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Written
by
Steven
Robinson
of
Darkstarr Rottweilers
The
purpose
of this
article
is to
provide
insight
regarding
the
unique
function
of the
hock.
In a
sense,
it is
where
movement
begins.
The
hock is
the
foundation
of
movement
for any
particular
dog.
Understanding
and
assessing
the
hock is
fundamental
in
understanding
and
assessing
a
dog’s
movement.
In a
vertical
line of
dominos,
the
hock
would
be the
lead
domino.
The
hock,
just
like
the
domino,
is what
sets
all
other
components
in
motion.
Because
of this
relationship,
the
efficiency
of the
lower
thigh,
upper
thigh,
back,
shoulder
blade,
and
upper
arm all
depend
on the
hock.
For
breeders,
understanding
the
function
and
importance
of the
hock is
essential
in
producing
structurally
sound
dogs
Diagram (1) shows the various parts of the hock. This article emphasizes the importance of the metatarsus, the hock joint, and the Achilles tendon.
Diagram
2
For
our
purposes,
as dog
breeders,
there
are
three
main
areas
to the
hock
that
greatly
determine
its
efficiency.
The
first
two of
these
have to
do with
their
lengths
in
proportion
to each
other
and the
third
one has
to do
with
the
angle
in
which
force
is
applied
to the
hock.
In
diagram
(2),
these
three
areas
of the
hock
have
been
illustrated.
The
action
of the
hock is
that of
a
lever,
and
because
it is a
lever,
it is
subject
to the
same
physical
laws as
any
other
lever.
A dog
uses
this
lever
to move
himself
along.
Once
the
hock is
conceptually
seen as
a
lever,
then
understanding
the
significance
of
these
three
areas
of the
hock
becomes
easier.
Diagram
3
Diagram
(3)
illustrates
the
components
of a
lever
and
their
corresponding
components
found
on the
hock.
Because
the
hock
acts as
a
lever,
we can
use the
physical
laws
that
govern
levers
to
point
out the
strength
and
weaknesses
of
different
proportioned
hocks.
If you
have
ever
been on
a
teeter
totter,
then
you
have
had
experience
with a
lever.
Many
teeter
totters
are
able to
be
adjusted
to
accommodate
different
sized
people.
This is
accomplished
by
adjusting
the
length
of each
side
until
it
becomes
balanced.
The
first
physical
law of
levers
has to
do with
mechanical
advantage.
In
order
for
equilibrium
to
occur,
the
opposing
sections
divided
by the
pivot
point
of the
fulcrum
must be
balance.
Equilibrium
occurs
when
Effort
X
Distance
from
Fulcrum
= Load
X
Distance
from
Fulcrum
When
looking
at
Diagrams
(2) and
(3), it
simply
means
the
effort
supplied
by the
Achilles
Tendon
multiplied
by the
distance
from A
to C
must
equal
the
distance
from C
to B
multiplied
by the
load in
order
for
equilibrium
to
occur.
For our
purposes,
we are
going
to
assume
the
load is
approximately
equal
to the
dog’s
weight.
So, if
we had
a 100
pound
dog
whose
hock
length
was 6
inches
and the
C
to B
section
is 5
inches
in
length,
then
the
following
calculations
would
apply:
(500
lb of
effort)
X (1
inch of
A to C
distance)
= (5
inches
of C to
B
distance)
X (100
lb of
load)
Diagram
4
In
the
above
example,
in
order
for
movement
to
occur,
the
Achilles
must
apply
more
than
500
pounds
of
effort
per
step.
Since
our
Rottweiler
is more
of an
endurance
trotter
than a
sprinter,
any
improvements
that
can be
made to
the
hock to
reduce
the
effort
expended
per
step,
will
create
less
fatigue
and
improve
endurance.
Actually,
what we
are
trying
to do,
is
improve
our
Rottweiler’s
mechanical
advantage.
Mechanical
Advantage
=
Distance
from
the
Fulcrum
to the
Effort
/
Distance
from
the
Fulcrum
to the
Load
The
goal in
most
lever
designs
is to
have a
greater
distance
between
the
fulcrum
and the
effort
than
the
fulcrum
and the
load.
This
makes
the
amount
of
effort
applied
less
than
the
load.
This is
a true
mechanical
advantage.
Unfortunately,
the
advantages
obtained
by such
a
design
in the
hock
area
would
create
greater
disadvantages
in
other
areas
of the
rear
assembly.
So, let
us look
at how
we can
reduce
the
effort
applied
by the
Achilles
but not
create
problems
in
other
areas.
There
are
three
components
of the
above
hock
leverage
system
which
directly
affect
the
effort
expended.
They
are the
distance
between
A
to C,
the
distance
between
C
to B
and the
amount
of the
load.
Since
our
Rottweiler
is
required
to be a
medium
large
dog to
perform
his
duties,
changes
in the
amount
of the
load
will
reduce
his
effectiveness,
and so,
changes
in the
load
are too
prohibitive
to
consider.
Now we
are
left
with
the A
to C
distance
and the
C
to
B
distance.
What
would
happen
if we
increased
the
size of
the
hock
joint
by
increasing
the
distance
between
A
to C
by ½
of an
inch?
