Exercise can be contagious, new social network analysis finds

Data from digital fitness trackers combined with social network analyses reveal that one person's running habits can influence their friends' running habits. (Dreamstime)

Now here's a contagion that might not be so bad to encounter. A new analysis of the running habits of about 1.1 million people reveals that exercise is indeed contagious – though its communicability depends on who's spreading it. 

The findings, published in the journal Nature Communications, also reveal that certain relationships are better at spreading the running bug than others – and could have implications for the study of other social contagions, such as obesity and smoking.