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.     

Effects of anger suppression on pain severity and pain behaviors among chronic pain patients: evaluation of an ironic process model

OBJECTIVE: Evidence for links between anger inhibition or suppression and chronic pain severity is based mostly on studies with correlation designs. Following from ironic process theory, we proposed that attempts to suppress angry thoughts during provocation would increase subsequent pain intensity among chronic low back pain (CLBP) patients, and do so through paradoxically enhanced accessibility of anger. DESIGN: CLBP patients (N = 58) were assigned to suppression and nonsuppression conditions while performing a computer maze task with a harassing confederate. A structured pain behavior task (SPBT) followed. MAIN OUTCOME MEASURES: Self-reported anger, anxiety, and sadness following maze task. Self-reported pain severity and number of observed pain behaviors during SPBT. RESULTS: Patients told to suppress during provocation: (a) reported greater anger following the maze task, reported greater pain intensity during the SPBT, and exhibited more pain behaviors than patients not suppressing; (b) postmaze anger levels significantly mediated group differences on pain behaviors. CONCLUSION: Attempts by CLBP patients to suppress anger may aggravate pain related to their clinical condition through ironically increased feelings of anger.     

Effects of varied-stimulus exposure on overpredictions of pain and behavioural performance in low back pain patients

The main objective of the present study was to investigate the benefits of exposure to a variety of movements versus exposure to the same movements on overprediction of pain and behavioural performance on a final behavioural test in a sample of chronic low back pain (CLBP) patients. Eighty-four CLBP patients were requested to perform four behavioural tests. Patients were assigned to two experimental conditions. The final behavioural test was the same for all patients. The first three behavioural tests consisted of three different movements in condition 1 and of three times the same movement in condition 2. During each behavioural test, baseline pain, expected pain and experienced pain were recorded. Furthermore, the peak torque and the variability of the produced muscle strength during the final behavioural test were assessed. Replicating and extending previous research, we found that patients overpredicted pain during a threatening behavioural test. Furthermore, pain-related fear and pain catastrophizing showed to be unique predictors of the peak torque of the final behavioural test. No support was found for our hypothesis that varied exposure facilitates generalization of exposure effects. Possible reasons for the failure to find an advantageous effect of varied-stimulus exposure and ideas for future research are discussed.     

Power spectral density changes in the EEG during mental arithmetic and eye-opening

Summary The effect of mental arithmetic (standard multiplication, with eyes closed) and eye-opening on the power spectral density of the EEG (recorded bipolarly from occipital and parietal regions) have been compared. The EEG was recorded on magnetic tape from normal subjects, (medical students) in a constant environment and subsequently analysed by an analogue computer (Noratom Instrument for Statistical Analysis and Computation, ISAC).Absolute measurements made from 15 subjects with eyes closed have shown that peaks of power at 10 Hz vary from 9 to 46 V² per Hz. Qualitatively, suppression of power at 10 Hz is greater due to eye-opening than mental arithmetic.Analysis of pooled power spectral density functions from 11 subjects showed that the effect of eye-opening differed significantly from the effect of mental arithmetic at 2.5 and 12.5 Hz. Suppression of lower frequency alpha activity was more pronounced during calculation than during eye-opening. Compared with the eyes closed condition, eye-opening showed a highly significant suppression at 10 and 12.5 Hz (alpha activity) and from 15 to 25 Hz (beta activity). Mental arithmetic induced significant suppression at 7.5 and 10 Hz and from 15 to 30 Hz. Eye-opening enhanced lower frequency activity which calculation suppressed.Variation was greater between first, second and third calculations in pooled power spectral densities than between corresponding eye-opening epochs. It is suggested that these differences in effects of eye-opening and mental arithmetic reflect differences in underlying cerebral activity, rather than that an underlying factor common to both effects may be orbital in origin.     

Pain anxiety among chronic pain patients: specific phobia or manifestation of anxiety sensitivity?

