The study offers some of the first hard evidence that health-related habits can spread — and so perhaps could be deliberately seeded and encouraged — by social influence and peer pressure. Previous research has sought such a contagious effect in factors such as obesity and smoking, but the results have been inconclusive.
The new study is a further example of the power of social data collected and made available routinely on a very large scale. Runners cannot lie about their times and distances as they might be tempted to do in self-reported surveys. (Although the competitive nature of running does drive some to cheat and ride a bike.)
Sillitoe’s lonely narrator liked to claim that running offered freedom. “I’ve got thoughts and secrets and bloody life inside me that he doesn’t know is there, and he’ll never know what’s there.” Perhaps not yet — but science is getting there fast.