The journal of pain : official journal of the American Pain Society
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Clinical Trial Controlled Clinical Trial
Contralateral attenuation of pain after short-duration submaximal isometric exercise.
Only a small amount of research has been conducted examining whether exercise-induced hypoalgesia (EIH) occurs after isometric exercise. Thus, the purpose of this investigation was to examine whether EIH occurred in women after short-duration submaximal isometric exercise and whether the responses were restricted to the exercised hand (ipsilateral) or also occurred in the nonexercised (contralateral) hand. Fourteen healthy women (mean age = 19.5 years) completed 2 sets of submaximal (40% to 50% of max) isometric exercise consisting of squeezing a dynamometer for 2 minutes with the dominant hand. A pressure stimulus was applied to the forefinger on the dominant and nondominant hands for 2 minutes before and after isometric exercise. Participants pressed a button when the stimulus became painful, indicating pain threshold (PT), and also rated the intensity of the stimulus every 15 seconds, using a pain rating scale (PR). Results indicated that there were significant trials effects (P < .05) for PT and PR, but the main effect for hands was not significant (P > .05). PTs were found to be elevated, whereas PRs were reduced for both hands after isometric exercise. It is concluded that submaximal isometric exercise performed for 2 minutes resulted in ipsilateral and contralateral hypoalgesic responses. ⋯ The findings from the present study demonstrated that short-duration nonexhaustive isometric exercise was associated with hypoalgesic responses in the exercised and nonexercised hands. It appears that short-duration submaximal isometric exercise resulted in generalized (ie, ipsilateral and contralateral) pain-inhibitory responses in healthy young women.
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Cognitive-behavioral models of chronic low back pain (CLBP) predict that dysfunctional assumptions about the harmfulness of activities may maintain pain-related fear and disability levels. The Photograph Series of Daily Activities (PHODA) is an instrument to determine the perceived harmfulness of daily activities in patients with CLBP. This study examined the psychometric properties of a short electronic version of the PHODA (PHODA-SeV). The results show that the PHODA-SeV measures a single factor and has a high internal consistency. The test-retest reliability and stability of the PHODA-SeV over a 2-week time interval are good, with discrepancies between 2 measurements over 20 points suggesting true change. The construct validity is supported by the finding that both self-reported pain severity and fear of movement/(re)injury were uniquely related to the PHODA-SeV. Validity is further corroborated by the finding that patients who have received exposure in vivo, that aimed to systematically reduce the perceived harmfulness of activities, had significantly lower PHODA-SeV scores after treatment than patients receiving graded activity that did not address these assumptions. The findings support the PHODA-SeV as a valid and reliable measure of the perceived harmfulness of activities in patients with CLBP. Preliminary normative data of the PHODA-SeV are presented. ⋯ This article describes a pictorial measurement tool (PHODA-SeV) for the assessment of the perceived harmfulness of activities in patients with chronic low back pain. The PHODA-SeV has good psychometric properties and can be used to elaborate on the contribution of beliefs about harmful consequences of activities to pain and disability.
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Thirty-two African American and 23 non-Hispanic white women were compared for experimental pain threshold and tolerance to thermal, ischemic, and cold pressor pain. Approximately half of each group had prior mood disorders (17 African Americans, 13 non-Hispanic whites), though all were free of current mood disturbance. Women with prior mood disorders were less sensitive to ischemic pain than women with no prior mood disorders (P < .05), whereas African Americans were more sensitive to ischemic pain than non-Hispanic whites, though only at pain tolerance (P < .001). For cold pressor pain, the effects of race were only seen in women with prior mood disorders, since African Americans with prior mood disorders were more sensitive than non-Hispanic whites with prior mood disorders (P < .05). These results indicate that experimental pain sensitivity in women is influenced by both race and histories of mood disorders. ⋯ We examined the association of race and histories of mood disorders with experimental pain sensitivity in an exclusively female sample. Our findings for racial differences in pain sensitivity may have implications for greater clinical pain in African American women. Persistent disturbance in pain modulatory mechanisms in women with a history of mood disorders may also have implications for the development of subsequent mood disturbances.
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Improgan is a congener of the H(2) antagonist cimetidine, which produces potent antinociception. Because a) the mechanism of action of improgan remains unknown and b) this drug may indirectly activate cannabinoid CB(1) receptors, the effects of the CB(1) antagonist/inverse agonist rimonabant (SR141716A) and 3 congeners with varying CB(1) potencies were studied on improgan antinociception after intracerebroventricular (icv) dosing in rats. Consistent with blockade of brain CB(1) receptors, rimonabant (K(d) = 0.23 nM), and O-1691 (K(d) = 0.22 nM) inhibited improgan antinociception by 48% and 70% after icv doses of 43 nmol and 25 nmol, respectively. However, 2 other derivatives with much lower CB(1) affinity (O-1876, K(d) = 139 nM and O-848, K(d) = 352 nM) unexpectedly blocked improgan antinociception by 65% and 50% after icv doses of 300 nmol and 30 nmol, respectively. These derivatives have 600-fold to 1500-fold lower CB(1) potencies than that of rimonabant, yet they retained improgan antagonist activity in vivo. In vitro dose-response curves with (35)S-GTPgammaS on CB(1) receptor-containing membranes confirmed the approximate relative potency of the derivatives at the CB(1) receptor. Although antagonism of improgan antinociception by rimonabant has previously implicated a mechanistic role for the CB(1) receptor, current findings with rimonabant congeners suggest that receptors other than, or in addition to CB(1) may participate in the pain-relieving mechanisms activated by this drug. The use of congeners such as O-848, which lack relevant CB(1)-blocking properties, will help to identify these cannabinoid-like, non-CB(1) mechanisms. ⋯ This article describes new pharmacological characteristics of improgan, a pain-relieving drug that acts by an unknown mechanism. Improgan may use a marijuana-like (cannabinoid) pain-relieving mechanism, but it is shown presently that the principal cannabinoid receptor in the brain (CB(1)) is not solely responsible for improgan analgesia.
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Because of a lack of evidence to support any treatment for phantom limb pain (PLP), interest has turned to preventing it instead. However, like other areas of PLP research, there is little consensus regarding factors that may be associated with the development of PLP. This study was devised to identify physical and psychological factors associated with PLP development and maintenance. It was a prospective study of 59 patients listed for amputation of a lower limb due to peripheral vascular disease. Each was interviewed before amputation, and the survivors were reinterviewed 6 months afterward. Pain and coping style were the primary outcome measures. The use of high levels of passive coping strategies (P = .001), especially catastrophizing (P = .02) before amputation, were found to be associated with PLP development. Pain was only weakly associated with the presence of PLP 6 months after amputation. The ability to move the phantom (P = .01) and stump pain (P = .01) were postamputation factors associated with PLP. The complexity of the relationship between previous pain and coping style and the development of PLP is discussed alongside aspects of pain memory. Pre-emptive treatment of PLP will need to include psychological as well as physical interventions. ⋯ During this study, preamputation passive coping (especially catastrophizing) was found to be associated with the development of PLP. This knowledge will help researchers and clinicians to identify future targets for pre-emption of this condition because once established, PLP is difficult to treat.