breathing problems, and hypothermia might be
expected. For the body as a whole, the metabolic
heat production during ski racing is usually
greater than the heat loss due to convection, con-
duction and radiation. Therefore, the skier must
sweat to maintain heat balance. During ski
racing, the weight loss, mainly due to water loss,
might be some 2–3% of body mass during 15- to
30-km races. This will undoubtedly impair per-
formance. Therefore, fluid replacement during
races longer than 15–20 km is needed.
Although heat production is high, cold injuries
to peripheral parts of the body, such as fingers,
toes, nosetip and ears, are not uncommon during
cold weather, since the wind velocity is high,
especially during long downhill segments of
a course. Furthermore, pulmonary ventilation
may be at least 100–150 l · min–1and, in many
cases or parts of a track, over 200 l · min–1. This
puts large demands on the airways, since cold air
is very dry and must be heated and saturated
with water before it reaches the alveolae. Many
skiers experience coughing problems during
races and after exercise. Therefore, many top elite
skiers use antiasthmatic medications. To avoid
local cold injuries and breathing problems, com-
petitions and hard training sessions should be
avoided at temperatures below –20°C.
Total energy yield
The energy cost of cross-country skiing is high, as
mentioned earlier. During the preparation or
main training part of the year, which often
includes two training sessions per day, the
estimated total energy turnover is some 20–
25 MJ · day–1 (4800–6000 kcal · day–1). During
training camps, it can be 4–8 MJ (950–1900 kcal)
higher. The total energy turnover for a 15- and
50-km race is about 4–5 MJ (950–1200 kcal) and
13–15 MJ (3100–3600 kcal), respectively.
One of the main nutritional problems is to
cover this high energy demand. In many cases,
this problem is solved by having three main
meals—breakfast, lunch and dinner—and,
added to that, small meals after each training
session. A carbohydrate-rich meal just before
660 sport-specific nutrition
bedtime facilitates restoring the muscle
glycogen.Quality of the meal
The glycogen concentration in activated arm and
leg muscles is low or almost empty in many
muscle cells at the end of a race or a long training
session. Thus, a meal rich in carbohydrates is an
essential part of an elite cross-country skier’s
diet. The post-training meal is especially impor-
tant, since the rate of glycogen resynthesis and
accumulation in the muscles seems to be faster
when a high-carbohydrate meal is consumed just
after the exercise. It is a general experience that
most skiers are not hungry immediately after a
race, but failure to eat at this time may delay
recovery and limit the training load. Of interest
for the hard training cross-country skier, there-
fore, is the observation that postexercise muscle
glycogen concentration can be enhanced above
normal with a carbohydrate–protein supplement
as a result of the interaction of carbohydrate and
protein on insulin secretion.
During the racing season, there may be specific
nutritional problems at hand. Racing and pro-
longed hard training sessions may damage the
muscle cells as indicated by a leakage of protein
and other molecules from slow-twitch fibres. If
this occurs, the rate of glycogen resynthesis may
be reduced after exhaustive exercise. Therefore,
it might not always be possible to fully replenish
glycogen stores within 24–48 h after hard races
and training sessions.Rehydration during skiing
During races, skiers may sweat a lot even in a
cold climate. The body mass loss for a 15- and 50-
km race may be in the range of 2–4% of initial
value of body mass. It is a well-known fact that
this can impair physical performance. Rehydra-
tion is therefore of great importance for counter-
acting the negative influence of the dehydration.
However, not only rehydration is of importance.
During prolonged exercise, as in cross-country
skiing, a carbohydrate intake during prolonged