What it's about:

[T]hese aren't just maps of the best places to go jogging. They're also maps which clearly match up very closely with the neighborhoods of rich and poor people in those cities.

Note, for example, there aren't many people using Runkeeper in London south of the Thames, or in Boston's South Side, or anywhere in New York but the financial district, the richest parts of Brooklyn, and the Upper East Side (exception: some people do appear to be crossing through the South Bronx to use the bridges there). Scenic D.C. is rich with routes; southeastern D.C. less so. The farther you get away from rich coastal San Francisco, the less people are jogging. It goes on and on.

This information points to or suggests the significance of location and class. A healthy lifestyle is not so much about fancy apps, or smartphones, or even education but about where one lives. Jogging and cycling are encouraged or discouraged by the character of an area, by its views, by the number of its parks or trees. And the locations that most encourage jogging will tend to be close to or are a part of rich neighborhoods.