Todd, thanks for the info.  Anymore like it?  I still
have questions.

You said this does not apply to anaerobic activities.
But the competitive nature of cycling requires a great
deal of anaerobic response. (Chasing down
breakaways/initiating breakaways...etc.)  Does this
then still discount my needs for more carbs.
Anaerobic activity requires lots of carbs.

The study did not state anything about anaerobic
power/capacity.  These cyclists simple rode at 62-64%
of VO2 max and then quit?

I definately agree with the glycogen sparring and
reduction of oxidation during steady state submaximal
workloads.

I think this study may be of more significance if it
simulated the actual conditions of bicycle racing.  Ie
repeated bouts of intensity exceeding 90% HRmax during
the duration of the ride to exaustion.

--- Todd Moody <[log in to unmask]> wrote:
> On Tue, 28 Dec 1999, Kenny Brown wrote:
>
> > All I wanted to know is if there is a metabolic
> need
> > for increased carbs with increased activity or if
> the
> > fat would be enough and fast acting enough.  Have
> you
> > ever been so low on blood sugar that you could not
> > hear, barely see, have fits of diziness along with
> > slurred speech while working at the bookstore?
>
> The simple answer is that for increased aerobic
> activity you
> should not require more carbs.  Studies by Phinney
> suggest that
> it may take a few weeks to adjust to lower carb
> levels, during
> which time performance may suffer, but after that
> you should do
> as well or better.  Note that this would not apply
> to anaerobic
> training such as weight lifting.
>
> The study below pertains to extreme low-carb diet
> (ketogenic),
> but should help to answer your question.
>
> Todd Moody
> [log in to unmask]
>
>
> Metabolism 1983 Aug;32(8):769-76
>
>
> The human metabolic response to chronic ketosis
> without caloric restriction:
> preservation of submaximal exercise capability with
> reduced carbohydrate
> oxidation.
>
> Phinney SD, Bistrian BR, Evans WJ, Gervino E,
> Blackburn GL
>
> To study the effect of chronic ketosis on exercise
> performance in
> endurance-trained humans, five well-trained cyclists
> were fed a eucaloric
> balanced diet (EBD) for one week providing 35-50
> kcal/kg/d, 1.75 g protein/kg/d
> and the remainder of kilocalories as two-thirds
> carbohydrate (CHO) and
> one-third fat. This was followed by four weeks of a
> eucaloric ketogenic diet
> (EKD), isocaloric and isonitrogenous with the EBD
> but providing less than 20 g
> CHO daily. Both diets were appropriately
> supplemented to meet the recommended
> daily allowances for vitamins and minerals. Pedal
> ergometer testing of maximal
> oxygen uptake (VO2max) was unchanged between the
> control week (EBD-1) and week
> 3 of the ketogenic diet (EKD-3). The mean ergometer
> endurance time for
> continuous exercise to exhaustion (ENDUR) at 62%-64%
> of VO2max was 147 minutes
> at EBD-1 and 151 minutes at EKD-4. The ENDUR
> steady-state RQ dropped from 0.83
> to 0.72 (P less than 0.01) from EBD-1 to EKD-4. In
> agreement with this were a
> three-fold drop in glucose oxidation (from 15.1 to
> 5.1 mg/kg/min, P less than
> 0.05) and a four-fold reduction in muscle glycogen
> use (0.61 to 0.13
> mmol/kg/min, P less than 0.01). Neither clinical nor
> biochemical evidence of
> hypoglycemia was observed during ENDUR at EKD-4.
> These results indicate that
> aerobic endurance exercise by well-trained cyclists
> was not compromised by four
> weeks of ketosis. This was accomplished by a
> dramatic physiologic adaptation
> that conserved limited carbohydrate stores (both
> glucose and muscle glycogen)
> and made fat the predominant muscle substrate at
> this submaximal power level.
>
> PMID: 6865776, UI: 83244130
>
> ----------
>


=====
-kb.
[log in to unmask]
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