By Julie Fidler | Natural Society
Everyone has heard of “runner’s high,” but it seems that it’s quite a literal statement.
For an all-natural high, tie on some running shoes and hit the pavement. Researchers from the University of Hamburg and University of Heidelberg say the same euphoric feeling that comes with smoking marijuana can be achieved through running and other forms of aerobic exercise because it impacts the brain in a similar way as marijuana. 
Scientists have long attributed post-workout ecstasy with a release of endorphins alone, but the new findings suggest the brain’s endocannabinoid system is affected by exercise, just as the brain is affected by cannabinoids in marijuana. Cannabinoids can also affect appetite, pain, mood, and memory.
“A runner’s high is a subjective sense of well-being some humans experience after prolonged exercise,” the German research team wrote in the Proceedings of the National Academy of Sciences. “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.”
“Running exercise increases blood levels of both beta-endorphin (an opioid) and anandamide (an endocannabinoid),” the team wrote.
Scientists had one group of mice run on a treadmill for 5 hours, while a second group of the rodents remained sedentary. The mice’s anxiety levels were tested using the dark-light box test, which measures the speed and frequency it took the animals to leave a well-lit area for a darker area that offers a place to hide. Researchers tested the rodents’ pain tolerance by placing them on a hot plate to see if they would jump or lick.
The mice that ran on the treadmill were found to be less anxious than the mice in the sedentary group. The treadmill group was also found to have a higher tolerance for pain when the team dosed both groups of mice with a chemical that blocked endocannabinoids. The findings suggest the process indeed plays a role in a “runner’s high.” 
“Here, we demonstrate that wheel running increases endocannabinoids and reduces both anxiety and sensation of pain in mice,” researchers added. “We thus show for the first time to our knowledge that cannabinoid receptors are crucial for main aspects of a runner’s high.” 
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Julie Fidler is a freelance writer, legal blogger, and the author of Adventures in Holy Matrimony: For Better or the Absolute Worst. She lives in Pennsylvania with her husband and two ridiculously spoiled cats. She occasionally pontificates on her blog.
This article originally appeared on Natural Society.