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Atlanta in July is the wrong time and place to hold an event in which
horses gallop around a 7-kilometre cross-country course at an average speed
of 34 kilometres an hour. The daytime temperatures can reach 30 °C with
humidities of up to 80 per cent. The heat alone may be no worse than that
experienced by competitors at previous games in Barcelona or Seoul. But
in combination with high humidity, it is potentially lethal for animals
undergoing strenuous exercise.

The Federation Equestre Internationale, the ruling body for all equestrian
sports, set up a research programme last year to gather enough information
about the causes and prevention of heat stress in horses to run a safe competition
in Atlanta. Groups of vets and exercise physiologists in Britain, the US,
Canada, Australia, Italy and Sweden are involved in the project. The FEI
has set a deadline of September for the work to be completed, and the researchers
will be meeting in Atlanta this weekend to discuss their preliminary findings.

The FEI fears a repetition of the incidents that have threatened the
future of three-day eventing as an Olympic sport. In 1992, several horses
collapsed with exhaustion during the cross-country phase of the Barcelona
Olympics and a Russian horse went down in front of the main stand during
the showjumping. The horses recovered, but two years earlier a Danish horse
died from heat stress at the World Championships in Stockholm.

Stung by the bad publicity that these incidents generated, the International
Olympic Committee warned the FEI that eventing could be removed from the
Olympic calendar. In any case, equestrian sports are unpopular with some
members of the Olympic movement because of the huge cost of organising
the transport of horses, veterinary cover, stabling, farriers and so on.
Rightly or wrongly, there is also a strong feeling that three-day eventing
is an elitist sport.

The FEI’s chief vet, Leo Jeffcott, knows that the sport cannot afford
any more accidents. ‘There are critics both within the horse world and outside
who say it’s ridiculous to go ahead with a competition in Atlanta. Certainly,
there is no way that we would have chosen to have an event under those conditions.’
So why not switch the time or place to reduce the hazards to the horses’
welfare? After all, the equine sports events of the 1956 Melbourne Olympics
were held in Sweden.

Jeffcott, however, argues that equestrian events should not be ‘dislocated’
from the rest of the Olympics. Forty years ago the venue was switched because
of the strict Australian quarantine rules. At that time travelling to the
southern hemisphere was more difficult and costly and the Olympics was less
of a global media event than now. Even moving to another venue in the US
would be unsatisfactory because, in July, you would have to relocate hundreds,
possibly thousands, of kilometres away to find the temperate conditions
in which the sport developed, he says.

Given the realities of the 1990s, the FEI knows that it cannot run
the event on traditional lines, so its research programme is concentrating
on finding safe limits for exercising a horse under the conditions they
will meet in Atlanta. Strangely, considering the choice of venues such as
Mexico City for many recent sporting events, very little is known about
the acclimatisation of humans, let alone horses.

ENDURANCE TEST

In order to help the horses, the researchers first had to understand
the nature and demands of the sport. Modern three-day eventing actually
takes place over four days. The first two days are devoted to the intricate
ballet of the dressage discipline, a set programme of walks and trots. Showjumping
is held on the fourth and final day. But it is the third day in which most
of the problems with heat stress are likely to occur.

Speed and endurance are the hallmarks of this section, which is divided
into four stages. The first stage is a trot – just over 13 kilometres an
hour for around 10 minutes – followed by a fast steeplechase over jumps
around an oval track. The steeplechase, which takes a horse less than 5
minutes to complete at an average speed of 41 kilometres an hour, is immediately
followed by another trot. The fourth stage is the most testing: up to 14
minutes galloping over the cross-country course at a speed of 34 kilometres
an hour. There is just one compulsory rest of 10 minutes before the cross-country
section.

The duration of each of the four stages varies according to the level
of competition. Meetings are classed from one to four star events in ascending
order of difficulty. There are only two four-star meetings in the world
– at Britain’s Badminton and Burghley venues. The Olympic event is usually
classed as a three-and-a-half star competition.

The whole exercise tests the skill of the rider and the strength and
stamina of the horse. The horse is a natural athlete which can use oxygen
during exercise twice as efficiently as the best human athlete. It can raise
its normal metabolic rate more than twentyfold during endurance exercise
and up to sixtyfold during a race. Oxygen consumption at rest is normally
between 2 and 5 millilitres per kilogram of bodyweight per minute, rising
to between 48 and 65 ml/kg/min in the cross-country, and to between 160
and 200 ml/kg/min during a sprint. In comparison, the maximum oxygen consumption
for a human running in an Olympic middle distance event is 85 ml/kg/min.

The horse has a problem, however, because 80 per cent of the energy
used is wasted as heat. Because of its size, it also has a low surface area
compared with the volume of its body. Each square metre of surface area
must dissipate the heat from between 90 and 100 kg of body tissue compared
with between only 35 and 40 kg in humans.

Without some way of getting rid of this heat, the animal’s body temperature
would theoretically go up by 1 °C every four minutes during an endurance
ride. The animal copes with this heat load through a phenomenal ability
to sweat, losing up to 20 litres of fluid an hour. The sweat contains high
concentrations of electrolytes, such as sodium, potassium and chloride,
compared with the rest of its body fluids. It also contains latherin, a
protein with a low molecular weight which acts like detergent, spreading
the fluid over the body surface and speeding up evaporation.

LOSING CONTROL

In humid conditions this sweat may simply drip off rather than evaporating
to cool the animal down. To replenish fluid lost from the blood as sweat,
the horse can call on reserves of water from its body tissue, and particularly
its huge gut, which may make up 10 per cent of its total body weight. But
it cannot sustain losses of water and electrolytes at this rate for very
long. Once dehydration sets in, the animal quickly loses its ability to
control its body temperature. From its normal level of 38 °C, the body
temperature can rise safely to about 42 °C, but if it goes much higher
clinical signs of heat stress appear.

