Cervical Mobilizations Improve Deep Cervical Flexor Activity in Individuals With Chronic Neck Pain

Research Review: Cervical Mobilizations Decrease Superficial Neck Flexor Activity in Individuals With Chronic Neck Pain

By Nicholas Rolnick SPT, MS, CSCS

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Sterling M, Jull G, Wright A. Cervical mobilisation: concurrent effects on pain, sympathetic nervous system activity and motor activity. Manual Therapy. 2001, 6(2): 72-81. ABSTRACT

Why the Study Is Relevant: Increased superficial neck flexor activity has been observed in individuals with chronic neck pain (2). Cervical mobilizations are commonly used to decrease patients' pain, increase range of motion and improve function (1). This 2001 Australian study, suggests grade III unilateral posterior-to-anterior mobilization to a symptomatic C5/C6 segments in individuals with neck pain, resulted in mechanical hypoalgesia (reduced sensitivity), sympathetic nervous system excitability, reduced superficial neck flexor activity and enhanced recruitment of deep neck flexors .

Caption: Illustration of the Longus Colli: Gray's Anatomy, 20th Edition

Gray's Anatomy - Longus Colli - By modified by Uwe Gille - Gray387.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2526567

Study Summary

Caption: Image of individual performing a unilateral posterior to anterior cervical mobilization at about the C6/C7 level

Cervical Mobilization

Review & Commentary:

Spinal manual therapy (SMT) is used by human movement professionals (primarily physical therapists and chiropractors) working in rehab, fitness and performance settings to increase range of motion, reduce pain and/or improve neuromuscular control (1). Current research suggests that the acute effects of SMT are primarily neurophysiological through modulation of mechanical nociceptive receptors, both proximal and distal to the site of SMT (1, 3-4). One recent study hypothesized that spinal and supraspinal-mediated pathways were most likely responsible for changes in central nervous system activity following SMT (4); however, the exact mechanism of action remains unclear. Refer to the appendix below for additional background information about the context of the study design.

In consideration of the neurophysiological effects of mobilization, an interesting finding in this study was increased activity in the superficial neck flexors following the placebo intervention, but a decrease in activity of the superficial neck flexors in the experimental group. The placebo intervention was manual touch to the C5/C6 area without joint mobilization, where as the experimental group received joint mobilization to the same segment. It appears that specificity of manual therapy has an effect on the resulting changes in muscle activity. This may have important implications on practice, but more research is needed.

The study had many methodological strengths, including:

• This study used a condition randomized, placebo-controlled, double-blinded, repeated-measures, within-subject design. This minimized the effects of bias within the study. In manual therapy interventions, the probability for observer bias to influence results increases due to the inability to blind the experimental condition; however, this study attempted to minimize observer bias by blinding the researcher collecting the data and the researcher performing the manual therapy. A placebo group was also used, which is important because it recognizes the effect of manual touch alone on the outcomes of interest. The within-subjects design also strengthens the results of the study, as all subjects underwent each procedure.
• The use of clinically relevant exercises. The cranio-cervical flexion test performed in this study is a variation of a commonly used assessment known as the deep cervical flexor endurance test .
• The use of multiple outcome measures provides additional information about the acute systemic effects of a 6-minute cervical spine mobilization. Research has shown that the acute effects of SMT are not exclusively mechanical (1,3-4). This study builds on that data, providing supporting evidence, and ideas for future research on the multi-faceted affects of SMT.

Weaknesses that should be noted prior to clinical integration of the findings include:

• The reliability of the grade III postero-anterior mobilization was not established. Although the same clinician performed the mobilization throughout the study, intra-rater reliability measures would strengthen the results. Future studies should include a reliability assessment of the intervention used.
• The participants had chronic neck pain. Findings may not be generalizable to other populations. Future research should replicate this study in other populations,
• The acute nature of the study does not provide any information about long-term outcomes. It is unknown whether or not acute decreases in superficial neck flexor activity will produce long-term increases in deep neck flexors activity, motor control, and function. Future research should include longitudinal data.

Why This Study Is Important

This study suggests that unilateral grade III cervical mobilizations may decrease superficial neck flexor activity. This may be evidence that mobilizations not only affect joint motion, but alter motor unit recruitment. The results of this study also highlight the acute systemic neurophysiological effects of mobilizations. These include reductions in resting pain levels (although statistically significant, were small) and skin temperature, along with increases in the mechanical pain pressure threshold and skin conductance. Based on the findings of this study, it would appear that cerviccal mobilizations are effective and their impact is multi-factorial.

