Muscle breakdown isn't going to happen in your casual runner. It's only going to happen in high level distance runners. Everybody else will have enough energy resources to avoid the breakdown of muscle.
If you want an ass on a woman, she has it genetically or she builds one. Not every woman needs to lift to have an ass. But you'll probably have to lift to have a great one.
Signed,
Ass Expert
Unfortunately, your credentials as Ass Expert, must be given to you from taking courses...from
Foremost expert in Assology, Assametrics, Assanometry, Asstronomics, and Applied Asstrophysics. One must write a 4,000 word dissertation on the history of how the love of booty has shaped several Western countries.
That expert is moi.