Neck Solutions

Torque-EMG-velocity relationship in female workers with chronic neck muscle pain

From: Journal of Biomechanics. 2008 May 5

The present study investigated the effect of chronic neck muscle pain (defined as trapezius myalgia) on neck and shoulder muscle function during concentric, eccentric and static contraction. Forty-two female office workers with chronic neck muscle pain and 20 healthy matched controls participated. Isokinetic and static maximal voluntary shoulder abductions were performed in a Biodex dynamometer, and electromyography obtained in the trapezius and deltoideus muscles. Muscle thickness in the trapezius was measured with ultrasound. Pain and perceived exertion were registered before and after the dynamometer test. The main findings were that shoulder abduction torque and trapezius electromyography amplitude were significantly lower in chronic neck muscle pain compared with healthy matched controls. Deltoideus electromyography and trapezius muscle thickness were not significantly different between the groups. While perceived exertion increased in both groups in response to the test, pain increased in chronic neck muscle pain only. In conclusion, having chronic neck muscle pain was associated with decreased strength capacity and lowered activity of the painful trapezius muscle. The most consistent differences-in terms of both torque and electromyography were found during slow concentric and eccentric contractions. Activity of the synergistic pain free deltoideus muscle was not significantly lower, indicating specific inhibitory feedback of the painful trapezius muscle only. Parallel increase in pain and perceived exertion among chronic neck muscle pain were observed in response to the maximal contractions, emphasizing that heavy physical exertion provokes pain increase only in conditions of chronic neck pain due to myalgia.

Neck muscle fatigue and postural control in patients with whiplash injury

From: Clinical Neurophysiology. 2006 Mar;117(3):610-22

To examine if patients with whiplash injury show identifiable increases in neck muscle fatigability and associated increase in postural body sway after contractions of dorsal neck muscles, and if physiotherapy treatment reduces these effects.

Posture sway was measured during stance in 13 patients before and after 5 min of isometric dorsal neck muscle contractions and after recovery, pre and post physiotherapy, using a force platform. Amplitude and median frequency of neck muscle EMG were calculated during the contracting period. After each stance trial, patients gave a subjective score of posture sway.

Pre treatment, seven patients showed EMG signs of fatigue (increases in amplitude, decreases in median frequency) and increases in sway (eyes closed) after contractions. The other patients showed neither fatigue nor increased sway. Post treatment, no signs of fatigue or imbalance were recorded in all patients, for the same levels of muscle contraction.

As in normal human subjects, increases in postural sway are associated with signs of neck muscle fatigue in some whiplash injury patients. Physiotherapy decreases the susceptibility to fatigue of neck muscles and is an effective choice of treatment of subjective instability and sway. This study demonstrates a pathophysiological link between neck muscle fatigue and impaired postural control, and also that physiotherapy can relieve symptoms and signs of impaired neck muscle function by reducing muscle fatigability.

The influence of breathing type, expiration and cervical posture on the performance of the craniocervical flexion test in healthy subjects

From: Manual Therapy. 2008 Jun;13(3):232-8. Epub 2007 Mar 23

The craniocervical flexion test is used as a clinical evaluation tool for the deep neck flexors. The influence of breathing type, expiration and cervical posture on the performance of the test is evaluated in asymptomatic subjects. Thirty volunteers participated in the study and were classified according to their breathing type: costo-diaphragmatic breathing type and upper costal breathing type. Sternocleidomastoid electromyographic activity was recorded during five incremental levels of craniocervical flexion during normal breathing as well as during expiration. The craniovertebral angle of each subject was measured to quantify cervical posture. During normal inspiration, higher electromyographic activity of the sternocleidomastoid muscles was observed in subjects with an upper costal breathing pattern compared to costo-diaphragmatic breathing subjects. This difference was statistically significant at the three lowest stages of the test. In the upper costal breathing group a significantly lower electromyographic activity of the sternocleidomastoid muscles was observed while performing the craniocervical flexion test during slow expiration compared to normal breathing. No significant correlation was found between the craniovertebral angle and the electromyographic activity of the sternocleidomastoid muscles. Performing the craniocervical flexion test during slow expiration diminishes the activity of the sternocleidomastoid muscles in subjects with a predominantly upper costal breathing pattern. Using a costo-diaphragmatic breathing pattern while performing the test will optimize the performance. Studies on neck pain patients are required to further clarify this issue.

Chronic whiplash symptoms are related to altered regional cerebral blood flow in the resting state

From: European Journal of Pain. 2008 May 15; [Epub ahead of print]

The neural pathogenic mechanisms involved in mediating chronic pain and whiplash associated disorders after rear impact car collisions are largely unknown. This study’s first objective was to compare resting state regional cerebral blood flow by means of positron emission tomography with (15)O labelled water in 21 whiplash associated disorders patients with 18 healthy, pain-free controls. A second objective was to investigate the relations between brain areas with altered regional cerebral blood flow to pain experience, somatic symptoms, posttraumatic stress symptoms and personality traits in the patient group. Patients had heightened resting state regional cerebral blood flow bilaterally in the posterior parahippocampal and the posterior cingulate gyri, in the right thalamus and the right medial prefrontal gyrus as well as lowered tempero-occipital blood flow compared with healthy controls. The altered regional cerebral blood flow in the patient group was correlated to neck disability ratings. We thus suggest an involvement of the posterior cingulate, parahippocampal and medial prefrontal gyri in whiplash associated disorders and speculate that alterations in the resting state are linked to an increased self-relevant evaluation of pain and stress.

