Shermanet al.(1981) do not usually apply to
cycling at the highest level. Professional cyclists
and top-level amateurs have too many races in a
short time period and a week of nutritional
preparation is usually not possible. For this
group of cyclists, it is often recommended that
they eat high-CHO diets which are often
expressed in percentages of CHO in daily energy
intake. However, the absolute amounts may be
more important. In a 70-kg subject, the body
CHO stores are believed to amount to about
600–700 g (about 10 g · kg–1body weight). It is
believed that ingesting more than 600–700 g
(10 g · kg–1body weight) of CHO to replenish
these stores will not further improve glycogen
storage (Rauchet al.1995). This is especially
important for sports with repeated days of exer-
cise with very high energy expenditures, such as
in the Tour de France (Sariset al.1989). If these
athletes would consume a 70% CHO diet (as
often recommended), they would consume more
than a kilo of CHO, assuming an energy intake of
25 MJ (6000 kcal).
Recently, however, we observed increased
glycogen storage after ingestion of 12–13 g · kg-^1
body weight · day-^1 compared to 9 g· kg-^1 · day-^1
when athletes trained on a daily basis (A.E.
Jeukendrup et al., unpublished observations).
Prerace feedings
It is often recommended that CHO ingestion
should be avoided in the hours preceding the
race in order to prevent rebound hypoglycaemia.
CHO ingestion 30–120 min prior to exercise
raises plasma glucose and insulin levels, which
stimulates glucose uptake and inhibits fat mobi-
lization and oxidation during exercise. Early
studies showed that CHO ingestion in the fasted
state, about 45–60 min prior to an acute bout of
exercise, may result in a drop in the blood
glucose concentration as soon as exercise begins
(Fosteret al.1979; Koivistoet al.1981). During
intense exercise, this was shown in one study to
result in hypoglycaemia and decreased perfor-
mance (Fosteret al.1979). However, more recent
studies, in the fasted state (Gleesonet al.1986) as
well as in the non-fasted state, as is usual in ath-
letes going into competition, have not shown
these detrimental effects (Brounset al.1991). Due
to strong individual differences in response,
however, it is always possible that an individual
is prone to an exercise-induced insulin rebound
response after a CHO-rich solid or liquid meal. In
addition, pre-exercise CHO feedings 2–4 h before
the race may inhibit lipolysis, decrease the avail-
ability of plasma fatty acids and thereby deprivecycling 565
Fig. 43.2Pre-exercise feedings
will top up liver glycogen. Photo
© Cor Vos.