Superb Health

Know your back and whats going on with it. Part 1

August, 2009

Prepared by: Shane J. Lynch, D.C.

Harrison, DE et al. A review of biomechanics of the central nervous system-part III: Spinal cord stresses from postural loads and their neurologic effects. J Manipulative Physiol Ther 1999; 22(6): 399-410.

In this literature review the authors reviewed eighty-four studies that support the hypothesis that posture can have profound effects on our health. Specifically, the authors show that changes in the curves of the spinal column (twenty-four vertebrae and sacrum) can expose the spinal cord (bundles of nerve fibers that transmit nerve impulses/information between the body and brain) to various stressors by constricting its blood supply and putting it into contact with the surrounding spinal column causing varying degrees of compression . The authors suggest “that most pathological and neurological diseases of the spinal cord can be ascribed to the combination of both spinal cord tension and transverse loading (i.e. The blood flow to the spinal cord is reduced due to alterations/changes of the shape of the spinal column) and degenerative conditions (bone on nerve contact, for example). The following are key points from this paper.

* “The area where cardiac and respiratory nuclei (i.e. area that maintains control of heart and lung function) are located (brainstem ) deforms more than the entire thoracic spinal cord (this area is roughly located from the bottom of your neck to the beginning of your low back; twelve spinal segments long) during postural rotations and axial translations”.
* This simply means that changes in posture, such as when tucking your chin to your chest (neck flexion), initiates enough tension at the spinal cord to change the shape of the brainstem (bottom part of the brain located in the skull) where important centers that control heart and lung function reside. From this statement, it can be deductively reasoned that “deforming” this area in the brain can also affect cardiac and respiratory function.
* “Altered alignment of the spine, abnormal rotation, and translation (side to side motions) of human posture are known to increase the rate of bone formation and can lead to osteophyte (new bone) formation and early disk degeneration ( i.e. disc herniation)”.
* The formation of osteophytes in and around the spinal column and disc degeneration increases the likely hood of spinal cord and nerve compression syndromes. This type of mechanical pressure on these structures causes loss of function (muscle weakness, internal organ dysfunction, etc) and sensory distortions (loss of balance, touch and vibratory sense, numbness, pain, etc.).
* “The elongation of the spinal cord from flexion of the spine results in increased strain of the longitudinal (up and down) vessels (blood) of the cord. The anterior (located in front of the cord) vessels will be drawn out and have a slightly decreased lumen (opening in blood vessels where blood passes through).” The blood vessels supplying the posterior (back) portion of the cord are similarly strained.
* Flexing the spine strains the blood vessels of the spinal cord and consequently decreases the blood flow to these structures.
* “ The radicular and medullary arteries and veins (i.e. those supplying nerve roots that directly attach to the spinal cord) will be under tension and thus narrowed, with an increase in spinal canal length (i.e. such as through neck and trunk flexion) and will be relaxed in the extended posture (looking up for example).”
* Cerebrospinal fluid (CSF) is produced by the ventricles located in the brain and this fluid is responsible for surrounding the brain and spinal cord, providing a cushioning effect, nutrients, waste removal and message transmission. The movement of CSF around these structures occurs via pulsations provided by the arteries and veins supplying the spinal cord and canal. “When an abnormal static (i.e. not related to movement, meaning that through years of poor posture or due to some type of trauma the curves of your spinal column change. Normally straightening of the cervical (neck) curve occurs when flexing your chin to chest, but this can also occur with poor posture) posture is maintained such as kyphosis (curve of spine reverses) of the cervical (neck) or lumbar (low back) spines or thorax (mid-back) then this normal pumping action (i.e. movement of CSF) of the cord is impaired”.
* With elongation of the spinal cord, such as through posture related changes in the curves of the spine, there is an increase in the fluid pressure that surrounds this structure which decreases the efficacy of oxygen and metabolic (nutrients) and waste product materials passing to and from the cord. “Increased pressure in or around the cord is known to cause a decrease of afferent and efferent impulse conduction (i.e. a decrease in nerve activity) and will increase the risk of damage to the neural and supporting tissue”. Specifically, there is “derangement of neural tissue”, meaning that nerve cells die off as a result of a decreased oxygen supply, nutrient delivery and waste accumulation.
* Physiological changes are known to occur in astronauts exposed to micro-gravity conditions (space flight). Under these conditions the spine is de-compressed, which results in an increase in the height of the spinal column by approximately 7 cm. (Aside: The spinal cord is a downward continuation of the brain and is composed of nerve cells that relay information between the body and brain. The spinal column surrounds and protects the cord and is composed of 24 vertebrae and the sacrum at the very bottom of these structures. The spinal cord descends down to the 21st vertebra and is attached/anchored to the sacrum via connective tissue. Space travel reduces gravitational forces on the spinal column allowing it to straighten out resulting in tethering/stretching of the spinal cord. As discussed earlier, flexing your chin to chest, flexing at the hip and loss of spinal curves via trauma and poor posture also “decompresses the spine” and increases its height).
* The stress and strain occurring at the spinal cord as a result of lengthening of the spinal column causes a wide range of neurological dysfunctions found in astronauts and is referred to as “microgravity-related physiologic phenomena”.
* “Microgravity-related physiologic phenomena consists of nutritional, metabolic, cardiovascular, neuro-vestibular (balance), otolith-spinal reflex (associated with hearing), sensory, motor and autoimmune (internal organ) dysfunction such as hyperreflexia (over activity) back pain, paresthesia (abnormal, odd sensations) and muscle atrophy (decrease in muscle mass/size) were also associated”.
* “Tension in the spinal cord is transmitted several segments distal (away from) to the generated stress, and if large enough, it will be distributed throughout the entire spinal cord and (associated) nerve roots”.
* “The pathological (disease causing) changes in the spinal cord caused by transverse loads (this occurs when the spinal cord comes into contact with the spinal column as a result of degenerative changes occurring in conjunction with a loss of a spinal curve) is ascribed to varying degrees of ischemia (decreased blood flow to the spinal cord).
* “Postmortem (after death) evaluation of spinal cords of individuals with MS (multiple sclerosis) revealed deformed blood vessels with hyalinization (tissue hardens) organized thrombi (blood clots)and or complete occlusion, leading to myelomalacia (“morbid” softening of the spinal cord), gliosis (damaged areas of the nervous system) and local shrinking (of nerve cells)”.
* The authors hypothesized that two types of MS may exist; “an autoimmune response (this occurs when our cells go haywire and begin to attack surrounding tissue; the body attacks itself) of unknown cause and one caused by, or associated with myelin breakdown due to chronic or recurrent cord compression, leading to an autoimmune response”.
* “There is suggestive evidence that progressive neuronal dysfunction and degenerative changes may be counteracted, slowed or even reversed. This is only true is the stresses and strains are alleviated or eliminated”.

