Introduction
Without doubt, cycling is the sport most inten-
sively studied by exercise physiologists and
sport nutritionists. Christensen and Hansen
(1939) were among the first to report the effect of
different diets on cycling performance. These
early reports already demonstrated the impor-
tance of carbohydrates (CHO) for improving or
maintaining exercise performance. Since then,
many studies have investigated the effect of
CHO feedings during cycling, and the role of
CHO after exercise to replenish glycogen stores
and improve recovery (see Chapters 5–8). This
chapter will review some of the nutritional habits
of cyclists and will define some recommenda-
tions for nutrition during bicycling races or
intensive training. Although cycling obviously
has many disciplines (including road racing,
time trialing, track cycling, mountain biking,
BMX), this chapter will focus on road racing and
time trialling.
Energy cost of cycling
Cycling, triathlon and cross-country skiing are
among the sports with the highest reported
energy turnovers. The levels of energy expendi-
ture in these endurance sports have been mea-
sured in the field by using doubly labelled water,
an accurate technique which allows measure-
ments over longer periods (days) in the field
(Westerterpet al.1986). Of particular interest are
the data obtained during the most demanding
cycling race in the world: the Tour de France
(Sariset al.1989). This race has 20 stages and lasts
about 3 weeks in which the riders cover almost
4000 km. During these 3 weeks, energy expendi-
tures of up to 35 MJ · day-^1 (8300 kcal · day-^1 ) have
been reported during the long (300 km) stages
(Sariset al.1989). Recently, we performed meas-
urements of power output during the stages of
the Tour de France using a power-measuring
system (SRM Training System, Germany) which
is claimed to be accurate to ±1%, and to record
and store power data at 1-s intervals (G. Leinders
& A.E. Jeukendrup, unpublished findings).
These data show that average power output
during a 6-h stage may be over 240 W, which
indicates a very high energy turnover. With an
estimated average efficiency of 22%, this repre-
sents an energy expenditure of about 24 MJ
(5700 kcal) during the race itself. In order to
maintain energy balance, a similar amount of
energy has to be consumed on a daily basis.
Most of the energy intake is derived from CHO
(Sariset al.1989), which is less energy-dense
than lipid, and many CHO-rich foods are bulky
and rich in fibre. A high-CHO/high-energy diet
entails a large food volume and considerable
eating time. Since cyclists in the Tour de France
are usually on the bike for 4–6 h · day–1and they
avoid eating 1–3 h before the start, there is barely
time left to eat the large meals. Besides this,
appetite is usually depressed after strenuous
exercise. These factors make it very hard to main-
tain energy balance on a daily basis.
Studies on energy balance have usually