Neck muscle fatigue affects postural control in man

From: Neuroscience. 2003;121(2):277-85

Since anomalous neck proprioceptive input can produce perturbing effects on posture, neck muscle fatigue could alter body balance control through a mechanism connected to fatigue induced afferent inflow. Eighteen normal subjects underwent fatiguing contractions of head extensor muscles. Sway during quiet stance was recorded by a dynamometric platform, both prior to and after fatigue and recovery, with eyes open and eyes closed. After each trial, subjects were asked to rate their postural control. Fatigue was induced by having subjects stand upright and exert a force corresponding to about 35% of maximal voluntary effort against a device exerting a head-flexor torque. The first fatiguing period lasted 5 min (F1). After a 5-min recovery period (R1), a second period of fatiguing contraction (F2) and a second period of recovery (R2) followed. Surface EMG activity from dorsal neck muscles was recorded during the contractions and quiet stance trials. EMG median frequency progressively decreased and EMG amplitude progressively increased during fatiguing contractions, demonstrating that muscle fatigue occurred. After F1, subjects swayed to a larger extent compared with control conditions, recovering after R1. Similar findings were obtained after F2 and after R2. Although such behaviour was detectable under both visual conditions, the effects of fatigue reached significance only without vision. Subjective scores of postural control diminished when sway increased, but diminished more, for equal body sway, after fatigue and recovery. Contractions of the same duration, but not inducing EMG signs of fatigue, had much less influence on body sway or subjective scoring. We argue that neck muscle fatigue affects mechanisms of postural control by producing abnormal sensory input to the CNS and a lasting sense of instability. Vision is able to overcome the disturbing effects connected with neck muscle fatigue.

Gender specific adaptations of upper trapezius muscle activity to acute nociceptive stimulation

From: Pain. 2008 May 15; [Epub ahead of print]

This study examined gender differences in the effect of experimental muscle pain on changes in the relative activation of regions of the upper trapezius muscle during a sustained contraction. Surface electromyographic (EMG) signals were recorded from multiple locations over the upper trapezius muscle with a 10×5 grid of electrodes from nine women and nine men during 90 degrees shoulder abduction sustained for 60s. Measurements were performed before and after the injection of 0.4ml hypertonic (painful) and isotonic (control) saline into the cranial region of the upper trapezius muscle. The EMG root mean square (RMS) was computed for each location of the grid to form a map of the EMG amplitude distribution. The peak pain intensity following the injection of hypertonic saline was greater for women (numerical rating scale 0-10: women 6.0+/-2.1, men 4.2+/-0.9). For both genders, upper trapezius RMS averaged across the grid decreased following the injection of hypertonic saline. Moreover, there was a relatively larger pain-induced decrease in RMS in the cranial region compared to the caudal region of the muscle for both genders. During the non painful sustained contractions, the EMG RMS progressively increased more in the cranial than the caudal region, for both men and women, due to fatigue. This mechanism was maintained in men but not in women during the painful condition. The results demonstrate that muscle pain alters the normal adaptation of upper trapezius muscle activity to fatigue in women but not in men.

Muscle specificity in tests of cervical neck flexor muscle performance

From: Journal of Electromyography and Kinesiology. 2007 Feb;17(1):35-40

The deep neck flexor muscles are considered to be of substantial clinical importance in the management of neck pain. While conventional neck flexion conventional neck flexion dynamometry methods have been used frequently to assess the capacity of the cervical flexor muscles, it has been suggested that craniocervical flexion methods may provide a more specific test of deep neck flexor muscle performance. This study compared the activation of the deep and superficial cervical flexor muscles between tests of isometric craniocervical flexion and conventional neck flexion conventional neck flexion dynamometry. Values were recorded for the deep cervical flexor, sternocleidomastoid, anterior scalene, and sternohyoid muscles during isometric craniocervical flexion and conventional neck flexion tests at maximal voluntary contraction, 50% maximal voluntary contraction, and 20% maximal voluntary contraction in ten healthy volunteers. The results demonstrated significantly greater electromyography amplitude for the sternocleidomastoid and anterior scalene muscles in the conventional neck flexion test conditions compared to craniocervical flexion test conditions. Moreover, the sternohyoid muscle demonstrated significantly greater electromyography amplitude during conventional neck flexion compared to craniocervical flexion but only in the 50% maximal voluntary contraction and 20% maximal voluntary contraction conditions. These results demonstrate that dynamometry tests of conventional neck flexion result in greater activity of the superficial cervical flexor muscles compared to tests of craniocervical flexion. As a result, craniocervical flexion dynamometry may provide a more specific method to assess and retrain deep neck flexor muscle performance, compared to conventional neck flexion in which superficial muscle activity may mask impaired performance of the deep neck flexor muscles.

