good hip stretches, posture advice

[VeloVT]

So, I've had PT flexibility assessments twice recently, different docs (once for a running injury and one quick one for my bike fit), and both noted significant hip flexor tightness as well as hip rotator tightness and ITB tightness. I don't know exactly when this started, but it has not always been the case -- I was very flexible through my teens because I danced somewhat seriously (I'm 28 now). I would attribute it to two years of increasing amounts of cycling, and two marathon training cycles and generally increased running mileage even when not training for anything.

Lately I've noticed (and this is relatively new, over the past year I'd say), when I am in a relaxed standing position, my hips tilt VERY far forward, and if I'm not thinking about my posture, there's a pronounced curve/compression in my lower back. It's actually a little hard for me to achieve significant posterior tilt when I work at it. I can just about get to neutral but not farther. I'm sure this is NOT a good thing. During all of the bike fits, everyone says my back looks great -- I get approved for very aggressive positions because I can achieve them with no curve in my back -- partly due to flexible hamstrings, but probably partly also due to this forward tilting pelvis I've acquired?

I'm worried that my muscles are becoming pretty imbalanced, with tight hips and quads that are throwing everything else off and a body that's starting to adapt "too much" to the cycling position. Is this a reasonable concern, and if so, does anyone have stretches/strengthening exercises to recommend?

thanks !