glycogen is the most important substrate in
soccer and likely also in other team sports.
It should be noted that in team sports large
interindividual differences exist in the energy
production during a match due to the variety of
factors influencing the exercise intensity, e.g.
motivation, physical capacity and tactical limita-
tions. Therefore, there may be major individual
variations in the demand of players in the same
team.
Diet in team sports
In this section the importance of nutrition in
team sports is discussed and dietary recommen-
dations to accommodate nutritional require-
ments for training and matches are provided. It
should be emphasized that maintaining an ade-
quate diet will improve the potential to reach a
maximum level of performance, but does not
ensure good performance during a match. There
are many other factors that influence perfor-
mance, including technical abilities and tactical
understanding.
Diet and performance in intermittent exercise
It is well established that performance during
long-term continuous exercise is improved by
intake of a carbohydrate-rich diet in the days
before the exercise. In order to evaluate whether
a diet high in carbohydrate also affects perfor-
mance during prolonged intermittent exercise,
a study of eight top-class Danish players was
performed.
A soccer-specific intermittent exercise test was
used to evaluate performance (Fig. 44.4). The
players ran intermittently until they were
exhausted and the test result was the total
distance covered. The average exercise inten-
sity during the tests was 70–80% of maximum
oxygen uptake, which resembles the average
intensity during several team sports such as team
handball, soccer and basketball. The players per-
formed the test on two occasions separated by 14
days. On one of the occasions, the test was
carried out with the players having ingested a
diet containing 39% carbohydrate (control diet;
C-diet) during the days before the test, and on
the other occasion the players performed the test
having consumed a high (65%) carbohydrate diet
(CHO-diet) prior to the test. Both tests were
carried out 3 days after a competitive soccer
match, with the diets maintained during the 2
days following the match. The order of the tests
was assigned randomly. The total running dis-
tance of 17.1 km after the CHO-diet was signifi-
cantly longer (0.9 km) than after the C-diet. Thus,
increasing the carbohydrate content in the diet
from 39% or 355 g to 65% or 602 g · day–1(4.6 and
7.9 g · kg–1 body mass) improved intermittent
endurance performance. Similarly, it has been
observed that performance during long-term
intermittent exercise consisting of 6-s work
periods separated by 30-s rest periods was
related to the initial muscle glycogen concentra-
tion (Balsom 1995).
The findings in the above mentioned studies
suggest that elevated muscle glycogen levels
prior to competition can increase the mean work
rate during a team sport match. In agreement
with this suggestion are findings in a study of
soccer players. It was observed that the use of
glycogen was more pronounced in the first than
in the second half of a game (Saltin 1973). Fur-
thermore, the players with initially low glycogen
covered a shorter distance and sprinted signifi-
cantly less, particularly in the second half, than
the players with normal muscle glycogen levels
prior to a match (Saltin 1973). It can be assumed
that the players would have been better prepared
for the second half if the muscle glycogen stores
had been higher prior to the match.
In may not only be towards the end of a match
that the level of muscle glycogen affects perfor-
mance. In a study using 15 repeated 6-s sprints
separated by 30-s rest periods, it was found that
performance was significantly increased when
the subjects had elevated the muscle glycogen
stores prior to the exercise (Fig. 44.5). In agree-
ment with this finding, it has been observed that
high muscle glycogen levels did not affect per-
formance in single intense exercise periods, but
when exercise was repeated 1 h later, fatigue