Need some motivation to hit the gym? Perhaps some free merchandise will do the trick.

At least this is the premise that Nexercise is built upon. The free iPhone app that tracks activities ranging from running and weightlifting to fencing and polo and rewards users with free and discounted merchandise in the hopes that users will adopt long-term exercise habits.

We're trying to create a lifestyle - not a quick fix, said co-founder Benjamin Young. We don't focus on how many miles you ran or how many pounds you've lifted. You get points in the game for healthy behaviors.

Users can accumulate points based on the length of their workouts and for other behaviors that reinforce frequent exercise habits. Exercising with a friend or on a rainy day, for instance, allows users to accumulate bonus points.

A lot of it is driven by research studies. If you exercise with someone, you're more likely to continue to exercise. said Young.

Receiving prizes is more of a lottery rather than direct redemption. Users with more points have greater chances of winning prizes, and those that have reached higher levels have access to more valuable prizes.

According to Young, the chances of winning a prize at the lowest level are about 25 percent, with prizes ranging from $5 gift cards and coupons for items such as energy bars, up to $250 gift cards.

Recent integration earlier this month with Kiip, a San Francisco-based advertising startup, provides access to prizes from retailers such as makeup company Sephora and vitamin and supplements maker GNC among many others.

Having recently completed an experimental run at the University of Maryland, the app is still quite new and has some kinks.

It has been criticized for the quality of its rewards, which Young said have improved with its recent integration with Kiip, and will continually improve as the app matures.

It's a function of growth. We're growing and the more we grow, the more likely we'll have bigger vendors getting on board, he explained.

Another common complaint is that the app can't run in the background, which means the app has to be open at all times in order to fully track physical activity. Young said the problem is scheduled to be fixed in the fall.

Other upcoming plans for the app include a contextual notification system to increase engagement. For instance, if the app detects that a user is motivated by competition, it will notify them when their friends have surpassed them in the game.

A similar app called Earndit is also available on the App Store and has partnered with some of the same prize providers. Other popular fitness apps include Runkeeper and Nike+, which count calories and map trails, but do not provide prizes as incentives.

Nexercise is available worldwide on the App Store.

Advertising Apple inc. ITunes Iphone