Following a bit of a false-start reveal picked up by the eagle-eyed NeoGAF crowd, Microsoft has now officially unveiled Xbox Fitness, a Kinect-powered workout service for the upcoming Xbox One that will be offered free to Xbox Live subscribers until December 2014.

Xbox Fitness is a new online service built exclusively for Xbox One that takes the world’s most popular fitness videos and makes them interactive. The extensive library of videos from the world’s biggest fitness brands including Beachbody’s P90X® (Tony Horton) and INSANITY® (Shaun T), Jillian Michaels, Tracy Anderson and others, will be available for free with Xbox Live Gold memberships through December 2014.

Using precision Kinect technology, Xbox Fitness can read your heart rate without a monitor, see which muscles are most engaged by measuring the power, force and transfer of weight in your body, and track the quality of your performance by measuring your balance, tempo and form.

Xbox Fitness will deliver personalized program recommendations based on your workout history and past performance, highlight the most popular workouts among Xbox Fitness users, and offer a variety of workouts, from 10 to 60 minutes in length.

Xbox Fitness also helps you push yourself to work harder and stay motivated. Challenges are integrated into your workouts through Xbox Live, tracking your performance history and awards and delivering competitive social challenges. Take on your previous scores, challenge your friends to beat your performance and compare with the Xbox Fitness community.

A specific release date for the service wasn't noted, only that it will launch "just in time to get a jump-start on your New Year’s fitness resolution".