Is Runner’s High Real? The Endocannabinoid System Explains It
If you’ve ever experienced a surge of positive feelings after going for a long run or after a particularly intense workout, like most people, you probably chalked it up to a rush of endorphins, the body’s self-produced endogenous opioids, as responsible for the sudden good mood. For decades, we were told that the experience we refer to as ‘runner’s high’ was because of endorphins, but that may only be partially true. According to a number of studies, it’s actually been the lesser known endocannabinoid system (ECS) that’s primarily responsible and the increased concentration of anandamide, an endogenous cannabinoid also known as the ‘bliss molecule.’
In a study published in Neuroscience, researchers examined how exercise affects pain perception. The results showed that after exercise, cannabinoid receptors were activated on immune cells in the spinal cord, which had a numbing effect on exercise-related pain. It also increased the concentration of anandamide in the spine as well as caused immune cells to produce more CB2 receptors. Although previous research had already suggested anandamide’s role in runner’s high, this was the first study to implicate the immunoregulatory effect of CB2 receptors. In addition, researchers also found that anandamide’s lack of CB2 binding affinity suggested that exercise induced endocannabinoid activity at several levels.
The level of physical activity also matters when it comes to the ECS’ activation and anandamide increase. This explains why mild exercise and workouts that are too strenuous do not produce elevated ECS activity. In the study, researchers noted that injury modified the body’s and the ECS’ response to exercise, with a marked increase observed in animals with muscle injury, while healthy ones didn’t demonstrate any noticeable increases.
In another study done on mice by German researchers at the University of Heidelberg, they found that the mice were less sensitive to pain, less anxious, and calmer after running, which they did for fun. When researchers used medication to block the mice’s ECS receptors, they observed they were no longer relaxed after running and were just as anxious as they were pre-run. Their sensitivity to pain had also increased. Meanwhile, when the mice’s opioid receptors were blocked, researchers noted no difference to their post-run high. They also found that how far the mice had to run to experience the high mattered, clocking in at an average of three miles a day. Johannes Fuss, one of the scientists who conducted the study, said that this could explain how humans have evolved to move and cover longer distances, thanks to the reduced pain and less anxiety experienced during long-distance running.
In a lecture by Professor Daniel Lieberman from Harvard’s anthropology department titled “Why Humans Run: The Biology and Evolution of Marathon Running,” Lieberman noted that humans’ ability to sustain highly intense tests of endurance may be unique in the animal kingdom. Lieberman posited, “Hairless, clawless, and largely weaponless ancient humans used the unlikely combination of sweatiness and relentlessness to gain the upper hand over their faster, stronger, generally more dangerous animal prey.”
Runner’s high may have been integral to the survival of our species. Apart from motivating us to exercise and move our bodies, it also helps us sustain intensive aerobic activity by reducing pain, acting as a neurobiological reward that keeps us healthy and, well, alive.
Although its benefits are obvious, there may be a downside to runner’s high: addiction. Some people get so addicted to the feeling they get after intense workout and long runs to the point of doing harm to their bodies. This is also observed in mice, with some choosing to run over anything else, to the point of even dying. This led scientists to hypothesize how running may be just as addictive as morphine. In a 1984 article in the Washington Post, researchers at the University of Arizona Health Sciences Center identified what they called ‘obligatory runners’ or those ‘for whom running is a compulsive drive that preempts fulfillment in other life areas or who run to the point of inflicting physical damage on their bodies.”
At the end of the day, the positives outweigh the potential risks. Not only does increased anandamide result in runner’s high but some studies have shown that increased levels are also associated with a range of health benefits, including the ability to treat patients with acute schizophrenia and malignant lymphoblastic diseases. Some studies have also looked into its benefit for epilepsy patients, specifically when using CBD oil to increase levels of anandamide. This could be one of the reasons why CBD has become such a breakthrough drug for people suffering from seizures, with Epidiolex, the first drug containing CBD as an active ingredient being approved by the FDA back in 2018.
As research into how the endocannabinoid system works continues to be carried out, we’ll undoubtedly learn more about how it affects various bodily functions and change what we know about our bodies. One thing’s for sure, there’s still much more to learn and uncover about it.
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