Ah thanks Matthew. Now that you point it out it makes perfect sense the hips should be moving together, that would allow rotational power. But I don't understand what you said about one foot comes up and the other follows it. I mean if one knee is up that would mean that the front foot is down and the back foot is up or maybe facing backward if you are on the balls of your feet. So I'm missing your point about imagining the feet being tied together which is probably a key. Thanks again.
a pretty good example of what I'm trying to describe. I try for no lag between feet though: his back foot separates a little before rejoining.
I was just watching some other videos on youtube and they explain as an elastic band between feet where the feet do seperate, but only a little. I'm pretty out of practice so take what I say with a grain of salt.