There are in total in the fitness app 6 Level. From Wood to Diamond. Depending on how diligent you train, you can hold your level, descend a level or ascend a level. Therefore, stay it, because every 28 days you will be evaluated
How can you upgrade to a new level? For every completed workout, whether cardio, power, or agility you get points. When you got enough points you go up in the level. The app always shows how many points are still needed for the next level.
More information can be found here.