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Acute and chronic positive mood changes have been said to occur with running and jogging. It has been suggested that endogenous substances with opioid activity (endorphins) may serve as modulators of mood. The authors report experiments in which mood changes associated with long-distance running were measured by pre- and post-run difference--scores on a mood adjective checklist, the Profile of Mood States (POMS). Following this, the narcotic antagonist, naloxone, was given subcutaneously in double-blind fashion. The dose was 0.8 mg. The POMS was again presented 15 min later, and post-run/post-injection difference scores were obtained. No naloxone effect was found. The failure of naloxone to reverse the running-associated mood shift indicates that endorphins are not involved. The authors discuss the possible physiologic role of endorphins in light of these and other findings.
Markoff et al. (Fri,) studied this question.