competitor other than that provided by the orga-
nizers’. As water was the only drink available to
runners, it was clear that the IAAF had also
ignored the pioneering studies conducted in the
1920s showing the benefits of CHO ingestion
during long-distance running.
In the 1960s, the IAAF modified their rules
slightly, so that by 1967 refreshments were avail-
able after only 11 km of a race. Although competi-
tors could now make up their own drink, only
water was provided by the race organizers.
Between 1960 and 1970, the notion that water
was more important than CHO replacement
during exercise gained popularity. This was
because studies showed that runners who were
the most dehydrated after distance races had the
highest postrace rectal temperatures. Indeed,
the belief that fluid replacement alone was of
primary importance for optimizing performance
during prolonged exercise was promoted to
such an extent that CHO ingestion was actively
discouraged. As a result of the perceived
importance of fluid replacement, the IAAF again
altered their rules in 1977 to allow runners to
ingest water earlier and more frequently during
competition.
The question of whether water or CHO
replacement should be practised during
endurance exercise was not really resolved until
the late 1970s and early 1980s, when commercial
interests in the US revived research into the value
of CHO ingestion during exercise. These labora-
tory controlled studies conducted on cyclists
confirmed the findings reported some 50 years
earlier, which demonstrated that the ingestion
of CHO-containing solutions enhanced perfor-
mance and endurance during prolonged exercise
(for review, see Coggan & Coyle 1991). Today, the
consumption of CHO–electrolyte beverages is
advocated by the IAAF in all races of 10 km and
longer. But, the exact amounts that should be
consumed to provide sufficient fluid, CHO and
electrolytes to replace sweat and energy losses
during exercise remain to be established.Fluid loss and replacement
Fluid loss during exercise is determined princi-
pally by the athlete’s sweat rate, which is propor-
tional to their metabolic rate and the prevailing
ambient temperature. Estimated sweat rates for
endurance runners, along with their rates of fluid
intake and measured weight losses, are shown in
Table 42.5. One study conducted in the 1960s
reported very low rates of fluid intake during a
32-m race (150 ml · h–1), with resultant weight
losses of more than 2.4 kg and significantly ele-
vated postrace rectal temperatures (Wyndham
& Strydom 1969). Largely on the basis of this
single finding, it was recommended that runnersdistance running 555
Fig. 42.1Endurance events
provide an opportunity for intake
of fluids and substrate—usually
carbohydrate—during the event
itself. Photo © Allsport / G. Prior.