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When Carl Lewis, the American sprinter, completed the fastest-ever
100 metres at the World Athletics Championships in Tokyo last year, he ran
into controversy as well as the record books. Purists complained that the
track helped him to shave four hundredths of a second from the previous
best of 9.90 seconds. A similar complaint was levelled against Mike Powell,
the American long jumper, when he leapt 8.95 metres, adding 5 centimetres
to the long-standing world record of Bob Beamon, another American athlete.

Tests on samples later showed that the track was unusually hard, a property
that suits sprinters and jumpers who want as little as possible of the power
unleashed by their leg muscles to be dissipated by the track’s surface –
the harder the surface, the greater the reaction to the forces imposed on
the track. But what’s good news for one set of athletes is bad news for
another. Long-distance runners, including Liz McColgan, the British 10
000 metres champion, came back from Tokyo with unusually sore limbs because
of the prolonged jolting they received.

BREAKING THE RULES

According to Mike Gee, technical specialist at the International Amateur
Athletics Federation in London, the track was harder than IAAF specifications
allow. But the federation published its performance specifications for outdoor
synthetic tracks only in January 1990, followed two months later by guidelines
enabling accredited laboratories to test whether tracks comply. This was
after the venue for the 1991 world championships had been decided and the
Japanese government had finalised its plans for a new stadium to host them.
Though the records set at Tokyo will stand, Gee says that tracks at stadia
will have to conform to the specifications if they are to stage events recognised
by the IAAF. At Barcelona, the track meets the specifications with a surface
made from a form of rubber sheet that has rarely been used for outdoor tracks
and never before at an Olympic Games.

There are five accredited laboratories, all run by private companies,
of which two are in Germany, and one each in Switzerland, the US and Britain.
Another is due to open in Australia later this year. Graeme Tipp, the co-director
of the British laboratory, the Centre for Sports Technology, says that the
federation’s standards achieve a trade-off between the soft surfaces favoured
by long-distance runners and the hard surfaces preferred by sprinters and
jumpers. Though the standards require that surfaces should not assist performance,
their main aim, says the IAAF, is to prevent injury to athletes, in training
as well as in competition.

The federation bases its specifications on studies of how athletes move.
These biomechanical experiments show, for example, that a track should be
capable of absorbing the impact of a runner’s foot landing on it. To prevent
injury, scientists determined that the force on the foot should be reduced
by between 35 and 50 per cent of what it would be if the runner was pounding
an inflexible surface such as concrete. To achieve this, the specifications
dictate that the synthetic surface layer should never be thinner than 12
millimetres and should never deform under the pressure of an athlete’s foot
by less than 0.6 millimetres or more than 1.8 millimetres.

The specifications are also designed to prevent athletes slipping in
the wet. A measure of a surface’s slipperiness is its coefficient of friction,
the ratio of the force resisting slippage to the force acting down on the
sliding surfaces. The specifications say that the coefficient should not
be less than 0.5. This compares with coefficients of 0.1 for surfaces of
nonstick saucepans and 1 for a new car tyre on a dry road. The specifications
also dictate that the colour of a surface must be uniform.

Synthetic tracks made their Olympic debut at Mexico City in 1968, the
games that saw Beamon stretch the world record for the long jump by an astonishing
55 centimetres to 8.9 metres. But the stadium was 2275 metres above sea
level, and any contribution from the track was masked by the advantage of
reduced air resistance at such high altitude. Before 1968, tracks were made
either of cinder or crushed stone. Both types were designed to be drain
freely and give good grip but neither could cope with downpours. ‘What
was needed was a surface with good properties that would be consistent in
all weathers,’ says Tipp.

ON THE LEVEL

The answer was synthetic rubber. The most widely used is polyurethane,
made by reacting polyethylene glycol with an organic isocyanate, which is
poured over a layer of macadam that sits on a bed of stone aggregate. The
dense liquid is self-levelling and, because its two main components form
a chemical compound, joints between sections of the track blend in curing
to obliterate any seams.

An alternative, which is making its Olympic debut at Barcelona, is neoprene.
This synthetic rubber of polychloroprene comes in the form of prefabricated
sheets, which are laid down in the same way that a floor covering might
be. They are more commonly used for indoor tracks, which must be banked
and so cannot easily be formed using a liquid surfacing. Though the sheets
are cleaner to install, they are not self-levelling and the base onto which
they are laid must be prepared with greater care.

PIONEERING HORSES

The first synthetic surfaces were developed for horse-and-buggy trotting
in the US by the chemicals group 3M. But Germany pioneered research into
their wider use and, in 1974, was the first country to adopt standards for
running tracks. Manufacturers can now manipulate the properties of a surface
with additives and by adjusting the ratios of the two main components. Balsam,
a German company based at Steinhagen in North Rhine-Westphalia, estimates
that between 300 and 400 different types of polyurethane exist. According
to Volker Kettler, a chemist at Balsam, additives range from elastomers,
which make the surface more flexible, to stabilisers, which protect it from
degradation by ultraviolet light.

Researchers at Balsam are also looking at ways of providing surfaces
to meet the specific demands of field events. Their latest biomechanics
experiments are aimed at improving the shock absorption, deformation and
sliding resistance characteristics of surfaces. Such developments may force
the IAAF to revise its specifications, which apply the same criteria to
all stadium surfaces used by athletes. ‘The same requirements apply everywhere
because at most stadia the same surface is used for several different events,’
notes Tipp. ‘The only concessions are for the end of the javelin runway,
which is especially thick to accommodate the very long spikes of javelin
throwers as they come to a halt, and for the take-off point in the high
jump, which likewise suffers special wear.’

But the specifications do try to ensure that tracks are durable and
weatherproof. This may be crucial in Barcelona where, Gee recalls, rain
disrupted the 1989 world championships. ‘The whole place was flooded by
a thunderstorm and we stopped the competition and field events for safety
reasons,’ he says. Athletes at the 1992 Olympics will be hoping that the
rain in Spain falls well away from Barcelona.