Gavin video-taped my running. It was painful to watch. I don't run, I lumber. Despite that I keep an erect posture, which I accomplish by arching my lower back. Tight hip-flexors mean my lower back arches even further with each stride in order to achieve any follow-through. My feet kick sideways to clear the ground because I don't kick off enough with my feet and calves. My hips dip by greater than 10 degrees side-to-side. I spend a long time in the air between foot-strikes. And my stride is really slow.
Current drill: run 4 x 3' at 170 strikes/minute and 2' at my "normal" stride. By the end of the series it is painful -- literally -- to return to the normal stride. I see the treadmill shake as I land on it. My knees and ankles hurt as I land with the longer, slower stride. In contrast, the 170 strikes per minute running is light, easy, lovely.
I don't know how long it will take to internalize this particular change and I don't think the fight is nearly over, but so far this week has been a remarkable exercise in learning how to run.