Noticing a light contact on the ball of the little toe enables us to activate deep plantar muscles that run close to the outside edge of the foot. Their tensing gives us a little 'push' back towards center. When too much of our weight falls upon this outside edge, however, these muscles cannot handle the load. We have already fallen too far laterally, and are employing large leg and pelvic muscles to stop our lateral topple. We would like to avoid this.
Falling Onto the Outside Edge
Staying Atop the inside Edge