Runner's High

How do you feel when you finish a run? Elated? Invincible? About a month ago, the New York Times ran a story entitled Phys Ed: What Really Causes Runner's High discussing the cause of "runner's high." The article first points out that endorphins are not the cause of runner's high.

Endorphins first gained notoriety in exercise back in the 1980s when researchers discovered increased blood levels of the substance after prolonged workouts. (Endorphins, for those who know the word but not the molecules’ actual function, are the body’s home-brewed opiates, with receptors and actions much like those of pain-relieving morphine.) Endorphins, however, are composed of relatively large molecules, “which are unable to pass the blood-brain barrier,” said Matthew Hill, a postdoctoral fellow at Rockefeller University in New York. Finding endorphins in the bloodstream after exercise could not, in other words, constitute proof that the substance was having an effect on the mind. So researchers started to look for other candidates to help explain runner’s high. Now an emerging field of neuroscience indicates that an altogether-different neurochemical system within the body and brain, the endocannabinoid system, may be more responsible for that feeling.

The article detailed a few different research studies concerning the effect of endocannabinoids during and after exercise. What appears without question is that "the endocannabinoid system 'is well known to impact onto central reward networks.' . . . Without it, exercise [seems to provide] less buzz. . ." In fact, in experiments on rats, the rats with non-functioning endocannabinoid systems did not indulge in exercising on their running wheel as much as those rats with properly functioning systems.

Although the full intricacies of the endocannabinoid system’s role in motivating and rewarding exercise is not yet understood, it seems obvious, the researchers say, that the cannabinoid-deprived mice were not getting some necessary internal message.

While the article concluded that current research is not decisive on the issue of whether endocannabinoids are the cause of "runner's high," "endocannabinoids are a more persuasive candidate, especially given the overlap between the high associated with marijuana use and descriptions of the euphoria associated with strenuous exercise."