The anatomical position has the spine in its erect posture, including its normal curvatures. Some of the true back muscles posterior to the spine maintain our normal posture. These are skeletal muscles, and, if I tell you to sit up straight, you can activate those muscles voluntarily. But all day long, subgroups of muscle cells in our postural muscles take turns stabilizing the spine.
Strong yet Flexible
Sitting up straight really doesn’t wear us out—our butt gets tired of sitting long before our back does. We don’t even have to think about that, it’s part of our muscle memory, which is subconscious control that is learned in infancy. When we want to flex the spine, however, as in touching our toes, we use muscles anterior to the spine, like our abdominal muscles.
For rotation, we also primarily use abdominal muscles, but we do have some obliquely oriented muscles posterior to our spine that aid twisting motions of the trunk. Plus, as we will see in an upcoming lesson, a unique group of muscles govern the important head-turning movements that happen between the atlas and axis vertebrae.
Some laterally placed muscles, including some true back muscles and some in the abdominal wall, help us with lateral flexion of the spine, as in a side bend. Some of these anterior abdominal muscles are often called muscles of the core, and as you probably know—especially if you are a fitness enthusiast—a strong core is key to maintaining a healthy back. And a healthy back is not only important to posture, but It’s also important to support the entire trunk of the body during movement.
So, the body has this central axis of vertebrae that is both strong and flexible. We have two kinds of joints to keep the spine stable—the intervertebral discs uniting adjacent vertebral bodies, and the synovial joints that unite the superior and inferior articular facets of adjacent vertebrae.
Why Stabilization of the Spine Is Important
Then we add the series of ligaments that support the spine from nearly all directions. On top of that, we have numerous muscles that prop up the spine. Really, from every angle, and from many surrounding structures, comes the net result of stabilization of the spine.
Why is that so important? The spinal cord is within the canal that runs down the stack of vertebrae, and The spinal cord is the conduit that allows for communication between the brain and the peripheral nerves. This includes both the motor pathways for controlling the muscles, and the sensory pathways that connect the skin, joints, and muscles to the brain.
This not only helps us perceive stimuli—from pain to touch—but it also helps us balance. And I don’t just mean for a gymnast or other athlete; balance is absolutely essential for any animal—human or otherwise—if they are to successfully navigate their environment, capture food, and escape from danger.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Where Does Back Pain Come From?
So, if the support of the spine is so essential and is so reinforced, then why do so many people have back problems? Published estimates indicate that nearly 80% of us will have some sort of back pain during our lifetime.
One university study estimates that each year about 8% of adults in the United States suffers from back pain—whether chronic or acute—and concludes that back issues are the sixth most costly medical condition in the US, affecting people of all ages and socioeconomic levels, and routinely causing issues with work productivity.
Numerous research studies have shown that the upright posture and bipedal locomotion, characteristic of humans, is correlated with a variety of spinal pathologies. A fellow anatomist who is also a paleoanthropologist has said that taking the primate spine from the horizontal pattern that was ideal for an arboreal—tree-dwelling—lifestyle to the upright pattern in humans was like placing the skull atop a series of 26 cups and saucers stacked on top of each other and expecting that to go well.
Changes in the spine—from the straight spine of most other primates—to the modern spine we bear today, with its primary and secondary curvatures, occurred relatively quickly during human evolution. These modifications can be tracked in the fossil record, and by comparing the spine of modern apes to our own.
The bottom line is that the human vertebral column is definitely not designed for the stresses and strains of upright posture, but rather has been co-opted to accomplish it. After all, evolution is not goal-oriented—and playing on the words of the great Lisa Simpson, “Perhaps there is no moral to this story,” to which Homer replies, “Exactly, it’s just a bunch of stuff that happened!”
Nevertheless, the end result of this spinal jury-rigging is the widespread back pain seen among humans, but that is paired and offset with the increased functionality we have gained in the process. Maybe that’s the moral of the story.
Common Questions about the Spine and Back Pain
This stability of the spine is caused by two kinds of joints: the intervertebral disc bodies and the synovial joints.
The spinal cord within the canal which runs down the stack of vertebrae helps our body balance. It connects the skin, joints, and muscles to the brain and helps us balance, and this is essential for any animal.
It’s because the human spine is not designed for the stresses and strains of upright posture. Our bodies rather have been co-opted to accomplish it. This results in widespread back pain among humans.