Differences in isometric neck muscle strength between healthy controls and women with chronic neck pain: the use of a reliable measurement

Cagnie B, Cools A, De Loose V, Cambier D, Danneels L. Differences in isometric neck muscle strength between healthy controls and women with chronic neck pain: the use of a reliable measurement.

Objectives

To determine the intra- and interrater reliability of the Biodex isokinetic dynamometer to measure the maximal isometric strength of the cervical flexors and extensors, to develop an age- and sex-based normative database in a healthy population, and to evaluate the differences in neck strength between women with chronic neck pain and healthy controls.

Design

Cross-sectional.

Setting

Physical and rehabilitation medicine department.

Participants

Ninety-six healthy volunteers (4 age groups: 20-29, 30-39, 40-49, 50-59y; each consisting of 12 men and 12 women) and 30 women with chronic neck pain.

Interventions

Not applicable.

Main Outcome Measures

Peak isometric strength of the cervical muscles was tested for flexion and extension by using the Biodex isokinetic dynamometer. The intra- and interrater reliability of the protocol was evaluated in 12 volunteers.

Results

The reliability for strength was high for both flexion and extension (intraclass correlation coefficient, .92-.96). The mean peak torque for flexion and extension was significantly higher in men (24Nm, 36.4Nm, respectively) compared with women (16.6Nm, 26.5Nm, respectively) (P<.001). Peak torque production for extension was significantly lower in the patient group (22.3Nm) compared with the healthy female control group (26.5Nm) (P=.003). No significant differences in flexion strength between patient and female control group were found.

Conclusions

Results show a high degree of intra- and interrater reliability in measuring isometric neck muscle strength when using the Biodex isokinetic dynamometer. The use of normative data for neck strength when evaluating patients with neck disorders needs to take sex into account. The current study has shown that women with chronic neck pain have lower neck muscle strength in extension than the healthy female group.     

Decreased isometric neck strength in women with chronic neck pain and the repeatability of neck strength measurements

OBJECTIVES: To evaluate neck flexion, extension, and, especially, rotation strength in women with chronic neck pain compared with healthy controls and to evaluate the repeatability of peak isometric neck strength measurements in patients with neck pain. DESIGN: Cross-sectional. SETTINGS: Rehabilitation center and physical and rehabilitation medicine department at a Finnish hospital. PARTICIPANTS: Twenty-one women with chronic neck pain and healthy controls matched for sex, age, anthropometric measures, and occupation. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak isometric strength of the cervical muscles was tested in rotation, flexion, and extension. RESULTS: Significantly lower flexion (29%), extension (29%), and rotation forces (23%) were produced by the chronic neck pain group compared with controls. When the repeated test results were compared pairwise against their mean, considerable variation was observed in the measures on the individual level. Intratester repeatability of the neck muscle strength measurements was good in all the 4 directions tested in the chronic neck pain group (intraclass correlation coefficient range,.74-.94). The coefficient of repeatability was 15N, both in flexion and extension, and 1.8 Nm in rotation. On the group level, improvement up to 10% due to repeated testing was observed. CONCLUSIONS: The group with neck pain had lower neck muscle strength in all the directions tested than the control group. This factor should be considered when planning rehabilitation programs. Strength tests may be useful in monitoring training progress in clinical settings, but training programs should be planned so that the improvement in results is well above biologic variation, measurement error, and learning effect because of repeated testing.     

Effect of topical heat on electromyographic power density spectrum in subjects with myofascial pain and normal controls: a pilot study.

OBJECTIVE: To investigate the influence of superficial heat on the fatigue cascade of the upper trapezius muscle in subjects with myofascial pain and matched normal controls. DESIGN: In a prospective randomized block crossover pilot study, eight female subjects, ages 20-35 yr, with upper trapezius muscle trigger points and eight matched female control subjects without pain were studied. Subjects performed six 100-sec shoulder shrug contractions to fatigue, with subjects randomly chosen to receive heat during the first three or last three trials. The initial median frequency and the slope of the median frequency decline were calculated from the data. RESULTS: In the subjects with pain, the slope of the median frequency was elevated in ambient room temperature as compared with controls. There was no difference in slope of the median frequency under heated conditions. Heat application in controls before fatiguing exercise caused an increase in initial median frequency, whereas exercise before heat treatment resulted in a significantly lower initial median frequency. Subjects with myofascial pain had no significant change in initial median frequency. CONCLUSIONS: Heat seems to have a positive effect on muscle function in normal individuals when applied before exercise. Subjects with myofascial pain respond differently to exercise and heat challenge, which suggests a difference in their muscle physiology.     

Differentiating temporal electromyographic waveforms between those with chronic low back pain and healthy controls

Objectives. Temporal activation patterns from abdominal and lumbar muscles were compared between healthy control subjects and those with chronic low back pain.

Study design. A cross-sectional comparative study.

Background. Synergist and antagonist coactivity has been considered an important neuromuscular control strategy to maintain spinal stability. Differences in onset times and amplitudes have been reported from trunk muscle EMG recordings between healthy subjects and those with low back pain;however, evaluating temporal EMG waveforms should demonstrate whether differences exist in the ability of those with and those without low back pain to respond to changing perturbations.