Rather than viewing anxiety among chronic pain patients as simply a component of negative affectivity, investigators have developed a model of "pain anxiety" in which patients develop fear and avoidance of activity linked to pain. We examined whether pain anxiety can be conceptualized as a specific phobia, or whether evidence supported the notion that pain anxiety is better understood as a manifestation of anxiety sensitivity in the context of chronic pain. Chronic musculoskeletal pain patients (N=70) underwent cold pressor and mental arithmetic tasks while cardiovascular, self-report, and behavior indexes were recorded. They completed measures of pain anxiety, anxiety sensitivity, fear of negative evaluation, depression and trait anxiety. Correlation analyses showed pain anxiety was related to pain-relevant responses during cold pressor, but it was also related to evaluation-relevant responses during cold pressor, and to pain- and evaluation-relevant responses (including subtraction accuracy) during mental arithmetic. Regression analyses showed that almost all effects of pain anxiety on task responses were accounted for by anxiety sensitivity. Fear of negative evaluation, in contrast, correlated only with evaluation-relevant responses, and mostly during mental arithmetic. These effects remained significant when depression, trait anxiety, or anxiety sensitivity were statistically controlled. Pain anxiety may be an expression of anxiety sensitivity rather than a circumscribed phobia; a distinction that could profitably guide treatment strategies.     

Catastrophizing,locus of control,pain, and disability in chinese chronic low back pain patients

Abstract

The present study examined the associations of locus of control (LOC) and catastrophizing with pain intensity and disability in Chinese chronic low back pain (CLBP) patients. In the study, 56 respondents (21 men and 35 women) with a mean age of 36.98 years (SD= 12.22) completed measures assessing locus of control, catastrophizing tendency, pain intensity, disability, and psychological distress. Results showed that after partialling out the effects of gender, duration of pain, and psychological distress, internal LOC significantly explained the variance of disability. For pain intensity, only catastrophizing accounted for a large portion of the variance. Limitations of the study and suggestions for future work were discussed.     

Local dynamic stability of the spine and its coordinated lower joints during repetitive Lifting: Effects of fatigue and chronic low back pain

The nonlinear Lyapunov exponent (LyE) has been proven effective for evaluating the local stability of human movement and exploring the effects of load, speed and direction of individuals with and without nonspecific chronic low back pain (CLBP). The purpose of this study was to examine spinal and lower joint stability and response to fatigue of individuals with and without CLBP while performing lifting-lowering movements. Fourteen healthy individuals and 14 patients with nonspecific CLBP were recruited to perform lifting movement repeatedly while holding two equally-sized dumbbells in their hands. The participants continued lifting until they reported their highest level of fatigue. Kinematic data for the spine and its coordinated lower joints were recorded during the task (more than 40 lifting cycles on average). The first and last 20 cycles of each cyclic time series were defined as early- and late-fatigue conditions, respectively. The maximum LyE was estimated to quantify the local dynamic stability of the angular displacement time series of the spine, hip, knee and ankle on different anatomical planes in both the early- and late-fatigue conditions. The results revealed that local stability of the spine and hip was affected by fatigue. Spinal stability decreased as fatigue increased on the sagittal plane (p < 0.05). The hip exhibited a similar affectation (destabilization under fatigue) on all anatomical planes. Patients with CLBP showed more stable hip movement on the frontal and transverse planes (p < 0.05). These results suggested that lifting/progressive fatigue could increase the risk of injury to the spine and hip. These findings indicate that patients with CLBP applied different control strategies for the hip; thus, spinal control stability should be evaluated together with the stability of the lower joints.     

Quality of Well-Being Scale and Chronic Low Back Pain

Outcome measures that assess quality of life for use in health policy decisions need to be investigated in chronic pain patients. In the present study, the validity of the Quality of Well-Being Scale (QWB) was evaluated on 67 adult chronic low back pain (CLBP) patients who were enrolled in a 12-week multidisciplinary pain treatment program. Participants completed the QWB, a battery of pain measures, a behavioral observation task, and a medical exam. The findings indicated that CLBP patients have a low level of functioning or quality of life (M = .567, SD = .08) compared with persons with life-threatening diseases. The QWB score was significantly correlated with observational measures of pain behavior and pain-related coping strategies. Multivariate analysis indicated that interference in daily activities, distorted ambulation, affective distress, pain duration, and guarding were the most significant predictors of quality of well-being (multiple R = .84, p < .0001). Patients with medically incongruent physical signs had significantly lower QWB scores than patients with congruent signs. Overall, the data supported the validity of the QWB in a sample of CLBP patients.     

