I think it is more just "pumping" the energy from the toes to whatever level and back down again to the and through the toes.
So, for example, on the third step, in round one, you imagine the energy coming up from the toes through the feet, legs, torso, chest, up to shoulders, and then back down again. I think of it, kind of like the body is a big body-shaped-bottle, and the energy is coming up, clearing channels as it goes and back down again, also clearing channels as you pump the energy through.
I have never done it as a straight line, so I may be only dong "good" and maybe a straight line is better. I don't know.
I thought the idea was to clear ALL the channels from the feet, up to each level and back down, with ALL points in between.
Straight line sounds more like Small Universe or something.
