How adjustments improve proprioception

How Chiropractic Joint Manipulation / Adjustment helps improve proprioception.

 

The effects of normalizing proprioception and fine motor tuning:

 

1.     Enhanced kinesthetic perception, agility and balance.

 

2.     Increased range and symmetry of motion.

 

3.     Improved joint stability.

 

4.     Better coordination and balance of muscle tone.

 

5.     More symmetrical load distribution, less localized biomechanical stress.

 

6.     Component of optimizing performance.

 

7.     Reduced risk of injury and degeneration.

 

 

McCloskey, (School of Physiotherapy and Pharmacology).  Physiologic Reviews.  1978; 58(4):  763-820.  The greatest level of afferent firing occurs at or near the extremes of flexion and extension with comparatively little activity in between.  Units’ rate of firing is related to rate of displacement.  The nearer the joint approaches maximal extension or flexion the greater the number of units active and the greater their discharge frequencies.

 

Zimny, (Dept. of Anatomy).  American Journal of Anatomy.  1988; 182:  16-32.  Joint and muscle receptors detect limits of movement of a joint and play a role in synchronizing mechanisms involved with control of movement.  The densities of mechanoreceptors are greater in areas related to extreme movements.  Mechanoreceptors are the first line of defense in sensing the safe limits of range of motion of a joint.  Discharges provide the central nervous system with information about possible joint injury.  This input activates reflex mechanisms that act to prevent joint injury.

 

Schaible, HG, Gribb, BD.  (Department of Physiology).  Pain.  1993; 55:  5-54.  Reflexes from joint afferents are important in eliciting protective muscular responses.  Afferents help regulate joint stability through discharges in gamma-motoneurons.  Articular mechanoreceptors are activated by innocuous movements and exhibit an immediate increase in their discharges when the joint is being moved to the extreme of the working range.

 

McLain, M.D.  Spine 1994; 19(5):  495-501.  Articular proprioceptors respond primarily to the extremes rather than to the mid ranges of joint motion.  They may initiate protective muscular reflexes important in preventing joint degeneration and instability.  Altered mechanoreception has a direct effect on reflex activity of muscle crossing the joint.  Joint deafferentation may accelerate degenerative changes.  Disturbance of articular innervation may play a role in the development of degenerative and inflammatory diseases and joint dysfunction.

 

Michelson, M.D., Huthcins, M.D.  Journal of Bone and Joint Surgery.  1995; 77-B(2) March:  219-224.  Type III mechanoreceptors provide sensation at the extremes of movement and act to alert the central nervous system of imminent danger to the joint.  Ligaments provide more than structural support.  Sensory output from ligaments aid in controlling muscle stiffness and coordination, thereby increasing joint stability.  Mechanoreceptors influence gamma motoneurons output, and thereby, the discharge of alpha motoneurons, enhancing muscle contractility.  At the extremes of motion, mechanoreceptors elicit protective reflexes to prevent injury to the joint.

 

Kirkaldy-Willis, M.D., Cassidy, D.C., Ph.D.:  Canadian Family Physician.  1985; 31: 535-540.  Articular mechanoreceptor stimulation has a reflexogenic effect on motor unit activity in the muscles operating the joint.  Stretching the facet joint capsules can reflexively inhibit facilitated motoneuron pools which are responsible for the increased muscle excitability and spasms that commonly accompany low back pain.  In more chronic cases, there is shortening of periarticular connective tissue and intra-articular adhesions may form.  We believe that in some cases, manipulation will stretch or break these adhesions.  Through these mechanisms spinal manipulation can break the cycle of pain, muscle spasm and immobility.

 

Nansel, Ph.D., Slazak, D.C.  Advances in Chiropractic 1994; 373-415.  Joint capsule proprioceptors connect with gamma-motoneurons and can alter the sensitivity of muscle spindles causing disturbances in muscle tone and restricts motion.  Gapping of the joint by spinal manipulation induces a sudden burst of capsular afferent activity which can cause reflex decreases in muscle tone allowing for an increase in joint movement.  Postural muscles (multifidi, rotatores, etc.) can sustain contractions for long periods.  Asymmetries in their contractile state can account for asymmetries of range of motion.  The sudden stretch of muscles by spinal manipulation causes increase in tension stimulating golgi tendon receptors to inhibit alpha-motoneurons, relaxing muscles.  Such changes in muscle activity can last for hours, sometimes days.

 

Thabe, M.D., Manual Medicine.  1986; 2:  53-58.  Spinal manipulation applied to restricted atlanto-occipital joint results in an immediate disappearance of spontaneous activity in the oblique capitus superior muscle.  With spinal manipulation this is more rapid than either anesthetic applied to the joint capsule or to the muscle directly.

