To follow up on the study, the researchers tested two groups of mice by giving them drugs to compare the effect to that of the exercise.  One group was given a drug that blocked the endorphins only, while the other set of mice was given a drug to block endocannabinoids, like anandamide.

The set of mice that had the drug to block their endorphins, but were still able to produce anandamide, showed the same result as the group that had been exercising.  That group registered less stress and pain sensitivity to pain compared to the group that had their anandamide production blocked.

The researchers said, “Here, we demonstrate that wheel running increases endocannabinoids and reduces both anxiety and sensation of pain in mice.  Ablation of cannabinoid receptor 1 receptors on GABAergic neurons inhibits running-induced anxiolysis, and pharmacological blockage of central and peripheral cannabinoid receptors inhibits analgesia. We thus show for the first time to our knowledge that cannabinoid receptors are crucial for main aspects of a runner’s high.”

Several studies have been done since 2003 that show a connection to endocannabinoids and a runner’s high, even some done on humans, but the new study strengthens the theory, by minimizing the chance that endorphins could be the cause.

Despite the results of the study indicating that cannabinoids are the cause of the euphoric feeling runners get, the researchers can not say that the mice actually felt a feeling of euphoria.  The study authors wrote, “euphoria is a highly subjective feeling that may be difficult to model in mice.”

In releasing the results of the study, the German research team wrote, “A runner’s high is a subjective sense of well-being some humans experience after prolonged exercise.  For decades, it was hypothesized that exercise-induced endorphin release is solely responsible for a runner’s high, but recent evidence has suggested that endocannabinoids also may play a role.”

A runner’s high does seem to be of a benefit to overall health, regardless of what process plays a part in creating it.  Researchers in a recent study form the University of Iowa found some of the benefits of cardiac exercise are derived from the body’s release of opioid peptides, which could improve the efficiency of a workout by increasing the runners’ top oxygen intake.

So lace up your sneakers and head out for the open road.  Getting a buzz while exercising could not only make your day more enjoyable, it could actually have long-term health benefits as well.

The study was published in the Proceedings of the National Academy of Sciences.