This is
why our
standard
insists
that
the
hock
joint
needs
to be
strong.
The
strength
of the
hock
joint
is
greatly
dependent
on the
vertical
distance
between
A
and
C.
The
greater
this
distance
the
stronger
the
joint,
the
less
effort
needed.
Using
our
first
example,
we will
have
the
following:
(333
lbs of
effort)
X (1 ½
inches
of A to
C
distance)
= (5
inches
of C to
B
distance)
X (100
lbs
load)
Diagram
5
So,
a
significant
reduction
in
effort
applied
by the
Achilles
was
accomplished
with a
little
increase
between
A
to C.
This
created
a 33%
reduction
in the
effort
required.
This is
called
Archimedes
Principle
of the
lever.
Archimedes
Principle
of the
lever
The
longer
the arm
of the
lever
to
which
force
is
applied,
the
less
force
needs
to be.
What
are the
advantages
and
disadvantages
to
lengthening
or
shortening
C
to
B?
When
the
distance
between
C
to
B
is
lengthened,
the
working
arch of
the
hock is
increased
which
accomplishes
more
work
per
step.
Even
so, it
requires
more
effort
per
step
which
can
quickly
fatigue
the
Achilles.
If the
distance
between
C
to B
is
shortened,
the
working
arch of
the
hock is
decreased
which
accomplishes
less
work
per
step;
but it
also
requires
less
effort,
which
fatigues
the
Achilles
less.
These
two
comparisons
are
examples
of The
Theory
of
Conservation
of
Energy.
Theory
of
Conservation
of
Energy
Hard
effort
over a
short
distance
= Easy
effort
over a
long
distance
This
theory
can be
applied
to
animals
in the
field.
Two
examples
of
extreme
opposing
hock
lengths
and
their
corresponding
applications
are the
jack
rabbit
and the
coyote.
The
jack
rabbit
has an
extremely
long
hock
and is
known
for
extreme
burst
of
speed.
This is
nature’s
way of
getting
him out
of
harms
way
quickly,
and for
this
advantage
of
early
speed,
he
gives
up
endurance.
On the
other
hand,
the
coyote
has a
very
short
hock
and is
one of
the
best
endurance
trotters
in
nature.
He
doesn’t
have
the
early
speed,
but he
has the
patience
and the
endurance
to
catch
his
share
of the
rabbits.
This is
the
reason
the FCI
standard
requires
the
hock
not to
be
steep.
Another
point
these
examples
can
demonstrate,
is how
the
length
of the
hock
affects
the
length
of the
other
bones
of the
rear
assembly.
Just
like
the
jack
rabbit,
dogs
with
long
hocks
tend to
have
shorter
lower
and
upper
thighs.
This
too
creates
problems
because
short
lower
and
upper
thighs
have
shorter
muscles
making
them
less
efficient.
“Why?”
you
ask.
The
longer
the
second
thigh
is, the
longer
the
muscles
are
that
act on
the
hock.
The
longer
the
muscles
are,
the
greater
the
distance
they
will
contract.
Generally,
muscles
will
contract
2/3 of
their
length.
This
means
longer
muscles
have a
greater
capacity
to
pull.
This is
one of
the
reasons
our
Rottweiler
standard
calls
for a
fairly
long
upper
thigh
and a
long
lower
thigh.
In
addition,
a long
hock
can
reach
further
up
under a
dog’s
body,
and in
doing
so, it
can
create
interference
with
the
working
arch of
the
front
assembly.
This
interference
can
contribute
to
crabbing.
There
is a
reason
rabbits
don’t
trot!
Diagram
6
Another
area of
importance
is the
angle
created
by the
intersection
of the
Achilles
and the
horizontal.
Diagram
(6),
illustrates
how
changes
in the
angle
of the
Achilles
affects
the
force
required
to do
the
same
work.
Position
1
is the
most
effective
position,
because
it
directly
opposes
the
resistance
of the
load.
This
position
is the
position
of
choice
for the
Dachshund,
but for
breeds
whose
functions
require
trotting
for
longer
distances,
this
position
prohibitively
compromises
the
efficiency
of
other
areas
of the
rear
assembly.
So, as
with
many
areas
of
canine
structure,
we
compromise.
Even
so, our
hock
joint
needs
to
remain
moderately
well
bent.
Position
4
depicted
in
diagram
(6)
illustrates
the
effect
of
having
too
little
bend.
At 60
degrees
from
the
horizontal,
twice
as much
force
needs
to be
applied
to
affect
the
same
amount
of work
as
position
1.
This is
why the
FCI
standard
requires
our
Rottweiler’s
hock be
well
angulated.
As
has
been
demonstrated,
there
are
three
areas
of the
hock
that
greatly
affect
its
efficiency.
Since
our
Rottweiler
is
required
to have
endurance
and his
movement
is that
of a
trotter,
a hock
that is
well
bent,
having
a thick
hock
joint
and a
short
metatarsus,
will
provide
the
efficiency
and
endurance
required
of his
duties.
It will
also
provide
a good
foundation
for
movement
without
prohibitively
impacting
other
important
structures.
**Not for reprint without authors consent**