These signs include ataxia, or lack of muscular coordination. The animal
staggers around and can become a physical danger to itself and those around
it. Other signs include ‘tying up’ (stiffness) and degeneration of the muscle
tissue, and ‘thumps’ (spasmodic contractions of the diaphragm). If left
unchecked the animal may lapse into a coma and die.

Researchers in the FEI programme are hoping to find reliable early indicators
of the onset of heat exhaustion. Vets could then use the compulsory 10-minute
rest before the cross-country section to look for signs of trouble.

In animals which have drawn too much water from their alimentary tract,
for example, the movement of gut contents stops and the vet would be unable
to hear the normal gut sounds, called borborygmus. Once gut movement stops,
the horse may develop colic – a painful and life-threatening condition in
this species. Other useful indicators of dehydration may include congestion
of the mucous membranes and loss of muscle tone in the anal sphincter,
allowing it to be pushed in by the vet’s fingers. The FEI hopes the project
will come up with objective indicators of heat exhaustion.

Even more useful would be information on the limits to an animal’s performance
before clinical signs of heat stress develop. Cathy Kohn, of the Ohio State
University veterinary school, is studying the workload of horses undergoing
exercise on a high-speed laboratory treadmill over speeds and distances
comparable to those during normal competition. This should provide some
clues to the maximum distances that can be ridden in particular combinations
of heat and humidity. The theories will then be tested in the field at a
specially organised three-day event in Georgia in August this year.

Jeffcott emphasises that the scientists can only give advice, it is
up to the FEI as organisers of the Atlanta competition to decide how the
event is run. ‘If we can’t give appropriate assurances, we will have to
recommend that it does not take place at all, but we won’t do that until
we have sufficient scientific data.’

Hugh Thomas is the FEI’s technical adviser on eventing and a former
competitor with the British three-day event team at Montreal in 1976. He
has ultimate responsibility for deciding if the Atlanta event will go ahead
– and under what rules. The three-day event course is already being built
at the Georgia International Horse Park at Conyers, near Atlanta. Thomas
is working with the course designer, Roger Haller, on arranging a layout
which includes various loops so that the distances can be adjusted according
to the research findings and the conditions on the day.

‘It is likely that the longer the horse runs, the more severe the effects
of the climate are going to be. We feel that it will be possible to reduce
the duration of different sections of the endurance trials and still have
a meaningful competition. A course of, say, 5000 metres under the conditions
in Atlanta may be just as testing as 7000 metres in a northern European
climate,’ Thomas says.

A big part of FEI’s research programme is finding ways of acclimatising
horses from temperate climates for the heat and humidity of Atlanta. Last
year, Dave Marlin and his colleagues at the Animal Health Trust laboratory
in Newmarket, took measurements of the physiological condition of the horses
competing during the three-day event at the Burghley horse trials. As in
Kohn’s studies, they used the measurements to design a treadmill exercise
regime that mimicked the effects of running in an event.

The building containing the treadmill has been modified to allow the
researchers to maintain high levels of heat and humidity – in effect an
equine sauna. The researchers then exercised the horses in three different
‘climates’: 20 °C and 40 per cent humidity typical of a warm British
summer day, 30 °C and 40 per cent humidity as in Barcelona, and 30
°C and 80 per cent humidity to reproduce the conditions in Atlanta.
As expected, horses adapted to the low ambient temperatures of an English
winter were unable to cope with the full duration of exercise in ‘Atlanta’
conditions.

In tests later this year the same horses will be exercised for the same
periods after being stabled in a controlled environment similar to the
Atlanta conditions. The results should show how long it takes to acclimatise
the horses and what improvement is possible in their performance. Marlin
suspects that it may be unnecessary to keep horses at the higher temperatures
and humidities continuously. He thinks that a few hours a day, perhaps over
a few weeks, should be enough to acclimatise the animals before they set
off for the US.

During the event itself, the rules could be modified to allow a longer
resting phase between the two most strenuous stages of the competition,
the steeplechase and the cross-country course. At the University of Sydney,
David Hodgson has been looking at methods of rehydrating horses quickly
between these phases.

DRINKING STUDIES

His initial studies show that warm isotonic fluid, which would also
replace some of the electrolytes lost in sweating, is absorbed the quickest.
A horse of average size weighing about 500 kg could absorb between 6 and
8 litres of fluid during the compulsory 10-minute rest period. However,
horses usually like to eat and drink at the same time and may be too excited
to drink during a competition. Hodgson thinks that they may need special
training to encourage them to drink. Further studies are also needed to
find out if unabsorbed water in the stomach has any effect on the animal’s
performance.

The FEI research programme is designed to anticipate the worst possible
combination of heat and humidity likely to be encountered in Atlanta. On
the day, the organisers may be lucky enough to have relatively mild weather,
but they cannot trust in good fortune if the 1996 Olympic Games is not to
be the last one involving the three-day event.

Jeffcott believes that with the knowledge gained from this research,
the competitors will be better prepared than ever before. However, better
preparation and management of the horses – together with possible changes
to the rules of the event – may not be enough to guarantee the health of
the animals. In the end, the FEI must rely on old-fashioned horse sense.

‘It is mainly going to boil down to having an experienced team of riders
and vets who are aware of the limits of their animals and know what they
are looking for,’ Jeffcott says.

John Bonner is a veterinary writer gased in London.