Methods. The Karhunen–Loève expansion was applied to the ensemble-average EMG profiles recorded from four abdominal and three trunk extensor muscle sites while subjects performed a leg-lifting task aimed at challenging lumbar spine stability. The principal patterns were derived and the weighting coefficients for each pattern were the main dependent variables in a series of two-factor (group and muscle) mixed models.

Results. Three principal patterns explained 96% of the variance in the temporal EMG profiles. The s revealed statistically significant group and muscle main effects (P<0.05) for the principal pattern and significant group by muscle interactions (P<0.05) for patterns two and three. Post hoc analysis showed that patterns were not different among all muscle sites for the healthy controls, but differences were significant for the low back pain group.

Conclusions. The healthy group coactivated all seven sites with the same temporal pattern of activation. The low back pain group used different activation patterns indicative of a lack of synergistic coactivitation among the muscle sites examined.

Relevance

These results provide a foundation for developing a diagnostic classifier of neuromuscular impairment associated with low back pain, that could be used to evaluate the effectiveness of therapeutic interventions to improve muscle coactivation.     

Submental surface electromyographic measurement and pharyngeal pressures during normal and effortful swallowing

OBJECTIVE: To evaluate the influence of 2 swallowing maneuvers on anterior suprahyoid surface electromyographic measurement and pharyngeal manometric pressure. DESIGN: Correlational analysis of biomechanic measures of swallowing. SETTING: Research laboratory in a community hospital. PARTICIPANTS: A consecutive volunteer sample of 22 healthy subjects (mean, 29.7y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak amplitude of submental surface electromyographic and pharyngeal manometric pressure at 3 locations. RESULTS: Effortful swallow generated greater pharyngeal pressure than normal swallow at the 2 proximal pharyngeal sensors (sensor 1: P=.017; sensor 2: P=.009) and lower pressure at the distal sensor (upper esophageal sphincter) (P<.001). Pressure in the upper pharynx was lower than that in the lower pharynx (P=.027). Effortful swallow generated greater surface electromyographic amplitudes than normal swallowing (P<.001). A statistically significant but weak negative correlation was identified between surface electromyographic and mid-pharyngeal pressure for normal swallowing condition (r=-.21, P<.01). For the effortful swallowing condition, statistically significant but weak negative correlations were identified between surface electromyographic and pressure measurements at all sensors (sensor 1: r=-.16, P=.02; sensor 2: r=-.30, P<.01; sensor 3: r=-.18, P<.01). CONCLUSIONS: There is a significant change in both suprahyoid surface electromyographic and pharyngeal pressures during effortful swallow compared with normal swallow.     

Evaluating patterns of EMG amplitudes for trunk and neck muscles of patients and controls

We used ratios of EMG amplitudes to characterize neural strategies of motoneuron recruitment for seven bilateral muscle groups of the back and neck during nine motor tasks to discriminate patients who sustained sprain/strain injuries (n=61) from a control population (n=400). Compensatory relationships between muscle pairs improved the predictability of hypoactivity or hyperactivity based on the probability distribution of muscle ratios obtained from uninjured subjects. We defined severity of hypoactive or hyperactive EMG activity by (a) the number of ratios that exceeded the normal range (95% confidence interval), (b) the compensatory relationship between these muscle pairs during each motor task, and (c) the consistency and frequency of hypoactivity or hyperactivity across nine motor tasks. Accuracy of the classification system was 88% with a specificity of 90% and a sensitivity of 70%. Between-session reliability for the overall classification of 40 controls and 44 patients was 93%. These results indicate that muscle ratios can objectively quantify altered strategies of motoneuron recruitment attributed to muscle trauma and pain common to spain/strain injuries.     

Immediate effects on electromyographic activity and pressure pain thresholds after a cervical manipulation in mechanical neck pain: a randomized controlled trial

Objective

The purpose of this study was to identify the immediate effects of a manipulation of C5/C6 level on electromyography (EMG) of the deltoid muscle and in pressure pain thresholds (PPTs) in patients with mechanical neck pain.

Methods

Thirty-seven subjects with mechanical neck pain were randomly divided into 2 groups: manipulative group, which received a cervical spine manipulation targeted to C5/C6 segment, and a control group, which did not receive any procedure. Outcomes were EMG data of the deltoid muscle (rest, isometric contraction for 5 or 30 seconds, and isotonic contraction) and PPT over upper trapezius and deltoid muscles and C5 spinous process. They were assessed before and 5 minutes after treatment by a blinded assessor. A 3-way repeated-measures analysis of variance was used to examine the effects of the manipulation.

Results

A significant group time interaction for MF at the beginning of isometric contraction for 30 seconds (F = 7.957, P = .006) was also found: the manipulative group experienced a greater increase in MF at the beginning of the isometric contraction than did the control group. A significant group time interaction was also found for root mean square during isometric contraction for 30 seconds (P = .003); however, changes were small. Patients within the manipulative group experienced an increase on PPT over the deltoid (P = .010) and C5 spinous process (P = .025), but not over upper trapezius (P = .776).

