Tuesday 10 January 2023

What is a runner's high?


If you’ve ever cheered on a group of exhausted marathon runners with big smiles on their

faces, you may find yourself wondering why they look so happy. As it turns out, there is a phenomenon called the “runner’s high” which floods the brain and body with feel-good chemicals.

Ask a runner to explain themselves and chances are they'll say something about the fabled runner's high. But what exactly is a runner's high? How does it affect the body? And can it really make you feel intoxicated?

Despite the challenging amount of effort required when you run, you may finish a session with a smile on your face, feeling lighter than air. This is the runner's high — the strange euphoria that sets in after a long bout of aerobic exercise. 

The term "runner's high" probably originated sometime in the 1970s during the United States' first recreational running boom, according to reporting by the Chicago Tribune(opens in new tab).

"In the scientific literature, it's used as more of a shorthand for a range of changes to your physiological state that occur with exercise," David Raichlen(opens in new tab), an evolutionary biologist at the University of Southern California, told Live Science.

The range of changes include subjective things like improved mood and a general sense of wellbeing, as well as measurable alterations in body chemistry. Over the past few decades, one particular group of exercise-related chemicals has received a lot of scientific attention for its link to a runner's high: endorphins.

As the character Elle Woods famously remarked in the 2001 film "Legally Blonde," "Exercise gives you endorphins. Endorphins make you happy. Happy people just don't shoot their husbands."

During aerobic exercise, your body begins to release a cocktail of chemicals, including several different endorphins. Functionally, these compounds mimic the effects of opioids but on a much milder scale. Studies show that they help to relax your body and decrease your perception of pain, according to a 2010 review paper published in the Hawaii Medical Journal(opens in new tab). This might explain how after a gruelling run, people still feel great, despite pain caused by the exertion.

For decades, many scientists believed that in addition to relieving pain, endorphins also boosted a tired runner's mood. There was just one problem: Endorphins don't cross the blood-brain barrier, meaning that they shouldn't be directly linked to happiness. 

When scientists began to take a closer look at the chemicals coursing through runners' bodies, they found a whole slew of lipid chemicals — called endocannabinoids — and neurotransmitters that hadn't previously been associated with exercise percolating in various tissues. Like endorphins, endocannabinoids can influence mood. But unlike endorphins, these chemicals can cross the blood-brain barrier. 

A 2021 review published in the journal Psychoneuroendocrinology(opens in new tab) suggests that endocannabinoids are actually the key to unlocking that feeling of inner peace. Meanwhile 2019 research in the journal Acta pharmacologica sinica(opens in new tab) indicates that endocannabinoids are chemically related to the active ingredient in cannabis, tetrahydrocannabinol (THC), which might be why people feel “high” when they are coursing through the body.

Like THC, endocannabinoids — especially one called anandamide — can cross the blood-brain barrier and bind to receptors on neurons. However, unlike THC, which "just kind of piggybacks on our body's own systems," Raichlen said, endocannabinoids are produced naturally within the body and tend to have more subtle effects on our mental state. That's why it feels quite different, Raichlen said, a runner's high is less of a high and more of a gentle lift. 

In addition to endorphins and endocannabinoids, exercise also releases the "feel-good" chemical dopamine, a heavy-hitter for the body's reward system, related to motivation and why some people are more motivated than others. This pleasure inducing neurotransmitter is also released when you win the lottery, orgasm or take a bite of an ice cream sundae. Dopamine might contribute to the overall sensation of the runner's high as well, providing your body with a little mood boost for its hard work, according to 2016 research published in the journal Frontiers in Psychology(opens in new tab)

The most obvious way to get a runner's high is to start running, particularly long-distance running. It may take several miles for the effects to kick in, though it's difficult to quantify exactly when, where and for how long a runner's high will occur, Gina Kolata reported for the New York Times(opens in new tab)

And not every runner — or every run — will be able to produce a runner's high, according to David Linden, a professor of neuroscience at Johns Hopkins University, writing on the Hopkins health site(opens in new tab)

While the moniker “runner’s high” indicates that you can only experience these physiological changes while pounding the pavement, other aerobic activities, including biking, swimming and strenuous hiking, can trigger the same response.

Interestingly, humans aren't the only animals that have exhibited signs of runner's high. Several experiments have observed a similar phenomenon in mice. Raichlen's lab has also tested dogs and ferrets by putting them on a treadmill and looking for exercise-induced euphoria, according to research published in the Journal of Experimental Biology(opens in new tab). After 30 minutes of running, the dogs appeared at-ease; blood tests revealed elevated levels of endocannabinoids in their systems. 

"We didn't see that in the ferrets," Raichlen said.

One major benefit to achieving a runner's high is that it makes exercise more enjoyable. By extension, this makes people more likely to stick to an exercise routine, which, according to the American Heart Association(opens in new tab), is a key component of long-term heart health. There is also good evidence that, over the long term, exercise can have significant mental health benefits such as reducing anxiety and stress, according to 2006 research published in the Primary Care Companion to The Journal of Clinical Psychiatry(opens in new tab).

So far, there is little evidence that a runner's high is healthy in and of itself. But at the very least, Raichlen said, "It's not unhealthy." So go ahead and lace up your shoes. You're free to chase that runner's high as far as it takes you.

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