Medicine and science in sports and exercise
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Med Sci Sports Exerc · Mar 1991
Clinical Trial Controlled Clinical TrialExperimental pain thresholds and plasma beta-endorphin levels during exercise.
Experimental pain thresholds (electrical intracutaneous finger and dental pulp stimulation) and plasma hormone levels (beta-endorphin, cortisol, and catecholamines) were measured in ten healthy sportive men before, during, and after progressively more strenuous physical exercise. In a double-blind study conducted on two different days, 20 mg of the opioid-antagonist naloxone or placebo was administered prior to exercise. A significant pain threshold elevation was found during exercise for finger (ANOVA, P less than 0.004) and dental pulp stimulation (P less than 0.01). ⋯ Naloxone failed to affect pain thresholds, although beta-endorphin and cortisol increased significantly more (P less than 0.02) during exercise after naloxone. It is concluded that short-term, exhaustive physical exercise can evoke a transient elevation in pain thresholds. This exercise-induced elevation in pain threshold does not, however, appear to be directly related to plasma endorphin levels.