Squat ROM and Hip Tilt

I’ve had lower back problems over the years and due to various articles on T-Nation, I’ve been looking at my form during squats and my general posture.

My normal posture has my hip tilt down in the front. I thought this meant my quads/hip flexors were shorter and/or stronger than my hamstrings, so I’ve been stretching them at the end of my workouts. On the other hand, I can’t do ATG back squats and maintain the proper lower back shape without a squat platform that raises my heels.

Without that stand my hamstrings apparently overpower the quad/hip flexors and pull my hip in, rounding my back. I found that out the hard way over year ago.

So, do I have a combination of quads stronger than my hamstrings, but my hamstring/posterior chain lacking flexibility in extreme ROM?

I’m thinking if that’s the case I need to focus more on stretching the posterior chain than what I’m currently doing.

Does that make sense?