occasional hip tightness (Read 51 times)

Hi all - Looking for help/guidance on an issue I've faced recently. I recently (last 4-6 months) have been developing tightness in my right hip flexor anytime I run more than 7 miles.  It only feels tight during the run - once I stop I feel completely fine.  If I stop mid-run and do a standing fire-hydrant with my right leg, the tightness seems to go away.  I am able to squat, jump on one leg and do all other common hip injury tests without pain, which hopefully rules out a stress fx or labrum tear.  To complicate matters, it seems to randomly occur - i.e. I have occasional long runs where my hip does not get tight.  However, on the runs when it does tighten up, it does adversely impact my form to the point where I can see this leading to serious injury.  I have tried doing the typical hip stretches, but it hasn't seemed to of made a difference. I also do a fair amount of core and stability exercises.   I have plans to continue running and training for marathons, so definitely looking for answers.  Has anyone ever dealt with a similar issue?

thanks!