Cervical flexion: a study of dynamic surface electromyography and range of motion

Immediate effect of craniocervical flexion exercise and Mulligan mobilisation in patients with mechanical neck pain - A randomised clinical trial

Background

Mechanical neck pain (MNP) is one of the most prevalent musculoskeletal pathologies in the present time. Physiotherapy management strategies comprising manual therapy and exercise therapy are routinely administered in patients with MNP.

Objective

To compare the immediate effect of craniocervical flexion (CCF) exercise and Mulligan mobilisation on pain, active cervical range of motion (CROM) and CCF test performance in patients with MNP.

Methods

This prospective, randomised, single-blinded study involved 26 patients with MNP (16 females; mean age; 31 . 12 ± 8 . 40 years) randomised to a single session of active CCF exercise (3 sets of 10 repetitions) or Mulligan mobilisation (3 sets of 6-10 repetitions). Pain intensity was measured on a numerical pain rating scale (NPRS), active CROM was measured using CROM device, and CCF test performance with surface electromyography (EMG) from bilateral sternocleidomastoid (SCM) and anterior scalene (AS) muscles recorded pre- and immediately post-intervention by an assessor blinded to the treatment groups. Mann-Whitney U test was used to analyse between groups and Wilcoxon signed rank test was used to analyse within-group significance for pain and CROM, Cochran-Mantel-Haenszel correlation test was used to analyse the CCF test performance on EMG from the bilateral SCM and AS muscles.

Results

Comparison between pre- and post-intervention readings revealed statistically significant within-group (p < 0 . 05 ) and no between-group significant difference for pain, ROM, and CCF test performance, indicating both interventions were equally effective.

Conclusion

Patients with MNP who received active CCF exercise or Mulligan mobilisation exhibited similar reduction in pain intensity and increased CROM and CCF test performance post-intervention. Surprisingly, AS surface EMG amplitudes were increased post-intervention in both groups warranting further exploration of its role in neck pain.

Quantification of isometric cervical strength at different ranges of flexion and extension

BACKGROUND

Studies have demonstrated that cervical strength is affected by injury to the neck. Cervical strength measurements are influenced by the protocol used for the measurements. Previous studies have determined the isometric cervical strength only at a few degrees of range of neck motion. The present study was aimed at quantifying cervical strength at neutral, 25%, 50% and 75% of flexion and extension.

METHODS

Using a correlation study design, 39 volunteers in the age range of 18-30 years were recruited in two sessions, one for flexion and the other extension. Their sequence was randomized. The cervical strength was measured using a force measuring device. The device was firmly bolted in the floor. A rotating metal tube was pivoted, adjustably counterweighted and attached to the device at one end and an immovable object with a load cell in its path at the other. The neck was positioned in the desired posture and isometric efforts were exerted on the horizontal resistance arm.

FINDINGS

Cervical strength was found to be highest in the neutral posture for both flexion (19.8 N females and 31.4 N males) and extension (39.5 females and 45.1 males) and significantly decreased with an increasing angular deviation of the neck (P<0.01). Males exerted significantly higher forces than females. The overall flexion-extension ratio was 1:1.7 (P<0.01).

INTERPRETATION

The maximum force was exerted in the neutral posture of the neck and it was directionally dependent being less in flexion than extension (P<0.01). Males were stronger than females. The findings may assist in targeting rehabilitation goals.

Actions of the scalene muscles for rotation of the cervical spine in macaque and human

STUDY DESIGN

Multiple single-subject design in 2 parts: 1 in anesthetized monkeys and a follow-up in human cadavers.

OBJECTIVES

To determine whether anterior, middle, and posterior scalene muscles rotate the cervical spine to the same (ipsilateral to the muscle) or opposite (contralateral to the muscle) side.

BACKGROUND

Some physical therapy and anatomy textbooks indicate that all 3 scalenes rotate the cervical spine to the same side, some indicate that all rotate to the opposite side, and the rest ascribe different functions to the different scalenes.

METHODS AND MEASURES

While under anesthesia, macaques (n = 3) already scheduled for euthanasia were implanted with stimulating electrodes in each scalene muscle on one side, and then a neuromuscular junction blocker was administered to prevent confounding movement from brachial plexus stimulation. Three observers independently rated the direction of rotation produced by electrical stimulation. Postmortem dissection of the macaques was used to determine which direction of passive rotation stretched each scalene. Postmortem analyses in 2 human cadavers were also conducted to determine which direction of rotation stretched the human scalenes.

RESULTS

Electrical stimulation in the macaque produced rotation to the same side for each of the 3 scalenes. Passive rotation to the opposite side put each scalene muscle of the macaque on stretch. In the human, rotation to the opposite side also stretched each scalene.

CONCLUSIONS

All 3 scalene muscles produce rotation of the cervical spine to the same side. Maximum stretching of the scalenes should include rotation to the opposite side.

Location of innervation zones of sternocleidomastoid and scalene muscles--a basis for clinical and research electromyography applications

OBJECTIVES

Advances in surface electromyography (sEMG) techniques provide a clear indication that refinement of electrode location relative to innervation zones (IZ) is required in order to optimise the accuracy, relevance and repeatability of the sEMG signals. The aim of this study was to identify the IZ for the sternocleidomastoid and anterior scalene muscles to provide guidelines for electrode positioning for future clinical and research applications.

METHODS

Eleven volunteer subjects participated in this study. Myoelectric signals were detected from the sternal and clavicular heads of the sternocleidomastoid and the anterior scalene muscles bilaterally using a linear array of 8 electrodes during isometric cervical flexion contractions. The signals were reviewed and the IZ(s) were identified, marked on the subjects' skin and measurements were obtained relative to selected anatomical landmarks.

RESULTS

The position of the IZ lay consistently around the mid-point or in the superior portion of the muscles studied.

CONCLUSIONS

Results suggest that electrodes should be positioned over the lower portion of the muscle and not the mid-point, which has been commonly used in previous studies. Recommendations for sensor placement on these muscles should assist investigators and clinicians to ensure improved validity in future sEMG applications.