Why does movement have to go from the inside out, or what we commonly refer to as 'fluidity'?

I think the example that Mabel Todd gives is beautiful: “At night walking is easier and quieter than by day. This is because, undistracted by sight, the body falls into the ancient, unlearned patterns of movement in which the mechanics are blocked less by self-conscious constraints, and the primary reflexes may carry through.” The body is a mechanical unit in which each part does not stand alone. Each part is dependent on the parts below and above, and it is the systematic movement of equalized internal action and reaction that makes movement fluid. Fluidity is independent of forces outside the the body. For authentic, pain-free movement it has to come from consciousness within, an ability to move by understanding how to create stability and lengthening from that stability within.