Sometimes we get it, sometimes we don't. But we always want it—and more of it. It's the runner's high, and when we are lucky enough to tap into it, our runs feel easy, exhilarating, even euphoric. But we aren't always that lucky, are we?
Recently, researchers studied how the brain responds to running and found that the ability to get "high" while logging miles might be hard-wired within us. Years ago, our ancestors' survival likely depended on chasing down food.
The desire to live was possibly their motivation to run and run fast, and the feel-good brain chemicals released when they did so may have helped them achieve the speed and distances required, says David A. Raichlen, Ph.D., an associate professor of anthropology at the University of Arizona. The runner's high may have served (and serves today) as a natural painkiller, masking tired legs and blistered feet, he says.
Even though you no longer have to chase down dinner, learning how happy brain reactions are sparked may help you achieve the runner's high more often.
The Trigger: Endorphins
Nature's home-brewed opiates, endorphins are chemicals that act a lot like their medically engineered counterpart, morphine. Runners have credited them for their feel-good effects for decades, but it wasn't until 2008 that German researchers used brain scans on runners and were able to identify exactly where they originated.
The scientists found that during two-hour-long runs, subjects' pre-frontal and limbic regions (which light up in response to emotions like love) spewed out endorphins. The greater the endorphin surge in these brain areas, the more euphoric the runners reported feeling.
Get It: Push yourself—hard, but not too hard. Endorphins are painkillers produced in response to physical discomfort, says Matthew Hill, Ph.D., an assistant professor at the University of Calgary's Hotchkiss Brain Institute. But that doesn't mean your runs should be excruciating; you need to find a sweet spot where they are comfortably challenging (think tempo run).
In the German study, for example, the subjects were experienced runners for whom a two-hour run at a six-to seven-mile-an-hour pace wasn't easy nor was it gut-busting. "Most runners I have worked with experience endorphins when they are pushing their bodies, but not usually at max effort," says Cindra S. Kamphoff, Ph.D., director of the Center for Sport and Performance Psychology at Minnesota State University. A short, casual run likely won't produce enough discomfort to trigger a rush.
Attempt a pace or distance that's too aggressive, and you'll possibly be too overwhelmed by the effort to feel good. As powerful as they are, endorphins can't override an injury or lack of training (which is why newbies aren't likely to feel elated when they are just starting out).
Hooking up with others could also help: An Oxford University study reported that rowers who exercised together significantly increased their endorphin release compared with solo rowers. When you are on your own, consider wearing headphones: Research shows that listening to your favorite music may spike endorphins.
The Trigger: Endocannabinoids
Endorphins get all the attention, but your body also pumps out endocannabinoids, which are a naturally synthesized version of THC, the chemical responsible for the buzz that marijuana produces.
The most examined endocannabinoid produced in the body, anandamide, is believed to create a feeling of calmness, Hill says. Endorphins can be created only by specialized neurons, but pretty much any cell in the body is capable of making endocannabinoids, which means they have the potential to make a bigger impact on your brain.