The effect of forearm posture on wrist flexion in computer workers with chronic upper extremity musculoskeletal disorders.

BACKGROUND: Occupational computer use has been associated with upper extremity musculoskeletal disorders (UEMSDs), but the etiology and pathophysiology of some of these disorders are poorly understood. Various theories attribute the symptoms to biomechanical and/or psychosocial stressors. The results of several clinical studies suggest that elevated antagonist muscle tension may be a biomechanical stress factor. Affected computer users often exhibit limited wrist range of motion, particularly wrist flexion, which has been attributed to increased extensor muscle tension, rather than to pain symptoms. Recreational or domestic activities requiring extremes of wrist flexion may produce injurious stress on the wrist joint and muscles, the symptoms of which are then exacerbated by computer use. As these activities may involve a variety of forearm postures, we examined whether changes in forearm posture have an effect on pain reports during wrist flexion, or whether pain would have a limiting effect on flexion angle. METHODS: We measured maximum active wrist flexion using a goniometer with the forearm supported in the prone, neutral, and supine postures. Data was obtained from 5 subjects with UEMSDs attributed to computer use and from 13 control subjects. RESULTS: The UEMSD group exhibited significantly restricted wrist flexion compared to the control group in both wrists at all forearm postures with the exception of the non-dominant wrist with the forearm prone. In both groups, maximum active wrist flexion decreased at the supine forearm posture compared to the prone posture. No UEMSD subjects reported an increase in pain symptoms during testing. CONCLUSION: The UEMSD group exhibited reduced wrist flexion compared to controls that did not appear to be pain related. A supine forearm posture reduced wrist flexion in both groups, but the reduction was approximately 100% greater in the UEMSD group. The effect of a supine forearm posture on wrist flexion is consistent with known biomechanical changes in the distal extensor carpi ulnaris tendon that occur with forearm supination. We infer from these results that wrist extensor muscle passive tension may be elevated in UEMSD subjects compared to controls, particularly in the extensor carpi ulnaris muscle. Measuring wrist flexion at the supine forearm posture may highlight flexion restrictions that are not otherwise apparent.

Pain additivity, diffuse noxious inhibitory controls, and attention: a functional measurement analysis.

This study utilized the methodology of Functional Measurement theory to investigate the additivity of painful and non-painful thermally induced experiences at one body site with those produced by brief noxious and innocuous electrical stimuli at another. Forty healthy young subjects were tested, using a Peltier thermode to induce tonic pain and an electrocutaneous stimulator for presenting phasic pain, under conditions of either full attention or visual/cognitive distraction (counting numerous light signals) in order to evaluate whether the summed effects are attributable to refocused attention. Six levels of intensity were combined in a factorial design for both tonic and phasic pain. Subjects indicated the overall strength of their dual perception on a visual analog scale. Stimuli showed complex patterns of interaction. Two stimuli were generally rated as greater than one, but the summation was far from additive and greatly influenced by the intensity of the stronger stimulus, suggesting inhibitory action. In general, tonic heat pain strongly affected the perception of phasic electrocutaneous pain whereas the reverse was only partly true. Distraction had a very small effect, suggesting that the "pain inhibits pain" phenomenon attributable to diffuse noxious inhibitory controls (DNIC) is not due to attentional processes. Our data also relate to issues regarding spatial summation across dermatomes and to adaptation level effects in pain, in which a strong painful experience serves as an anchor or comparison point by which others are judged. The psychophysical findings provide a perceptual foundation for clinical phenomena in which patients face with comorbid pain disorders.

Exposure to a specific pulsed low-frequency magnetic field: a double-blind placebo-controlled study of effects on pain ratings in rheumatoid arthritis and fibromyalgia patients.

