1 04 SEaloN II CLINICAL OBSERVATIONS AND ADVANCED ASSESSMENT PROCEDURES
system, which is responsible for the motion and stabilization of the lumbar spine.
Solomonow et al. received the 1 999 Volvo Award in Biomechanical Studies for their work on the in vivo lumbar multifidus of
the cat. l 74 Biomechanical evidence indicates there is creep in the viscoelastic tissues of the spine that causes increased laxity in
the intervertebral joints, and that cyclic occupational functions expose workers to a tenfold increase in episodes of low back
injury and pain. The results of the study described for the first time the neurophysiologic process responsible for increased
exposure of the spine to injury and pain during cyclic loading. Investigators concluded the following:
1 . Laxity induced in the viscoelastic tissues of the spine (ligaments, disc, and joint capsule) by cyclic passive loading, as studied
in the in vivo feline lumbar spine, desensitizes the mechanoreceptors within and causes significant decreases or complete
elimination of reflexive muscular stabilizing forces in the multifidus muscles.
2. The decrease in activity of the multifidus muscle was most pronounced in the first 5 minutes of cyclic loading, with additional
decreases observed over the 50-minute period. Overall activity was decreased by 85% in the first 5 minutes, and by additional
subsequent 5% to 1 0% decreases.
3. During passive cyclic loading of the lumbar
spine, a significant decrease in reflexive muscular activity of the multifidus muscles was
linked directly to laxity in the viscoelastic
structures but excluded muscle fatigue, neurologic habituation, or both.
4. "A 1O-minute rest after a 50-minute cyclic passive loading of the lumbar spine results in a minor restoration of reflexive
muscular activity, which diminishes at an accelerated rate.
5. The compound effect of increased intervertebral laxity caused by creep in the ligaments
and disc together with the significant decrease
or elimination of reflexive muscular forces
from the paraspinal muscles during cyclic
activity fully exposes the lumbar spine to
instability and possible injury even when
subjected to unloaded activity.,,175
A 2005 publication by DeVocht et al. 1 76 collected surface EMG data on 1 6 participants who were divided into two equal
groups. One group received spinal manipulation following Diversified Protocol, and the other group Activator Protocol with the
use of an Activator II Adjusting Instrument. The authors noted that chiropractors frequently will palpate for tight muscle bundles
as an indication of where to adjust. It was
expected that through observation of preadjustment and postadjustment EMG recordings, the tight muscle bundles would be
associated with a higher EMG level, which would diminish after appropriate spinal manipulation (SM). "It was presumed that
elevated resting EMG levels would be indicative of some aberrant neuromuscular and/or biomechanical state that was correctable
by SM. Most of the cases observed were consistent with our expectations."I77 Investigators note that in three out of four cases, a
small increase in EMG activity from pretreatment was noted. They also reported that EMG recordings did not necessarily
correlate with the level of symptoms the patient had claimed. This study had limitations, but the results support the notion that
SM has a virtually immediate and presumable beneficial effect on at least some patients with low back pain; this resulted in lower
EMG activity associated with hyperactive paraspinal muscles. It also supported findings consistent with the belief that tight
muscle bundles are signs of spinal dysfunction that are correctable by SM.
Slosberg in three different publications4.51 gives an excellent review of the literature and explanations of how leg length
reactivity occurs within AM. He cites Denslow's work,8.1 78.1 79 published in the 1940s, in which he described locating areas of
hypertonicity by palpation and inserting needle electrodes into the areas of tight muscles. (In theory, some similarities may be
noted to the previous study by DeVocht et al. ) Denslow divided the areas of hypertonicity into "major" and "minor" lesions.
During relaxation, normal areas exhibited no spontaneous electrical activity; however, in 20 of 25 areas of major lesions,
spontaneous electrical activity was observed. He further noted factors that increased spontaneous activity; these included
inhalation, painful stimuli, apprehension, and fatigue. Such stimuli in adjacent normal areas did not cause any activity. Slosberg
noted that studies using EMG recordings confirm that in normal relaxed musculature, there is no electrical activity. 180·182
Exaggerated reaction to minor stimuli or normal movement was postulated as an "enduring central excitatory state (C.E.S.)
created by subthreshold stimuli." Slosberg noted in 1987 that today, "such a low threshold area would be identified as a
'facilitated segment.",4.183 The term
defines a spinal segment that responds to various stimuli in a more intense and prolonged manner than is normal. "The reason for
such excessive responsiveness is due to the summation of sub-threshold stimuli at an involved spinal
