Being a runner can take a toll on a person. The physical exertion, mental challenges, and financial costs are notable. But an element that might not be so obvious is what running does to someone’s social life.

Those who’ve trained for a marathon know the scene well. The movie to which everyone’s going starts at 8:30pm. A quick calculation reveals that this will put you in bed around 11:30, allowing less than six hours sleep before tomorrow’s scheduled 16-miler. Sadly, you decline.

More often than not, the runner’s night is winding down just as the party is winding up. There’s not much there he or she could eat anyway. Sour cream onion dip doesn’t mix well with a monster track workout the next day before sun up.

After a few years of one’s schedule zigging while most others’ zag, the invitations dwindle. Active relationships turn into an occasional touch base. A few of the old gang might make adjustments to accommodate their aerobically-obsessed companion. (Such efforts are much appreciated, and reciprocated whenever possible.) More often, however, the bigger crowd goes out, while the lone athlete goes to bed.

On the other hand, deep bonds form with a new group. These people truly understand and become close friends. They talk about everything, including this very topic, during glorious conversations along dark streets while they’re running together.