BACKGROUND: Specific pulsed electromagnetic fields (PEMFs) have been shown to induce analgesia (antinociception) in snails, rodents and healthy human volunteers. OBJECTIVE: The effect of specific PEMF exposure on pain and anxiety ratings was investigated in two patient populations. DESIGN: A double-blind, randomized, placebo-controlled parallel design was used. METHOD: The present study investigated the effects of an acute 30 min magnetic field exposure (less than or equal to 400 microTpk; less than 3 kHz) on pain (McGill Pain Questionnaire [MPQ], visual analogue scale [VAS]) and anxiety (VAS) ratings in female rheumatoid arthritis (RA) (n=13; mean age 52 years) and fibromyalgia (FM) patients (n=18; mean age 51 years) who received either the PEMF or sham exposure treatment. RESULTS: A repeated measures analysis revealed a significant pre-post-testing by condition interaction for the MPQ Pain Rating Index total for the RA patients, F(1,11)=5.09, P<0.05, estimate of effect size = 0.32, power = 0.54. A significant pre-post-effect for the same variable was present for the FM patients, F(1,15)=16.2, P<0.01, estimate of effect size = 0.52, power =0.96. Similar findings were found for MPQ subcomponents and the VAS (pain). There was no significant reduction in VAS anxiety ratings pre- to post-exposure for either the RA or FM patients. CONCLUSION: These findings provide some initial support for the use of PEMF exposure in reducing pain in chronic pain populations and warrants continued investigation into the use of PEMF exposure for short-term pain relief.

Does past pain influence current pain: biological and psychosocial models of sex differences.

Previous studies have generally indicated sizeable sex differences for both laboratory pain reactivity and clinical pain reports. Numerous biological and psychosocial models have been invoked to account for these findings, but the laboratory and clinical findings have generally been examined in isolation. This paper reviews data which show a relationship between past clinical pain experiences and current responses to experimentally induced pain. Individuals with a greater pain history tend to show lower pain tolerance. Since women often have high pain experience levels and lower pain tolerance, one might ask whether the two factors are related. We review several models, based upon concepts of neonatal differences in pain reactivity, hypervigilance following early pain experiences, and concepts of peripheral and central sensitization or plasticity which might help to bridge the gap between clinical and experimental findings.

The relationship between cognitive appraisal, affect, and catastrophizing in patients with chronic pain.

A study was conducted to clarify the nature of catastrophizing, a construct that is frequently referred to in the chronic pain literature. Information regarding 3 affective experience and 3 affect regulation dimensions was gathered from a heterogeneous sample of 104 chronic pain patients by using a semistructured clinical interview and the Affect Regulation and Experience Q-Sort (AREQ). Self-report questionnaires included visual analog pain scales, the Coping Strategies Questionnaire (CSQ), Multidimensional Pain Inventory (MPI), McGill Pain Questionnaire (MPQ), and Center for Epidemiological Studies Depression scale (CES-D). Hierarchical multiple regression was used to demonstrate the relative contributions of affective and cognitive appraisal components of catastrophizing. Thirty-one percent of the variance in CSQ-Catastrophizing scores was explained by a combination of cognitive appraisal variables (perceived ability to control pain; MPI Life Control) and AREQ scores, even after adjusting for pain severity and chronicity, age, and sex of participants. Results of the study strongly suggest that, rather than thinking of catastrophizing primarily as a cognitive coping construct, it should be described as an elaborate construct made up of both cognitive appraisal and affective components. Implications for tailoring interventions to match individual styles of affect regulation are discussed.

Menstrual cycle modulation of tender points.

Changes in pain sensitivity throughout the menstrual cycle were assessed in 36 normally menstruating women and 30 users of oral contraceptives. Pain sensitivity was measured with palpation of rheumatological tender points and with pressure dolorimetry. The number of tender points identified by palpation was greater in the follicular (postmenstrual) phase of the cycle as compared to the luteal (intermenstrual) phase in normally cycling women but not in users of oral contraceptives. These findings are related to previously described physiological and psychological features of the menstrual cycle, with particular emphasis on the role of hormonal events in modulating pain perception, particularly in musculoskeletal disorders such as fibromyalgia.

Sex differences in responsiveness to painful and non-painful stimuli are dependent upon the stimulation method.

