Hello all! I've done some internet searches and haven't been able to find a great answer to my specific question, so I figured this would be a good place to start. I am a new runner. I started last August and I must admit, I'm a "Born to Run" inspired noob. I run solely in xero shoes and I'm having a blast doing it. I typically run 3-5 miles, 2-3 times a week. Often my runs are on aggressive trails. I always feel great. However, when I run between 5-8 miles, I start getting inner hip flexor pain that progressively gets worse until I feel almost crippled. After a few days off from running I'm back to normal. At first I thought it was a strength issue that would get better as time went by. However it has stayed pretty much the same, so I'm concerned that maybe I'm just doing something terribly wrong. I run with a mid-forefoot stride and I don't get soreness anywhere else. All of the hip flexor exercises seem to be designed to relieve soreness, but I'd like to prevent the soreness. I feel like this pain is all that stands between me and a half marathon. If you have any suggestions, I'd be thrilled to hear them. Thank you in advance!