i think Cinderella isn't involved in any of the hard physical activities but just longer hours of work, that would require general stamina but not muscular strength. Rapunzel on the other hand is extremely active - sitting on tower ceiling beams, pulling Gothel up with just her hair, taking a plunge off the cliff.

Cinderella may do housework, which can be strenuous, and flee down the staircases of the palace, but Rapunzel pulls Gothel up that tower every day (even with magic hair, that must take a lot of physical strength), uses her hair to swing from one side to the other, digs her way out of a cave and struggles in the chains that hold her. (iron, maybe?)