Is Exercise Socially Contagious?

Social media can actually influence your physical health. We all know #lifestyles and #feelings can travel like viruses through our social networks, both digital and analog. Now researchers have linked this same phenomenon to fitness.

Brock Armstrong,
Episode #358

Photo of a business man doing a curl at his computerDo you want to be happier? Of course you do, who doesn’t? Perhaps you should try to surround yourself with happy friends. A study that was published back in 2008 in the British Medical Journal called Dynamic spread of happiness in a large social network: longitudinal analysis over 20 years says that happiness can go viral within your social network (like a good Keanu meme or a hilarious cat video). The researchers concluded that, “People’s happiness depends on the happiness of others with whom they are connected. This provides further justification for seeing happiness, like health, as a collective phenomenon.”

In a similar way, if your friends are overweight, that can apparently have an effect on you too. In a a study called The spread of obesity in a large social network over 32 years, it was concluded that, “Network phenomena appear to be relevant to the biologic and behavioral trait of obesity, and obesity appears to spread through social ties.”

If you find that interesting, intriguing, or maybe even terrifying, now researchers have identified that exercise can also be contagious and spread via social media.

Exercise Contagion

In a paper called Exercise contagion in a global social network published in Nature Communications, researchers say that, “we show that exercise is socially contagious and that its contagiousness varies with the relative activity of and gender relationships between friends.”

To come to this conclusion, they looked at the running habits of about a 1.1 million runners around the world who used some variety of fitness trackers for five years. The runners collectively had about 3.4 million social network ties of which the researchers analyzed 2.1 million users for whom they could target specific geographic and weather information. Over the five years, these social media runners ran a total 350 million kilometers and all of this running was automatically posted online for their friends to see.


I am going to pause for a moment and point out that the fact the data was automatically posted is important. It reduces the inherent issues that come with self-reporting. And that is not just for exercise data but really anything that you want to study thoroughly. The problems with self-reporting include:

  • Honesty management: researchers who use self-report questionnaires are relying on the honesty of their participants.

  • Introspective ability: even if a participant is trying to be honest, they may lack the introspective ability to provide an accurate response to a question.

  • Understanding: participants may all vary in their understanding or interpretation of particular questions.

  • Rating scales: many questionnaires use rating scales to allow respondents to provide more nuanced responses than just a yes or no.

  • Response bias: the  individual’s tendency to respond a certain way, regardless of the actual evidence they are assessing.

  • Control of sample: which has become more of an issue with the boom of online questionnaire distribution sites like Survey Monkey.

When the researchers looked at the automatically uploaded run data and then weather patterns of the cities the runners lived in, they used the information to examine different parts of the network. Letting the weather set up their experiment for them, acting on the assumption that nice weather is more likely to make people run, they found some very cool correlations.

Fair Weather Runners

This experiment was able to determine whether the weather in Vancouver can cause changes in the running behavior of New Yorkers.

Let’s say that it is a nice day where you live, then you and your friends are likely to go out and run. If it's crappy outside where I live, me and my friends will find excuses to skip our jog. Since all cities have quite different weather at any given point in the year, this experiment was able to determine whether the weather in Vancouver can cause changes in the running behavior of folks in New York. If it does, this can really only be happening due to peer to peer influences of friends who live between Vancouver and New York.

That is exactly what the researchers saw. One city’s running could have a direct effect on another city’s runners if the cities were socially connected. The paper states that “... we found strong evidence of the possibility of social contagion in running behaviours ...”

In a nutshell, this is what they saw: on the same day, an additional kilometer that is run by your friend influences you to run an additional 0.3 kilometers. Or speeding up your own run an extra kilometer per minute pushes your friends to run an additional 0.3 kilometers per minute faster than usual. Or if your friends run 10 minutes longer than usual, you may be inclined to run about three minutes longer. If you burn an extra 10 calories, then your friends wind up burning 3.5 more calories.


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