ridecamp@endurance.net: Re: ridecamp-d Digest V97 #266

Re: ridecamp-d Digest V97 #266

Beth Glace (lb@nismat.org)
Tue, 22 Apr 1997 11:02:54 +0000

> Immediate post-ex glucose feedings are not intended for glycogen resynthesis
> but for recovery and avoidance of Delayed Onset Muscle Soreness. I don't know
> what part feeding post ex plays in glycogen resynthesis because at that point
> the liver is very active in that regard.
Actually, immediate post exercise carbohydrate feedings are exactly
intended to promote glycogen synthesis.
One of the most important limitations in endurance performance is the
depletion of glycogen in the working muscle. The resynthesis of
muscle glycogen during the recovery period is therfore an important
metabolic process that is dependent on adequate carbohydrate intake
[Costill et al 1992, Holloszy and Booth, 1976]. In humans,
carbohydrate rich sources immediately following exercise and at 2
hour intervals follwing cessation of exercise have been shown to
augment the replacement of muscle glycogen [Ivy et al 1988]. Delaying
the feeding by several hours in these studies reduced the glycogen
rate of storage by about 50% [Reed et al 1989]. A major
rate-limiting factor is the level of the enzyme that is
responsible for glycogen synthesis, glycogen synthase. Exericse
activates the conversion of this enzyme from a less active to a more
active state and thus resynthesis of glycogen occurs more rapidly
post exercise.
It is important to distinguish between glycogen
resynthesis occurring in the muscle and that in liver. The liver
glycogen stores supply glucose during exercise to maintain blood
sugar levels, which are to some extent utilized during the exercise
bout. However, the main site of glycogen depletion is at the site of
the contracting muscle. Liver glycogen resynthesis post exercise
does not per se regulate muscle glycogen resynthesis. Regardless,
you need dietary carbohydrate to regenerate the
glycogen effectively at either site.
What is the supposed basis for glycogen in diminishing delayed muscle
soreness? Muscle soreness has been correlated with collagen breakdown
but not blood lactic acid levels [Schachat,1980]. The preponderance
of evidence at this time points to the "torn tissue" theory of muscle
damage as a cause of delayed soreness. In that light, I am unclear
as to the role of post exericise carbohydrate intake in avoiding
soreness. Interested to hear of any literature that might state
otherwise.
Beth Glace, M.S.
Sports Nutritionist
lb@nismat.org

Home Events Groups Rider Directory Market RideCamp Stuff