Sex differences in thermo- and electrocutaneous responsiveness to painful and non-painful stimuli were investigated in 20 women and 20 men. Heat pain, warmth, and cold thresholds were assessed on the hand and foot with a Peltier thermode system. In addition, subjects used magnitude estimation to judge the sensation intensity evoked by temperatures ranging from 38 degrees C to 48 degrees C applied to the forearm. To measure detection, pain, and tolerance thresholds of electrocutaneous sensitivity, electrical pulses were administered to the hand. Magnitude estimates of sensation intensity were assessed for stimuli ranging from 0.5 mA to 4.0 mA. There were no sex differences in heat pain, warmth and cold thresholds. There were significant sex differences in electrical detection, pain and tolerance thresholds, with lower thresholds in women. Correspondingly, magnitude estimates were similar in women and men when using thermal stimuli while women judged stimuli from 2.5 mA on as more intense than men when using electrical stimuli. Despite these discrepancies, the measures for pain responsiveness from the two stimulation methods correlated significantly. In contrast, no significant correlations between the methods were found when considering the responsiveness to non-painful stimuli. The findings help to clarify controversies in the pain literature about sex differences. Results affirming and denying such differences could be obtained within a single sample, with stimulation method as the critical variable.

Psychosocial correlates of temporomandibular joint pain and dysfunction.

This study examines psychological differences between temporomandibular joint pain and dysfunction (TMJPD) patients, pain controls, and healthy controls. Two hundred and two patients were classified, according to the diagnostic criteria of Eversole and Machado, as either myogenic facial pain (n = 42), internal derangement type I (n = 69), internal derangement type II (n = 85), or internal derangement type III (n = 6). Patients completed the Basic Personality Inventory, the Illness Behavior Questionnaire, the Multidimensional Health Locus of Control, the Perceived Stress Scale, and the Ways of Coping Checklist. Subjects also answered question pertaining to TMJPD symptomatology, including chronicity and severity. After conservative treatment with simple jaw exercise and ultrasound, patients were contacted again at 5 months to complete follow-up questionnaires similar to those previously completed. Comparison groups were comprised of 79 patients attending outpatient physiotherapy clinics for pain-related injuries not involving the temporomandibular joint and 71 pain-free, healthy students. Data were analyzed using multivariate statistics. The results indicate a significant relationship between pain intensity (and to some extent chronicity) and diverse measures of personality among the pain controls but not among the TMJPD patients. This calls into question the validity of assuming individual pain disorders are subsets of a larger, homogenous pain disorder population. TMJPD patients and pain controls score higher on hypochondriasis and anxiety than the pain-free controls but these elevations are not clinically significant. The elevations decrease to normal levels in response to a positive treatment outcome. There were no differences between the TMJPD patients and the pain controls on any of the measures. These results suggests that TMJPD patients do not appear to be significantly different from other pain patients or healthy controls in personality type, response to illness, attitudes towards health care, or ways of coping with stress.

The validity of experimental pain measures.

Forty subjects served in a study investigating the characteristics of experimental pain measures. Subjects indicated when their pain threshold and tolerance levels had been reached with each of three stressors: cold, pressure, and electrical shock. Using the multitrait-multimethod matrix procedure, the measures of threshold and tolerance were found to show both generality and discriminant validity across stressors. Threshold judgements, which emphasize discrimination of nociceptive quality, and tolerance decisions, which indicate an unwillingness to receive more intense stimuli, are not equivalent measures of responsiveness. Both should be obtained in studies involving experimental pain. Stressors, while related, are also not equivalent. Minimum method variance was associated with the discomfort produced by electrical pulse trains.

Signal detection theory pain measures: empirical validation studies and adaptation-level effects.

Proponents of the use of signal detection theory (SDT) in the assessment of pain modulation have generally looked for changes in d' to indicate a reduction of sensory function, and a change in criterion to indicate a modification of the subject's response bias or attitudinal predisposition. In the first experiment, both assumptions failed to receive empirical verification. Discrimination d' was eqivalent before and after two strong levels of electrical current was reduced. The criterion parameter appeared to shift in a more conservative direction after the stimulus diminution. These results are used to question the validity of both detection and discrimination indices in the measurement of pain. An alternative means for describing the experimental results revealed a striking adaptation-level effect with implications for the assessment of both experimentally induced and endogenous pain. The outcome of a second experiment reinforced the adaptation-level theory interpretation of the results and provided additional evidence concerning the difficultuies in evaluating SDT parameters in studies of potential analgesics.