The research showed that similar runners tended to cluster as friends on the data collection site. Also, if one friend ran more than the others, then a spike in the others' running was observed.
Basically, members in these unofficial circles would work to keep up with each other. Weather conditions didn't seem to matter either. If a runner ran more in one part of the country, a runner in another part of the country would run more (not necessarily more than the other runner, but more than he/she had previously run) even if there were adverse weather conditions.
Men seemed to be affected by this more than women. Males were definitely influenced by what their male counterparts were doing. Males were also influenced by their female counterparts but not to the same extent. Females, however, didn't seem to be influenced by their male counterparts, but they were influenced by their female counterparts.