An endurance strength training regime is effective in reducing myoelectric manifestations of cervical flexor muscle fatigue in females with chronic neck pain

From: Clinical Neurophysiology. 2006 Apr;117(4):828-37.

To investigate whether an endurance strength training program is effective in reducing myoelectric manifestations of sternocleidomastoid and anterior scalene muscle fatigue which have been found to be greater in people with chronic neck pain.

Fifty-eight female patients with chronic non severe neck pain were randomized into one of two 6-week exercise intervention groups: an endurance strength training regime for the neck flexor muscles or a referent exercise intervention involving low load retraining of the craniocervical flexor muscles. The primary outcomes were a change in maximum voluntary contraction force and change of the initial value and rate of change of the mean frequency, average rectified value and conduction velocity detected from the sternocleidomastoid and anterior scalene muscles during submaximal isometric neck flexion contractions at 50, 25 and 10% maximum voluntary contraction.

At the 7th week follow-up assessment, the endurance-strength training group revealed a significant increase in maximum voluntary contraction force and a reduction in the estimates of the initial value and rate of change of the mean frequency for both the sternocleidomastoid and anterior scalene muscles. Both exercise groups reported a reduced average intensity of neck pain and reduced neck disability index score.

An endurance strength exercise regime for the neck flexor muscles is effective in reducing myoelectric manifestations of superficial neck flexor muscle fatigue as well as increasing neck flexion strength in a group of patients with chronic non severe neck pain. Provision of load to challenge the neck flexor muscles is required to reduce the fatigability of the sternocleidomastoid and anterior scalene muscles in people with neck pain. Improvements in neck muscle strength and reduced fatigability may be responsible for the reported efficacy with this type of exercise program.

A specific exercise program and modification of postural alignment for treatment of cervicogenic headache: a case report.

From: J Orthop Sports Phys Ther. 2005 Jan;35(1):3-15

An intervention approach consisting of a specific active exercise program and modification of postural alignment for an individual with cervicogenic headache. The patient was a 46-year-old male with a 7-year history of cervicogenic headache. He reported constant symptoms with an average intensity of 5/10 on a visual analogue scale where 0 indicated no pain and 10 the worst pain imaginable. Average pain intensity in the week prior to the initial evaluation was 3/10 secondary to trigger point injections. The patient’s headache symptoms worsened with activities that involved use of his arms and prolonged sitting.

The patient was treated 7 times over a 3-month period. Impairments of alignment, muscle function, and movement of the cervical, scapulothoracic, and lumbar regions were identified. Outcome measurements included headache frequency, intensity, and the Neck Disability Index questionnaire. Intervention included modification of alignment and movement during active cervical and upper extremity movements. The patient also received functional instructions focused on diminishing the effect of the weight of the upper extremities on the cervical spine.

The patient reported a decrease in headache frequency and intensity (1 headache in 3 weeks, intensity 1/10) and a decrease in his NDI score from 31 (severe disability) to 11 (mild disability). The patient also demonstrated improvement in upper cervical joint mobility, cervical range of motion, scapular alignment, and scapulothoracic muscle strength.

Interventions that included modification of alignment in the cervical, scapulothoracic, and lumbar region, along with instruction in a specific active-exercise program to address movement impairments in these 3 regions, appeared to have been successful in relieving headaches and improving function in this patient.

(more…)

Survey of faulty postures and associated factors among Chinese adolescents

From: Journal of Manipulative Physiological Therapeutics. 2008 Mar;31(3):224-9

This study investigated the prevalence of common faulty postures among adolescents and identify if significant relationships existed among the number of faulty postures, psychologic distress, and musculoskeletal symptoms. The Musculoskeletal Questionnaire and Chinese Health Questionnaire were randomly distributed to 300 high school students in the Tainan area. On-campus postural screening, which included digital photography, manual muscle tests, and flexibility tests, was also performed.

Two hundred eighty-seven participants completed all of the evaluations. The most common faulty posture was uneven shoulder level (36%), followed by forward head posture (25%). There was a sex difference between groups. The incidence of forward head posture for the male students was higher than that of the female students. In addition, the high psychologic distress group tended to have a higher prevalence of uneven shoulder height than that of the low psychologic distress group. As for the correlation analysis, the researchers did not find a high correlation among the scores of the faulty posture, psychologic distress, and musculoskeletal symptoms.

The results of this study show that the incidence of faulty posture was high for the adolescent group, especially for the uneven shoulder level. Subjects’ awareness about being assessed might decrease the incidence for some faulty posture. However, the relationships among the number of faulty postures, psychologic distress, and musculoskeletal symptoms were low. We suggest that there are multiple factors that might contribute to musculoskeletal symptoms; faulty posture could be one important factor that causes symptoms.