The Chiropractic Adjustment Changes Brain Function
The Evidence of Increased Muscle Strength is Added to Pain Sensitivity and Autonomic Changes
Mark Studin DC, FASBE(C), DAAPM, DAAMLP
William J. Owens DC, DAAMLP
Matt Erickson DC, FSBT
A report on the scientific literature
There is a growing body of evidence that a high-velocity, low-amplitude (HVLA) chiropractic spinal adjustment (CSA) has a significant influence on cortical (brain) and other central (cord) changes. This is significant as the evidence is now answering more questions on why has chiropractic has had such a profound effect on a myriad of conditions beyond back pain. Technology, including but not limited to functional MRI, NCV, EEG and sEMG renders demonstrable validation of the effect the chiropractic spinal adjustment has on changes in central function.
A chiropractic spinal manipulation/adjustment is a specific HVLA thrust maneuver designed to correct spinal patho-neuro-biomechanics (remove nerve irritation/interference, restore biomechanical balance), increases important proteins such as Substance P (Evans 2002) and makes plastic changes to the central nervous system. Conversely, a spinal manipulation as manual therapy or thrust joint manipulation (TJM) performed by physical therapists (PT’s) is a generalized non-specific low-velocity, low-amplitude of non-specific HVLA thrust maneuver of joints and connective tissue to improve motion and decrease muscle tension.
Essentially, the intent of TJM is in treating pain and dysfunction. That is not to say a non-specific manipulation will not help a patient. However, when spinal manipulation is not performed as a chiropractic based neuro-biomechanical corrective adjustment or from a salutogenic health management perspective, it is something else entirely. Therefore, spinal manipulation as a chiropractic adjustment delivered by a chiropractor is not synonymous with TJM, mobilization or spinal manipulation delivered by a PT.
Reed, Pickar, Sozio, and Long (2014) reported, “.forms of manual therapy have been clinically shown to increase mechanical pressure pain thresholds (i.e., decrease sensitivity) in both symptomatic and asymptomatic subjects. Cervical spinal manipulation (chiropractic HVLA) has been shown to result in unilateral as well as bilateral mechanical hypoalgesia. Compared with no manual therapy, oscillatory spinal manual therapy at T12 and L4 produced significantly higher paraspinal pain thresholds at T6, L1, and L3 in individuals with rheumatoid arthritis. The immediate and widespread hypoalgesia associated with manual therapy treatments has been attributed to alterations in peripheral and/or central pain processing including activation of descending pain inhibitory systems. Increasing evidence from animal models suggests that manual therapy activates the central nervous system and, in so doing, affects areas well beyond those being treated. (p. 277)
Reed et al. (2014) also reported, The finding that only the higher intensity manipulative stimulus (ie, 85% BW [body weight] vs 55% BW or control) decreased the mechanical sensitivity of lateral thalamic neurons to mechanical trunk stimulation coincides with other reports relating graded mechanical or electrical stimulus intensity to the magnitude of central inhibition. Several clinical studies indicate that spinal manipulation [chiropractic spinal adjustment] alters central processing of mechanical stimuli evidenced by increased pressure pain thresholds and decreased pain sensitivity in asymptomatic and symptomatic subjects following manipulation. (p. 282)
Daligadu, Haavik, Yielder, Baarbe, and Murphy (2013) reported, There is also evidence in the literature to suggest that muscle impairment occurs early in the history of onset of spinal complaints, and that such muscle impairment does not automatically resolve even when pain symptoms improve. This has led some authors to suggest that the deficits in proprioception and motor control, rather than the pain itself, may be the main factors defining the clinical picture and chronicity of various chronic pain conditions. Furthermore, recent evidence has demonstrated that spinal manipulation (CSA) can alter neuromuscular and proprioceptive function in patients with neck and back pain as well as in asymptomatic participants. For instance, cervical spine manipulation (CSA) has been shown to produce greater changes in pressure pain threshold in lateral epicondylalgia than thoracic manipulation; and in asymptomatic patients, lumbar spine manipulation (CSA) was found to significantly influence corticospinal and spinal reflex excitability. Interestingly, Soon et al did not find neurophysiological changes following mobilization on motor function and pressure pain threshold in asymptomatic individuals, perhaps suggesting that manipulation [chiropractic spinal adjustments], as distinct from mobilization, induces unique physiological changes. There is also accumulating evidence to suggest that chiropractic manipulation can result in changes to central nervous system function including reflex excitability, cognitive processing, sensory processing, and motor output. There is also evidence in SCNP [sub-clinical neck pain] individuals that chiropractic manipulation alters cortical somatosensory processing and elbow joint position sense. This evidence suggests that chiropractic manipulation may have a positive neuromodulatory effect on the central nervous system, and this may play a role in the effect it has in the treatment of neck pain. It is hoped improving our understanding of the neurophysiological mechanisms that may precede the development of chronic neck pain in individuals with sub-clinical neck pain (SCNP) will help provide a neurophysiological marker of altered sensory processing that could help determine if an individual is showing evidence of disordered sensorimotor integration and thus might benefit from early intervention to prevent the progression of SCNP into more long-term pain states. (p. 528)
Christriansen, Niazi, Holt, Nedergaard, Duehr, Allen, Marshall, Turker and Haarvik (2018) discussed the effects of a single session of a chiropractic spinal manipulation (CSA) on strength and cortical drive. They studied the effects upwards of 60 minutes and further testing is needed to determine the long-term effects of the adjustment. They found in “blinded studies” that “the increased maximum voluntary contraction force lasted for 30 min and the corticospinal excitability increase persisted for at least 60 minutes.” (pg. 737)
Christiansen et. Al (2018) also reported, “The increased V-wave amplitudes observed in the current study possibly reflect an increased cortical drive in the corticospinal pathways and corresponding increased excitability of the MNs following SM found differences in the cortical drive in volleyball athletes competing at different levels, and argued that elite players had increased cortical drive correlating to their biomechanical performance. The absence of change in the H-reflex in the presence of the increased MVC along with increased V-waves suggests that it's possible that the change post manipulation occurred at supraspinal centers involving a cortical neural drive. The V-waves represent cortical drive. The absence of change in the H-reflex alone suggests that the spinal motor neurons and the excitability of the spindle primary afferent synapses on the spinal motor neurons did not change as a result of SM.” (pg. 745) The above paragraph indicates there is no input at the cord level as the H-Reflex exhibited no changes.
Increased motor function for a minimum of 60 minutes post-chiropractic spinal adjustment has far-reaching manifestations for a dichotomy of the population. Athletes at every level will benefit from increased motor function and patients suffering from either muscular or neuro-degenerative illnesses, such as Parkinson’s, Amyotrophic lateral sclerosis (ALS), Muscular Dystrophy and others will also potentially benefit. Although this article touched on PT manual therapy, low-velocity, low-amplitude or non-specific thrust joint manipulation; these forms of treatment do not render the outcomes a chiropractic spinal adjustment.
Christiansen et. Al (2018) concluded and perfectly positioned the effect of a chiropractic spinal adjustment and the effect on the brain, “this study supports a growing body of research that suggests chiropractic spinal manipulation’s main effect is neuroplastic in nature and affects corticospinal excitability. Changes in both cerebellum and prefrontal cortex function have been implicated post-spinal manipulation in previous research studies. The presence of mild, recurrent spinal dysfunction has been shown to be associated with maladaptive neural plastic changes, such as alterations in elbow joint position sense mental rotation ability, and even multisensory integration Furthermore, spinal manipulation of dysfunctional spinal segments has been shown to impact somatosensory processing, sensorimotor integration and motor control.” (pg. 746)