Assignment Week 2 3/25/2008– Discuss the physiological processes of balanced hoof
loading. (How does the horse land on a balanced hoof and what are the effects i.e. concussive
shock dissipation, bearing surface load distribution, etc.)
Ed Preble.
NC101:14
First one must define what is a balanced hoof, and from our week 2 readings (Glossary of
Podiatry Terms from Drs Steve O’Grady et all, comes the following, “balance – a
concept that describes the relationship between the hoof capsule and the underlying
musculosketetal structures.” The definition goes on to say that balance is a “harmonious
relationship” in the hoof/foot structure. The bones, ligaments, blood vessels, hoof wall,
frog etc. express a sound solid structure which supports the horse.
The hoof must support the horse at rest and in motion with the outer structure of wall,
sole, bars, frog and inner structure:
(Hoof Anatomy – NC101 readings - From Dr. John Stewart, MA VET, MB, MRVCS)
When a hoof strikes the ground in balance, it will generally strike heel first and flow
forward to the breakover point. During this period significant stresses and forces affect
the hoof, internal structures of the hoof on up through the leg.
In readings prior to the class, and for the class there have been many questions as to how
the hoof reacts to striking the ground. One web site put it in quite an interesting way.
This was written by an individual who attended a clinic put on by Dr. Robert Bowker and
Mr. Gene Ovnicek
There have been a couple of long standing theories as to how energy is
dissipated within the hoof. The Depression Theory is based on force being
applied down the limb, through the components of the hoof, and
downward to the ground and to a lesser degree outward to the hoof wall.
The Compression Theory is a mirror image of the Depression Theory, with
the energy coming up from ground.
Dr. Bowker was able to record the pressure events which occurred within
the hoof. What he found was remarkable.
When the maximum force was applied by the hoof of a galloping horse
striking hard ground, a negative force was actually generated within the
structures above the sole. When Bowker asked an engineer to quantify the
negative pressure values obtained in layman's terms, the engineer
described the negative pressure as a "Helatious sucking force."
http://www.ecis.com/~hplove/clo/heum9803.html
Jamie Jameson in HOGTNHC, in the section on a natural hoof pg. 29 also talks about
how the weight of the horse – or force is spread through the hoof structures. But, the hoof
is only efficient when the toe is short – or a balanced hoof. A long hoof (toe) is not as
efficient as the laminar is weakened and the breakover is at the wrong point.
A balanced hoof also uses the frog as a passive structure during impact, spreading out
helping the hoof wall spread evenly and absorbing some of the impact. The balanced
hoof by its concave shape also springs to help in the massive impact when the hoof
strikes the ground. As Les Sellonow explained in his “Anatomy and Physiology Part 5:
The Equine Foot” (class readings), the frog is an important part of the foot as it acts as a
shock absorber in both directions – from the ground and back down the leg. In both cases
the frog provides significant absorption of force.
In one study on impact, Luca Bein, in a 1983 dissertation in Zurich, measured the shock
absorption of horses. His conclusion was that the shod horse lacked or missed better than
60% of the shock absorption shown by an unshod horse. In the same article, a study was
done on physical movement of the hoof. During striking forces the coronet band moves
inward toward P3, P2 and P1 which is only possible when the side walls of the hoof
move outward. This outward movement combined with the flattening of the concave
solar surface allows the inner structures to move, fill with blood and release on
breakover. http://www.hoofcareunltd.com/Harmful%20effects%20of%20shoeing.htm
The process, although mostly understood, is extremely complex. In a study by University
of British Columbia, John Gosline and Mario Kasapi, they took hoof tissue and put it
through a number of tests that twisted, bent, tore, pulled and squeezed the tissue and
measured how the tissue reacted to the forces. In their tests they determined that hoof
tissue is also complex in its own nature.
http://findarticles.com/p/articles/mi_m1134/is_7_108/ai_55698598
One significant observation on the forces affecting the balanced hoof came from KC La
Pierre in her article (class readings), “A New Angle on Hoof Wall Growth. His
hypothesis is that in response to a stimuli (foot strike), the inner wall produces tubules
which get pushed out and down. These tubules provide absorption of the force of the
strike so that in a proper analogy, the movement of the horse on a balanced hoof grows
and creates the necessary tubules to provide for proper absorption of that force and in
turn that growth creates the proper hoof to support the horse in balance.
In the article “Natural Trimming and Showing – The Hairline Tells it All”, normal
expansion and contraction of the hoof absorbs some of the impact in the hoof, and other
stress loads move up the skeleton to the horse. The sole, as Bergy states, flexes and
moves to aid in absorption of force and should not be restricted. The frog, as earlier
stated, expands and returns to shape supporting both the structures above it internally, but
also the skeletal structure of the leg.
In many of the readings, the same points kept coming out with regard to points of contact
with the ground. Gene Ovnicek’s study probably said it clearest in his long term study of
horses in Montana. The wild horse hoofs he examined with consistently in balance,
appeared to have been trimmed and had definite pressure points or contact points with the
ground. http://www.ecis.com/~hplove/clo/heum9801.html The hoof wall except for either
3 or 4 definite contact points makes no contact. Thus the entire force gets absorbed by
the contact points, sole and frog – when the horse’s hoof is in balance. The hoof wall is
actually more of a containment structure – a point made by many of this week’s articles
and outside readings.
My conclusion from these readings and research is that if you can maintain the hoof as a
balanced hoof, stress caused by movement (walking, galloping, trotting etc.) will cause
the inner structures to grow adapting to the stress. In turn this growth causes the parts of
the hoof that need support and structure (sole callus, hoof wall) to grow and eliminate
those parts that are extraneous (excess hoof wall, sole that is sloughing). This growth
creates or works toward a natural balanced hoof as in the wild horse. This becomes a
reinforcing circle – balanced hoof – stress – proper growth – hoof adjustments – balanced
hoof – naturally.