Electromyographic recordings of low back pain subjects and non-pain controls in six different positions: effect of pain levels

EEG individual power profiles correlate with tension along spine in horses

Assessing chronic pain is a challenge given its subjective dimension. In humans, resting state electroencephalography (EEG) is a promising tool although the results of various studies are contradictory. Spontaneous chronic pain is understudied in animals but could be of the highest interest for a comparative study. Riding horses show a very high prevalence of back disorders thought to be associated with chronic pain. Moreover, horses with known back problems show cognitive alterations, such as a lower attentional engagement. Therefore, we hypothesized that the individual EEG power profiles resting state (i.e. quiet standing) of different horses could reflect the state of their back, that we measured using static sEMG, a tool first promoted to assess lower back pain in human patients. Results show that 1) EEG profiles are highly stable at the intra-individual level, 2) horses with elevated back tension showed resting state EEG profiles characterized by more fast (beta and gamma) and less slow (theta and alpha) waves. The proportion of theta waves was particularly negatively correlated with muscular tension along the spine. Moreover, elevated back tension was positively correlated with the frequency of stereotypic behaviours (an "addictive- like" repetitive behavior) performed by the horses in their stall. Resting state quantitative EEG appears therefore as a very promising tool that may allow to assess individual subjective chronic pain experience, beyond more objective measures of tension. These results open new lines of research for a multi-species comparative approach and might reveal very important in the context of animal welfare.

Investigating differences in trunk muscle activity in non-specific chronic low back pain subgroups and no-low back pain controls during functional tasks: a case-control study

BACKGROUND

Trunk muscle dysfunction is often regarded as a key feature of non-specific chronic low back pain (NSCLBP) despite being poorly understood and variable with increases, decreases and no change in muscle activity reported. Differences in thoraco-lumbar kinematics have been observed in motor control impairment NSCLBP subgroups (Flexion Pattern, Active Extension Pattern) during static postures and dynamic activities. However, potential differences in muscle activity during functional tasks has not been established in these subgroups to date.

METHODS

A case-control study design recruited 50 NSCLBP subjects (27 Flexion Pattern, 23 Active Extension Pattern) and 28 healthy individuals. Surface electromyography determined muscle activity during functional tasks: reaching upwards, step-down, step-up, lifting and replacing a box, stand-to-sit, sit-to-stand, bending to retrieve (and returning from retrieving) a pen from the floor. Normalised (% sub-maximal voluntary contraction) mean amplitude electromyography of bilateral musculature (transversus abdominis/internal oblique, external oblique, superficial lumbar multifidus and longissimus thoracis) was analysed using Kruskal-Wallis and post-hoc Mann-Whitney U tests.

RESULTS

Transversus abdominis/internal oblique activity was significantly increased in the Flexion Pattern group compared to controls during stand-to-sit (p = 0.009) on the left side only. External oblique activity was significantly greater in the Active Extension Pattern group compared to controls during box lift (p = 0.016) on the right side only. Significantly greater activity was identified in the right Superficial lumbar multifidus during step up (p = 0.029), reach up (p = 0.013) and box replace (p = 0.007) in the Active Extension Pattern group compared to controls. However left-sided superficial lumbar multifidus activity was significantly greater in the Flexion Pattern group (compared to controls) only during stand-to-sit (p = 0.009). No significant differences were observed in longissimus thoracis activity bilaterally during any task. No significant differences between NSCLBP subgroups were observed.

CONCLUSIONS

Muscle activity in these NSCLBP subgroups appears to be highly variable during functional tasks with no clear pattern of activity identified. The findings reflect inconsistencies and variability in trunk muscle activity previously observed in these NSCLBP subgroups. Further work evaluating ratios of muscle activity and changes in muscle activity throughout task duration is warranted.

Effects of myofascial release in erector spinae myoelectric activity and lumbar spine kinematics in non-specific chronic low back pain: Randomized controlled trial

BACKGROUND

Flexion-relaxation response of the lumbar erector spinae has been previously studied after different interventions such as exercise programs or spinal manipulation, in subjects with chronic low back pain. The objective of the study was to investigate the effects of an isolated myofascial release protocol on erector spinae myoelectric activity and lumbar spine kinematics in chronic low back pain.

METHODS

Thirty-six participants, with nonspecific chronic low back pain, were randomized to myofascial release group (n = 18) receiving four sessions of myofascial treatment, each lasting 40 min, and to control group (n = 18) receiving a sham myofascial release. Electromyographic and kinematic variables as well as pain and disability questionnaires were analyzed.

FINDINGS

There was a bilateral reduction of the flexion relaxation ratio in individuals receiving myofascial release and who did not show myoelectric silence at baseline (right difference M = 0.34, 95% CI [0.16, 0.33], p ≤ .05 and left difference M = 0.45, 95% CI [0.16, 0.73], p ≤ .05). There was also a significant reduction in pain in the myofascial release group (difference M = -9.1, 95% CI [-16.3, -1.8], p ≤ .05) and disability (difference M = -5.6, 95% CI [-9.1, -2.1], p ≤ .05), compared with control group. No significant differences between groups were found for the kinematic variables.

INTERPRETATION

The myofascial release protocol contributed to the normalization of the flexion- relaxation response in individuals who did not show myoelectric silence before the intervention, and also showed a significant reduction in pain and disability compared with the sham group.

Clinical utility of flexion-extension ratio measured by surface electromyography for patients with nonspecific chronic low-back pain

BACKGROUND

Patients with chronic nonspecific low-back pain (CNSLBP) lack the flexion-relaxation phenomenon in full-trunk bending. This can be quantified by surface electromyography (SEMG) measurement of lumbar erector muscle. The study objective is to explore the clinical utility of the SEMG flexion-extension ratio (FER) in distinguishing patients with CNSLBP from painfree persons.

METHODS

This was a comparative cross-sectional study. We adopted a balanced study design by recruiting 130 participants each for the CNSLBP and control arms. Each participant underwent dynamic SEMG measurement in full-trunk bending, which consisted of standing, flexion, relaxation, and extension. The FER ratio was the ratio of the maximum SEMG in flexion to the maximum SEMG during extension. Receiver-operating characteristic (ROC) analysis was conducted to identify optimal values of the FER and associated sensitivity, specificity, and diagnostic accuracy.

