Amy Prescott grew up doing gymnastics, moving on to pole vaulting, and track and field in college. Her muscularity is dense, she's never been very bulky, preferring to keep herself tight. You can read more about Amy in my latest 40 page story Size Check 3: Meghan's Revenge.
I also made a brunette version of this picture that could easily be a young Jenna Raleigh, why not?