There hasn't been a lot of great news about friendships lately. One paper suggested that laziness and impatience can rub off on peers and another concluded that obesity is socially contagious. But there’s finally some good news about being social—a new study suggests exercise can be contagious, too.
According to Amina Khan at the Los Angeles Times, researchers from MIT delved into fitness tracker data from 1.1 million people on a social network who used an app to automatically post data from their runs online. Over a five-year period, those runners logged roughly 223 million miles.
When a runner saw that one of their friends had put in an extra 10 minutes on the pavement, it caused them to push on an extra three minutes during their run, reports Rachael Rettner at LiveScience. For every extra kilometer their cyber-buddy pressed on, they ran an extra 0.3 kilometers.
Of course there are lots of factors that could influence why a person runs a little extra on any given day. So the researchers, who published their study in the journal Nature Communications, came up with an experiment based on the weather. “In our mind, we have the pseudo question, ‘Is a rainy day in Chicago [affecting the] running of your friends [in] Boston?,’" Christos Nicolaides, a co-author of the study, tells Rettner. “If yes, that means that there is causal influence of the running behavior of Chicagoans [on] the running behavior of their friends in Boston.”
It turns out that when it’s nice and sunny in the Midwest (perfect running conditions) it pushes friends in other cities where the weather was not as nice to pound the pavement a little longer, reports Matthew Hutson at Science.
The study teases out some interesting trends as well, Khan writes. The effect is strongest on the same day and fades over time. Men were motivated to run strongly by their male peers and moderately motivated by women friends. Women, however, seemed to only pay attention to other women. Also, less active runners had an outsized influence on everyone. People were more motivated to run when they saw that friends who were previously less active or less in shape started putting in extra miles.
“Comparisons to those ahead of us may motivate our own self-improvement, while comparisons to those behind us may create ‘competitive behavior to protect one’s superiority,” the authors write in the study. “Our findings are consistent with both arguments, but the effects are much larger for downward comparisons than for upward comparisons.”
There are limits to the study, however. Rettner reports that the researchers do not know when or if the subjects saw each others' runs posted online. It could be the case that some people check the postings more frequently and are more influenced by the postings than others.
But the study isn’t just about running. Learning how peer groups and social networks influence individuals could help researchers find ways to support healthy behaviors and discourage negative choices in general. “New interventions that take into account the fact that there is social influence in ‘healthy’ behaviors like exercise can be more effective than other ones that do not,” Nicolaides tells Rettner.
So go out and hit the pavement. You could be motivating a distant friend to do the same.