NUTRITION IN SPORT

occurred at a later stage when the subjects started
with superior muscle glycogen concentrations
(Bangsboet al. 1992a). It is worthwhile to note
that in both studies the muscle glycogen level
was still high at the point of fatigue where fatigue
was defined as an inability to maintain the

578 sport-specific nutrition

required power output. During intense intermit-

tent exercise, both slow-twitch (ST) and fast-

twitch (FT) fibres are involved (Essen 1978) and a

partial depletion of glycogen in some fibres, par-

ticular the FT fibres, may result in a reduction in

performance. These studies demonstrate that if

Speed (km

.h

–1)

0

18

12

102

Time (min)

8

Gas

collection

Gas

collection

0 109 113 120 127

Speed (km

.h

–1)

0

18

15

1

Time (min)

8

0 2345

25

12

6

Blood

sample

(^0954660) Time (min)
Field running Rest Treadmill running
Exercise
period
1–7
3, 5
4
(b)
(a)
(c)
Blood
sample
ABC
Fig. 44.4Protocol of an
intermittent endurance test.
(a) The test consisted of 46 min of
intermittent field running
followed by 14 min of rest and
then by two parts of intermittent
treadmill running to exhaustion.
(b) The first part of the treadmill
running consisted of seven
identical 5-min intermittent
exercise periods. (c) The second
part of the treadmill running
shows where the treadmill speed
was alternated between 8 and 18
km · h–1for 10 s (
) and 15 s ( ),
respectively. After 17 min, the
lower speed was elevated to
12 km · h–1, and the running was
continued until exhaustion.
Adapted from Bangsbo et al.
(1992b), with permission from the
International Journal of Sport
Medicine.