By Karin Krisher

Though not every runner would reveal this about him or herself (or even know it) runner’s high is probably one of the most common personal motivators. Running is a survival tactic. At first, we used it to catch and evade prey and predators, respectively. Then we used it as a means of communication, sending Pheidippides on an epic sprint that gave us the term (and the distance for) “marathons.” Now we use it as a form of physical fitness, though its roots in escapism remain visible to those who know and freely admit that they’re in it for the high.

It turns out there may be an evolutionary reason for runner’s high. That light, energized/exhausted wonderful feeling you attain after a couple of miles on the pavement isn’t just a fringe benefit, but an actual motivator, one that creates a desire to exert energy when so many other biological mechanisms are designed to conserve it.

It all has to do with endocannabinoids. Researchers wanted to find out if those species that don’t run distance would experience the same high as humans do. Using ferrets as an example, the conclusion was simple: They don’t.

“It turned out that, as expected, the humans had shown significantly increased levels of endocannabinoids after running.” Fun fact? “So had the dogs, suggesting, for the first time, that they, too, experience a runner’s high.”

“But neither species had developed increased endocannabinoid levels after walking.”

“And the ferrets didn’t show higher endocannabinoid levels after either session. They gained, it seems, no neurobiological pleasure from running.” (NYTimes)

These results indicate that we want to move. We are genetically hardwired to desire this energy expenditure—so much so that we get a sense of pleasure from it that can only be appropriately described as a high.

With that in mind, the mystery of making a choice not to exercise grows deeper. It is likely the results of a lost battle with our energy-conserving biological mechanisms. Obesity is now the number one annual health care cost incurred in the United States, surpassing even smoking, which details just how far we are from the days of Pheidippides.

We no longer have to run. We no longer even want to—despite the fact that our bodies, from an evolutionary perspective, truly do. Think about that next time you’re frustrated about the distance between the remote and your hand, and negate that frustration with a good dose of endocannabinoids, the product of your natural desire to stretch both your legs and your mind.

Escape cabin fever with a run—because we’ve always been designed to get away.