar spine meets the thoracic spine above it at what is called the thoracolumbar junction. The thoracolumbar junction is the area from T-11 or T-12 through L-1 or L-2. In this area, where the thoracic vertebrae meet the lumbar vertebrae, the angle of orientation of the vertebrae transitions from being more in the horizontal plane to being more in the sagittal plane. Or you could describe this area as where a primary curve going in one direction meets a secondary curve that goes in the opposite direction.
The lumbosacral junction
On the inferior end, the lumbar spine connects to the sacrum. They meet where L-5 articulates with the superior surface of the sacrum. The superior surface of the sacrum is actually the first sacral vertebrae in younger people. Before age 30 or so, the five sacral vertebrae have not yet completely fused into a single structure. Like the thoracolumbar junction, at the lumbosacral junction, we have a primary curve going one direction meeting a secondary curve that goes the other direction.
Why are the spinal transition areas important?
The areas where the spinal vertebrae change shape, angle, or both are important areas to be aware of in the body. Because those are areas where vertebrae of different shapes meet one another, our available movement at those spots is a little more restricted than areas where the vertebrae are shaped similarly. Sometimes that also means that this is where we experience pain or dysfunction.
What holds the lumbar spine together?
The vertebrae in the lumbar spine are connected to one another by ligaments and muscles. There is more than one layer of connection within the area that we refer to as the lumbar spine. The lumbar spine is connected by more superficial muscles like some of the erector spinae as well as deep muscles like the multifidus. Specifically, the longissimus, spinalis, multifidus, quadratus lumborum, and psoas major all attach somewhere on vertebrae in the lumbar spine. There are also muscles that affect movement at the lumbar spine but don’t directly attach there, like latissimus dorsi.
The lumbar spine in yoga
The lumbar spine is critically important for our movement and that includes our movement in yoga. The anatomy of our lumbar spine is especially important for how we back bend, forward bend, and twist. The lumbar spine easily does flexion, extension, and side-bending. The shape of the vertebrae and how they are arranged support that ease of movement. The more vertical orientation of the facet joints and the greater space between the spinous processes mean that more movement in a forward and backward direction is possible. Due to the shape, orientation, and spacing of the lumbar vertebrae, twisting through this lower section of the spine is more restricted than in other parts of our spine. Let’s break each of these categories of poses down a little further and look at how our lumbar spine contributes to or potentially restricts our movement.
We can back bend fairly easily in the lumbar spine. But sometimes that is exactly what gets us in trouble in backbending. Because we can easily bend our lumbar spine, we tend to overemphasize it. In reality, this probably means we should deemphasize it. Instead, we should be intentional about maximizing our ability to back bend throughout the whole spine. This includes working with the difficult and elusive thoracic spine in backbending. In addition, when the pelvis is free to tilt posteriorly, backbending begins from the pelvis. Overemphasis on backbending from the lumbar spine can easily result in excessive compression and can cause discomfort or pain.
As with backbending, we can forward bend easily in the lumbar spine if other factors don’t prevent it, like tight hamstrings holding the pelvis in place. If those hamstrings are tight though, our ability to access the first part of a forward bend, the hip flexion, is reduced. Imagine that in a forward bend, the weight of your head and torso are pulling forward in one direction. Simultaneously, imagine tight hamstrings preventing your pelvis from rotating forward at the hip joint. You can see how the curve at the lumbar spine would be reduced. You could probably also imagine that the two forces pulling in opposite directions could potentially even lead to discomfort or pain in the lumbar area of the spine.
We don’t twist easily through the lumbar spine because of the direction of the facet joints. The bony connections of one vertebra to another bump into each other quickly when we twist. For that reason, it’s important to be intentional about doing most of our twisting through the thoracic spine, where twisting happens more easily. We should also be aware of not forcing more twisting than is possible through the lumbar spine. Doing so can put stress on the sacroiliac joint below as well as on the thoracolumbar junction. Being mindful of not forcing too much twisting through the lumbar spine can help avoid long-term pain or an injury.