65–70% of dietary energy (American Dietetic
Association 1993). However, the rigid interpreta-
tion of this guideline may prove unnecessary and
unfeasible for some athletes. Athletes with very
high energy intakes (e.g. >16–20 MJ · day–1or
4000–5000 kcal · day–1) will achieve absolute
carbohydrates of over 700–800 g CHO · day–1
with such a dietary prescription. This may
exceed their combined requirement for daily
glycogen storage and training fuel and, further-
more, be bulky to consume. Athletes with such
high energy intakes may be able to meet their
daily needs for glycogen recovery with a diet of
50–60% of energy. Therefore, it is preferable to
provide CHO intake recommendations in grams
(relative to the BM of the athlete) and allow flexi-
bility for the athlete to meet their requirements
82 nutrition and exercise
within the context of their energy needs and
other dietary goals. Some athletes, principally
females, appear to have lower energy intakes
than might be expected. These athletes may need
to devote a greater proportion of their dietary
intake (e.g. up to 65–70% of energy) to CHO
intake, and even then may fail to meet the
absolute CHO intakes suggested for optimal
daily glycogen recovery (for review, see Burke
1995).
The most interesting point of debate about
current CHO intake recommendations, however,
lies with the failure of longitudinal studies to
show clear-cut benefits to training adaptation
and performance with high CHO intakes com-
pared to moderate CHO diets (Table 5.5).
Although studies show that higher CHO intakes,Table 5.5Longitudinal studies comparing high CHO intakes (HCHO) and moderate CHO intakes (MCHO) on the
training adaptation and performance of athletes in intensive training.
Duration Daily CHO
of study intake*
Reference Athletes (days) (g · kg-^1 BM) Muscle glycogen Effects on performance
Costill Swimmers 10 8.2 vs. 5.3 Declined in MCHO, Training performance
et al. 1988 maintained in HCHO impaired in MCHO group,
but swim trials unchanged
Kirwan Runners 5 8.0 vs. 3.9 Declined in both Reduction in running
et al. 1988 groups, but greater economy and increase in
reductions in MCHO perception of effort
during training sessions
in MCHO
Lambet al. Swimmers 9 12.1 vs. 6.5 NA No difference in
1990 performance of interval
training
Simonsen Rowers 28 10 vs. 5 Maintained in MCHO, Power output maintained
et al. 1991 increased in HCHO during ergometer trials in
MCHO; trend toward
small improvement at end
of study in HCHO
Sherman Runners 7 10 vs. 5 Declined in MCHO, No impairment of high-
et al. 1993 maintained in HCHO intensity run to exhaustion
in either group
Sherman Cyclists 7 10 vs. 5 Declined in MCHO, No impairment of high-
et al. 1993 maintained in HCHO intensity cycle to
exhaustion in either group
BM, body mass; NA, not available.
- High intake vs. moderate intake of CHO compared in each study.