Wanted to know how well this superpower would work?

So the idea is a power based on density where you have the same strength but can switch between various degrees of giant but the strength becomes more compact depending on how close you are to your original size.

For example you could workout by lifting incredibly large objects and then when you go back to normal size all of that strength caries over into your body being super dense and durable? Would that even be worth it for a superpower