the muscle of substrate. This, in turn, may accel-
erate glycogenolysis and increase whole-body
CHO oxidation. Large pre-exercise CHO feed-
ings may compensate for the excess oxidized
CHO by providing sufficient glucose through the
blood, whereas small CHO feedings may not
provide sufficient substrate and result in prema-
ture glycogen depletion and fatigue. So, pre-
exercise CHO feedings should be large enough
(>200 g) to provide substrate to the muscle to
compensate for the accelerated glycogen break-
down and increased CHO oxidation.
Recommendations for
precompetition nutrition
1 Ensure a CHO intake of 10 g · kg–1 body
weight · day–1during the 3 days before the race.
This amount of CHO should maximize glycogen
storage.
2 Drink plenty of fluids during the days before
the race, to ensure euhydration at the start. If
large sweat losses are to be expected, add a little
sodium (a pinch of salt) to the drinks.
3 Avoid food with a high dietary fibre content
during the days before the competition to
prevent gastrointestinal problems.
4 Eat a CHO-rich meal 2–4 h before the race to
replenish the liver glycogen stores: before short
races, light digestible CHO foods or energy
drinks; before long races, semisolid or solid food
such as energy bars and bread. Too much protein
and fat should be avoided since this may slow
gastric emptying and may cause gastrointestinal
discomfort. This meal should contain a fair
amount of CHO (>200 g) to compensate for the
increased glycogen breakdown and CHO
oxidation.
5 Although in general the intake of CHO in the
hours before a race does not have adverse effects
on performance, some individuals may develop
rebound hypoglycaemia when ingesting a high-
CHO meal or drinks before the race. These
individuals should delay eating CHO until the
warming up or 5 min before the race. An oral
glucose tolerance test can be used to determine
which individuals are prone to develop rebound
hypoglycaemia.
566 sport-specific nutrition
Nutrition during exercise
Nutrition during exercise longer than 90 min
CHO ingestion during exercise has been shown
to improve exercise performance in events of
90 min duration and longer by maintaining high
plasma glucose levels and high levels of CHO
oxidation. The increased availability of plasma
glucose enables the athlete to postpone fatigue or
to develop a higher power output in a final sprint
following endurance exercise (Hargreaveset al.
1984; Coggan & Coyle 1987, 1988, 1989; Mitchell
et al.1988; Goodpasteret al.1996). From numer-
ous studies, we know that most of the soluble
CHO (glucose, maltose, sucrose, glucose poly-
mers, soluble starch) are oxidized at similar rates,
as reviewed by Hawleyet al.(1992), and similar
improvements in cycling performance have been
observed when ingesting glucose, maltodextrins
or soluble starch (Goodpasteret al.1996). Excep-
tions are fructose, galactose and insoluble starch,
which are oxidized at slightly lower rates (Sariset
al.1993; Leijssenet al.1995) and do not seem to
have the same positive effect on performance
(Goodpaster et al. 1996). Therefore, glucose,
maltose, sucrose, glucose polymers and soluble
starch are all good CHO types to ingest during
exercise. Ingested CHO may be oxidized at rates
up to 1 g · min–1, which appears to be the maximal
exogenous CHO oxidation rate (for review, see
Hawleyet al.1992). Recently, we reported that
the oxidation rate of ingested CHO was similar
in well-trained cyclists and untrained individ-
uals when they are exercising at the same relative
intensity and same rates of total CHO oxidation
(Jeukendrupet al.1997b). The oxidation of exoge-
nous CHO seems related to the amount ingested
(up to a certain limit) and the exercise intensity
and active muscle mass rather than any other
variables. Its maximal oxidation rate may be
determined by the absorption rate or by liver
metabolism (Jeukendrup 1997; Jeukendrup et al.
1999). However, additional research is required
to study the factors limiting exogenous CHO
oxidation. In order to maximize the contribution
of oral CHO to total energy expenditure, it may
be advised that 1–1.2 g CHO · min–1(60–70 g · h–1)