Extract from thread on podiatry arena-

"Practical implications of the balancing effects of the intrinsic action on "talocalcaneal stack " ? With regard to acquired pes planus (flat feet ) , a medial arch support will restore the vertical component of the talocalcaneal stack allowing ,amongst other things , a better intrinsic /calcaneus balancing mechanism leading to better fine control of postural stability and stronger intrinsics . That is what seems to happen in these cases . "