Whether by means of competitions, social features, bragging rights or goals, these digital tools are keeping tabs on your workouts -- and letting your friends do the same.
"It really changes the dynamic because it's almost like you're on stage or in a race," says Jason Jacobs, the founder of fitness tracking app RunKeeper. "If you stop and walk halfway, people will know. If you finish strong, people will know. Whether a million or people see it or nobody sees it, just the perception people will see it is accountability."
Since it launched in 2008, Runkeeper has added features that allow users to post their workouts on Twitter and Facebook, keep a feed of their pals' activity, and even invite others to track them on a live map as they're completing the workouts.
Jacobs says that users who use the social features end up logging more workouts and sticking around longer than those who don't.
A recent study at the Vanderbilt School of Medicine supports the theory that peers can influence exercise. It found that hanging out with active peers may encourage kids to be more active.
Can the same hold true for adults' social media pals? Researchers have yet to take this question on, but there are several apps that could make good case studies when they do.