Runtastic has all sorts of apps (many of which have absolutely nothing to do with running) – everything from cycling, to heart rate monitoring, to abs, and so much more. Its newest app, however, really wants to help users get their ass in shape... literally. It's called Butt Trainer, and well, the name speaks for itself. (For the record, I suggested "RuntASStic," but they didn't go for it.)

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If you've used any of Runtastic's other training apps – like Six Pack Abs, for example – then you're already familiar with how Butt Trainer works. It's loaded with easy-to-follow asscercises, all of which are led by a virtual trainer that shows how to execute each move correctly.

Once a training plan in selected, Butt Trainer guides you through a series of moves each day, and they increase in intensity as the weeks go on. The free version of the app offers one workout level, but to get the full experience it'll set you back a five spot for the full version, which also includes the option to build custom routines, filter exercises by type, get tips, remove ads, and access additional workouts.