direstraits: [Supertraining] Re: Post-Training Carb Sources

Indeed, it's very interesting and I speculate that the better results
obtained with GF ingestion can be due the replenishment of liver glycogen
mediated by fructose metabolism.

Liver glycogen is essential to maintain blood glucose concentration and
during prolonged exercise (>90 min) it can be drastically reduced.

At that point if no carbohydrate is ingested during exertion endogenous
sources will be further mobilised (e.g. muscle glycogen and to a smaller
extent amino acids, alanine and glutamine).

There is no surprise in seeing the investigators concluded that a GF drink
has a sparing effect on endogenous carbohydrate stores.

In addition, as I had previously said all the popular sport drinks contain
at least 3 sources of carbohydrates, glucose, fructose and maltodextrin.

Cheers,

Luca Cardilli,
Oxford, UK.

> --- In Supertraining@yahoogroups.com, "Paul Rogers" <paulr99@...>
> wrote:
>>
>> Miguel,
>>
>> It might even help. Fructose is thought to be a glucose 'signaller'
>> (and then insulin) in small amounts. I'm not sure of the
> evolutionary
>> theory behind this, but the idea is that fructose says to the
>> body: "get ready, here come the real carbs". (I did say 'small
>> amounts'.)
>
> *****
> The below abstract may be relevant:
>
> Superior endurance performance with ingestion of multiple
> transportable carbohydrates.
> Med Sci Sports Exerc. 2008 Feb;40(2):275-81.Links
> Currell K, Jeukendrup AE.
>
> INTRODUCTION:: The aim of the present study was to investigate the
> effect of ingesting a glucose plus fructose drink compared with a
> glucose-only drink (both delivering carbohydrate at a rate of 1.8
> g.min) and a water placebo on endurance performance.
>
> METHODS:: Eight male trained cyclists were recruited (age 32 +/- 7
> yr, weight 84.4 +/- 6.9 kg, V O2max 64.7 +/- 3.9 mL.kg.min, Wmax 364
> +/- 31 W). Subjects ingested either a water placebo (P), a glucose
> (G)-only beverage (1.8 g.min), or a glucose and fructose (GF)
> beverage in a 2:1 ratio (1.8 g.min) during 120 min of cycling
> exercise at 55% Wmax followed by a time trial in which subjects had
> to complete a set amount of work as quickly as possible (~1 h). Every
> 15 min, expired gases were analyzed and blood samples were collected.
>
> RESULTS:: Ingestion of GF resulted in an 8% quicker time to
> completion during the time trial (4022 s) compared with G (3641 s)
> and a 19% improvement compared with W (3367 s). Total carbohydrate
> (CHO) oxidation was not different between GF (2.54 +/- 0.25 g.min)
> and G (2.50 g.min), suggesting that GF led to a sparing of endogenous
> CHO stores, because GF has been shown to have a greater exogenous CHO
> oxidation than G.
>
> CONCLUSION:: Ingestion of GF led to an 8% improvement in cycling time-
> trial performance compared with ingestion of G.
>
> ===================
> Jamie Carruthers
> Wakefield, UK
>
>
>

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