The high values of maximum oxygen uptake
in elite cross-country skiers are the result of
a high maximum cardiac output elicited by a
large stroke volume. Maximum cardiac output
over 40 l · min–1and stroke volumes over 200 ml
have been measured in skiers with maximum
oxygen uptake values over 6 l · min–1(Ekblom &
Hermansen 1968). The maximum heart rates
and the arteriovenous differences were close to
values obtained in less successful athletes and
non-athletes and cannot account for the observed
differences between the different groups of
individuals. Blood volume is also high in
these athletes, while haemoglobin concentra-
tions are within the normal ranges of non-
athletes and less successful athletes (Ekblom &
Hermansen 1968).
The information on muscular strength of the
elite competitor is not very extensive. Available
data indicate that the maximum strength of the
legs is only slightly greater than that of the
average person. However, in endurance tests—
such as 50 consecutive knee joint extensions—
skiers show superior endurance values to
those of most other endurance athletes. The arm
muscle strength for poling and, thus, skiing per-
formance, is also of the utmost importance.
Ski racing
Energy expenditure
The skier has to expend power in order to move
forward. This power is used for:
1 overcoming friction between ski and snow;
2 elevating the body mass in uphill skiing and
for each stride during level skiing;
3 accelerating the different body segments and
the centre of mass; and
4 overcoming air resistance.
The relative importance of these factors for
energy expenditure during skiing is dependent
on several factors, including body composition,
type of skiing technique, level of coordination
and technique, type of terrain, snow conditions,
and racing speed. Hence, quantitative informa-
tion will only be valid under specific conditions.
658 sport-specific nutrition
It is, however, safe to state that on uphill terrain
the cost of elevating the centre of mass accounts
for the major part of the energy expenditure. In
downhill sections, the main resistances are the
friction between the ski and the snow and the air
resistance. The power to sustain this power
expenditure comes from the metabolism except
in downhill terrain. Hence, skiing speed will
depend on the power producing capacity of the
metabolism.
As stated above, the capacity and effectiveness
of the aerobic energy system is the most impor-
tant factor for physical performance during ski
racing, indicating that the central circulation and
the regulation of its distribution are of primary
importance for skiing capacity. Maximal uphill
skiing produces higher oxygen uptake than
maximal running (Stromme et al.1977). There is
no difference in maximum oxygen uptake
between maximal uphill skiing using the classic
or free-style technique (Bergh & Forsberg 1991).
Thus, the muscle mass used during maximal
skiing has a metabolic potential which exceeds
the transport capacity of oxygen of the central
circulation. Any variation in the amount of
oxygen from the heart to the peripheral muscles
will undoubtedly influence skiing performance.
During uphill skiing, the heart rate is close to or
even exceeds peak heart rate obtained during
conventional all-out maximal running on a
treadmill. During the downhill parts, the heart
rate is some 20 beats · min–1below maximum,
mainly because the strain on the circulation is
still high. During level skiing, the heart rate is on
the average 10–15 beats · min–1below maximum
and, during longer races, such as the 50 km, the
heart rate is on the average somewhat lower than
in the shorter races on the same parts of the track
due to the lower average speed in the longer race.Training
Important characteristics of cross-country skiing
are as follows.
1 Metabolism is mainly aerobic.
2 Oxygen uptake can be taxed maximally.
3 Certain techniques cannot elicit maximum