the muscle glycogen levels are not high prior to a
game, performance of repeated intense exercise
during the game may be impaired.
Diets of athletes in team sports
The above mentioned studies clearly show that
high glycogen levels are essential to optimize
performance during intense intermittent exer-
cise. However, athletes in team sports may not
actually consume sufficient amounts of carbohy-
drate, as illustrated in a study of Swedish elite
soccer players. After a competitive match played
on a Sunday, the players were monitored until
the following Wednesday, when they played a
European Cup match. One light training session
was performed on the Tuesday. Immediately
after the match on Sunday, and on the following
2 days, muscle samples were taken from a
quadriceps muscle for determination of glyco-
gen content (Fig. 44.6). After the match, the
muscle glycogen content was found to be
reduced to approximately 25% of the level before
the match. Twenty-four hours (Monday) and 48 h
(Tuesday) later, the glycogen stores had only
increased to 37% and 39% of the prematch level,
respectively. Muscle samples were not taken on
the Wednesday because of the European Cup
match, but it can be assumed that the glycogen
stores were less than 50% of the prematch levels.
Thus, the players started the match with only
about half of their normal muscle glycogen
stores, which most likely reduced their physical
performance potential.
The food intake of each player was analysed
during the same period (Sunday to Wednesday).
The average energy intake per day was 20.7 MJ
(4900 kcal), with a variation between players
from 10.5 to 26.8 MJ (2500–6400 kcal). By use of
the activity profile and body weight of each
player, it was calculated that most of the players
should have had an intake of at least 20 MJteam sports 579
End pedalling frequency (rev.min–1
)1400
No. of work periods1301201 2 3 4 5 6 7 8 9 10 11 12 13 14 15* *
* *Fig. 44.5Pedalling frequency during the last 2 s of 15 ¥6-s periods of intense cycling separated by 30-s rest periods
with a diet low () and high ( ) in carbohydrates in the days before the test. The subjects were supposed to
maintain a pedalling frequency of 140 rev · min–1. Note that after the high-carbohydrate diet the subjects were better
able to keep a high pedalling frequency. *, significant difference between high- and low-carbohydrate diet. Adapted
from Balsom (1995), with permission.