The journal of pain : official journal of the American Pain Society
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This study examined coping predictors of laboratory-induced pain tolerance, intensity, and unpleasantness among 244 healthy children and adolescents (50.8% female; mean age, 12.73 +/- 2.98 years; range, 8-18 years). Participants were exposed to separate 4-trial blocks of pressure and thermal (heat) pain stimuli, as well as 1 trial of cold pain stimuli. Strategies for coping with pain were measured using the Pain Coping Questionnaire (PCQ). Linear regression analyses were conducted to examine the associations between the 8 PCQ subscales and pain responses (pain tolerance, intensity, and unpleasantness) to all 3 pain tasks, controlling for age and sex. We found that internalizing/catastrophizing predicted higher pain intensity across the 3 pain tasks and higher cold pain unpleasantness; seeking emotional support predicted lower pressure pain tolerance; positive self-statements predicted lower pressure pain intensity and lower cold pain intensity and unpleasantness; and behavioral distraction predicted higher pressure pain tolerance and lower heat pain unpleasantness. These results suggest that in healthy children, internalizing/catastrophizing, and seeking emotional support may be conceptualized as pain-prone coping strategies, and positive self-statements and behavioral distraction as pain-resistant coping strategies within the context of laboratory pain. ⋯ These results support investigation of interventions with children that aim to reduce acute pain responses by modifying coping to reduce seeking of emotional support and catastrophizing and enhance the use of positive self statements and behavioral distraction.
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Chronic muscle pain is a major clinical problem that is often associated with fatigue. Conversely, chronic fatigue conditions are commonly associated with muscle pain. We tested the hypothesis that muscle fatigue enhances hyperalgesia associated with injection of acidic saline into muscle. We evaluated mechanical sensitivity of the paw (von Frey) in mice after 2 intramuscular injections of saline (20 microL; pH 4, pH 5, pH 6, pH 7.2) in a fatigue and a control group. To induce fatigue, mice were run for 2 h/day for 2 days prior to the first injection and 2 h/day for 2 days prior to the second injection. Muscle lactate, pCO(2), pO(2), creatinine kinase, phosphate, and histology were examined after the fatigue task and compared to a control group. Grip force was significantly decreased after 2 h of running indicating fatigue. The fatigue task did not induce muscle damage as there was no difference in muscle lactate, pCO(2), pO(2), creatinine kinase, phosphate, or histology. The fatigue task altered the dose-response relationship to intramuscular acidic saline injections. Mechanical hyperalgesia was observed in both fatigue and control groups after intramuscular injection of pH 4.0, but only the fatigue group after injection of pH 5. Neither the fatigue nor the control group developed hyperalgesia in response to intramuscular injection of pH 6 or pH 7.2. In conclusion, fatigue modified the susceptibility of mice to acid injection of pH 5.0 to result in mechanical hyperalgesia after 2 injections of pH 5.0. The fatigue task did not produce measurable changes in the muscle tissue suggesting a central mechanism mediating the enhancement of hyperalgesia. ⋯ These data therefore show that muscle fatigue can enhance the likelihood that one develops pain to a mild insult. Clinically, this could relate to the development of pain from such conditions as repetitive strain injury, and may relate to the interrelationship between chronic pain and fatigue.