back of my head and heels. Ouch! But also sensed the parts in motion. A bit of reflection went on while on the floor: "If I move this way it feels like this but if move slightly differently it feels like this." and I got into a motion that suited me the most. Interesting and a bit tricky.
"The aim is a body that is organised to move with minimum effort and maximum efficiency, not through muscular strength but increased consciousness of how it works."