Conclusions

Manipulation at C5/C6 level in the study participants seemed to increase EMG amplitude signal and fatigue resistance in a nonspinal (deltoid) muscle innervated by the same segment in patients with mechanical neck pain. However, these changes were relative small. An increase on PPT over those tissues innervated by the manipulated segment was also found after the manipulative procedure.     

Recruitment and termination of electromyographic activity in the hemiparetic forearm

Motor unit control measured by timed recruitment and termination of intramuscular electromyographic (EMG) activity provides muscle-specific quantification of deficits of the arm in chronic hemiparesis. Latencies to recruitment and termination of EMG activity of flexor carpi radialis and extensor carpi radialis longus were recorded from nine stroke patients and five age- and sex-matched control subjects, in response to buzzer signals, during maximal isometric wrist flexion and extension. Both agonist and antagonist recruitment times were slower in paretic than in control forearms (p less than .01). Termination of EMG activity occurred earlier in paretic forearms, primarily because of inability to maintain a prolonged muscular contraction. The effects of the variable lengths of testing trials reinforced these conclusions. The paretic extensor carpi radialis longus showed the greatest impairment with a very long latency to contract, and frequent failure to maintain a contraction. This study presents a new method of quantifying a common clinical problem in rehabilitation medicine.     

Doppler ultrasonography of normal neck veins

Doppler ultrasonography was used to examine 198 neck-vein systems (67 right, 131 left) in 148 patients. The vessel lumen is usually echo-free: the veins are supple, and the internal jugular and sometimes the subclavian veins can be compressed. The venous confluence is Y-shaped. Blood flow was symmetrical and biphasic in 57% of cases, continuous in 29% of cases, and monophasic in 13% of cases. Blood flow velocity was less than 1 m/s in all cases and varied with respiration and heart rate. Color Doppler allows flow imaging and increases the speed and reliability of the procedure. This investigation is useful for following-up patients with indwelling venous catheters and is the investigation of choice whenever pathology of the neck veins is suspected. © 1994 John Wiley & Sons, Inc.     

Altered skin temperature and electromyographic activity in the irritable bowel syndrome

A prospective study to determine the presence or absence of any difference in skin temperature and electromyographic (EMG) activity in 20 patients with irritable bowel syndrome (IBS) compared with 20 age- and sex-matched controls was conducted. A representative digital temperature and EMG activity during 4 phases, baseline, mental activity (arithmetic), unpleasant thoughts and audio biofeedback relaxation, were recorded using standard biofeedback equipment. Results showed the IBS group to have a significantly lower digital temperature and significantly higher EMG activity during the baseline and arithmetic phases. No difference was found in EMG activity for the unpleasant thought or audio biofeedback relaxation phases. Indeed, the IBS group were able to achieve a level of EMG activity during the audio feedback relaxation phase that approximated very closely that of the control group. These results provide further evidence suggestive of altered autonomic nervous system function in IBS patients and indicate that further studies should be undertaken to determine whether the reduction achieved in EMG activity post-relaxation is sustained, and if so, if it is associated with a corresponding improvement in symptoms.     

Effectiveness of electromyographic biofeedback training on quadriceps muscle strength in osteoarthritis of knee

The objective of this randomised controlled trial was to evaluate the effectiveness of electromyographic biofeedback as an add-on therapy with isometric exercise on quadriceps strengthening in patients with osteoarthritis of knee. Thirty three, 10 men and 23 women, patients with osteoarthritis of knee participated in the study. Patients were randomly placed into two groups: a biofeedback group (n = 17) and a control group (n = 16). The biofeedback group received electromyographic biofeedback-guided isometric exercise programme for 5 days a week for 5 weeks, whereas the control group received an exercise programme only. On between-group comparisons, the maximum isometric quadriceps strength in biofeedback group, at the end of 5^th week was significantly greater than that of the control group (p < 0.004). The addition of electromyographic biofeedback to a 5-week isometric exercise program appeared to increase quadriceps muscle strength, compared to the exercise program alone for people with knee osteoarthritis. The finding, however, should be interpreted with caution due to limitations of the study design.     

Diffuse abnormal electromyographic insertional activity: a preliminary report.

The authors observed 10 patients referred for electromyographic examination in whom EMG findings were normal except for the presence of provoked positive sharp waves in essentially every muscle tested. The positive sharp waves were present only following needle electrode insertion. No fibrillation or fasciculation potentials were seen. Motor unit action potentials were normal, as were nerve conduction and repetitive stimulation studies. The quantity of provoked positive sharp waves was found to vary from time to time, from muscle to muscle and from 1 region of the muscle to another. Detailed clinical evaluations for neuromuscular disorders, electrolyte and metabolic abnormalities and underlying carcinomas were negative. Muscle biopsy in 2 patients, including histochemical analysis in one of them, was normal. Results of single-fiber electromyography were normal in 1 patient. The abnormality was found in family members and appears to be of an autosomal dominant inheritance.