What you can do:

* Be aware of your posture. When standing make sure that your head is centered and that it is not leaning forward. To get an idea of what this posture feels like, stand against the wall with your heels, hips, shoulders and head all touching, then step away. Another option is to have a family member or friend observe your posture from the side. Ask them to be especially aware that your head is lined up with the center of your torso. Continue to do this on a daily basis to get an idea of what a proper posture feels like and with time it will be easier to maintain.
* When seated make sure your head is lined up with the center of your torso, your shoulders with your hips, your knees should be bent at ninety degrees and your feet flat on the ground. This is especially important if you are seated at the computer. In addition to the above recommendations, make sure your monitor is at eye level and the desk is situated at a height that allows your elbows to bend at ninety degrees. If lounging, at least make sure that your head is centered and your shoulders are lined up with your hips.
* Get chiropractic adjustments. A subluxation, or spinal misalignment results in a weakness at that area of your spine, which in turn off-shoots the proprioception (balance and coordination) centers of the brain. In response the brain initiates body wide muscle contractions to compensate for the weak area(s). If misalignments are substantial enough it is believed that anterior compartment flexors (muscles in front of body), such as neck flexors (these muscles normally contract to flex the chin to chest and if activated in a normal standing posture, they could straighten the cervical/neck curve, which lengthens the spine and exerts tension on the spinal cord) are continuously activated eventually effecting the curve of the spine.