RESULTS

The CNSLBP group and control group were generally comparable in terms of demographics and clinical profile. The CNSLBP group had higher SEMG amplitudes during flexion but lower SEMG during extension. The mean (SD) FER of the CNSLBP group was 0.90 (0.26), which was almost double that of controls 0.47 (0.14). The ROC curve identified an optimal FER cutoff of ≥ 0.692, for which sensitivity and specificity were 76.15% (95%confidence interval [CI], 68.14-82.66) and 98.46% (95%CI, 94.56-99.58). The diagnostic accuracy was 92.1% (95%CI, 88.70-95.54).

CONCLUSION

The FER derived by lumbar muscle SEMG is able to distinguish patients with CNSLBP from pain-free people with excellent accuracy. This provides good evidence that a customized FER can be used in various clinical scenarios.

The relationship between functionality and erector spinae activity in patients with specific low back pain during dynamic and static movements

BACKGROUND

Alterations in the activity of the lumbar erector spinae (LES) muscles on both sides of the spine have been inconsistently reported in patients with specific low back pain (sLBP) after measuring the muscular activity with surface electromyography (sEMG). It also remains unclear whether these alterations in LES activity can be related to the functional level of patients with sLBP.

RESEARCH QUESTION

This study investigated the LES activity in patients with sLBP during activities of daily living (ADL) which included dynamic and static movement tasks. Moreover, the alterations in LES activity were correlated with the first seven questions of the Zurich Claudication Questionnaire (ZCQ-SS).

METHODS

Thirty patients with specific LBP and twenty healthy subjects were recruited to perform five ADLs including 'static waist flexion', 'sit to stand',' 30-seconds standing', '6-minutes walking' and 'climbing stairs'. sEMG sensors were mounted on the left and right LES muscles. The integrated EMG (IEMG) was calculated from the preprocessed sEMG data as statistical comparison criteria.

RESULTS

LES activity was significantly higher in patients during 'sit to stand',' 30-seconds standing' and 'climbing stairs' and significantly lower during 'static waist flexion' compared to healthy controls. All tasks showed a significant correlation with the ZCQ-SS score except for '6-minutes walking', whereby LES activity and ZCQ-SS score correspondingly increased during 'sit to stand' and 'climbing stairs' and the LES activity decreased with an increasing ZCQ-SS score during 'static waist flexion' and' 30-seconds standing'.

SIGNIFICANCE

There was a high correlation between alterations in LES activity and the level of functionality in LBP patients. However, the LES activity showed an opposite behavior during static and dynamic movement tasks. The methodology presented can be a useful tool for quantifying improvements in functionality after rehabilitation processes.

Surface Electromyographic (SEMG) Biofeedback for Chronic Low Back Pain

Biofeedback is a process in which biological information is measured and fed back to a patient and clinician for the purpose of gaining increased awareness and control over physiological domains. Surface electromyography (SEMG), a measure of muscle activity, allows both a patient and clinician to have direct and immediate access to muscle functioning that is not possible with manual palpation or visual observation. SEMG biofeedback can be used to help “down-train” elevated muscle activity or to “up-train” weak, inhibited, or paretic muscles. This article presents a historical and clinical overview of SEMG and its use in chronic low back pain assessment and biofeedback training.

Time-varying surface electromyography topography as a prognostic tool for chronic low back pain rehabilitation

BACKGROUND CONTEXT

Nonsurgical rehabilitation therapy is a commonly used strategy to treat chronic low back pain (LBP). The selection of the most appropriate therapeutic options is still a big challenge in clinical practices. Surface electromyography (sEMG) topography has been proposed to be an objective assessment of LBP rehabilitation. The quantitative analysis of dynamic sEMG would provide an objective tool of prognosis for LBP rehabilitation.

PURPOSE

To evaluate the prognostic value of quantitative sEMG topographic analysis and to verify the accuracy of the performance of proposed time-varying topographic parameters for identifying the patients who have better response toward the rehabilitation program.

STUDY DESIGN

A retrospective study of consecutive patients.

PATIENT SAMPLE

Thirty-eight patients with chronic nonspecific LBP and 43 healthy subjects.

OUTCOME MEASURES

The accuracy of the time-varying quantitative sEMG topographic analysis for monitoring LBP rehabilitation progress was determined by calculating the corresponding receiver-operating characteristic (ROC) curves. Physiologic measure was the sEMG during lumbar flexion and extension.

METHODS

Patients who suffered from chronic nonspecific LBP without the history of back surgery and any medical conditions causing acute exacerbation of LBP during the clinical test were enlisted to perform the clinical test during the 12-week physiotherapy (PT) treatment. Low back pain patients were classified into two groups: "responding" and "nonresponding" based on the clinical assessment. The responding group referred to the LBP patients who began to recover after the PT treatment, whereas the nonresponding group referred to some LBP patients who did not recover or got worse after the treatment. The results of the time-varying analysis in the responding group were compared with those in the nonresponding group. In addition, the accuracy of the analysis was analyzed through ROC curves.

RESULTS

The time-varying analysis showed discrepancies in the root-mean-square difference (RMSD) parameters between the responding and nonresponding groups. The relative area (RA) and relative width (RW) of RMSD at flexion and extension in the responding group were significantly lower than those in the nonresponding group (p<.05). The areas under the ROC curve of RA and RW of RMSD at flexion and extension were greater than 0.7 and were statistically significant.

CONCLUSIONS

The quantitative time-varying analysis of sEMG topography showed significant difference between the healthy and LBP groups. The discrepancies in quantitative dynamic sEMG topography of LBP group from normal group, in terms of RA and RW of RMSD at flexion and extension, were able to identify those LBP subjects who would respond to a conservative rehabilitation program focused on functional restoration of lumbar muscle.

Towards a postural indicator of back pain in horses (Equus caballus)

Postures have long been used and proved useful to describe animals' behaviours and emotional states, but remains difficult to assess objectively in field conditions. A recent study performed on horses using geometric morphometrics revealed important postural differences between 2 horse populations differing in management conditions (leisure horses living in social groups used for occasional "relaxed" riding/riding school horses living in individual boxes used in daily riding lessons with more constraining techniques). It was suggested that these postural differences may reflect chronic effects of riding techniques on the horses' kinematics and muscular development. In the present study, we tried to evaluate the interest of postural measures to assess welfare in horses. This study was separated into 2 parts. First, 18 horses coming from these 2 types of populations (leisure/riding school horses) were submitted to 2 back evaluations by 1) manual examination (experienced practitioner) and 2) sEMG measures along the spine. We then measured neck roundness on 16 of these 18 horses. The results highlighted high correlations between manual and sEMG examinations over the spine. sEMG measures at the different locations were strongly correlated all over the spine. Moreover, neck postures and muscular activities were strongly correlated, horses with concave necks having higher sEMG measures both at precise locations (i.e. cervical sites) but also when comparing neck postures to the whole spine muscular activity highlighting the functioning of horses' back as a whole. Lastly, strong differences appeared between the populations, leisure horses being evaluated as having sounder spines, exhibiting lower sEMG measures and rounder neck than the riding school horses. sEMG measures and neck "roundness" seemed therefore to be reliable indicators of back disorders, easy to evaluate in field conditions. This highlights the accuracy of using postural elements to evaluate the animals' general state and has important implications for animals' welfare evaluations.

