I have also figure out that mechanics cannot be improved if posture is not improved. If someone with less than ideal posture tries to limit the back-kick they will most likely cut off the stride too early which will limit force output. I know this because I have had problems with this. Now I just focus on having the best posture possible, pump the arms, and step down. Those cues have really help to make dramatic changes to my mechanics. I still have a long way to go but I now know that my training on the track, in the weight room, during stretches, and foam rolling are suppose to be geared towards improving my posture by releasing tension and/or increasing the strength of the antagonist muscles. Now I am focusing on release the quads/psoas while increasing the strength of the hip ex-tensors and abdominal muscles.