NUTRITION IN SPORT

each 2-min intermittent contraction period (Fig.
44.2). Thus, although the net utilization of PCr is
quantitatively small during competition in team
sports, PCr has a very important function as an
energy buffer, providing phosphate for the
resynthesis of ATP reaction during rapid eleva-
tions in the exercise intensity, and the availability
of PCr may determine performance during some
intense periods of a game.
Lactate in the blood taken during match-play
may reflect, but underestimate, the lactate pro-
duction in a short period prior to the sampling.
Thus, the concentration of lactate in the blood
is often used as an indicator of the anaerobic
lactacid energy production in sports. In several
team sports like basketball and soccer, high
lactate concentrations are often found, suggest-
ing that lactate production during a match can be
very high.

Aerobic energy production

Heart rate determinations during match-play
can give an indication of the extent to which the
aerobic energy system is taxed. In many team
sports, such as basketball, team handball and
soccer, the aerobic energy production is high. For
example, it has been estimated that the mean
relative work rate in soccer is around 70% of
maximum oxygen uptake, although the players
are standing or walking for more than one third
of the game (Bangsbo 1994a). One explanation of

team sports 575

100-m

sprint

VO2 max

Basketball

Marathon

Ice hockey

Time (s)

.

100%

0 20 40 60 80 100 120 140 160

Fig. 44.1Examples of pattern of
exercise intensities in various
sports.

(a)

100

90

80

70

60

50

40

100

80

60

40

20

0

0123456

(b) Time (min)

Phosphocreatine (% of rest)

Work load (% of MVC)

0123456

Fig. 44.2(a) Phosphocreatine concentration in the

gastrocnemius muscle determined by NMR during

isometric contractions with the calf muscles at

alternating work loads (b). The exercise consisted of

three identical 2-min contraction periods, each

including a maximal contraction. MVC, maximum

voluntary force of contraction. Adapted from Bangsbo

(1994a), with permission from Acta Physiologica

Scandinavica.