vet notes

Cramping


Greyhounds are particularly prone to
developing cramped muscles if they are not
fit enough for the speed or distance of
racing, or if their diets are imbalanced or
lack physiological salts such as potassium
to counteract increased losses.
Cramping is the failure of a contracted
muscle to relax so that it remains
contracted and appears hard or “knotted
up” when examined.
Studies indicate 10% of cramping
occurs in the shoulder over the front triceps
area, 30-40% in the back line muscles, and
more than 50% of cramping involved the
larger hind limb driving muscles.
Cramping can occur before a race,
during a race, or within 60 minutes after a
race.
One major muscle, such as the
semitendonsis, or a group of muscles
may become knotted as muscle
relaxation is prevented.
In hard walking, excitable greyhounds,
or those that become stressed when
travelling or waiting in the kennels or
starting boxes prior to racing, cramping
can severely affect their performance.

Feeding a high starch
diet, such as more than two slices of bread
or a high starch, low protein dry food or
biscuit, can increase the risk of cramping in
some
greyhounds.
A lack of vitamin E, calcium and
electrolytes such as potassium and
magnesium in the diet can also increase the
frequency of muscle cramps.
Subclinical cramping
Up to 40% of greyhounds that finish
poorly in a race and slow down in the
home straight are likely to have developed
a less acute form of muscle cramping, often
referred to as subclinical cramping.
Affected greyhounds do not show
obvious signs of restricted stride, hunching
in the back or dragging a leg as is typical in
more severe forms.
However, they will react to pressure
applied over the muscle groups involved
when caught and examined immediately
after racing.
These symptoms often disappear by the
time the greyhound is rested and walked
back to the kennels, as walking will often
relieve the knotted muscles and restore

Often this form of cramping is confined
to the hindlimb driving muscles in then left
hind leg, which tire more quickly in an
unfit greyhound, or one that is suffering
from dehydration and reduced blood
profusion or body salt imbalances in the
blood.
If these greyhounds are not examined to
identify the subclinical muscle cramp, the
underlying reason for repeated poor
performances may not be recognised.
Severe cramping
Greyhounds are most likely to cramp
up after the first 300 metres of a race.
In an unfit or an anaemic
greyhound, this is thought to be
caused by oxygen debt in the rapidly
contracting muscles during the
gallop.
Cold conditions, particularly at
night race meetings, also increase the
risk of cramping, especially in
greyhounds that have been kennelled
for long periods waiting for later races.

Nervy, excitable greyhounds,
especially bitches, are more likely to
cramp if not warmed up properly by a
brisk walk or muscle massage prior to
being boxed.
The cramped muscles feel firm, hard
and knotted, and if cramping occurs in the
hind limb driving muscles, the greyhound
will be reluctant to walk because of the
pain and restriction in stride.
Exercise hyperthermia
This is associated with heat stress from
long distance travel, over-excitement in the
kennels, and can also be due to inherited
risk of cramping referred to as Exercise
Induced Malignant Hyperthermia in certain
bloodlines.
Lactic acid levels in the muscles and
body temperature reach their peak
immediately after a race.
This condition can lead to severe pain,
distress and internal damage to the affected
muscles if a greyhound overheats during a
race or gallop.
Cramped muscles virtually break down
in their structure, with protein loss and
pigment excretion, leading to dark urine,
dehydration and loss of body weight and
muscle mass in severe cases, often referred
to as exertional rhabdomyolysis.
Hot weather, dehydration and build-up
of lactic acid in the driving muscles can
result in an acute acidosis syndrome caused
by physical stress due to an extreme effort,
often combined with dehydration or
electrolyte imbalance.