[mym1990]

This feels a little harsh. It is known that when humans see other humans doing similar things a bond(empathy) can be created without ever even talking to that person.

When I drive my Jeep and do that little Jeep wave to other Jeeps, that gives me a sense of community with those people(no matter how dumb or weird people driving other cars think it is).

When you run and someone runs past you and you do the little head nod, that is absolutely social, you absolutely relate to that person and create a small social bond.

[Jtsummers]

It's also fun running into those other runners later. I used to run on a 5k trail near my office (for about 5 years), and would see a lot of colleagues later and recognize them from an afternoon or lunchtime run. It created another point of relation for us besides just sharing an office and a mutual boss four levels above us.