With regard to the above , Professor Chris Nester has just started his own blog site . In one of his articles he states -

"The foot is only ever a pure mechanical structure when it is detached from the control system. Have you ever held a fresh cadaver foot? It’s quite difficult to make the foot stand normally or simulate ground contact in a way you would recognise as “gait”. It just flops about and is quite unwieldy. It is not what you see in clinic or when you take your shoes and socks off.
The foot is therefore never a purely mechanical structure and it is always under some level of intelligent control."

Exactly . The foot is designed to be unstable especially in the rearfoot area . Unstable that is until you add in the intrinsic and extrinsic musculature and neural control . Once you add these in to the equation , the narrow heel of the human foot makes balancing the body above easier .

His blog site can be found here - talkingfeet.online/2018/01/04/why-am-i-blogging/ … via @ProfChrisNester

Actually , to be fair ,this is exactly the type of thing Professor Irene Davis has been going on about for years . Just not the short foot exercise please !