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Tuesday, June 6, 2023

Cervical Flexion Training Improves Amplitude and Activation Timing of Deep Cervical Flexors

Brent Brookbush

Brent Brookbush


Research Review: Staged cervical flexion training improves amplitude and activation timing of deep cervical flexors

By Stefanie DiCarrado DPT, PT, NASM CPT, CES, PES

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

Original Citation: 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. - ABSTRACT

By modified by Uwe Gille - Gray387.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2526567
Caption: By modified by Uwe Gille - Gray387.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2526567

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

Why is this relevant?: Neck pain is a common malady that seems to be more prevalent as the hours we spend staring at laptops and smartphones increases. Previous research has linked deep cervical flexor (longus colli & longus capitus) dysfunction and dominance of the superficial cervical muscles with neck pain (Jull et al., 2004 as cited within this article). Dysfunction includes both decreased strength and a delayed activation during rapid upper extremity movement. Rehabilitation specialists have recommended general strengthening programs for cervical muscles to address neck pain, but recent research indicates low load motor control training of the cervical flexors may be more appropriate. This article provides additional information pertaining to appropriate treatment strategies based on proper cervical motion assessment.

Study Summary

Study Design Randomized Controlled Trial (RCT)
Level of Evidence II: Evidence from at least one well-designed RCT
Subject Demographics
  • Age (years):
    • Motor control 39.6 + 12.2
    • Strength training  37.1 + 10.3

  • Gender: 46 females divided equally
  • Characteristics: Chronic neck pain for > 3 months
    • Motor Control (MC)
      • Pain History (years): 10.1 + 10.6
      • Onset: 91.3% insidious
      • Neck Pain Intensity: 4.5 + 1.6
      • Neck Disability Index: 11.0 +2.7

    • Strength training (ST)
      • Pain History (years): 9.2 + 6.6
      • Onset: 91.3% insidious
      • Neck Pain Intensity: 4.2 + 2.1
      • Neck Disability Index: 9.6 + 3.1

  • Inclusion: Neck Disability Index < 15 / 50 indicating non-severe neck pain; poor performance on the Cranio-cervical flexion test (CCFT)
  • Exclusion: History of cervical spinal surgery, neurological signs/symptoms in upper extremity, participated in neck rehabilitation program within previous year
Outcome Measures
  • Collected at baseline and immediately after intervention (7 weeks)
  • Primary EMG amplitude during Cranio-cervical flexion test (CCFT)
    • Deep Cervical Flexors (DCF)
    • Sternocleidomastoid (SCM)
    • Anterior Scalenes (AS)

  • Cervical flexion Range of Motion (ROM) during the five stages of the CCFT
  • EMG activation latency as compared to Deltoid activation in upper extremity movement
    • DCF

  • Secondary: Self report of pain, disability, perceived benefit of exercise
  • Primary EMG amplitude during CCFT
    • MC
      • DCF: significant increase
      • SCM: significant decrease except in last stage of CCFT
      • AS: significant decrease except in last stage of CCFT

    • ST
      • DCF: no significant increase
      • SCM: only significant decrease in left SCM at 28mmHg
      • AS: only significant decrease at 30mmHg Cervical flexion

  • ROM during the five stages of the CCFT
    • MC
      • Increased cervical range during CCFT at all stages

    • ST
      • Increased cervical range durin CCFT only at 22mmHg and 28mmHg stages

  • EMG activation latency as compared to Deltoid activation in upper extremity movement
    • MC
      • DCF: earlier onsets in 83.5% during shoulder flexion, 89% during shoulder extension

    • ST
      • DCF: earlier onset in 55% in flexion and extension

  • Secondary
    • Self report of pain, disability: decreased in both groups without significant differences
    • Perceived benefit of exercise: no significant differences between groups

ConclusionsExercises with the intent to activate the deep cervical flexors decreased the amount of time to the onset of activation, and decreased the activity in commonly dominant superficial synergists (SCM & AS).  This is thought to be the reason for improvement noted in the cervical flexion movement pattern during the CCFT. Note, the improvement noted may be, in part, due to task specific training as the deep cervical flexor activation exercises were very similar to the CCFT.
Conclusions of the ResearchersTask specific, low load cervical flexion training improved the activation pattern and timing of the deep and superficial cervical muscles during the CCFT, resulting in activation and movement similar to non-painful individuals.

