NUTRITION IN SPORT

mance in some athletes at 9 mg · kg–1(Graham &

Spriet 1995).

Caffeine generally produced no change in

venous plasma noradrenaline (norepinephrine)

concentration at rest or exercise, a twofold

increase in plasma adrenaline (epinephrine) con-

centration at rest and exercise and increased

plasma FFA concentration at rest. The elevated

FFA concentration at the onset of exercise with

caffeine was no longer present after 15–20 min of

exercise. At the lowest caffeine dose (3 mg · kg–1),

performance was increased without a significant

increase in plasma venous adrenaline and

FFA. Muscle glycogen utilization was reduced

following caffeine ingestion, but the ‘sparing’

was limited to the initial 15 min of exercise at

approximately 80% V

.

o2max..

Caffeine and short-term

exercise performance

There has been recent interest in the effects of caf-

feine ingestion on performance of short-term

exercise lasting between 30 s and 20–40 min. If

caffeine has an ergogenic effect during short-

term exercise, the mechanism will not be related

caffeine 381

70

0

60

40

0

20

Time (min)

6

50

30

10

Dose (mg.kg–1 body wt)

39

Fig. 28.2Performance times during running to
exhaustion at 85% V

.
o2max.following placebo or
caffeine ingestion (3, 6 or 9 mg · kg–1body weight) 1 h
prior to exercise. All caffeine conditions were
significantly different from placebo. From Graham and
Spriet (1995), with permission.

30

25

20

15

10

5

0

5913

Caffeine (mg.kg–1 body wt)

Urinary caffeine (

μg

.ml

–1

)

Fig. 28.3Individual urine caffeine concentrations in
15 men following exhaustive cycling at approximately
80%V
.
o2max.and the ingestion of 5, 9 or 13 mg caffeine ·
kg–1body weight. The horizontal line depicts the
acceptable level of less than 12mg caffeine · ml–1urine,
as outlined by the International Olympic Committee.
From Pasman et al. (1995), with permission.

80

70

60

50

40

30

20

10

0

–60 0 5 15 Exh.

Time (min)

Caffeine (

μM

)

9 mg

6 mg

3 mg

Placebo

Fig. 28.4Plasma caffeine concentrations during

exhaustive (Exh.) cycling at 80% V

.

o2max.following

the ingestion of placebo or 3, 6 and 9 mg caffeine · kg–1

body mass 1 h prior to exercise. Exhaustion occurred

between 50 and 62 min in all trials. From Graham and

Spriet (1995), with permission.