diet, the muscle glycogen concentration was
205.5mmol·g–1wet weight. This represented a
100% increase above the initial muscle glycogen
concentration. When the high carbohydrate diet
preceded the high fat–protein diet, the muscle
glycogen concentration was 183.9mmol · g–1wet
weight following the high carbohydrate diet. It
was suggested that a period of carbohydrate-free
diet further stimulated glycogen synthesis when
carbohydrates were given following exercise.
Based on this study and several similar studies
(Ahlborg et al. 1967b; Bergström & Hultman
1967a), it was recommended that the best way to
glycogen supercompensate was, first, to deplete
the muscle glycogen stores with an exhaustive
exercise bout; second, to eat a carbohydrate-free
diet for 3 days; third, to deplete the glycogen
stores once more with an exhaustive exercise
bout; and fourth, to consume a high carbohy-
drate diet for 3 days.
Because of the strenuous nature of this
regimen, many athletes have found it impracti-
cal, even though it has been used successfully by
very elite performers. The 3 days of low carbohy-
drate diet may cause hypoglycaemia, irritability
and chronic fatigue. The two bouts of exhaustive
exercise prior to competition may result in injury,
soreness and fatigue, and prevents a proper taper
before competition. To address this problem,
Shermanet al. (1981) studied three types of
muscle glycogen supercompensation regimens
on six trained runners. Over a 6-day period,
the subjects ran at approximately 75% of V
.
o2max.
for 90 min, 40 min, 40 min, 20 min, 20 min, and
rested, respectively. During each taper, the sub-
jects received one of three dietary treatments:
1 a mixed diet composed of 50% carbohydrate
(control diet),
2 a low carbohydrate diet (25% carbohydrate)
for the first 3 days and a high carbohydrate diet
(70% carbohydrate) for the last 3 days (classic
diet), and
3 a mixed diet (50% carbohydrate) for the first
3 days and a high carbohydrate diet (70% carbo-
hydrate) the last 3 days (modified diet).
Muscle biopsies were obtained on the morning
of the 4th and 7th days of each trial. During the
control treatment, muscle glycogen concen-
trations of the gastrocnemius were 135 and
163 mmol · g–1wet weight on days 4 and 7, respec-
tively. During the classic treatment, the corre-
sponding muscle glycogen concentrations were
80 and 210mmol·g–1wet weight, and during
the modified treatment they were 135 and
204 mmol · g–1wet weight (Fig. 7.2). These results
suggest that a normal training taper in conjunc-
tion with a moderate carbohydrate–high carbo-
hydrate diet sequence is as effective as the classic
glycogen supercompensation regimen for highly
trained endurance athletes.Enhancement of glycogen synthesis
after exercise
Long-term recovery
The amount of carbohydrate consumed has a sig-
nificant effect on the rate of glycogen storage
after exercise. Unless sufficient carbohydrate
is ingested, muscle glycogen will not be nor-
malized on a day-to-day basis between training
bouts, nor will efforts to supercompensate
muscle glycogen stores be successful. In general,
with an increase in carbohydrate ingestion there
is an increase in muscle glycogen storage. Costill
et al. (1981) reported that consuming 150–650 g
carbohydrate · day–1 resulted in a proportion-
ately greater muscle glycogen synthesis during
the initial 24 h after exercise, and that consump-
tion of more than 600 g carbohydrate · day–1was
of no additional benefit (Fig. 7.3). It has also been
demonstrated that when the carbohydrate con-
centration of the diet was inadequate, successive
days of intense, prolonged exercise resulted in a
gradual reduction in the muscle glycogen stores
and a deterioration in performance (Costill et al.
1971; Sherman et al. 1993). For example, Sherman
et al. (1993) fed endurance athletes either 5 or 10 g
carbohydrate · kg–1· day–1 over 7 days of con-
trolled training. The lower carbohydrate diet
contained 42% of energy from carbohydrate and
the higher carbohydrate diet contained 84% of
energy from carbohydrate. Both diet and exercise
were controlled during the 7 days prior to the