Fitness platform Fitocracy will be debuting a new feature named Duels early next week. Duels will further Fitocracy’s goal of encouraging exercise through competition, adding the caveat “…on Fitocracy” to the end of “I’m going to kick your ass!”

Duels use the points system already present in Fitocracy’s gamified approach to exercise, encouraging a race for “Most Swimming Distance” or “Most Weights Lifted” between two users. Founder and CEO Brian Wang says that the feature is a result of users’ requests for more game-like features and is designed to encourage a bit of friendly competition.

While challenges can only be issued by Heroes (Fitocracy’s term for premium members), any user can accept a challenge once it lands in their inbox. And, because no battle is complete without a frenzied mob, other users can sign-on as Spectators to cheer for their team and talk smack about the opposition.

On the surface it seems like other services compete with Fitocracy for mindshare and traction, but the company has always left its doors open to sharing from those “competitors.” By integrating with “rivals” like RunKeeper and Fitbit, Fitocracy enables users to gather stats about their workouts via their preferred method while providing access to Fitocracy’s tools and community. Wang says that he is looking forward to integrating with even more services, such as Nike’s FuelBand, once the technology is available.

Fitocracy left private beta after participating in 500 Startups’ 2012 class. Since the public launch the service’s community has grown to 400,000 users, and its iPhone application has been reviewed over 2,000 times with a consistent 4- or 5-star rating. Since the public launch, users visit the site for 11 minutes each day on average.

Because the main draw of the site – logging a workout and racking up points – doesn’t take even a quarter of that time, Wang says that the longer stay is probably a result of  the service’s social aspects. “Every time we ask a user if Fitocracy has had an impact on their lives,” he says,  “Time and time again the community has been the #1 thing that they talk about.”

400,000 users isn’t bad for a relatively young service that, as Wang says, stumbled into social network territory as a “happy accident.”  Without a sufficient number of users, Duels wouldn’t be possible. The “friendly” part of friendly competition can only come from a community as large and supportive as Fitocracy’s. Without it, challenges would either remain unanswered or quickly devolve into mean-spirited attempts to prove one’s worth.

Duels will be Web-only at launch, but the feature should arrive for mobile devices shortly. When asked about the possibility of releasing an app for the iPad, Wang says that there has been “very small interest” in the possibility and that devoting the time to developing the application for such a small number of users wouldn’t be worth the trade-offs in time and effort.

Fitocracy’s goal is clear: Use the lessons learned from too many hours playing video games and apply them to physical activity. Duels are simply one feature of many coming down the pipeline that will leverage the service’s growing social factors and gamification roots to teach the current generation what it really means to be “mobile.”