Balance is a complex human skill. There are motors and circuits in the body that are necessary for balance, and they come into play unconsciously as you try to maintain equilibrium.
I sort of marvel looking at this as my arms, legs, and rest of body move in different directions, instinctively, to maintain balance — the body working without the brain.
Indo Boards are used by surfers and skiers, not only for balancing, but for strengthening leg muscles. Some people have a very high level of skill on Indo Boards these days.