Suppression of anger and subsequent pain intensity and behavior among chronic low back pain patients: the role of symptom-specific physiological reactivity

Suppression of anger may be linked to heightened pain report and pain behavior during a subsequent painful event among chronic low back patients, but it is not clear whether these effects are partly accounted for by increased physiological reactivity during suppression. Chronic low back pain patients (N = 58) were assigned to Suppression or No Suppression conditions for a "cooperative" computer maze task during which a confederate harassed them. During baseline and maze task, patients' lower paraspinal and trapezius muscle tension, blood pressure and heart rate were recorded. After the maze task, patients underwent a structured pain behavior task (behaviors were videotaped and coded). Results showed that: (a) Suppression condition patients revealed greater lower paraspinal muscle tension and systolic blood pressure (SBP) increases during maze task than No Suppression patients (previously published results showed that Suppression condition patients exhibited more pain behaviors than No Suppression patients); (b) residualized lower paraspinal and SBP change scores were related significantly to pain behaviors; (c) both lower paraspinal and SBP reactivity significantly mediated the relationship between Condition and frequency of pain behaviors. Results suggest that suppression-induced lower paraspinal muscle tension and SBP increases may link the actual suppression of anger during provocation to signs of clinically relevant pain among chronic low back pain patients.

Decrease in postural sway and trunk stiffness during cognitive dual-task in nonspecific chronic low back pain patients, performance compared to healthy control subjects

STUDY DESIGN

A 2-group experimental design.

OBJECTIVE

To investigate the effect of a cognitive dual-task on postural sway of pelvis and trunk during unstable sitting in nonspecific chronic patients with low back pain (CLBP) compared to healthy control subjects.

SUMMARY OF BACKGROUND DATA

Higher cognitive systems as well as sensory processes contribute to postural control. An increase in postural sway due to a cognitive dual task could mean more need of cognitive systems to control balance.

METHODS

A total of 21 CLBP patients and 21 control subjects were included based on detailed clinical criteria. Every subject was submitted to 2 postural control tests in an unstable sitting position (easy test position: 2 feet on the ground and difficult test position: 1 foot lifted). Both tests were performed with and without cognitive dual-task. A 3-dimensional motion analysis system was used measure angular displacement of trunk and pelvis in the 3 cardinal planes.

RESULTS

In the most difficult balance position, postural sway increases in the control group when the cognitive dual-task is added, for 50% of the variables the increase is significant (P between 0.02 and 0.05). On the contrary, postural sway decreases, not significantly, in the CLBP group when the dual-task is added. These findings are the same for trunk as for pelvis deviations. The Pearson correlation coefficient between trunk and pelvis movement from the CLBP group are lower for all 3 movement directions in the dual-task condition (r between 0.441 and 0.988) compared to the single task condition (r between 0.982 and 0.995).

CONCLUSION

In nonspecific CLBP patients, a cognitive dual-task reduces both postural sway and trunk stiffness due to the distracting effect of the dual-task. This effect is only visible when the balance task is difficult.

The myth of core stability

The principle of core stability has gained wide acceptance in training for the prevention of injury and as a treatment modality for rehabilitation of various musculoskeletal conditions in particular of the lower back. There has been surprisingly little criticism of this approach up to date. This article re-examines the original findings and the principles of core stability/spinal stabilisation approaches and how well they fare within the wider knowledge of motor control, prevention of injury and rehabilitation of neuromuscular and musculoskeletal systems following injury.

Anger management style moderates effects of attention strategy during acute pain induction on physiological responses to subsequent mental stress and recovery: a comparison of chronic pain patients and healthy nonpatients

OBJECTIVES

To examine whether high trait anger-out chronic low back (CLBP) patients would show exceptionally large symptom-specific lower paraspinal (LP) responses, compared with healthy nonpatients, during pain induction, a subsequent mental stressor, and recovery when they were urged to suppress awareness of pain and suffering.

METHODS

CLBP patients (n = 93) and nonpatients (n = 105) were assigned randomly to one of four attention strategy conditions for use during pain induction: sensory-focus, distraction, suppression, or control. All participants underwent a cold pressor, and then performed mental arithmetic. They completed the anger-out (AOS) and anger-in (AIS) subscales of the Anger Expression Inventory.

RESULTS

General Linear Model procedures were used to test Attention Strategy Condition x Patient/Nonpatient Status x AOS (or AIS) x Period interactions for physiological indices. Significant interactions were found such that: a) high trait anger-out patients in the Suppression condition seemed to show the greatest LP reactivity during the mental arithmetic followed by the slowest recovery compared with other conditions; b) high trait anger-out patients and nonpatients in the Suppression condition seemed to show the slowest systolic blood pressure recoveries compared with other conditions.

CONCLUSIONS

Results extend previous work by suggesting that an anger-out style moderates effects of how attention is allocated during pain on responses to and recovery from a subsequent mental stressor. Results provide further evidence that trait anger-out and trait anger-in among CLBP patients are associated with increased LP muscle tension during and after pain and mental stress.

Trait anger management style moderates effects of actual ("state") anger regulation on symptom-specific reactivity and recovery among chronic low back pain patients

OBJECTIVES

We examined whether "state" anger regulation-inhibition or expression-among chronic low back pain (CLBP) patients would affect lower paraspinal (LP) muscle tension following anger-induction, and whether these effects were moderated by trait anger management style.

METHOD

Eighty-four CLBP patients underwent harassment, then they regulated anger under one of two conditions: half expressed anger by telling stories about people depicted in pictures, whereas half inhibited anger by only describing objects appearing in the same pictures. They completed the anger-out and anger-in subscales (AOS; AIS) of the anger expression inventory.

RESULTS

General Linear Model procedures were used to test anger regulation condition by AOS/AIS by period interactions for physiological indexes. Significant three-way interactions were found such that: a) high trait anger-out patients in the inhibition condition appeared to show the greatest LP reactivity during the inhibition period followed by the slowest recovery; b) high trait anger-out patients in the expression condition appeared to show the greatest systolic blood pressure (SBP) reactivity during the expression period followed by rapid recovery.