The influence of deep vs superficial muscles on cervical spine mechanics

Review & Commentary: This study provides a comparison of two different methodologies for addressing cervical dysfunction. The specificity of inclusion criteria was a strong point of this study. Neck pain may be attributed to multiple etiologies and tissues, one of which may be weakness and/or poor onset timing of the deep cervical flexors (longus capitus and longus colli). These muscles provide segmental stabilization and stiffen the cervical spine so it may better accommodate the stress and forces of daily activity. Larger superficial muscles such as the sternocleidomastoid (SCM) and anterior scalenes (AS) exert greater amounts of force, due to larger lever arms on vertebral segments, which may pull the segments out of optimal alignment and create ligamentous, facet or nerve related pain. The researchers required poor performance on the carnio-cervical flexion test (CCFT) as an inclusion criteria to ensure their intervention was appropriate. Further increasing the strength of the study was the design; a randomized controlled trial. The use of EMG allowed for unbiased data collection. The authors clearly described the duration and frequency of the exercise sessions and home programs. The article clearly described the deep cervical flexor and superficial flexor protocols so they may be easily replicated. The authors implemented a previously documented cranio-cervical flexion training protocol as outlined in Jull et al (2002) and Jull et al (2008) and a superficial muscle strengthening protocol as outlined in McArdle et al (1996). The authors provided adequate details pertaining to equipment and set up, and included a description of the complicated placement of an EMG electrode for the deep cervical flexors (on the posterior otopharyngeal wall). The evaluation of deep cervical flexor activity compared to that of the superficial muscles during arm motion, is interesting from a clinical perspective as some patients report the onset of neck pain may occur during reaching or lifting tasks.

There are few weaknesses in this study, but a question may be asked regarding the EMG data collected. The researchers only collected EMG data of the deep cervical flexors on the painful side. Why not collect that data bilaterally, allowing for some inference regarding healthy versus dysfunctional muscle activity and the effect of the 2 interventions? It is assumed that the painful side displays dysfunction, but it even if this is true it may have been interesting to compare pain-free vs painful side and whether training resulted in equal EMG amplitudes on both sides.

Both groups of subjects reported pain relief and found the exercises to be beneficial. Since the groups demonstrated different objective but similar subjective data, it is plausible that a placebo effect occurs when a person is prescribed any exercise that is meant to target their compalaint.

Why is this study important?

This study provides important evidence to support activation of the deep cervical flexors to address individuals with chronic neck pain who exhibit poor performance on the CCFT.

How does it affect practice?

Practitioners should evaluate an individual's ability to activate the deep cervical flexors if they report neck pain (see videos below). Further, it may be recommended that practitioners learn and practice techniques for activation of the deep cervical flexors to be included in sessions and home exercise programs

How does it relate to Brookbush Institute Content?

Currently, the Brookbush Institute describes cervical dysfunction as it relates to the predictive model of Upper Body Dysfunction (UBD) . A thorough review of research and clinical experience will help create a predictive model of cervical dysfunction in the future. Here is some of the conceptual framework developed thus far: muscles attaching to the cervical/thoracic spine and shoulder girdle (scapula and clavicle) can impact spinal, clavicular, scapular, and glenohumeral motion (Brent's first rule of Human Movement Science ). These muscles, along with the integrated motion of the scapula and thoracic spine, may be the bridge between UBD and cervical dysfunction as noted in the UBD article. Individuals with UBD and related cervical dysfunction will likely present with excessive flexion (limited extension) at the cervicothoracic junction, cervical facet dysfunction related to hypertonicity in the levator scapulae (LS) and sternocleidomastoid (SCM), and an elevated 1st rib due to hypertonicity in the scalene muscles. The time course of dysfunction as hypothesized in the predictive model of UBD is as follows:

"UBD is a progressive syndrome that slowly modifies structures over time” Clinically, the following trend is identified as:

1. Latissimus dorsi and/or thoracic Spine restriction

2. Hyper-tonicity of scapular downward rotators

3. Rotator-cuff dysfunction (“Short” supraspinatus and subscapularis , “Long” infraspinatus and teres minor )

4. Adaptive shortening of global shoulder musculature (pectoralis major , deltoid, etc.)

5. Cervical spine dysfunction

Overactivity within certain superficial, global muscles can cause hypomobility, hypermobility, or even subluxation of vertebral segments. Hypermobility and subluxation create ligamentous strain which has been shown in the lumbar spine to reduce activity and timing within the transverse abdominus (Hodges & Richardson, 1996 ). An individual presenting with cervical dysfunction related to UBD would benefit from an integrated warm up routine following the Brookbush Institute’s model: Release, Mobilize (When appropriate), Stretch, Isolated Activation, Core Support (Optional), Stability Integration (Optional), Reactive Integration (Optional), Subsystem Integration. This research study's exercise protocol focused only on isolated activation of the deep cervical flexors -- which is appropriate for research and the isolation of variables. In a clinical setting, the Brookbush Institute recommends the following sample protocol: Release anterior scalenes (AS), SCM, upper trapezius (UT) , LS ; mobilize cervical and thoracic spine as indicated and if within scope; stretch AS, SCM, UT (if needed) , LS , activate deep cervical flexors (longus colli and capitus) and reactive integration. Videos below demonstrate Deep Cervical Flexor Endurance Testing (similar to the CCFT used in this study) and a progression of deep cervical flexor activation and stabilization exercises

Deep Cervical Flexor Endurance Test

Deep Cervical Flexor Isolated Activation (Longus Colli, Longus Capitis & Rectus Capitis Anterior)

Prone Cobra on Foam Roll (Activation for muscles of the scapula, thorax & deep cervical flexors)

Deep Cervical Flexor Activation and Progressions for Stabilization 1

Deep Cervical Flexor Activation and Progressions for Stabilization 2

Reactive Activation for Deep Cervical Flexors

© 2016 Brent Brookbush

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