Here is the trick. Forget about an athletic girl I have found most of those to be a bit on the crazy side OR a bit self-absorbed with athletics. Find one with more common interests to yours besides running.
For example. I run about 90-120minutes a day, and am pretty serious about it (consistent 66 HM guy) but also focus on my career outside of running and other interests. I don't want to obsess over running outside of the two hours I'm doing it or in the 45 minutes in the morning where I write in my log and check LR. Though clearly it means a lot to me, it don't want it to be the crux of a relationship. It won't work most of the time.
I've found that finding a girl who is into general fitness (yoga, skiing, rock climbing, running, riding) with a healthy balance of that is better.
Common interests can spark many great dates, adventures, trips, talks about culture which lead to better deeper conversations.
Find an artistic one, with good taste in music, literature, art, and photography. I promise you'll be doing yourself a favor here. You can find these at small shows, art galleries, beer tastings, museums, historical sites DIY project events, scenic overlooks, at book stores and usually in the gardening section of any hardware or plant store.
You're welcome.