physiology & nutrition question

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20 years ago 04/13/2004 9:37am EDT

1) reading through the radcliffe link on the main page paula states that she eats within 30 minutes of her run. i've obviously heard this a lot. but i've never learned of the physiology behind it ... does it improve muscle glycogen storage, or liver? or both? , etc. and why is this a benefit to training? i know it would help if you were racing every day. can anyone explain the physiology, first, and then the application to training and then racing, second?

2) this came up a while ago, but i only had weekly access to a computer and have since been unable to find it: some people were advocating taking glucose during a run (in whatever form, apple, banana, power-gu, or whatever) as it increase sugar AND fat oxidation. from the hadd threads i've come to understand that it makes more sense to keep away from exogenous sugar sources during a run because you force your body to dig deeper (muscle glycogen-wise, at least) and perhaps adapt to it. was this ever answered? whether it makes sense -- during TRAINING -- to have a snack in the middle of a long run (say 2.5 to 3.5 hours)?

thanks,

hrm

20 years ago 04/13/2004 11:20am EDT

re: hrm

1. The average size male distance runners needs about 200g of Carbohydrates in the two hours following a long hard run, starting preferably within 30 minutes after the hard part of the run. This helps to maximise glycogen storage, which gives you better recovery and more energy for the next run.

2. Consuming Carbs after the first hour of a long run allows you to raise the level of fat burning whilst running at a slow to moderate pace. I assume that the extra energy boosts the metabolism of fat because the brain is able to use more of the extra blood sugar, thereby increasing muscular co-ordination, making your running more efficient, so you can run at the same pace as before but with more economy of glycogen.

This is my guess based on my experience of having had low blood sugar during racing and training many times, sometimes quite severe. In the case of hitting the wall badly, the very low blood sugar has a very noticeable effect on the ability to think clearly and run properly even at lower speeds. Your brain uses about 40% of your blood sugar.

The experts say we should consume 60 grams of carbs per hour in the form of a drink, once we start to take extra food during excercise. On very long runs, solid food with water is better, with energy drinks taken in the last hour or so.

20 years ago 04/20/2004 2:36am EDT

re: JonnyO

JonnyO, thanks for your reply, however ... :).

i really am interested in the physiology first, and then the speculation on training, second, and racing, third. what adaptations would the body go through, say, if you consistently refrained from the standard 30-minute-post-run gorge? would you somehow train your body to better oxidize body fat into liver and muscle glycogen? or, as a total non-physiology guy, am i just talking about an impossiblity?, etc.

and with respect to the 2nd question. if hadd (and others, i guess) maintain that something's going on when we exhaust one muscle fiber's sugar supply -- that is, perhaps we have some kind of lactate shuttle from fast twitch, perhaps we're moving on to the next muscle fiber strand, etc. -- does it then not make sense to push this out, without exogenous glucose, at least semi-frequently? perhaps -every-other- long-run?

thanks

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