This is an actual computer test of a runner taken at one of our marathon expos, shown at about 1/30th the normal speed. It demonstrates the “balance and stability” of the foot in motion.
This foot belongs to a high arched supinator—who still pronatesas he steps across a pressure plate designed to capture theground reactive forces (Newton's 3rd law) generated against the ground, first in the barefoot mode, then with the individuals own traditional orthotic and lastly, wearing a prescriptive silicone orthotic.
Every foot has a certain amount of imbalance (DUE TO OVERPRONATION) to it (this is seen in the barefoot mode as colors, red is high, blue is low), that’s normal. It’s how it hold’s you up over the long run that matters (pun intended).
With the Silicone orthotic what you are seeing, is that the fluid is filling in the arch (by displacement
of heel contact) to an equilibrium state*
of the the foot's own natural position and the distribution of weight and function.
More contact surface of the foot (reduces the force per unit area) on the floor, all the contact points of the foot are also making contact and are stable on the floor.
All the joints are in better “functional” balance ( due to: joint axial congruety), muscles are “tracking” with better efficiency (AKA—lever arm efficiency)
Hydrodynamic pressure spreads the weight and forces more equally on the floor.