CONCLUSIONS

Results implicate LP muscle tension as a potential physiological mechanism that links the actual inhibition of anger following provocation to chronic pain severity among CLBP patients. Results also highlight the importance of mismatch situations for patients who typically regulate anger by expressing it. These CLBP patients may be at particular risk for elevated pain severity if circumstances at work or home regularly dictate that they should inhibit anger expression.

Pain catastrophizing, physiological indexes, and chronic pain severity: tests of mediation and moderation models

Catastrophizing about pain is related to elevated pain severity and poor adjustment among chronic pain patients, but few physiological mechanisms by which pain catastrophizing maintains and exacerbates pain have been explored. We hypothesized that resting levels of lower paraspinal muscle tension and/or lower paraspinal and cardiovascular reactivity to emotional arousal may: (a) mediate links between pain catastrophizing and chronic pain intensity; (b) moderate these links such that only patients described by certain combinations of pain catastrophizing and physiological indexes would report pronounced chronic pain. Chronic low back pain patients (N = 97) participated in anger recall and sadness recall interviews while lower paraspinal and trapezius EMG and systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were recorded. Mediation models were not supported. However, pain catastrophizing significantly interacted with resting lower paraspinal muscle tension to predict pain severity such that high catastrophizers with high resting lower paraspinal tension reported the greatest pain. Pain catastrophizing also interacted with SBP, DBP and HR reactivity to affect pain such that high catastrophizers who showed low cardiovascular reactivity to the interviews reported the greatest pain. Results support a multi-variable profile approach to identifying pain catastrophizers at greatest risk for pain severity by virtue of resting muscle tension and cardiovascular stress function.

Anger inhibition and pain: conceptualizations, evidence and new directions

Anger and how anger is regulated appear to affect acute and chronic pain intensity. The inhibition of anger (anger-in), in particular, has received much attention, and it is widely believed that suppressing or inhibiting the verbal or physical expression of anger is related to increased pain severity. We examine theoretical accounts for expecting that anger inhibition should affect pain, and review evidence for this claim. We suggest that the evidence for a link between trait anger-in (the self-reported tendency to inhibit anger expression when angry) and acute and chronic pain severity is quite limited owing to a number of factors including a inadequate definition of trait anger-in embodied in the popular anger-in subscale of Spielberger's Anger Expression Inventory, and a strong overlap between trait anger-in scores and measures of general negative affect (NA). We argue that in order to determine whether something unique to the process of anger inhibition exerts direct effects on subsequent pain intensity, new conceptualizations and approaches are needed that go beyond self-report assessments of trait anger-in. We present one model of anger inhibition and pain that adopts elements of Wegner's ironic process theory of thought suppression. Findings from this emerging research paradigm indicate that state anger suppression (suppression manipulated in the laboratory) may indeed affect sensitivity to subsequent painful stimuli, and we outline potentially productive avenues of future inquiry that build on this model. We conclude that although studies employing correlational designs and self-reports of trait anger-in have not upheld the claim that anger inhibition affects pain severity, evidence from studies using new models suggests that actually inhibiting anger expression during a provocative event may increase perceived pain at a later time.

Muscular reactivity and specificity in chronic back pain patients

OBJECTIVE

To compare the muscular reactivity of patients with chronic back pain (CBP) to different psychological stressors with the reactions of healthy controls. We also investigated the specificity of muscular reaction near the site of pain in comparison to distal sites. The symptom-specificity model of chronic pain postulates that increased muscle tension in CBP patients may be responsible for the development and maintenance of chronic pain.

METHOD

We studied a total of 54 CBP patients with musculoskeletal pain of the lower back, midback, or neck and 62 healthy controls, matched with CPB patients. Muscle tension and skin conductance level (SCL) were assessed. The four experimental conditions included back focusing, a personally relevant stressor, a cognitive stressor, and a social stressor.

RESULTS

CBP patients showed patterns of higher muscular reactivity in the lower back region for chronic low back pain (CLBP) patients during the exposure to a personally relevant stressor, a cognitive stressor, and a social stressor. Additionally, CLBP patients showed specific muscular responses in the lower back.

CONCLUSION

The results support the assumptions made by the symptom-specificity model of CBP, but only for lower back, not for midback and neck. Treatment programs of CLBP should include specific combined relaxation and stress management components.

Three-dimensional kinetics of the lumbar spine and hips in low back pain patients during sit-to-stand and stand-to-sit

STUDY DESIGN

Experimental, biomechanical study to determine the kinetics of the lumbar spine and hips during sit-to-stand and stand-to-sit.

OBJECTIVE

To investigate the effects of back pain, with and without limitation in straight leg raise, on the joint moment and power of the lumbar and hips during sit-to-stand and stand-to-sit.

SUMMARY OF BACKGROUND DATA

Movements of the lumbar spine and hips, and their coordination have been reported to be affected by the presence of low back pain (LBP), especially in those with a positive straight leg raise. However, the literature has no information concerning moment and power characteristics of the lumbar spine and hips during sit-to-stand and stand-to-sit in such patients.

METHODS

Twenty asymptomatic subjects, 20 LBP patients, and 20 patients with LBP and a positive straight leg raise sign were requested to perform the sit-to-stand and stand-to-sit activities. Electromagnetic sensors were attached to the body segments to measure their kinematics while 2 nonconductive force plates gathered ground reaction force data. Biomechanical models were used to determine the muscle moments and power at the lumbosacral (L5/S1) joint and hips.

RESULTS

Muscle moments acting at the lumbar spine and hip in the sagittal plane were found to decrease in subjects with LBP, but there were significant increases in moments in other planes of motion. The power patterns of the spine and hips were also significantly altered, particularly in subjects with a positive straight leg raise sign.

CONCLUSIONS

Back pain subjects exhibit compensatory movements and altered load sharing strategies during the sit-to-stand and stand-to-sit activities. Exercise therapy should take account of these changes so that the normal kinematic and kinetic characteristics of the spine and hips can be restored.

Dynamic Surface Electromyographic Responses in Chronic Low Back Pain Treated by Traditional Bone Setting and Conventional Physical Therapy

OBJECTIVE

This study compared the dynamic surface electromyographic (EMG) activities of back muscles and pain before and after traditional bone setting and physical therapy.

