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Your Braggy Runner Friends Are Actually Doing You a Favor

Those social media overshares can be strangely motivational, a new study finds.

Running is better with friends—sure, that's obvious. But what if those friends are thousands of miles away? Can you still get some benefit just knowing that your friends are out running, even if they're not pacing you in person? A new study suggests yes: Knowing that your friends are pounding the pavement may affect your run, particularly if you're a man.

To reach that conclusion, researchers examined five years worth of data from a global social network of runners. They looked at around 1.1 million individuals who'd cumulatively run almost 225 million miles over that time. The data was reported by fitness trackers, which helped researchers get around the problem of unreliable reporting. (Surveyed about their exercise habits, people sometimes, believe it or not, provide dubious answers.) That let them analyze how often people were running, how far, and how fast. Then they started comparing data among "friends."


Intuitively, you wouldn't be surprised if friends showed similar habits. But that doesn't tell us much; it provokes the question of homophily, or the "birds of a feather flock together" problem. We might expect marathoners, for example, to befriend one another because they already have similar habits. That doesn't mean they're causing one another to run marathons; they're simply coming together to do something they've already been doing individually.

So the researchers set out to tease apart the question in an ingenious way. "We used the weather as a natural experiment," Sinan Aral, who led the study, says. They compared data from global weather stations with the running data, figuring that people were more likely to run (and run farther) on nice days.

They found that their friends—even those in other places, with completely different weather—were influenced. If a friend ran for ten minutes more than usual, other friends extended their runs by about three minutes, regardless of weather. Faster paces were contagious, too.

Intriguingly, it was the relatively slower runners who provoked the biggest effect. If a slower runner suddenly started pounding the pavement more, friends responded by upping their own routines. Gender also played a role, with men responding most to competition from other men, but to a lesser extent to challenges from their female friends. Women, on the other hand, responded mostly to other women, and were largely unaffected by their male friends.

Aral says that the research is just beginning to scratch the surface, but it suggests a few different things. If you're a runner and want to stay motivated, virtual peers actually can help. On a broader scale, this kind of research can help us understand peer-to-peer effects, which can lead to smarter public-health interventions. It suggests how we might leverage people's already existing relationships to motivate them to make healthier choices. Even virtual peer pressure, it turns out, can have an effect.

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