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When excersising at an elevated threshold your body uses carbs as energy. Do to the availibility of them stored in your muscles, a natural dependancy, and fat becoming difficult to process do to lack of o2. So carbs become necissary to avoid hitting "the wall".
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The body uses fat and carbs both durning anything aerobic with a natural tendancy to use fat early on to save carbs for later when O2 is not so easy to get. When hitting the wall, it usually happens when the body becomes depleted of glycogen so now it has to start relying on other means to get energy.
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Where is the drop off point though to where this occurs? I've read that it is possible to gain effiency at fat oxidazation...creating more usable fat energy from o2 and carbs thru intense prolonged endurance training and possibly from a reduced carb diet in general.
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By drop off point are you refering to when someone hits the wall? Because from what I am reading it seems to be around 18-24 miles during a marathon for most runners. From some research it seems that the average person can run for about 10 miles on stored glycogen if doing so on an empty stomach. Not sure about gaining ability at fat oxidation. It makes sense though and I am sure someone else will be able to jump in.
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Is it possible or even likely that with a persistant diet and excersise regiment that you could reasonibly stay below that window to where carbs are absolutely necissary to maintain an aerobic threshold for an extended period of time?
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Yes, this is where the winner seperates from the rest of the pack. The ability to remove the fatty acids from the blood to preserve glucose can be trained and some elite level marathoners can even support 70% of their power output with fatty acids. In average people it tends to be closer to 40% during optimal conditions.
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And just to muddy the waters a little more. Protein breaks down...to create energy (ironically enough) so there comes a point to where protien intake is important. Would it not be better to have some protein in your system as is...possibly in the form of caisin to maintain a nutrient stream to the muscles to help prevent or at least minimalize protein breakdown?
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This is where what activity we are doing comes in. Gluconeogenesis (using protein for glucose) only comes in under fatigue situations and is a really ineffective way to gain energy so should be avoided if possible. Ideally the drink should have enough carbs to keep the body from using too much muscle tissue in the first place. But it seems like a good idea to at least have some amino acids in the mix. I wouldn't use casein or whey though, much too thick and would bog you down in the race and hurt performance. A branch chain amino acid mix seems like a better idea mixed with some dextrose for carbs. That is what I would drink if possible. Keep in mind it needs to be really really watered down though. The ratio given in my book is 5 grams of glucose to 100 ml of water. Too much glucose to water is going to actually slow you down and dehydrate you.
All the info I used here I took out of my exercise phy book, so if something is off, I either read it wrong or the authors messed something up. I am not a runner, especially at any sort of distance, so this is all hypotheical. I also hope its clear, I don't have a ton of time to write this, if it is unclear hopefully I can come clean it up later tonight.
Danny
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