METHODS

This study was a prospective clinical trial that compared surface EMG dynamic activities after traditional bone setting and physical therapy. Sixty-one patients (mean age, 41 years) with nonspecific low back pain were randomized into two subgroups by treatment. The patients underwent a dynamic EMG evaluation for which they were asked to stand and then bend forward as far as possible, stay fully flexed, and return to standing. A flexion-relaxation ratio was calculated by comparing maximal EMG activity while flexing with the average EMG activity in full flexion. Concentric (maximal EMG activity during extension) and eccentric (maximal EMG activity during flexion) ratios were also used in the analyses.

RESULTS

Disability, depression, and visual analog scale scores decreased significantly after both treatments. The concentric ratio increased statistically in both groups after the treatments. The study failed to show a significant association between experienced back pain and EMG parameters.

CONCLUSIONS

Both treatments seem to have a positive influence on back muscle function by improving muscle symmetry; however, the treatments had no effect on the flexion-relaxation phenomenon after 1 month. Active back exercise at home together with rehabilitation treatments might be effective and improve function for patients with chronic low back pain.

Arousal of negative emotions and symptom-specific reactivity in chronic low back pain patients

Anger may have greater effects on chronic pain severity than other negative emotions and may do so by increasing muscle tension near the site of injury (symptom-specific reactivity). For patients with chronic low back pain (CLBP), relevant muscles are lower paraspinals (LP). Ninety-four CLBP patients and 79 controls underwent anger and sadness recall interviews. EMG and cardiovascular activity were recorded. Patients exhibited greater LP tension increases during anger and slower recovery than controls. Only patients showed greater LP reactivity during anger than sadness. For both groups, trapezius reactivity during anger and sadness did not differ. LP reactivity to anger correlated with everyday pain severity for patients. Anger-induced symptom-specific LP reactivity may be linked to chronic pain aggravation among CLBP patients.

Anger management style and hostility among patients with chronic pain: effects on symptom-specific physiological reactivity during anger- and sadness-recall interviews

OBJECTIVES

We examined whether anger-in, anger-out, and hostility predicted symptom-specific muscle tension reactivity during anger induction (but not sadness induction) among patients with chronic low back pain (CLBP). For patients with CLBP, relevant muscles are the lower paraspinals (LPs). Anger-in x hostility and anger-out x hostility interactions were tested to determine whether particularly reactive groups of patients could be identified with a multivariable profile approach.

METHODS

Ninety-four patients with CLBP underwent anger recall (ARI) and sadness recall (SRI) interviews, whereas LP and trapezius electromyography and systolic blood pressure, diastolic blood pressure, and heart rate were recorded. They completed anger-in, anger-out, hostility, and trait anger measures.

RESULTS

Hierarchical regressions were used to test anger-in x hostility and anger-out x hostility interactions for physiological changes during the ARI and SRI. A significant anger-in x hostility interaction was found for LP change during the ARI (but not SRI) such that high anger-in/high hostility patients evinced the greatest reactivity. Effects for trapezius reactivity were nonsignificant. Significant anger-in x hostility interactions were also found for systolic blood pressure and diastolic blood pressure changes during the ARI such that high anger-in/low hostility patients showed the smallest changes. The anger-out x hostility interaction for diastolic blood pressure change during ARI was also significant such that high anger-out/low hostility patients showed the smallest changes. All effects remained significant with trait anger controlled.

CONCLUSIONS

A multivariable profile approach may help identify especially vulnerable patient groups. Patients with CLBP who tend to suppress anger and are cynically hostile may be more likely to experience high levels of muscle tension near the site of pain and injury during anger, but not during sadness, than other groups.

Altered patterns of superficial trunk muscle activation during sitting in nonspecific chronic low back pain patients: importance of subclassification

STUDY DESIGN

A cross-sectional comparative study between healthy controls and two subgroups of nonspecific chronic low back pain (LBP) patients.

OBJECTIVES

To determine differences in trunk muscle activation during usual unsupported sitting.

SUMMARY OF BACKGROUND DATA

Patients with LBP commonly report exacerbation of pain on sitting. Little evidence exists to confirm that subgroups of patients with nonspecific chronic LBP patients use different motor patterns in sitting than pain-free controls.

METHODS

A total of 34 pain-free and 33 nonspecific chronic LBP subjects were recruited. Two blinded clinicians classified nonspecific chronic LBP patients into two subgroups (active extension pattern and flexion pattern). Surface electromyography (sEMG) was recorded from five trunk muscles during subjects' unsupported "usual" and "slumped" sitting.

RESULTS

No differences in trunk muscle activity were observed between healthy controls and nonspecific chronic LBP groups for usual sitting. When the classification system was applied, differences were identified. Compared with no-LBP controls, the active extension pattern group presented with higher levels of cocontraction of superficial fibers of lumbar multifidus (12%), iliocostalis lumborum pars thoracis (36%) and transverse fibers of internal oblique (43%). while the flexion pattern group showed a trend toward lower activation patterns (lumbar multifidus, -7%; iliocostalis lumborum pars thoracis, -6%, and transverse fibers of internal oblique, -5%). The flexion relaxation ratio of the back muscles was lower for nonspecific chronic LBP (superficial lumbar multifidus: t = 4.5; P < 0.001 and iliocostalis lumborum pars thoracis:t = 2.7; P < 0.001), suggesting a lack of flexion relaxation for the nonspecific chronic LBP.

CONCLUSION

Subclassifying nonspecific chronic LBP patients revealed clear differences in sEMG activity during sitting between pain-free subjects and subgroups of nonspecific chronic LBP patients.

The role of attentional strategies in moderating links between acute pain induction and subsequent psychological stress: Evidence for symptom-specific reactivity among patients with chronic pain versus healthy nonpatients

Vulnerability to stressors after pain may depend on the degree to which the strategy used to process information about pain perpetuates thoughts of suffering and distress. Patients with chronic low back pain (CLBP) may show susceptibility to stress after pain through symptom-specific (lower paraspinal [LP]) muscle reactivity. Patients with CLBP (n = 100) and healthy nonpatients (n = 105) underwent a cold pressor, under sensory focus, distraction, suppression, or control conditions, and then performed mental arithmetic. Only patients under the suppression condition revealed increased LP tension during pain that was sustained during mental arithmetic and sustained systolic blood pressure after mental arithmetic. Patients with CLBP who suppress pain may detrimentally affect responses to the next noxious event, particularly through prolonged LP muscle tension, that may contribute to a cycle of pain-stress-pain.

