Yes and no.
Exercising in a dream will never build up muscle mass. It might build up confidence, (or cockiness), but you will never have the same experience as actually running 10 miles.

Say you need to practice running through the forest, you could very well practice this in your dream, but it wouldn't be the same as in waking life, nor would that "dream like state" be carried over, obviously.

Muscles mass? No. Confidence? Yes.