It's got a lot of exercise options, I'd guess something around 40 to 50 of them? Assuming I've unlocked them all, it's possible there's more out there but since I've started getting "lvl 2" versions of stuff I already have I assume I've seen most if not all of the unique exercises.
It's an RPG, not a rhythm game, so you "equip" different exercises to damage monsters or heal yourself. You start off with just 4 exercise slots but gain more as the game progresses. Different monsters have weakness to different types of exercise (arms, abs, legs, or yoga). The exercises themselves are more at your own pace, there may be a suggested rhythm but there's no penalty for not following it, except that strength/flexibility type exercises have a minimum hold time for some positions.
Gameplay is extremely simple, you're locked onto a path and can only move forward and "jump", making the maps effectively like a 2D scroller from a gameplay standpoint. Colliding with a monster (unavoidable until later in the game) takes you into turn-based RPG style battle.
There's also some minigames which have a little more of a skill aspect to them. But the bulk of the game is grinding out exercise.