A Meta-Analytic Review of Surface Electromyography Among Persons With Low Back Pain and Normal, Healthy Controls

Significant differences in surface electromyography (SEMG) have been reported between persons with low back pain (LBP) and normal, healthy controls. This manuscript presents a systematic meta-analytic review of studies examining SEMG differences between these groups. Forty-four articles were identified using MEDLINE and a review of reference lists in articles. For static SEMG, the largest effect size was observed for SEMG while standing, with subjects having LBP demonstrating higher SEMG. The effect size for flexion/relaxation measures was found to be very high (d = -1.71). Studies examining SEMG during isometric exercise or muscle recovery following exercise produced inconsistent findings. Sensitivity and specificity of SEMG for dynamic SEMG measures averaged 88.8% and 81.3%. Most classification schemes were statistically determined and utilized a combination of measures. Only one published study prospectively validated a classification scheme. SEMG measures of flexion-relaxation appear to distinguish LBP subjects from controls with good accuracy, and the sensitivity and specificity of SEMG can be increased by using multiple measures. Further research is needed to determine the combination of measures that are cost-effective, reliable, valid and discriminate with a high degree of accuracy between healthy persons and those with LBP.

PERSPECTIVE

SEMG is a simple and noninvasive measure of muscle activity. SEMG measures hold promise as an objective marker of LBP.

The value of electromyography of the lumbar paraspinal muscles in discriminating between chronic-low-back-pain sufferers and normal subjects

The authors studied the surface electromyographic (EMG) spectrum of the paraspinal muscles of 350 subjects. They were classified by their history as normal (n=175), chronic low back pain (n=145), or past history (n=30). They pulled upwards on a floor-mounted load cell at two-thirds of their maximum voluntary contraction for 30 s, while the EMG was measured from the paraspinal muscles at the L4/L5 level. From the EMG signal the root-mean-square (RMS) was calculated. Power spectrum analysis allowed calculation of the median frequency slope, the initial median frequency (IMF), modal frequency, peak amplitude and spectral width at half peak amplitude (half-width). All of the variables of the chronic group were significantly different from the normal group, except the median frequency slope, RMS slope and mode. Half-width, age and maximum voluntary contraction were shown to be independent predictors of back pain classification. Half-width classified the subjects with a sensitivity of 0.65 and a specificity of 0.75.

A Clinical and Pharmacologic Review of Skeletal Muscle Relaxants for Musculoskeletal Conditions

Muscle strains and other musculoskeletal disorders (MSDs) are a leading cause of work absenteeism. Muscle pain, spasm, swelling, and inflammation are symptomatic of strains. The precise relationship between musculoskeletal pain and spasm is not well understood. The dictum that pain induces spasm, which causes more pain, is not substantiated by critical analysis. The painful muscle may not show EMG activity, and when there is, the timing and intensity often do not correlate with the pain. Clinical and physiologic studies show that pain tends to inhibit rather than facilitate reflex contractile activity. The decision to treat and choice of therapy are largely dictated by the duration, severity of symptoms, and degree of dysfunction. Trigger point injections are sometimes used with excellent results in the treatment of muscle spasm in myofacial pain and low-back pain. NSAIDs are used with much greater frequency than oral skeletal muscle relaxants (SMRs) or opioids in the treatment of acute MSDs. Unfortunately, remarkably little sound science guides the choice of drug for the treatment of acute, uncomplicated MSDs, and the evaluation of efficacy of one agent over another is complicated by numerous factors. Only a limited number of high-quality, randomized, controlled trials (RCTs) provide evidence of the effectiveness of NSAIDs or SMRs in the treatment of acute, uncomplicated MSDs. The quality of design, execution, and reporting of trials for the treatment of MSDs needs to be improved. The combination of an SMR and an NSAID or COX-2 inhibitor or the combination of SMR and tramadol/acetaminophen is superior to single agents alone.

Pain-Related Fear, Lumbar Flexion, and Dynamic EMG Among Persons With Chronic Musculoskeletal Low Back Pain

OBJECTIVES

The purpose of this study was to examine the relationship between pain-related fear, lumbar flexion, and dynamic EMG activity among persons with chronic musculoskeletal low back pain. It was hypothesized that pain-related fear would be significantly related to decreased lumbar flexion and specific patterns of EMG activity during flexion and extension.

STUDY DESIGN

Data was obtained from subjects who, on a single day, completed self-report measures of pain and pain-related fear, and were interviewed to determine demographic and pain information. Subjects then underwent a dynamic EMG evaluation for which they were asked to stand, then bend forward as far as possible, stay fully flexed, and return to standing. Lumbar EMG and angle of flexion were recorded during this time. A flexion-relaxation ratio (FRR) was computed by comparing maximal EMG while flexing to the average EMG in full flexion.

SUBJECTS

Seventy-six persons with chronic musculoskeletal low back pain.

RESULTS

Zero-order correlations indicated that pain-related fear was significantly related to reduced lumber flexion (r = -0.55), maximum EMG during flexion (r = -0.38) and extension (r = -0.51), and the FRR (r = -0.40). When controlling for pain and demographic factors, pain-related fear continued to be related to reduced lumbar flexion. Using a path-analytic model to examine whether angle of flexion mediated the relationship between fear and EMG activity, the models examining maximal EMG during flexion and extension supported the notion that pain-related fear influences these measures indirectly through its association with decreased range of motion. Conversely, pain-related fear was independently related to higher average EMG in full flexion, while angle of flexion was not significantly related. Pain-related fear was directly related to a smaller FRR, as well as indirectly through angle of flexion.

CONCLUSIONS

Pain-related fear is significantly associated with reduced lumbar flexion, greater EMG in full flexion, and a smaller FRR. The relationship between pain-related fear and EMG during flexion and extension appears to be mediated by reduced lumbar flexion. These results suggest that pain-related fear is directly associated with musculoskeletal abnormalities observed among persons with chronic low back pain, as well as indirectly through limited lumbar flexion. These musculoskeletal abnormalities as well as limited movement may be involved in the development and maintenance of chronic low back pain. In addition, changes in musculoskeletal functioning and flexion associated with pain-related fear may warrant greater attention as part of treatment.

Trunk muscle activation in low-back pain patients, an analysis of the literature

This paper provides an analysis of the literature on trunk muscle recruitment in low-back pain patients. Two models proposed in the literature, the pain-spasm-pain model and the pain adaptation model, yield conflicting predictions on how low- back pain would affect trunk muscle recruitment in various activities. The two models are outlined and evidence for the two from neurophsysiological studies is reviewed. Subsequently, specific predictions with respect to changes in activation of the lumbar extensor musculature are derived from both models. These predictions are compared to the results from 30 clinical studies and three induced pain studies retrieved in a comprehensive literature search. Neither of the two models is unequivocally supported by the literature. These data and further data on timing of muscle activity and load sharing between muscles suggest an alternative model to explain the alterations of trunk muscle recruitment due to low-back pain. It is proposed that motor control changes in patients are functional in that they enhance spinal stability.

