Last November, avid biker Leon Shaner found himself pushing harder than usual to keep up with a new friend.
The two were locked in a fierce monthlong competition to bike at least 1,000 miles. They rode at the same time, trading small talk and stats after each ride, and urged each other on. Shaner said that because of the close competition, he doubled the number of miles he would normally have biked in a month.
The biking, sweat and pain were all real.
But the race itself was virtual. The conversations were on Twitter, the rides tracked by an iPhone app. The friend, someone Shaner had never met, lives halfway around the world in Japan.
Welcome to the new world of fitness-tracking technology.
The tech has taken off over the past few years, led by small wearable pedometers like the FitBit and Nike Fuel Band, and apps that use the GPS and accelerometers in smartphones, like RunKeeper and Endomondo.
On their own, these tools can be helpful for anyone trying to get into shape. They collect all manner of data, tracking workouts so people can set goals and self-monitor their progress along the way. That's an important factor in changing any behavior, according to sports psychologists.
But newer social features are turning the gadgets into even more powerful motivation tools. People are connecting with friends on the apps and embracing official and unofficial ways of swapping encouraging messages and trash talk, comparing workout stats, and using peer pressure and the need for approval to push each other to work out more and meet their goals.
People who have friends on RunKeeper, even just one, are two to three times more active than people who use the app solo, according to CEO Jason Jacobs. FitBit says its users who use the social features on FitBit also tend to be more active.
Working out for approval
What is it about friends that makes us work out a little harder?
When deciding how to add social features, many of the app and device makers were influenced by the research of Stanford professor BJ Fogg, who studies behavioral motivation.
Fogg said social features on fitness devices play three roles: They motivate people; the various interactions act as triggers for action; and sharing information and tips can increase ability.
Almost all fitness tracking tools now let you share your workout through the apps or on social media sites so people can see that you just finished a workout. Some even let them track you during the workout or, for example, a big race.
You've probably noticed some of these in your Twitter or Facebook feed. They might seem like a brag at first (even if they did trigger you to do some cardio). But publicly sharing workouts has real benefits, especially for people who are just getting into shape and are trying to stick to new behaviors.
"People tend to continue exercise if they feel it's approved by other people who are meaningful to them," said sports psychologist Jen Gapin.
Even light positive feedback can be a motivator, such as a simple "Like" on Facebook, "Cheer" on FitBit or a "Healthy" vote on RunKeeper, which is the app's equivalent of a like.
The RunKeeper app has a leaderboard that lets you compare your activity levels over the past month to your friends who also use the app.
If one of your less motivated friends has been inactive for over 30 days, a shaming couch icon appears to the left of their name and a megaphone button to the right. The megaphone lets you send a message to your less-active friend telling them to go for a walk, run or bike ride -- but you can only bully them once every seven days.
FitBit also has a leaderboard but doesn't currently allow messaging through the mobile apps, though you can tweet out your progress. On the FitBit website, friends can communicate with short messages or send each other a "Cheer" or "Taunt."
"They tend to send more cheers than they do taunts, so it does tilt towards positive encouragement," said Nichiketa Choudary a senior product manager at FitBit. "At the same time we have some very interesting trash talk, more so on the playful side."
'There's no gunshot start'
Built-in social features are still in their infancy for many trackers, but the people using them are finding creative ways to communicate with friends.
Knowing that people are rooting for him keeps Dan Gillis running.
He'll post details about a run on Facebook and Twitter. And he'll share it live as on the RunKeeper app, where his friends can see stats like a map of the route he ran and his pace. He pops in his headphones and turns on the accessibility option in his iPhone so that any supportive texts and tweets he gets are read aloud while he's running.