Deep Neck Flexor Inhibition Occurs in Individuals with Chronic Neck Pain

• 32 Females 38.0 ± 11.6 years old

Inclusion Criteria:

• Between 18-60 years old
• History of neck pain for longer than 6 months
• Neck Disability Index (NDI) score of greater than 5/50
• Positive clinical exam findings suggesting cervical dysfunction

Exclusion Criteria:

• History of cervical spine surgery
• Presence of neurological signs in the upper extremities
• Participation in a neck strengthening program during the past 12 months

Prior to the start of the study, each participant rated her pain on the Numerical Rating Scale (NRS) and perceived function using the Neck Disability Index (NDI).

Pre-Study Measures - Electromyography (EMG)

• In supine, electrodes were placed onto the deep neck flexors (DNF) on the side of greatest pain (The left side was more painful in 25/32 participants) with a suction catheter through the nose to the posterior oropharyngeal wall.
  • Validity and reliability of this technique was previously established in an earlier study by the authors (4).

• The electrode was positioned ~1 cm lateral to the midline at the level of the uvula and confirmed via inspection through the mouth.
• Surface electrodes were placed on the sternal head of sternocleidomastoid (SCM) and the anterior scalenes (AS) bilaterally. The reference electrode was placed on the upper thoracic spine.

Cranio-cervical flexion ROM was determined for each participant during each stage using digital imaging that had been described in earlier studies.

Each participant performed the cranio-cervical flexion test twice at the 5 different levels of pressure (22, 24, 26, 28 and 30 mm Hg) prior to data collection.  Each position was held at each level for 10 seconds before progressing to the next level, with a 30-second rest between levels. This served to familiarize the participants to the required pressure.

• EMG values were recorded at each level of pressure following familiarization.
• EMG values were recorded as root mean square (RMS) over 1-second intervals during each 10-second contraction.
  • These values were standardized to the head lift and expressed as a percentage across the 5 different levels of the cranio-cervical flexion task.

• Cranio-cervical flexion active ROM at each stage was calculated by subtracting the mean angle of the end position from the mean angle of the starting position and expressed as a percentage.

• Pearson Product-moment correlation coefficients determined the association between average normalized RMS of the DNF, SCM and AS across all stages.
• Mean range of cranio-cervical flexion was calculated for each stage.
• Significance was set at p < 0.05

• Normalized RMS (nRMS) EMG Values for DNFs, SCM and AS
• Cranio-cervical flexion ROM (%CCF) across all levels of the cranio-cervical flexion test

Correlation between DNF and SCM nRMS values across the five stages: r = -0.45; p < 0.01

Correlation between DNF and AS nRMS values across the five stages: r = -0.34; p = 0.053

Our Conclusions

Chronic neck pain appears to be correlated with DNF inhibition and synergistic dominance of the sternocleidomastoid.

This implies that the DNF may play an important role in optimizing cervical motion and should be selectively activated in those individuals displaying signs of cervical dysfunction. Further, manual practitioners may consider sternocleidomastoid release prior to DNF Activation .

Conclusions of the Researchers

In individuals with chronic neck pain, higher levels of superficial neck flexor activity is associated with lower levels of DNF activity.

Future studies should investigate motor control strategies in these individuals to further shape clinical practice.

Caption: Cadaver Dissection reveiling the anterior side of the cervical spine with clear depiction of the deep neck flexors (longus colli and longus capitis)

Anterior Cervical Spine in Cadaveric Dissection - By Anatomist90 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19544659

Review & Commentary:

This groundbreaking study confirms the hypothesis (1-3) that a reduction in deep neck flexor (DNF) activity is correlated with an increase in sternocleidomastoid activity, and chronic neck pain. This study was the first to place electrodes on the deep neck flexors (DNF) with a suction catheter through the nose to the posterior oropharyngeal wall.

