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Chasing the runner's high

As a runner, you may have experienced “runner’s high” - the feeling of euphoria during and after a long or intense run. Your skin feels sandy from the sweat that has crystallized, your legs more jelly-like than flesh, but you don’t feel tired really, and you don’t feel pain like you know you should feel after pounding out 20 miles. Instead you feel goofy, or emotional, or blissful. You feel happy. But why? Or how?

Turns out, we don’t really know. The actual cause of runner’s high remains unknown, and some would even call it a myth. But if you’ve experienced it, there’s no doubt it exists, but the how and why are explained in two competing hypothesis.

The endogenous opioid hypothesis

The runner’s high is described differently from person to person, but no matter how you feel it, you’re certainly not feeling pain, which is what led researchers to believe for years that the “high” was the result of a rush of endorphins in the athlete’s brain.

Since endorphins are some of the body’s natural opiates, or painkillers, it was easy to assume that’s what caused the high that many feel when they’re pounding the pavement. Of course a rush of endorphins was the cause of runner’s high, a seemingly natural response to the continuous impact your joints were being forced to sustain, stride after stride, how else could anyone get through 26.2 miles of that?

There is proof that endorphins are present in the blood of an athlete after a long run, but endorphins in the blood are part of the body’s stress response and can not travel from the blood to the brain (endorphins are too large to pass through the blood-brain barrier that border patrols our gray matter), and not responsible for elevating one’s mood.

Few studies exist, but one study by Dr. Henning Boecker involved taking PET scans of athlete’s brain before and after a long run. Data showed that endorphins were produced in the brain during running and also attaching themselves to the limbic and prefrontal areas of the brain, which are the parts of the brain associated with emotions.

So, ok then, it’s endorphins right?

Not necessarily.

The cannabinoid hypothesis

Back in 1990 during a study on the effect of marijuana on the brain, a new receptor site in the brain was discovered as the receptor for THC, the active ingredient in marijuana. That receptor was named the cannabinoid receptor. But since the body is a brilliant system that wouldn’t develop receptors for no reason, researchers knew that the cannabinoid receptor must be home to a naturally-occurring chemical, which turned out to be anandamide (ironically derived from the sanskrit word for “bliss”). Anandamide has a THC-like effect, producing feelings of relaxation and pain cessation.

It was Arne Dietrich, Ph.D., a marathon runner and neuroscientist, who devised the simple experiment to give runner’s high a biological explanation. In this experiment, a small group of subjects ran or bicycled for 40 minutes at 76 percent of their maximum heart rate. After which, blood samples were taken which showed that both runners and the bicyclists in the study had significantly more anandamide in their blood after exercising, the greatest increases being among the runners.

Also, anandamide doesn’t have the blood-brain barrier problem that endorphins have, so if an athlete has anandamide in their blood, it will no doubt reach their brain and be snagged by the cannabinoid receptor. Anandamide also dilates your blood vessels and the bronchial tubes in your lungs, which should help your body run better and longer.

So, what now?

Maybe runner’s high is a combination of these hypothesis, maybe one will eventually prevail. For now, the actual cause is still a bit of a mystery. But the reason is probably not a big concern of yours, as long as you’re catching that buzz! (A natural one, that is!)

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