Dr. Bowker uses the foot of a feral horse in an abrasive environment as a
model.  His hypothesis is based on the incompressibility of fluids and
the ability of moving fluids within elastic containment to dissipate
energy, a phenomenon he calls, "hemodynamic flow."  Bowker hypothesizes
that when the foot impacts the ground, outward movement of lateral
cartilages creates a vacuum that pulls blood from beneath P3 into the
rear portion of the foot and dissipates the energy caused by impact.

To achieve this theoretical end, he touts something called a
"physiological trim." According to this protocol, the toe is shortened
and the heels are gradually lowered until the frog is on the ground.
The frog is not trimmed, the bars left intact, a sole plane established,
and sole pressure encouraged.  The object of the trim is to create a
foot that that has a solar surface 1/3 distal to the apex of the frog,
2/3 proximal.

Bowker's press releases claim anecdotal evidence demonstrating the
superiority of Bowker's "physiological trim" to conventional farriery in
the treatment of navicular syndrome.

Such claims are open to criticism.

A feral foot modeled by an abrasive environment serves the feral horse
well.  Feral horses have no natural enemies, do not carry weight, pull
loads, or engage in forced exercise; as a consequence, they don't
require an efficient foot for survival.  On the other hand, a domestic
horse requires an efficient foot, with efficiency commensurate with
use:  a pasture ornament does not require a particularly efficient foot;
a race horse requires an extremely efficient foot.  For this reason, a
model based on feral horses has relevance to feral horses, not domestic
horses. The ideal model for domestic horses in use is the foot of horses
that have demonstrated superior efficiency in use.

Bowker's advocacy of gradually lowering the heels on every horse does
not consider phalangeal alignment and the possible deleterious effect
such a procedure may have on the individual.  He does not consider the
increased compression of the navicular bone by the deep digital flexor
tendon or distal interphalangeal joint extension on lowering the heels.
He does not consider the effect of lowering the heels on bruises to the
navicular bursa, fractures or bony changes of the navicular bone, or
other causes of pain in the posterior third of the foot.

Pain on pressuring the middle third of the frog with hoof testers is
a classic symptom of navicular syndrome, yet Bowker advocates lowering
the heels until the frog is on the ground. Lowering the heels of horses
diagnosed with many forms of NS invariably cause pain on loading the
foot - yet, the pain of such a horse is not a consideration.

Bowker does not consider the individual's conformation or use.

Bowker's hypothesis has not been tested.  The plural of anecdote is
not data.

On paper, Bowker's hypothesis apparently has a great deal of appeal to
anyone lacking practical experience with the treatment of the various
pathologies affecting the heel.  "Hemodynamic flow" sounds good and
promises much; but despite all the hoopla and self-aggrandizing press,
in reality, there is no evidence that suggests the application of
Bowker's protocols are as beneficial in the treatment of navicular
syndrome as are traditional, short toe, natural angle, trimming/shoeing
methods.