Spinal Stabilization part 1

By Ann West

This is part 1 of 3 part a series on Spinal Stabilization.

Many people who suffer from back pain know that developing a strong, awake core is essential for spine health. But did you know that there are two layers of core muscles – an inner layer of stabilizing muscles that connect directly to your spine, as well as an outer, supporting layer?

Researchers have discovered that for many persistent back pain sufferers the inner layer of muscles are caught up in a continuous cycle of misfiring or not engaging at all. The outer layers then react by overcompensating and often end up tight or in spasm. It only takes one of the inner layer muscles to ‘forget’ how to fire to become stuck in this continual pain cycle, and until it relearns how to engage correctly the problem will persist.

This post explains how an injured spine can get caught up in this negative cycle.

The moving spine

Spinal joint & disc backward bending (left) & forward bending (right)

There are 24 articulating joints in the vertebral column that move constantly by sliding and tilting in motion with the rest of the body. Almost every time you make a move, your spine does too.

These motions must be controlled so the spine can move efficiently and safely. In a healthy, normally functioning spine they are held in check by the discs, ligaments, inner layer muscles and outer layer muscles.

There are three layers to the trunk, each with a specific function:

1. Deep layer

The deep trunk layer is primarily made up of the vertebrae, discs and ligaments. Spinal discs and ligaments offer the first line of defense against excessive movement by providing a small degree of stability to the spinal joints. However, they are relatively weak and fragile, and unable to fully stabilize the spine without major support from the inner layer trunk muscles.

The discs and ligaments are also home to nerve receptors which relay sensory information to the brain via nervous system regarding spinal joint position.

Inner layer trunk muscles

2. Inner muscle layer

The inner muscle layer is made up of medium size muscles responsible for stabilizing and protecting the spinal joints in all postures. Inner layer muscles include the pelvic floor, transversus abdominis, multifidus and diaphragm. Some anatomists also include the quadratus lumborum and psoas as inner layer muscles.

All muscle action in the body is coordinated by the nervous system. The position sense information sent to the nervous system by the disc and ligament receptors is used to activate these inner layer muscles, which are specifically designed to stabilize the individual spinal joints.

3. Outer muscle layer

The outer muscle layer is made up of large, powerful muscles which move the spine and maintain the overall posture of the spinal column in almost all movement, including lifting heavy loads. The outer trunk muscles include the rectus abdominus, internal and external obliques, erector spinae, latissimus dorsi, and gluteal muscles.

If any part of the spine is injured two serious problems can develop:

The injured joint begins to move excessively, which can cause pain to be felt in the lower back and/or down the leg.
The positional information sent to the nervous system by the spine receptors is impaired, making it difficult for the nervous system to activate muscles, especially the inner layer muscles.

Inner layer muscle problems

When the spine’s deep layer is injured the transversus abdominus and the multifidus muscles fail to activate correctly because the nervous system no longer has optimal control over them due to the spinal position receptors being impaired. Both of these muscles are key ‘first-responder’ spine stabilizers that would normally protect the injured spinal joint. Just when the spine needs extra protective support, these crucial muscles are unable to step into their role. This can happen rapidly and last indefinitely, even after the initial pain appears to have settled.

Outer layer muscle problems

Injury to the deep trunk layer and firing problems with the inner muscle layer can also have a knock on effect to some of the outer layer muscles, causing them to go into spasm. While spasm is uncomfortable it is mainly a symptom of a greater underlying problem.

Spasms can occur when the nervous system experiences difficulty activating the inner layer muscles following an injury. The nervous system still recognizes the injured spinal joint needs support, so it uses the next best thing at its disposal to prevent movement at the vulnerable joint – the outer layer muscles. However, the outer layer muscles are not built for single joint stabilization. Therefore, the nervous system must dramatically increase the level of activation at the injury site so the larger outer layer muscles can offer some degree of splinting and stabilization.

The above situation occurs in nearly all people with lower back pain and can lead to a viscous cycle of further problems as the joints, discs and nerves are left unprotected because the protective inner layer muscles no longer activate properly.

Types of back pain & core stability exercises

The majority of acute back pain is caused by mechanical injuries and pathologies including injuries from trauma (strains and sprains), age related wear and tear (degenerative discs and osteoarthritis), and genetic conditions (scoliosis, stenosis and hypermobility). All of these mechanical problems have the potential to be positively impacted through regular practice of therapeutic core stability exercises.

Back pain with atypical causes including infections, tumors, referred pain, centralized pain and stress all need to be treated according to their root cause and will not respond as readily, if at all, to core stability exercises.

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