The effects of muscle tension on cerebral circulation in blood-phobic and non-phobic subjects

This study aimed to assess whether (1) a muscle tensing procedure which has been found to be useful in the treatment of blood-phobic patients produces an increase in heart rate and cerebral blood flow and (2) whether this increase is greater than that produced by mental effort alone. Subjects were 17 volunteers with a history of fainting in response to blood-injury stimuli, (12 were phobic) and 8 volunteers with no fainting history. They were required to (a) rest, (b) do mental arithmetic, and (c) repeatedly tense and release their arm and leg muscles. It was found that Ss, heart rate and cerebral blood flow velocity were significantly greater during the muscle tensing procedure than during mental arithmetic or resting conditions. The increased cerebral blood flow produced by muscle tensing may enable blood phobic patients to prevent fainting during exposure treatment.     

High-performers use the phonological loop less to process mental arithmetic during working memory tasks

This study investigated the effects of three working memory components—the central executive, phonological loop, and visuospatial sketchpad—on performance differences in complex mental arithmetic between individuals. Using the dual-task method, we examined how performance during two-digit addition was affected by load on the central executive (random tapping condition), phonological loop (articulatory suppression condition), and visuospatial sketchpad (spatial tapping condition) compared to that under no load (control condition) in high- and low-performers of complex mental arithmetic in Experiment 1. Low-performers showed an increase in errors under the random tapping and articulatory suppression conditions, whereas high-performers showed an increase of errors only under the random tapping condition. In Experiment 2, we conducted similar experiments on only the high-performers but used a shorter presentation time of each number. We found the same pattern for performing complex mental arithmetic as seen in Experiment 1. These results indicate that high-performers might reduce their dependence on the phonological loop, because the central executive enables them to choose a strategy in which they use less working memory capacity.     

Hemodynamic characteristics of young men at risk for hypertension at rest and during laboratory stressors.

Examined hemodynamic activity--at rest, during mental arithmetic, and during hand cold pressor--in young men varying in risk for hypertension. Classification into low-risk (n = 72), moderate-risk (n = 20), and high-risk (n = 13) groups was based on resting systolic blood pressure (SBP) and parental history of essential hypertension (PH). Dependent variables were SBP, diastolic BP (DBP), heart rate, and rate-pressure product (RPP). Progressively greater hemodynamic activity was seen across risk groups at rest and during the tasks. Risk groups differed significantly in SBP, DBP, and RPP at baseline (ps less than .003) and in size of response to mental arithmetic (ps less than .05) but not to cold pressor. These relationships were either absent or weaker when using either risk factor alone to form risk groups. These findings suggest that hemodynamic reactivity to mental stress is predicted better by a combination of resting SBP and PH than by either risk factor alone and that physiological reactivity may be an important accompaniment of increased risk for hypertension.     

A contextual approach on sex-related biases in pain judgements: the moderator effects of evidence of pathology and patients' distress cues on nurses' judgements of chronic low-back pain

Although women report feeling more pain than men, their pain is often underdiagnosed and undertreated. By proposing a gender-based theoretical conceptualisation, we argue that such sex-related biases may be enhanced or suppressed by contextual variables pertaining to the clinical situation, the perceiver or the patient. Consequently, we aimed to explore the moderator role of two clinically relevant variables in a chronic low-back pain (CLBP) scenario: diagnostic evidence of pathology (EP) and pain behaviours conveying distress. One-hundred and twenty-six female nurses (M?=?35.33, SD?=?7.64) participated in an experimental between-subjects design, 2 (patient's sex)?×?2 (EP: present vs. absent)?×?2 (pain behaviours: with vs. without distress). Independent variables were operationalised by vignettes depicting a patient with CLBP. Nurses judged the patient's pain on several dimensions: (1) credibility; (2) disability; (3) severity of the clinical situation; (4) psychological attributions and (5) willingness to offer support. Main findings showed that judgements of women's pain were influenced by EP, while judgements of men's pain were not. Moreover, nurses showed biases against men, but only in the presence of EP. The influence of distress cues was less consistent. Theoretical and practical implications are drawn.     

Meta-analysis of psychological interventions for chronic low back pain.

