Download The need for speed in horses that go the distance

Photograph courtesy of Sandra Osborn
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The need for speed in horses that go
the distance
Dr Catherine Dunnett BSc, PhD, R.Nutr
Stamina is a pre requisite for endurance horses.
Arabian horses are said to have a natural
advantage, being endowed with a muscle fibre
composition which allows them to power their
muscles more efficiently with aerobic energy
generating pathways. Races around the
world, however, are getting faster with speeds
of over 20Km/hour being frequently seen in
FEI race events. At relatively slow speeds,
muscle contraction can be sustained almost
entirely by aerobic metabolism, with a lower
contribution from anaerobic energy generating
pathways. Lactic acid is the bi-product
of anaerobic metabolism of glucose and it
accumulates in muscle when this method of
energy production is used extensively during
exercise. This means that at slow speeds,
the amount of lactic acid that accumulates in
muscle is low, but when you step on the gas
the amount of lactic acid produced increases.
There is a clear relationship between speed and
the accumulation of lactic acid and essentially
the faster a horse runs the greater the intensity
of exercise and the greater the lactic acid
build up in muscle is likely to be. Lactic acid
accumulation in muscle produces an ‘acid’
environment, which interferes with the muscle
contraction mechanism and leads eventually
to muscle fatigue. Interestingly, it is not a
straightforward or linear relationship between
speed and lactic acid accumulation. There is
initially a lag phase, where a horse is still able
to ‘reprocess’ or metabolise the lactic acid in
muscle, keeping pace with its production. The
anaerobic threshold also known as the lactate
threshold is the speed at which lactic acid starts
to rapidly accumulate in blood, as it is released
from muscle. Horses, such as flat racehorses,
compete at speeds way above the anaerobic
threshold and so lactic acid accumulates in their
muscle relatively quickly and they can therefore
only sustain such a high speed over a relatively
short distance and time.
The key, metabolically for an endurance horse
is to be able to compete for sustained periods
during a race near to the anaerobic threshold.
This strategy allows a balance between
optimising speed, whilst keeping lactic acid
levels low and muscle fatigue at bay. The
anaerobic threshold is foremost in the mind
of many endurance riders and trainers, as
their target is to push it upwards through their
training program. If achieved, this means
that a horse would be able to travel at a
consistently higher speed before lactic acid
started to accumulate in muscle in earnest.
A vital aspect to managing lactic acid
production in muscle is the ability to clear it
from muscle into blood, but also to buffer the
lactic acid where it is produced in muscle.
There are various ways in which lactic acid or
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(Dunnett and Harris 1999)
its acidic hydrogen ions (H+) can be buffered
in muscle, but the most significant in horses
is from the action of carnosine. Carnosine is
a peptide or ‘small protein’ synthesised within
muscle from two key amino acids beta alanine
and histidine. The level of carnosine within
muscle varies between horses and decreases
with age and can also be increased slightly
by training. The level of carnosine is higher in
the fast twitch type 2 muscle fibres compared
to slow twitch type 1 fibres. As Arabian
horses have been reported to have a higher
proportion of type 1 fibres compared to breeds
such as Thoroughbreds or Standardbreds,
it has been proposed that they may have a
lower muscle carnosine content. Logically it
would follow that they may be less efficient
at buffering lactic acid in muscle by this
mechanism, although to date this has not
been confirmed.
Dietary beta alanine is a limiting factor to the
synthesis of carnosine in muscle. Although
beta alanine is found within the horse’s diet in
plants, as part of the B vitamin pantothenic
acid and also the substance co-Enzyme A,
the level present is extremely low. Research
conducted at The Animal Health Trust in
Newmarket, carried out by Dr Mark Dunnett
and Dr Roger Harris, discovered that the
horse’s diet could be supplemented with a
particular form of beta alanine effectively. They
confirmed that this form of beta alanine was
absorbed from the digestive tract and that it
resulted in an average 20% increase in muscle
carnosine content after only one month
of supplementation. This groundbreaking
research paved the way for a large integrated
program of research into the effects of
beta alanine supplementation in humans.
This human research has subsequently,
convincingly established the beneficial effects
of beta alanine supplementation for athletes
in many different disciplines. Of particular
interest and relevance for endurance horses
is the finding that the anaerobic threshold or
lactate threshold is increased in endurance
athletes following supplementation with beta
(Dunnett and Harris 1999)
alanine. This means that a higher speed can
be maintained before lactic acid is produced
to a level that starts to drive muscle fatigue.
In addition, for that final sprint to the line
the ability of muscle to buffer lactic acid is
improved, allowing a horse to maintain its top
speed for slightly longer.
The supplementation of beta alanine,
including its inclusion in feeds or
supplements, is protected by world-wide
patents. Racing Blue is the company that
was inspired by the beta alanine research in
horses. Racing Blue STORM® is the worldwide exclusive source of sport patented beta
alanine for horses. STORM® was launched
in the UAE in 2011 and then went on to
win the coveted BETA Innovation award
for feeds and supplements in 2012. It is
co-manufactured in the UK and California
in the USA by accredited facilities and
each batch of raw materials and finished
product is rigorously tested by Independent
Equine Nutrition, the UK’s largest provider of
prohibited substance testing services for feed
and supplement manufacturers. STORM®
is available via a world-wide network of
distributors, or directly via their website
www.racingblue.com. In my role as Racing
Blue’s consultant nutritionist I offer guidance
on the most effective use of STORM®, but
also broad nutritional support to help ensure
optimum performance for endurance.
Official members publication for Endurance GB