Runners High

If you find yourself chasing that enviable, happy feeling that appears at the end of a workout, you’re not alone. The runner’s high, seems to magically materialize at the end of your route, makes you smile, makes you more cheerful, and is one of the best byproducts of any run.

We’ve probably all heard someone exclaim, “Ah, my endorphins are kicking in!” at the end of a good run. Endorphins are famous for supposedly producing “runner’s high,” that fleeting sense of calm and euphoria that engulfs many of us after a satisfying workout. For years, it’s been said that the high is a result of an endorphin release that eventually leads to this happy-go-lucky boost.

Endorphins may be unfairly hogging the credit, Endorphins first became a household word in the 1980s, when researchers found that blood levels increased after prolonged exercise. This finding made sense. Exercise can cause discomfort or pain, and endorphins are the body’s self-produced opiates, with pain-relieving properties much like morphine. From that discovery, it was a short step to believing that endorphins must also produce the pleasurable mental, “lifted” sensation that many people feel after exercise.

There is a substantial problem with that idea, and it involves the substantial-ness of endorphins. They are large molecules, too big to pass through the blood-brain barrier. They might effect pain in the muscles, but they wouldn’t have effects directly inside the brain, where any high would originate. So for the past decade or so, scientists have been looking for other substances that might be involved in making exercisers feel high, which led them, perhaps unsurprisingly, to endocannabinoids.

According to a new study, published in the Proceedings of the National Academy of Sciences, a runner’s “high” could be the result of a different substance: Anandamide .

Anandamide is a neurotransmitter and endocannabinoid, meaning a cannabinoid produced within the body. Anandamide, also known as N-Arachidonoylethanolamine or AEA, is an endogenous cannabinoid that acts as a “key” molecule fitting into the “locks” of the CB1 and CB2 receptors around the body. It’s name is taken from the Sanskrit word ananda, which means bliss, and the word amide, which refers to a type of acid found within the body. Anandamide is thus the bliss amide, though it is more widely called the bliss compound. Scientists believe the endocannabinoid anandamide has an especially potent ability to lift mood, dull pain, and dilate the blood vessels and bronchial tubes in the lungs. When your brain and body cells release enough of these happiness molecules, you get the rush of good feelings that lead to the runner’s high.

 Researchers with the Central Institute of Mental Health at the University of Heidelberg medical school in Mannheim, Germany, rounded up healthy lab mice, tested their anxiety levels by putting them in cages with pockets of darkness and light (anxious animals stick to the shadows), and then gave them running wheels.

Mice generally like running, engaging in the activity even when they are not being pursued. That suggests, researchers believe, that they gain some kind of mental satisfaction or reward from it, experiencing the mouse version of a runner’s high.

Scientists noted elevated levels of both endorphins and endocannabinoids in the animals’ bloodstreams after running. The scientists also found that the animals were more tranquil after running, spending longer periods of time in lighted areas within their cages — something that anxious, twitchy animals won’t do — and that they were more pain tolerant when exposed to slight physical discomfort.

In general, these post-running mice were more chill than before.

When the researchers used drugs to block the workings of some of the animals’ endocannabinoid system, so that receptors in the animals’ brains couldn’t take up the molecules, their post-run cool disappeared. The animals proved to be as anxious then after running as they had been before and very sensitive to pain.

Without a working endocannabinoid system, they developed no runner’s high.

However, when the researchers similarly blocked the animals’ response to endorphins, while leaving their endocannabinoid system unchanged, the mice enjoyed all of the soothing effects of running. They were calmer in their cages afterward and seemed to experience less sensitivity to pain.

Even without the ability to respond to endorphins, in other words, they experienced the rodent version of a runner’s high, strongly suggesting that endorphins do not contribute to the high, but endocannabinoids do.

The results should remind us that, like mice, we were built through evolution to be in motion. Our ancestors ran to avoid danger and hunt food. For them, “reduced sensations of pain and less anxiety through long-distance running would have been a benefit,” says Johannes Fuss, now a professor at the University of Hamburg, who led the new study.

To survive as a species, we have needed to be vary active, and nature found ways to make this strenuous movement pleasurable by providing us with this “runner’s high”.

So the subtle upshot of the new study may be that we should run more. And if we don’t feel a high, perhaps try running more, until eventually a gentle euphoria may settle in and we can turn to our running companion and say, “Ah, my endocannabinoids are kicking in