The purpose of this meta-analysis of randomized controlled trials was to evaluate the efficacy of psychological interventions for adults with noncancerous chronic low back pain (CLBP). The authors updated and expanded upon prior meta-analyses by using broad definitions of CLBP and psychological intervention, a broad data search strategy, and state-of-the-art data analysis techniques. All relevant controlled clinical trials meeting the inclusion criteria were identified primarily through a computer-aided literature search. Two independent reviewers screened abstracts and articles for inclusion criteria and extracted relevant data. Cohen's d effect sizes were calculated by using a random effects model. Outcomes included pain intensity, emotional functioning, physical functioning (pain interference or pain-specific disability, health-related quality of life), participant ratings of global improvement, health care utilization, health care provider visits, pain medications, and employment/disability compensation status. A total of 205 effect sizes from 22 studies were pooled in 34 analyses. Positive effects of psychological interventions, contrasted with various control groups, were noted for pain intensity, pain-related interference, health-related quality of life, and depression. Cognitive-behavioral and self-regulatory treatments were specifically found to be efficacious. Multidisciplinary approaches that included a psychological component, when compared with active control conditions, were also noted to have positive short-term effects on pain interference and positive long-term effects on return to work. The results demonstrated positive effects of psychological interventions for CLBP. The rigor of the methods used, as well as the results that reflect mild to moderate heterogeneity and minimal publication bias, suggest confidence in the conclusions of this review.     

Modulation of motor variability related to experimental muscle pain during elbow-flexion contractions

Experimental muscle pain typically reorganizes the motor control. The pain effects may decrease when the three-dimensional force components are voluntarily adjusted, but it is not known if this could have negative consequences on other structures of the motor system. The present study assessed the effects of acute pain on the force variability during sustained elbow flexion when controlling task-related (one-dimensional) and all (three-dimensional) contraction force components via visual feedback. Experimental muscle pain was induced by bolus injection of hypertonic saline into m. biceps brachii, and isotonic saline was used as control. Twelve subjects performed sustained elbow flexion at different levels of the maximal voluntary contraction (5–30% MVC) before, during, and after the injections. Three-dimensional force components were measured simultaneously with surface electromyography (EMG) from elbow flexors and auxiliary muscles. Results showed that force variability was increased during pain compared to baseline for contractions using one-dimensional feedback (P < .05), but no significant differences were found for three-dimensional feedback. During painful contractions (1) EMG activity from m. trapezius was increased during contractions using both one-dimensional and three-dimensional feedback (P < .05), and (2) the complexity of EMG from m. triceps brachii and m. deltoid was higher for the three-dimensional feedback (P < .05). In conclusion, the three-dimensional feedback reduced the pain-related functional distortion at the cost of a more complex control of synergistic muscles.     

Menstrual cycle, beta-endorphins, and pain sensitivity in premenstrual dysphoric disorder.

This study examined pain sensitivity and pain modularity mechanisms (e.g., beta-endorphin levels, blood pressure) in women with premenstrual dysphoric disorder (PMDD; n = 27) and healthy controls (n = 27) during the follicular and luteal phases of the menstrual cycle. Physiological measures were taken during rest and ischemic pain testing. In both cycle phases, PMDD women (a) displayed lower resting cortisol and beta-endorphin levels and (b) exhibited shorter pain threshold and tolerance times and greater pain unpleasantness ratings during pain. PMDD women also reported greater pain unpleasantness and intensity and had lower beta-endorphin levels in their luteal phase and tended to display higher blood pressure levels at rest and during pain testing. Results suggest that endogenous opioids may be pathophysiologically relevant to PMDD and that the hypothalamic-pituitary-gonadal axis may modulate pain sensitivity in PMDD.     

Effects of anxiety sensitivity on anxiety and pain during a cold pressor challenge in patients with panic disorder

Fear of anxiety symptoms, or anxiety sensitivity (AS), has been extensively studied in anxiety disorders and more recently has been linked to other psychopathological conditions including pain. Asmundson and colleagues have suggested that AS may act as a risk factor for chronic pain and several studies have demonstrated an association between AS, avoidance behaviors and pain. The present study assessed whether AS levels would be predictive of pain and anxiety during a brief pain induction task. Clinical participants meeting DSM-IV criteria for panic disorder (n = 22) were age and sex matched with nonclinical controls (n = 22) and exposed to a 2-min cold pressor challenge. Diagnostic status and AS were significantly predictive of pain and anxiety during the cold pressor task. Moreover, AS appears to mediate the relationship between diagnostic status and pain. However, AS appears to be only indirectly associated with pain through its contribution to anxiety.     

