I've been observing this phenomenon for quite a while. why is it that girls at 20 years old can't run as well as they did at 16-17? I'm coaching a girl now who is averaging between 6:50-7:05 mile pace for 5 and 6k races, but was running 6:20 pace as a junior. I started coaching her in february of this year and she took some time off, but i thought that after 9 months of Lydiard-esque training she'd start to come around.
I've seen the same thing in other girls: the 3 b's at 16--boobs, butts and boyfriends. but why do some girls continue to run well in college? someone like sara hall for example. she ran well all through HS and college and now beyond.