A TEST OF EXERCISE ANALGESIA USING SIGNAL-DETECTION-THEORY AND A WITHIN-SUBJECTS DESIGN

Evidence for the existence of exercise-induced analgesia has been weak , inconsistent, or anecdotal. The present study addresses criticisms o f previous research by using a signal-detection analysis of pain perce ption in a within-subjects, repeated-measures research design with 22 endurance athletes who exercised in a naturalistic setting. Analysis s howed discriminability measures from the lower intensities of a radian t-heat pain-perception task were significantly lower after exercise th an the subjects' discriminability after a no-exercise period. This is consistent with discriminability decreases seen in studies of subjects who are under the influence of analgesic chemicals such as morphine a nd nitrous oxide. Discriminability differences were not seen in this s tudy at the higher intensities of the stimulus, suggesting that exerci se generates perceptual changes that may not reach pain-mediating leve ls. Visual analogue data suggest cognitive and motivational factors al so play a role in report of pain after exercise.