Spinal Hygiene: Part 2 by Johnny Cooke
In Spinal Hygiene: Part 1 we discussed the importance of spinal hygiene to remedy or prevent back pain and to improve overall spine health. In Part 2, we will examine the architecture of the spine and how it’s 3 distinctly different levels all perform different functions. Let’s dive in…
The spinal column is comprised of 33 individual bones called vertebrae that are stacked on top of one another. Of these vertebrae there are 24 that are moveable, and each of them have bony protrusions called processes that serve as anchors for muscles, tendons, and ligaments. The actual joints of the spine are called facets of which there are 2 for every disc. These facet joints guide the motion that is available at each spinal level (more on this later). Between each vertebrae lie intervertebral discs comprised of outer rings of collagen and an internal nucleus. These discs support load between the vertebrae and allow for motion and shock absorption.
The 24 vertebrae, their processes, their facet joints, and the discs, are divided into 3 categories according to their geography. Each of these 3 “levels” have unique architecture, and therefore unique function and available motion. The 3 spinal levels, from top to bottom, are the Cervical Spine, the Thoracic Spine, and the Lumbar Spine.
The Cervical Spine is comprised of 7 vertebrae (C1-C7), the hyoid bone, and the manubrium of the sternum. It assumes a lordotic curve (C shape) as its neutral position. The Thoracic Spine is comprised of 12 vertebrae (T1-T12), the rib cage, and the lower sternum. It assumes a kyphotic curve (reverse C) as its neutral position. The Lumbar Spine is comprised of 5 vertebrae (T1-T5), and the Sacrum. It assumes a lordotic curve (C shape) as its neutral position. Looking at the spine from a side view, normal curvature of all 3 levels combined resembles a soft 'S' shape. When viewing the spinal column from behind, the spine will appear vertically straight.
In addition to the unique curvature at each level, the size of each vertebrae and its processes, and the particular orientation of its facet joints, dictate the function and primary motion of each level . It is true that to some degree every level of the spine can flex, extend, and rotate. However, the percentage of contribution at each level to these motions should be predictable and purposeful to reducing unnecessary wear and tear. Below is a brief overview of the type of motion that each level best provides.
Cervical Spine; rotation at the Atlas (C1), and both flexion and extension at C2-C6. Interestingly, C2-C6 offer minimal rotation, and C7 acts as a base of support for the flexion and extension between C2-C6.
Thoracic Spine; T1-T12 offer the greatest amount of rotation of all 24 moveable vertebrae. T1-T12 offer moderate amounts of flexion and modest (if not minimal) amounts of extension due to large and inferior facing spinous processes.
Lumbar spine; L1-L5 are well suited for flexion and moderately capable of extension (forward and laterally). L1-L5 have minimal rotation due to its vertical facet joints and rely heavily upon the thoracic spine and the hips when rotating in space.
Right now, you might be asking why it is important to understand the architecture of the spine and its motion? Glad you asked… Understanding what the spine is intended to do and the types of forces it can favorably can produce or reduce, is critical to exercise selection and design. In essence, sound decisions about how to properly and safely train the muscles of the spine inherently require this knowledge. In an upcoming article we will identify some dos and don’ts of “core” training, taking into account everything that we have learned up to this point.