How the Findings Apply to Practice

Increased superficial neck flexor activity has been observed in individuals with chronic neck pain (6). Further, under-activity of the deep neck flexors is a proposed mechanism for pain and loss of function in this group (2). Human movement professionals may use deep cervical flexor activation techniques to facilitate recruitment of these muscles. However, the findings of this study suggest that cervical mobilizations may aid in optimizing recruitment. Human movement professionals whose scope of practice includes manual therapy (DPTs, ATCs, DCs) should consider using mobilization techniques prior to deep cervical flexor activation techniques .

Related Brookbush Institute Content

The results of this study support the Brookbush Institute’s (BI) use of mobilizations and the assertion that the various systems responsible for human movement are integrated (articular, neural, fascial and muscular). Further, the study supports BI's recommended order of intervention, implying that mobilizations alter muscle activity and should be performed prior to activation techniques. Cervical facet joint stiffness, over-activity of the superficial cervical flexors and inhibition of deep cervical flexors is commonly noted in cervical dysfunction, and upper body dysfunction (UBD) , implying that cervical mobilizations may be appropriate for both. In addition to the Overhead Squat Assessment and Goniometry , BI recommends the use of the the deep cervical flexor endurance test (as used in this study), in place of other traditional Manual Muscle Tests used for cervical muscles. Human movement professionals whose scope of practice includes manual therapy should consider mobilization of cervical facets, prior to deep cervical flexor activation  to improve the effectiveness of the intervention.

The following videos show deep cervical flexor activation  exercises and progressions, mobilization videos are in development.

Brookbush Institute Videos

Lewit Deep Neck Flexor Activation

Deep Cervical Flexor Isolated Activation:

Deep Cervical Flexor Activation Progressions for Stabilization:

Deep Cervical Flexor Activation Progressions for Range of Motion (ROM):

Appendix:

The dorsal periaqueductal gray matter (dPAG) is a group of structures within the brain that is thought to be responsible for the favorable outcomes of SMT (5). In one animal study, stimulation of the dPAG produced movements of the musculoskeletal system (5). Taken in context, if dPAG is the primary area responsible for the acute effects of SMT, it stands to reason that a concomitant effect on neuromuscular control exists in humans. No studies have yet clearly defined the relationship between the dPAG, SMT and its acute effect on muscle activity in human subjects.

Cervical mobilizations are a common form of SMT used to reduce pain and restore movement in individuals with neck pain (6). A common clinical finding in neck pain is decreased endurance of the deep cervical neck flexors and overactivity of the superficial neck flexors to stabilize the cervical spine (2). The authors of this 2001 study attempted to indirectly define the relationship between SMT, dPAG and the muscle activity in human subjects. This study investigated the acute effects of SMT on pain, sympathetic nervous system activity and superficial neck flexor muscle activity in individuals with chronic neck pain. The results of the study do not rule out the potential influence of the dPAG on producing the positive effects of SMT.

Bibiliography:

1. Millan M, Leboeuf-Yde C, Budgell B, Amorim MA. The effect of spinal manipulative therapy on experimentally induced pain: a systematic literature review. Chiropr Man Therap. 2012, 20(1): 26
2. Jull G, Falla D. Does increased superficial neck flexor activity in the craniocervical flexion test reflect reduced deep flexor activity in people with neck pain? Man Ther. 2016, 25:43-47.
3. Bialosky JE, George SZ, Horn ME, Price DD, Staud R, Robinson ME. Spinal Manipulative Therapy Specific Changes In Pain Sensitivity In Individuals With Low Back Pain (NCT01168999). The journal of pain : official journal of the American Pain Society. 2014, 15(2):136-148.
4. Coronado RA, Gay CW, Bialosky JE, et al. Changes in pain sensitivity following spinal manipulation: a systematic review and meta-analysis. J Electromyogr Kinesiol. 2012, 22(5): 752-767.
5. Lovick T. Interactions between descending pathways from the dorsal and ventrolateral periaqueductal gray matter in the rat. In: Depaulis A, Bandler R. The midbrain periaqueductal gray matter. Plenum Press, New York. 101-134.
6. Chu J, Allen DD, Pawlowsky S, Smoot B. Peripheral response to cervical or thoracic spine manual therapy: an evidence-based review with meta analysis. J Man Manip Ther. 2014, 22(4): 220-229.

© 2017 Brent Brookbush

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