Aral and Nicolaides did some serious number crunching and found that people were more influenced by their connections who shared mutual friends.
Researchers at the MIT Sloan School of Management in Cambridge, Massachusetts, examined data on over one million people, who had collectively run over 350 million kilometers in five years.
Turns out it's the friends who perform at roughly the same level as you who are more likely to motivate you to exercise - particularly the ones who perform a little bit worse.
A new research of exercise behaviours of over one million people, on Thursday, revealed that running could be contagious.
"On the same day, on average, an additional kilometer run by friends can inspire someone to run an additional three-tenths of a kilometer and an additional ten minutes run by friends can inspire someone to run three minutes longer", the authors wrote.
One of the key findings of the data revealed numerous runners often compared themselves to those ahead of themselves to motivate their own self-improvement.
And while you might assume it's the marathon runners influencing the everyday joggers to get out there and pound the pavement, the analysis suggested the opposite. On top of that, the researcher added, men were found to be influenced by both other men and women, while women are only influenced by other women.
In addition, it appeared that most motivations stemmed from good-old fashioned competitiveness: runners wanted to stay ahead of the pack, and strove to do better to make sure they stayed on top. Women, on the other hand, were typically only influenced by other females.
In that time, these runners also formed about 3.4 million new social network connections - from this group, the team isolated the 2.1 million ties for which they could pinpoint specific information such as geographic location and weather conditions for both users.