resynthesis. Once developed, this state of insulin
resistance persists for several hours. Providing a
carbohydrate supplement soon after exercise
therefore appears to benefit the muscle glycogen
recovery process by preventing the development
of muscle insulin resistance. Furthermore,
during the time between the end of exercise and
the consumption of a carbohydrate supplement,
there is very little muscle glycogen resynthesis
(approximately 1–2mmol · g–1wet weight · h–1)
(Ivyet al.1988a). Therefore, providing a carbo-
hydrate supplement soon after exercise has the
added benefit of starting the muscle glycogen
recovery process immediately.
frequency and amount of
carbohydrate consumption
after exercise
The frequency of carbohydrate supplementation
as well as the amount of carbohydrate in each
supplement is also of importance in the regula-
tion of muscle glycogen resynthesis. When an
adequate carbohydrate supplement is provided
immediately after exercise, its effect on muscle
glycogen recovery eventually declines as blood
glucose and insulin levels decline. However,
Blomet al. (1987) reported that providing a carbo-
hydrate supplement immediately after exercise
104 nutrition and exercise
and at 2-h intervals for the next 4 h maintained an
elevated blood glucose level and a rapid rate of
muscle glycogen resynthesis during a 6-h recov-
ery period. Blom et al.(1987) also found that a
critical amount of carbohydrate must be con-
sumed if the rate of muscle glycogen resynthesis
was to be maximized. When carbohydrate sup-
plements of 0.7 or 1.4 g glucose · kg–1body weight
were provided at 2-h intervals, the rate of glyco-
gen storage did not differ between treatments
and averaged 5.7mmol · g–1 wet weight · h–1.
However, when Blom et al. (1987) provided 0.35 g
glucose · kg–1body weight at 2-h intervals, the
rate of muscle glycogen resynthesis was reduced
by 50%.
To better evaluate the critical level of carbo-
hydrate supplementation required for maximal
glycogen resynthesis, we tested the effects of
supplements with different concentrations of
carbohydrate during 4 h of recovery from exer-
cise (Fig. 7.5). Very little muscle glycogen re-
synthesis was found when carbohydrate
was withheld from the subjects (approximately
0.6mmol·g–1wet weight · h–1). With increasing
concentration of carbohydrate supplementation,
however, the rate of muscle glycogen resyn-
thesis increased in a curvilinear pattern and
then plateaued at a rate of 5.5mmol · g–1wet
weight · h–1as the carbohydrate concentration7 6 5 4 3 2 1 0
Protein + CHO0 0.5 1.0 1.5 2.0 2.5 3.0
Carbohydrate supplement
(g.kg–1 body wt)Increase in muscle
glycogen concentration(μmol.g–1.h–1
)Fig. 7.5The average rate of
muscle glycogen resynthesis
during a 4-h exercise recovery
period after oral consumption of
different concentrations of
carbohydrate (CHO) from a liquid
supplement (ª21% wt/vol).
Supplements were provided
immediately after exercise and 2 h
after exercise. Protein+CHO
represents the average muscle
glycogen resynthesis rate when
1.5 g CHO · kg–1body weight plus
0.53 g protein · kg–1body weight
(milk and whey protein isolate
mixture, 7.6% wt/vol) was
provided.