EMG activity of trunk muscles and torque output during isometric axial rotation exertion: a comparison between back pain patients and matched controls

Abnormal patterns of trunk muscle activity could affect the biomechanics of spinal movements and result in back pain. The present study aimed to examine electromyographic (EMG) activity of abdominal and back muscles as well as triaxial torque output during isometric axial rotation at different exertion levels in back pain patients and matched controls. Twelve back pain patients and 12 matched controls performed isometric right and left axial rotation at 100%, 70%, 50% and 30% maximum voluntary contractions in a standing position. Surface EMG activity of rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus were recorded bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were measured. Results showed that there was a trend (P = 0.08) of higher flexion coupling torque during left axial rotation exertion in back pain patients. Higher activity for external oblique and lower activity for multifidus was shown during left axial rotation exertion in back pain group when compared to the control group. In right axial rotation, back pain patients exhibited lesser activity of rectus abdominis at higher levels of exertion when compared with matched controls. These findings demonstrated that decreased activation of one muscle may be compensated by overactivity in other muscles. The reduced levels of activity of the multifidus muscle during axial rotation exertion in back pain patients may indicate that spinal stability could be compromised. Future studies should consider these alternations in recruitment patterns in terms of spinal stability and internal loading. The findings also indicate the importance of training for coordination besides the strengthening of trunk muscles during rehabilitation process.

A review of temporomandibular disorder diagnostic techniques

The American Dental Association has approved several devices as aids in the diagnosis of temporomandibular disorders. Concerns remain, however, about their safety and effectiveness. This article reviews the validity and use of several instruments that claim to serve as aids in the detection of masticatory muscle pain, trismus, joint noises, and limitation of jaw motion. A review of data from 62 published articles indicated that, although commercial devices that measure jaw muscle tenderness, muscle activity levels, joint noises, and jaw motion are safe and can document these phenomena, cost-benefit analyses of these devices have not yet been conducted. Moreover, these devices have not been shown to have stand-alone diagnostic value and, when tested, they have demonstrated unacceptable sensitivity and specificity levels. None of the instruments reviewed in this article can be said to provide more than ancillary documentation.

Spinal reflex attenuation associated with spinal manipulation

STUDY DESIGN

This study evaluated the effect of lumbosacral spinal manipulation with thrust and spinal mobilization without thrust on the excitability of the alpha motoneuronal pool in human subjects without low back pain.

OBJECTIVES

To investigate the effect of high velocity, low amplitude thrust, or mobilization without thrust on the excitability of the alpha motoneuron pool, and to elucidate potential mechanisms in which manual procedures may affect back muscle activity.

SUMMARY OF BACKGROUND DATA

The physiologic mechanisms of spinal manipulation are largely unknown. It has been proposed that spinal manipulation may reduce back muscle electromyographic activity in patients with low back pain. Although positive outcomes of spinal manipulation intervention for low back pain have been reported in clinical trials, the mechanisms involved in the amelioration of symptoms are unknown.

METHODS

In this study, 17 nonpatient human subjects were used to investigate the effect of spinal manipulation and mobilization on the amplitude of the tibial nerve Hoffmann reflex recorded from the gastrocnemius muscle. Reflexes were recorded before and after manual spinal procedures.

RESULTS

Both spinal manipulation with thrust and mobilization without thrust significantly attenuated alpha motoneuronal activity, as measured by the amplitude of the gastrocnemius Hoffmann reflex. This suppression of motoneuronal activity was significant (P < 0.05) but transient, with a return to baseline values exhibited 30 seconds after intervention.

CONCLUSIONS

Both spinal manipulation with thrust and mobilization without thrust procedures produce a profound but transient attenuation of alpha motoneuronal excitability. These findings substantiate the theory that manual spinal therapy procedures may lead to short-term inhibitory effects on the human motor system.

Chronic low back pain assessment using surface electromyography

This investigation examined surface electromyography as an additional tool in the comprehensive clinical evaluation of patients with chronic low back pain (CLBP). Electromyographic signals from electrodes placed in the lumbar area of 30 CLBP patients and 30 non-pain control subjects were compared. Patients and controls were matched for age, gender, and body mass index. Paired t test showed a statistically significant difference between the two groups. The muscle activity mean values were threefold higher in CLBP patients than in controls (P < 0.00001) in the static testing, and twofold higher in CLBP patients than in controls (P < 0.00001) in the dynamic testing. Our findings indicate that surface electromyography assessment of the paraspinal muscle activity may be a useful objective diagnostic tool in the comprehensive evaluation of CLBP.

The comparison of trunk muscles EMG activation between subjects with and without chronic low back pain during flexion-extension and lateral bending tasks

The purpose of the study was to compare the electromyographic (EMG) activity of the trunk muscles between normal subjects and chronic low back pain (CLBP) patients during standardized trunk movements. Thirty-three male subjects (18 normals, 15 suffering from non specific CLBP) aged between 35 and 45 yr participated. A biomechanical analysis involving the recording of EMG signals from 12 trunk muscles, the kinematics of trunk segments and the computation of L5/S1 moments was performed. The subjects performed flexion-extension and lateral bending (left and right) tasks (three complete cycles) with and without a 12 kg load. Between group comparisons were performed on the full cycle average pattern of all biomechanical variables for each task. The reliability of EMG variables was evaluated for 10 subjects (5 normals and 5 CLBP) who performed the tasks on three different days. The reliability of EMG amplitude values was generally excellent for agonist muscles but poor to moderate for antagonists. The EMG amplitude analysis revealed significant differences between groups for some muscles (left lumbar and thoracic erector spinae). The abnormal (asymmetric) EMG patterns detected among CLBP patients were not explained by postural asymmetries.

Understanding and measurement of muscle tone as related to clinical muscle pain

Measurable sources of muscle tension include viscoelastic tone, physiological contracture (neither of which involve motor unit action potentials), voluntary contraction, and muscle spasm (which we define as involuntary muscle contraction). The latter two depend on motor unit action potentials to generate the tension. Total muscle tension is most accurately measured as stiffness. Thixotropy of muscle is an ubiquitous and functionally important phenomenon that is not commonly recognized. A clinical pain condition associated with increased muscle tension is tension-type headache, which is largely muscular in origin; it is often caused by myofascial trigger points, but not by a pain-spasm-pain cycle, which is a physiologically and clinically untenable concept. Clinical conditions associated with painful muscle spasm include spasmodic torticollis, trismus, unnecessary muscle tension, nocturnal leg cramps, and stiff-man syndrome.

