Increasing Spinal Muscle Function (through Chiropractic Adjustments)

Slosburg’s article “How Spinal Manipulation Activates Segmental Stabilization of the Spine” has a section that explains the neurology of an HVLA (high-velocity, low-amplitude) adjustment in the lumbar spine and how it affects the ligaments and musculature of that region.  Slosburg writes:

Scientific Basis for Understanding the Influence of the Manipulative Thrust

The findings of the above studies provide a scientific basis for understanding one of the major effects of the HVLA thrust applied to dysfunctional joints. In essence, this is what happens: A joint that is injured, inflamed, degenerated, restricted in motion or painful results in reflex inhibition, delayed activation and progressive atrophy of the multifidus muscle innervated by that segment.

By clinical examination, the chiropractor identifies such a lesion (subluxation / joint complex dysfunction) and then applies a HVLA thrust to the joint. This high-velocity force rapidly stretches the segmental ligaments, joint capsules, intertransversarii and interspinales muscles, and intervertebral discs, and intensely stimulates their numerous stretch receptors. This results in ligamento-muscular reflex activation of the multifidus, which attempts to stabilize the joint and protect it from possible injury as a result of the high-velocity stretch. The segmental multifidus, which has been reflexively inhibited and is atrophying, is stimulated to contract. This may reverse the reflex inhibition, progressive atrophy, and delayed muscle response documented to occur in the segmental multifidus which overlies a dysfunctional joint; and restore dynamic function and contractility to this primary joint stabilizer.”

So, in understanding the mechanism for helping to facilitate function in the paraspinal muscles through the HVLA chiropractic adjustment, I read through the referenced articles to see if anything gave more insight into what would specifically cause dysfunction in the musculature in the first place (in this case, the multifidus).  

Sanchez-Zuriaga’s article “Is activation of the back muscles impaired by creep or muscle fatigue?” answers this question in regards to soft tissue creep (caused by sitting in a slouched forward flexion position) and muscle fatigue.  The study monitored levels of bilateral muscle activity in the multifidus muscles at two levels (T10 and L3) after 1 hour of soft tissue creep compared to muscle activity after the Biering-Sorensen test (measuring strength-endurance of paraspinal muscles using a modified Glute Ham Raise) to induce fatigue, and results were monitored before and after the tests.  The tests found that prolonged spinal flexion (leading to soft tissue creep) can impair sensorimotor control mechanisms and reduce back muscle protection of the underlying spine, and that this effect is due to time-dependent “creep” in soft tissues rather than muscle fatigue.

We can conclude from that that soft tissue creep has far worse detrimental effects on the musculoskeletal system than simply fatiguing spinal muscles, and that inactivity is worse than activity (feels dumb writing something so obvious).  Avoiding prolonged periods of sitting (1 hour according to the study, but perhaps as little as 20 minutes) will keep the integrity of paraspinal muscles, since their job is to stabilize the cord, absorb force from movement, which ultimately protect that spinal cord. If sitting is the only option, reversing the damaging effects of creep can be achieved (to some degree) through movement, training, walking, hanging, etc. A recommendation would be to move to a standing desk unit (if the patient worked in an office setting) and breaking with sitting if necessary, rather than standing as a break from sitting all day.


References:

França FR, Burke TN, Hanada ES, Marques AP. Segmental stabilization and muscular strengthening in chronic low back pain ‐ a comparative study. Clinics. 2010;65(10):1013-1017. doi:10.1590/S1807-59322010001000015.

Spine (Phila Pa 1976). 2010 Mar 1;35(5):517-25. doi: 10.1097/BRS.0b013e3181b967ea., https://www.ncbi.nlm.nih.gov/pubmed/20147877

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