Did you focus on holding your abs tight, or what?
I think I just became more aware of my lower abs and the connection to my hip joints. Then I became more aware of the top of the hamstrings in the back and let the spin start from those low abs and into the tops of my legs. I don't know that I conciously tightened my abs more, just shifted my awareness of where the power was coming from. I used to practice Aikido, and the focus of the movement and power was from the that same place. It was a subtle shift of awareness that seemed to help me get up that hill.