The journal of pain : official journal of the American Pain Society
-
Review Meta Analysis
A meta-analytic review of the hypoalgesic effects of exercise.
The purpose of this article was to examine the effects of acute exercise on pain perception in healthy adults and adults with chronic pain using meta-analytic techniques. Specifically, studies using a repeated measures design to examine the effect of acute isometric, aerobic, or dynamic resistance exercise on pain threshold and pain intensity measures were included in this meta-analysis. The results suggest that all 3 types of exercise reduce perception of experimentally induced pain in healthy participants, with effects ranging from small to large depending on pain induction method and exercise protocol. In healthy participants, the mean effect size for aerobic exercise was moderate (d(thr) = .41, d(int) = .59), while the mean effect sizes for isometric exercise (d(thr) = 1.02, d(int) = .72) and dynamic resistance exercise (d(thr) = .83, d(int) = .75) were large. In chronic pain populations, the magnitude and direction of the effect sizes were highly variable for aerobic and isometric exercise and appeared to depend on the chronic pain condition being studied as well as the intensity of the exercise. While trends could be identified, the optimal dose of exercise that is needed to produce hypoalgesia could not be systematically determined with the amount of data available. ⋯ This article presents a quantitative review of the exercise-induced hypoalgesia literature. This review raises several important questions that need to be addressed while also demonstrating that acute exercise has a hypoalgesic effect on experimentally induced pain in healthy adults, and both a hypoalgesic and hyperalgesic effect in adults with chronic pain.
-
Randomized Controlled Trial
Effects of nicotine on spinal cord injury pain vary among subtypes of pain and smoking status: results from a randomized, controlled experiment.
Smoking has been associated with increased pain severity in general chronic pain populations. Less is known about the effects of smoking and nicotine on the multifaceted and often complex subtypes of pain that frequently occur following spinal cord injury (SCI). The purpose of this study was to examine the effects of nicotine on self-reported pain among individuals with SCI and to determine if the effect of nicotine varied by pain subtype. A randomized, placebo-controlled crossover design was used to determine the effect of nicotine exposure on subtypes of SCI-related pain among smokers and nonsmokers. A complex relationship emerged, such that the degree of reported pain with exposure to 2 mg of nicotine compared to placebo varied according to pain type and smoking status of the subject. Pain sites that had characteristics of both neuropathic and musculoskeletal symptoms (deemed complex neuropathic pain sites) exhibited pain reduction after nicotine exposure in nonsmokers. In sharp contrast, smokers with this form of pain exhibited an increase in pain severity. Data were also examined descriptively to determine potentially unique factors associated with complex neuropathic pain that may explain trends associated with clinically relevant changes following nicotine exposure. In sum, smoking or tobacco use history may determine the analgesic (or enhanced pain perception) effect of nicotine on post-SCI pain. ⋯ Pain characterized by both neuropathic and musculoskeletal symptoms decreased in severity after nicotine exposure in nonsmokers with SCI but increased in severity among smokers with SCI. The analgesic (or enhanced nociceptive) effect of nicotine may depend on tobacco use history.
-
Previous studies have associated depression and temporomandibular joint disorders (TMDs). The temporality, however, remains to be clarified. Most patient studies have selected subjects from treatment facilities, whereas in epidemiological studies a clinical examination has not been performed. In this study the 5-year follow-up data of the population-based Study of Health in Pomerania (SHIP) were analyzed. To estimate the effect of symptoms of depression and those of anxiety on the risk of TMD pain, the Composite International Diagnostic-Screener (CID-S) and a clinical functional examination with palpation of the temporomandibular joint and the masticatory muscles were used. After exclusion of subjects having joint pain at baseline, a sample of 3,006 Caucasian participants with a mean age of 49 years resulted. Of those, 122 participants had signs of TMD joint pain upon palpation. Subjects with symptoms of depression had an increased risk of TMD joint pain upon palpation (rate ratio: 2.1; 95% confidence interval: 1.5-3.0; P < .001). Anxiety symptoms were associated with joint and with muscle pain. The diagnosis, prevention, and therapy of TMD pain should also consider symptoms of depression and those of anxiety, and appropriate therapies if necessary. ⋯ Depressive and anxiety symptoms should be considered as risk factors for TMD pain. Depressive symptoms are specific for joint pain whereas anxiety symptoms are specific for muscle pain, findings that deserve detailed examination. These findings may support decision-making in treating TMD.
-
The nonselective sodium channel blocker lidocaine is widely used as a local anesthetic but also systemically for treatment of postoperative and neuropathic pain. Voltage-gated sodium channels are crucial for action potential generation and conduction, and their availability controls the amount of activity-dependent conduction velocity slowing. This important axonal property, as assessed by microneurography, is used to differentiate human mechanoinsensitive (silent) nociceptors from the classical polymodal nociceptors. In the current study, microneurography was used to assess axonal properties of the 2 main nociceptor classes in humans, before and after intradermal injection of lidocaine .1% or control saline solution in the receptive field. In mechanosensitive nociceptors, lidocaine reduced baseline conduction velocity and turned activity-dependent slowing into speeding of conduction. In contrast, mechanoinsensitive fibers were not affected in their baseline conduction velocity or their activity-dependent slowing, but probability of conduction block with repetitive stimulation increased. Recovery cycles showed reduced hyperpolarization in all C-fiber classes after lidocaine injections. These results support our hypothesis that sodium channel subtypes are differentially expressed in the 2 nociceptor classes of mechanosensitive C-fibers (CMs) and mechanoinsensitive C-fibers (CMis). ⋯ This study reveals that microneurography can be used to assess pharmacological effects on single C-fibers directly in humans.