Hoof Mechanics
The hoof as
a whole functions with efficiency, serving the horse for support,
traction and circulation. The mechanics of the hoof were
designed for movement, the more the better. It was also
designed to adapt to the terrain it lives on. In the wild
horse who is moving over lots of terrain from birth, the foot
naturally molds itself into the proper form for optimum mechanics.
In the domestic horse who travels less miles over more forgiving
footings, man often needs to step in to maintain proper form, and
thus proper mechanics of the hoof. But again, let's start at
the beginning....
The
Landing
The hoof is designed to
land heel first. The back half of the foot contains all
flexible structures designed to absorb shock and provide traction.
As the foot touches down the frog comes into contact with the ground
spreading the heels and the lateral cartilages. It is here that a
healthy digital cushion defuses the impact and protects the coffin
joint and the deep digital flexor tendon. They are not
"jarred" by the force of the stride because the digital cushion
muffles the shock. Unless the horse is moving on perfectly
flat ground with a totally straight leg, chances are the hoof will
land on one heel or the other for a split second before both are
grounded. The frog and heel bulbs (the lateral cartilages) flex the
heels to accommodate an asymmetrical landing. The flexibility of the
back of the hoof allows the joints to stay in line except on the
most unforgiving of terrains.
The
Support Phase
Shortly after the heels touch down, the rest of the
foot lands. First to make contact is the flexible inner wall
of the foot, which again absorbs impact and flexes outward allowing
the solar dome (the concavity of the sole) to descend under the
coffin bone. The weight of the horse touches down. As
the coffin bone descends, the back of the foot now acts as a vacuum
and sucks blood from under the coffin bone into the lateral
cartilages. This movement of blood acts very much like an
expensive running shoe to dissipate energy. As the pastern
joints flex the fetlock descends. At this stage, the frog
anchors the coronary band, which tightens around the upper rim of
the hoof and shuts off blood flow, allowing blood pressure to build
in the hoof.
The
Breakover
The front half of the hoof is more rigid than the back and is
designed to dig into and push off from the ground. The solid
attachment of the laminae between the coffin bone and the wall give
the toe its strength. So as the heel lifts and the horse rolls
over the toe, it's the toe that provides the "push" to the stride.
The toe is rounded to allow the hoof to break over at whatever angle
the terrain dictates. A natural bevel to the toe wall keeps pressure
from being transmitted up the wall and weakening the laminar
attachment. Also, as the heel is unweighted, the frog releases the
pressure on the coronary band and the blood that was under pressure
in the foot is pumped back up the leg. The heels recoil and
are made ready once again to receive the shock of landing.
Designed for
Movement
The hoof structure evolved in horses that
spent many many hours each day in travel over varied terrains.
The healthiest hoof is one that is allowed, even encouraged, to
move. It has been proven that horses raised barefoot and
allowed the freedom to move build stronger, more fibrous digital
cushions and also thicker lateral cartilages with more blood vessels
(and therefore greater circulation). Along these same lines,
the more movement in a horse's life, the stronger and thicker his
walls, sole and frog will be.
The horse's body is so large that nature has provided
him with four extra hearts to maintain healthy circulation
throughout his entire being. Horses who are encouraged to move
will be fitter and healthier overall.
But what happens when things
aren't perfect?
CONTINUE...
**Leaping horse photo: Trish Lowe; Amherst,
Nova Scotia.
**Other photos and text copyright Suzon Murray 2006,
not for reproduction
without the express written consent of the author.
