Orthotics Glossary.

Glossary

excessive pronation
This is really the same as overpronation except that this goes beyond overpronation as in running where the forces and pressures are higher. As in overpronation, this is the point where "wear and tear" begin to accumulate and eventually surface as an injury.
fluid mechanics
Fluid seeks the area (or path) of least resistance and greatest need under pressure.
forefoot
The front, where the ball of the foot meets the ground.
ground reactive force (GRF)
The pressure created by a point of contact with the ground and the ground pushing back up, "for every action there is an equal and opposite reaction".
metatarsals
The long bones of the foot. The heads of the metatarsals make up the "ball" of the foot.  The first metatarsal corresponds to the big toe.  The fifth metatarsal corresponds to the smallest toe.
maximum pronation
When all motion available in each bone of the foot has stopped moving (all maximum pronation is excessive too).
midfoot
The arch.
midstance
That moment in time where the whole foot, front and back, are on the ground at the same time.
neutral position
 This is a positional relationship of the front of the foot to the back of the foot in its best (optimal) operating position. The ideal relationship is the bottom surface of the front is parallel to the back. In actuality, this does not exist.  On average the most common relationship is a "valgus". This is by nature's design the more stable of the two. The second relationship is the "varus".
overpronation (wasted motion)
The motion of the foot as it goes beyond (neutral) the best working or healthy range of motion of the foot as a dynamic organ.
peaking
Peaking is the highest force generated (called ground reactive force) under each metatarsal head at that moment in time when the foot is maximally pronated.
peak pressure over time
The highest pressure (ground reactive force) over the time of the foot step.
phalanges
Toes.
pronation
The motion of the foot as it spreads and arch collapses as far as it can to the ground, absorbing incoming shock and preparing the foot to propel itself. Technically speaking the foot is moving in three directions simultaneously in each of the 3 areas of the foot itself. The rear or hind foot (comprised of the heel and ankle bones). The mid foot (comprised of the tarsal bones ) and the fore or front foot  (comprised of the metatarsals and phalanges).

For those interested in the technical aspect of pronation read further.  The areas of the foot revolve about two axis' of the foot (see image) and while each of the areas has all the components of pronation and supination, certain areas have greater motion in one or more of the components of pronation than the other.
rearfoot
The hind foot, comprised of the heel and ankle bones.
supination
The reverse of pronation.
tarsal bones
The area in front of the rearfoot, which make up the arch.  The cuboid, navicular and the three cuneiform bones.
tracking
A line of travel or motion.  In regards to muscles and tendons it is the path that they follow from their point of origin to insertion, even if it means going around the bend of another structure.