When we walk, the heel should flick away from the body as the foot leaves the ground. The same movement shows up in Michael Jordan, Ed Reed, Kate Moss and Chico Vakowski — straight feet, heel flicking away, fluid stride.
Most people move the opposite way: heavy in the heels, and the heel turns IN when the foot leaves the ground. The spiral still happens, but backwards — the foot drags behind the body instead of moving with it.
The drill: lift the leg as high as you can (no rocking), then PULSE at the top without bringing the leg all the way down. Opens the lower back and the entire back side of the body, creating the space that lets the heel flick away.