I don't know if it's that BUT I will say that while I was never a religious exerciser (let alone a runner!), whenever I did exercise I always always always noticed an immediate change in my period. Exercise would actually stunt my period! So for me, I do think that exercise tinkered with my hormones (even though exercise is supposed to be good for you).
Honestly, I wouldn't read any more into it than what it is. In all my cycling and monitoring, I registered a CD2 FSH of 25 once, and every other monitored cycle before and after that it was 14 or below. It could very well just be a wacky cycle for you.