The study had many methodological strengths, including:

• The study used a novel, validated approach to investigate an important clinical issue. Previous research inferred DNF activity from superficial neck flexor activity (1 - 3 ), where as this study directly measured the activity of the DNF in vivo, validating long-standing clinical assumptions that DNF inhibition occurs in individuals with neck pain and upper body dysfunction (1-3).
• The study measured activity during a test commonly used in clinical settings, the cranio-cervical flexion test.
• The clear descriptions of the methodology allow for future replication of the study.

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

• The gender of the subjects were middle-aged females. It is unknown whether or not similar trends in muscle activity would occur in males or in individuals of different ages. Future research should replicate this study with different populations.
• The inclusion criteria for classifying individuals with neck pain (the neck disability index, NDI) was not stringent. The average NDI score for the subjects was 11.0 ± 2.6. Scores within this range signify mild disability. Future studies should include individuals with higher perceived levels of disability (NDI scores greater than 15).

How This Study is Important:

This landmark study confirms that DNF inhibition occurs in individuals with chronic neck pain. The findings also show a moderate correlation between increased activity of the sternocleidomastoid (r = -0.45) and anterior scalenes (r = -0.34), and decreased activity of the DNF during the cranio-cervical flexion test.

How the Findings Apply to Practice:

Human movement professionals should consider assessing activity of the DNF in those with chronic neck pain using the cranio-cervical flexion test or deep cervical flexor endurance test . If assessment implies DNF under-activity, DNF Activation should likely be included in a routine designed to optimize motion. In addition, release of commonly overactive synergists (sternocleidomastoid, anterior scalenes, levator scapulae , and upper trapezius ) may be beneficial, especially when done prior to DNF Activation .

How does it relate to Brookbush Institute Content?

The Brookbush Institute's (BI) predictive model of upper body dysfunction (UBD) (as well as the Cervicothoracic Dysfunction Model in development) characterizes the deep neck flexors (DNF) (longus colli, longus capitis, rectus capitis anterior, and rectus capitis lateralis) as "long/underactive." In UBD , individuals will likely present with excessive flexion (limited extension) at the cervico-thoracic junction, cervical facet dysfunction related to hypertonicity of the levator scapulae , upper trapezius and sternocleidomastoid (SCM), and potentially elevation of the 1st rib due to hypertonicity in the scalene muscles. This presentation perpetuates inhibition of the local stabilizers (DNFs ) and helps feed-forward compensatory over-activity of the superficial neck flexors, as described in the current study.

An individual presenting with cervicothoracic dysfunction would present similar to the compensation pattern described above; however, further consideration would be given to the upper cervical spine, and the shoulder and shoulder girdle would not remain a priority during intervention.

A sample protocol for addressing cervical dysfunction and inhibited DNF activity would be: releasing the anterior scalenes, SCM, upper trapezius , levator scapulae and sub-occipitals ; mobilizing the cervical and thoracic spine (if within scope of practice); activating the DNFs , and potentially integrated DNF activity into other core and upper body movement patterns.

The videos below demonstrate some techniques that may be implicated by this study:

Brookbush Institute Videos

Deep Cervical Flexor Endurance Test

Sternocleidomastoid Manual Static Release

Scalene Static Manual Release

Lewit Deep Neck Flexor Activation

Isolated Activation of Deep Cervical Neck Flexors

Cobra with Cervical Retraction on Foam Roll:

Bibliography:

1. 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.
2. Jull, G.A., Falla, D., Vicenzino, B., Hodges, P.W. (2009). The effect of therapeutic exercise on activation of the deep cervical flexor muscles in people with chronic neck pain. Manual Therapy. 14: 696-701
3. 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
4. Falla, D., Jull, G., O’leary, S., & Dall’Alba, P. (2006). Further evaluation of an EMG technique for assessment of the deep cervical flexor muscles. Journal of Electromyography and Kinesiology, 16(6), 621-628.

© 2017 Brent Brookbush