What is a runner’s high, actually?

You hear people talk about a ‘runner’s high’ all the time, but what’s actually happening in the body when this happens? We spoke to exercise scientist Luke Andrew to find out.

A sense of ease. Liberation. Lightness: all the ways those who’ve experienced a runner’s high might describe that mysterious feeling of euphoria during or after a workout. It’s also sometimes referred to as being in a ‘flow state’, a phrase made famous by psychologist Mihaly Csikszentmihalyi that describes a mental state in which a person performing any activity–not just running–where they are entirely immersed and focused.

Here’s the thing: scientists still aren’t exactly sure what causes it and given that it’s a fleeting sensation, it makes it difficult to research. Self-reporting limits the validity of studies, too.

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“The closest we can get is to measure not flow but its effects, both emotionally and physically,” says exercise scientist Luke Andrew.

“Some physiological changes include a shift in brain wave from beta to alpha wavelength as neurochemicals like norepinephrine (fight or flight hormone) and dopamine (happy drug) flood into our bodies. This causes a rise in heart rate, an increase in focus, memory, pattern recognition and a reduction in limiting self-beliefs.”

He adds: “Elements in the brain get regulated, such as the pre-frontal cortex responsible for focused attention, anticipating events, controlling impulses and future planning, leading to a change in perceived time and hence the feeling of time running its own course.”

For decades, researchers believed that endorphins (feel-good chemicals) were responsible for a runner’s high, but new studies point to another type of molecule, endocannabinoids, which act on your endocannabinoid system. The same system that’s affected by the psychoactive compound in marijuana.

So, a runner’s high might actually be closer to the feeling you get when smoking a joint…without the illegality and harmful chemicals entering your lungs.

The surprising thing is that, while many people talk about a runner’s high, it’s actually rarer than you might think, with one study documenting the reported sensation in 10 percent of participants. But just because you don’t get high from running doesn’t mean you shouldn’t do it: there are plenty of other benefits of aerobic exercise, like reduced anxiety, increased memory and focus, and a boosted immune system. Can’t argue with that.