 

Murphy, D.C., Ph.D.  et al.  Electromyographic Clinical Neurophysiology.  1995; 35:  87-94.  Study of the effect of spinal manipulation or a sham manipulation of the sacroiliac joint on the  Hoffman (H) reflex (a monosynaptic reflex induced by electrically stimulating an afferent nerve eliciting an alpha motoneuron  response) by stimulating the tibial nerve and measuring the response in the soleus muscle in asymptomatic subjects.  H-reflex response was decreased (12.9%) in the ipsilateral leg post spinal manipulation but no change post sham.  An anesthetic cream was applied to the skin over the SI joint and SM was repeated.  There was still a decrease in reflex excitability suggesting the reflex changes are mediated by joint and or muscle afferents, not skin receptors.

 

Murphy, D.C., D.A.B.C.O..  American Journal of Clinical Chiropractic.  1997; 7(2):  23-24.  Golgi tendon organs (GTOs) are high threshold receptors and their input in inhibitory.  Because their threshold is higher than muscle spindles, it is difficult to have GTO input to the spinal cord be the predominate influence on alpha motoneurons.  Recent studies show that a fast stretch force of sufficient magnitude will primarily fire GTOs causing inhibition of alpha motoneurons ipsilaterally.  Speed appears to be a critical factor.  Insufficient speed will primarily fire low threshold muscle spindle resulting in excitation of alpha motoneurons and will perpetuate the increased muscle tone and biomechanical problems.  Fast stretch that fires GTOs achieves inhibition of alpha motoneurons.

 

Gillette, MS.  Manual Medicine.  1987; 3:  1-14.  Adjustive force (average 180 Newtons) was more than enough to stimulate every type of mechanoreceptor and nociceptor in all tissues which the force is transmitted, thereby generating a marked afferent barrage of the central nervous system.

 

Vernon, D.C.  Journal of Manipulative and Physiological Therapeutics.  1986; 9(2):  115-123.  Mechanisms of Pain Relief with Adjustments.  Spinal manipulation will cause stimulation of the dorsal columns stimulating supraspinal mechanisms of pain control including endorphin production via the hypothalamus-pituitary axis, and via the central raphe as well as segmental stimulation of met-enkephalin.

 

Cramer, D.C., Ph.D., Darby SA, Ph.D.  Topics in Clinical Chiropractic.  1996; 3(3):  1-8.  Neurotransmission of pain can be modulated at the segmental level- the Gate Control Theory.  Increased activity of large diameter, low threshold mechanoreceptive afferents competitively inhibit transmission of nociception to the higher centers.  Inhibition of nociceptive neurons is due to interneurons in lamina II (substantia gelatinosa) which use enkephalins as neurotransmitters.  These neurons receive excitatory input from large diameter fibers and in turn, inhibit projection (spinothalamic tract) neurons.  Supraspinal Control of Nociception:  descending pathways can also modulate nociceptive input.  The periaqueductal gray matter (PAG) of the midbrain projects to the nucleus raphe magnus.  From here seritonergic fibers in the dorsolateral funiculus of the spinal cord (raphe-spinal tract) descend and synapse on neurons in the superficial dorsal horn (lamina I and II).  This is the region that receives input from nociceptive fibers and is also the origin of the spinothalamic tracts.  This area is also involved with segmental modulation of nociception.  Descending fibers synapse with inhibitory inter neurons containing enkephalin.  The inhibitory interneurons are close to both primary nociceptive afferents and tract neurons.  The nociceptive afferent endings and the dendrites of the tract neurons both contain opiod receptors.  Release of opiod peptides from inhibitory interneurons blocks transmission of nociception by 1) binding to receptors and blocking release of neurotransmitters like substance P from the primary afferents and by 2) directly synapsing with the postsynaptic membrane of the tract neuron.  Endogenous opiods, peptides found in the brain can activate the descending system.

 

Gating Mechanisms of Pain Modulation:  Mechanoreceptors transmit through large myelinated fibers and compete with and block pain at the substantia gelatinosa stimulating the release of met-enkephalin which inhibits transmission of pain impulses to the central nervous system, closing the gate in the Substantia Gelatinosa.  Nociceptors (NCs) with Substance P as a primary neurotransmitter inhibit substantia gelatinosa cells, inhibiting the release of met-enkephalins which, doesn’t block the central transmission of pain, therefore the gate is open.  Counterirritants:  various forms of stimulation which selectively stimulate mechanoreceptors without stimulating nociceptors, this helps block the central transmission of pain.  They include:  massage, acupuncture, spinolators, ultrasound, TENS, heat cold.  Adjustments also work as a counterirritant, because the thrust stimulates many populations of sensory receptors, but this is only a side effect.  The central goal of restoration to motion by chiropractic adjustments permits the previously immobile joint which was generating very little mechanoreceptive input when immobilized to now generate its own ongoing mechanoreceptive input because now it’s movement is restored.  This allows the body to dampen its own pain input and may result in long term pain relief.

 

 

Basmajian, M.D., Nyberg, PT, MSc.  Rational Manual Therapy.  William and Wilkins.  1993:  451-467.  Capsular or ligamentous injury results in loss and deactivation of mechanoreceptors.  The proprioceptive role of the affected segment is adversely affected.  Spinal manipulation may help activate inactive receptors and restoring proprioceptive control reduces the chance of reinjury and hence is an important consideration in preventive care.