Tried out for my school's d1 xc program last fall, met with the coach, he told me they couldn't take me. When he found out I was planning on serving a two year LDS mission (this is a dominantly Mormon school) he told me that male runners sometimes go through a "second puberty" during their mission and that they come back and end up being a better runner than they were before (after building fitness up again).
Is there a physiological basis for this idea? That an 18 or 19 year old male who has been running for 4-5 years who takes a two year hiatus from training can benefit from it. Might is be weight gain, or just being older? And before you say that we get an extra two years of training, running is very limited because you have 30 minutes a day for exercise and have to stay with your companion.