Reorganised anticipatory postural adjustments due to experimental lower extremity muscle pain

Automated movements adjusting postural control may be hampered during musculoskeletal pain leaving a risk of incomplete control of balance. This study investigated the effect of experimental muscle pain on anticipatory postural adjustments by reaction task movements. While standing, nine healthy males performed two reaction time tasks (shoulder flexion of dominant side and bilateral heel lift) before, during and after experimental muscle pain. On two different days experimental pain was induced in the m. vastus medialis (VM) or the m. tibialis anterior (TA) of the dominant side by injections of hypertonic saline (1 ml, 5.8%). Isotonic saline (1 ml, 0.9%) was used as control injection. Electromyography (EMG) was recorded from 13 muscles. EMG onset, EMG amplitude, and kinematic parameters (shoulder and ankle joint) were extracted. During shoulder flexion and VM pain the onset of the ipsilateral biceps femoris was significantly faster than baseline and post injection sessions. During heels lift in the VM and TA pain conditions the onset of the contralateral TA was significantly faster than baseline and post injection sessions in bilateral side. VM pain significantly reduced m. quadriceps femoris activity and TA pain significantly reduced ipsilateral VM activity and TA activity during bilateral heel lift. The EMG reaction time was delayed in bilateral soleus muscles during heels lift with VM and TA pain. The faster onset of postural muscle activity during anticipatory postural adjustments may suggest a compensatory function to maintain postural control whereas the reduced postural muscle activity during APAs may indicate a pain adaptation strategy to avoid secondary damage.     

The effects of vicarious experience and stimulus intensity on pain termination and work avoidance

The purpose of the present investigation was to evaluate the role of vicarious experience in the acquisition of pain termination and work avoidance. Fifty-six experimental subjects were randomly assigned to view a film of a model who either terminated exposure to a pain stimulus and work task after 10 sec (high-avoidant) or 70 sec (low-avoidant). Following the film presentation, subjects were exposed to the pain stimulus and work task. Half of the subjects were randomly chosen to perform the task with a low-intensity pain stimulus (LP) and the other half performed the task while exposed to a high-intensity pain stimulus (HP). The results indicated that subjects in the high-avoidant model conditions (HA) did significantly less work and tolerated the pain stimulus for significantly fewer seconds compared to the low-avoidant model groups (LA). Subjects in the LP groups tolerated the pain stimulus significantly longer and did significantly more work compared to subjects in the HP groups. No significant interaction was observed. The results provide support for the hypothesis that behavioral reactions to pain can be acquired by vicarious experience. Implications for future research are discussed.     

Comparison of the trunk-pelvis and lower extremities sagittal plane inter-segmental coordination and variability during walking in persons with and without chronic low back pain

Inter-segmental coordination can be influenced by chronic low back pain (CLBP). The sagittal plane lower extremities inter-segmental coordination pattern and variability, in conjunction with the pelvis and trunk, were assessed in subjects with and without non-specific CLBP during free-speed walking. Kinematic data were collected from 10 non-specific CLBP and 10 non-CLBP control volunteers while the subjects were walking at their preferred speed. Sagittal plane time-normalized segmental angles and velocities were used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify the trunk-pelvis and bilateral pelvis-thigh, thigh-shank and shank-foot coordination pattern and variability over the stance and swing phases of gait. Mann-Whitney U test was employed to compare the means of DP and MARP values between two groups (same side comparison). Statistical analysis revealed more in-phase/less variable trunk-pelvis coordination in the CLBP group (P < 0.05). CLBP group demonstrated less variable right or left pelvis-thigh coordination pattern (P < 0.05). Moreover, the left thigh-shank and left shank-foot MARP values in the CLBP group, were more in-phase than left MARP values in the non-CLBP control group during the swing phase (P < 0.05). In conclusion, the sagittal plane lower extremities, pelvis and trunk coordination pattern and variability could be generally affected by CLBP during walking. These changes can be possible compensatory strategies of the motor control system which can be considered in the CLBP subjects.     

Effect of wave frequency of clinical electric shock: pain sensation and startle response

Contingent shock has been used in a number of studies to suppress health‐threatening self‐injurious behavior of individuals with mental retardation and autism. As sustained suppression is an issue of clinical concern, research into procedural variables of contingent shock is needed. As research on subjects who have mental retardation and who show self‐injurious behavior is ethically impossible, we conducted research on healthy volunteers. In this study, we compared the effect of wave frequency (i.e. Hz) of electric shock on subjects' pain sensation and startle response. It was found that 60 Hz revealed a significantly stronger pain sensation rating than 30 Hz and that 90 Hz revealed a significantly stronger rating than 60 Hz. Also, the magnitude of subjects' startle response significantly increased as wave frequency increased from 30 Hz to 60 Hz and from 60 to 90 Hz. Copyright © 2004 John Wiley & Sons, Ltd.