Surface electromyography in the identification of chronic low back pain patients: the development of the flexion relaxation ratio

OBJECTIVE: To develop a reliable and repeatable way to monitor changes in the flexion relaxation phenomenon of the lumbar paraspinal muscles during forward flexion by the development of a flexion relaxation ratio and observation of the sEMG activity in standing and during forward flexion in patients with chronic low back pain (CLBP) and healthy controls. DESIGN: Two experiments were conducted, the first to assess the test-retest reliability of the measure in a group of CLBP (n = 11) patients; the second compared the results between a group of normal healthy controls (n = 20) and a group of CLBP patients (n = 70). RESULTS: Repeated measurements over 4 weeks demonstrated between session reliability of between 0.81 and 0.98 for the dynamic activity. The levels of sEMG activity in the fully flexed position was significantly greater in the fully flexed position in the CLBP group than the controls. The flexion relaxation ratio (FRR), a comparison of the maximal sEMG activity during 1 s of forward flexion with activity in full flexion, demonstrated significantly lower values in the CLBP than the control group. The combined discriminant validity for the FRR for all four sites resulted in 93% sensitivity and 75% specificity. CONCLUSION: The FRR clearly discriminated the patients from the healthy controls. These results indicate that dynamic sEMG activity of the paraspinal muscles can be reliably measured and is useful in differentiating CLBP patients from normal controls. RELEVANCE: Analysis of the pattern of different levels of muscle activity during a forward flexion can be used in CLBP where normalization of the sEMG signal to the maximum voluntary contraction may be difficult. The FRR may be used in the assessment of change in the flexion relaxation phenomenon following treatment interventions.

Clinical neurophysiology of headache

Methods of clinical neurophysiology are of little use for the diagnosis of headache disorders. They are, however, invaluable tools for a better understanding of the pathophysiology of functional headaches. They are traumatic, able to explore simple or more complex neural activities, and to some extent capable of reflecting activity in certain neurotransmitter systems as well as the action of pharmacologic agents on the CNS. This article reviews the interest and limits of electroencephalography, evoked potentials, electromyography, and nocifensive reflexes in primary headaches. Because neurophysiologic methods are no more than indirect means of looking into the "black box," their results need to be interpreted with caution and, whenever possible, should be compared in the same study with clinical behavioral and biochemical data.

Assessment of lumbar EMG during static and dynamic activity in pain-free normals: implications for muscle scanning protocols

The purpose of this study was to provide a thorough description of lumbar surface integrated electromyography (EMG) in pain-free normals during a standardized assessment protocol of static isometric and unresisted dynamic tasks. It has been proposed that in pain-free normals, symmetrical tasks that bend the trunk forward or extend the trunk backward produce symmetrical paraspinal EMG activity, and asymmetrical tasks that rotate or laterally bend the trunk produce asymmetrical paraspinal EMG activity. In addition, it has been observed that lumbar EMG assessment during static tasks has been more consistent than tasks involving dynamic activities. Twenty-eight pain-free normals were assessed during symmetrical and asymmetrical tasks in both static and dynamic activities in a counterbalanced manner. The assessment of paraspinal EMG patterns was conducted while subjects were secured in a triaxial dynamometer, which provided standardization of body position and concurrent measurement of torque, range of motion, and velocity. The results provided experimental evidence for the above-stated propositions. An implication derived from this research is that clinicians may be better served utilizing local norms when using EMG for classification purposes.

Electromyographic recordings of paraspinal muscles: variations related to subcutaneous tissue thickness

The aim of this study was to assess the effect on EMG amplitude measures of variations in the thickness of underlying tissue between surface electrodes and the active muscle. 20 normal subjects with different amounts of subcutaneous tissue performed comparable constant force contractions for a 45-second period, during which paraspinal EMG recordings were taken. Three measures of subcutaneous tissue thickness were obtained from each subject: Body Mass Index, total body fat as calculated by Durnin's formula, and skinfold thickness at the recording sites. The results show that (i) the greater the thickness of subcutaneous tissue between the surface recording site and the contracting muscles, the lower the recorded electromyographic activity, and that (ii) up to 81.2% of the variance in the EMG measures can be explained by variation in the amount of subcutaneous tissue. These findings support the view that the absolute level of surface-recorded EMG cannot simply be taken at face value. The amplitude of the signal will be affected by, for example, the amount of body fat.

Reliability of an ambulatory electromyographic activity device for musculoskeletal pain disorders

A number of investigators in recent years have called for the development of devices that can monitor surface EMG levels in individuals' normal environments for use with patients who suffer from disorders in which the etiology or maintenance of the pathology is presumed to be due at least in part to musculoskeletal dysfunction, such as low back pain, phantom limb pain and tension headache. This study examined the test-retest reliability of just such a device. Twenty-six healthy controls wore a lightweight (24 ounce) device which measured bilateral upper trapezius EMG, as well as peak and integral motion, for 5 consecutive days for up to 18 h each day. ANOVAs on the four measures revealed no difference between any of the four measures over the 5 days. Intra-class correlation coefficients for the two EMG variables across 5 days were both significant with alpha levels set at 0.01. The two EMG measures were highly correlated (r = 0.77); the two motion measures were also highly correlated (r = 0.60), but at a lower magnitude than EMG values; the relationship between EMG and motion was significant, but the magnitude of the between EMG motion correlations (0.26 and 0.35) were lower than the within EMG or motion ones. It was concluded that the test-retest reliability of the ambulatory monitoring device is within acceptable limits. Implications for the use of the device with musculoskeletal pain disorders--particularly headache--are discussed.

The role of psychological factors in chronic pain. I. A half century of study

This review examines a half century of thought about the role of psychological factors in chronic pain. Changing views are discussed, and representative examples of pain research based on psychoanalytic, behavioural, cognitive, and psychophysiological theories are presented and evaluated. The evolution of thought from linear causal models of pain to multicausal explanations provides a conceptual framework for discussion. Studies reviewed show that an earlier concept, based on simple formulations of psychological causation, has been replaced by more comprehensive explanations comprising both physical and psychological influences. Further methodological and conceptual problems are discussed in the second paper of this 2-part review.