I won't lie, when I was in the military and we did PT in the morning, I made damn sure no girl was in front of me during runs. I was 17 and in good shape but there was this one girl who made that really tough sometimes. I'm too soft and old to keep that up now and there are some strong, strong female runners out there. I don't know what it is, I think it goes way back into our primal caveman days.