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Old 08-13-2010, 02:34 PM   #11
Derek Weaver
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Quote:
Originally Posted by Darryl Shaw View Post
Fasted training is the exact opposite of what you should be doing if you want to avoid losing muscle.
Do elaborate.
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Old 08-13-2010, 08:13 PM   #12
Randy Gurley
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Yes, I would like to hear why fasted training would increase muscle loss. Assuming someone had near full or full glycogen stores, wouldn't that be enough to fuel, say a hour long cardio session without the body resorting to breaking down protein? I could be way off here but I thought the body went to it's stores when it needs to fuel activity and doesn't immediately use what's digesting at the moment?
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Old 08-14-2010, 04:49 AM   #13
Darryl Shaw
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Originally Posted by Randy Gurley View Post
Yes, I would like to hear why fasted training would increase muscle loss. Assuming someone had near full or full glycogen stores, wouldn't that be enough to fuel, say a hour long cardio session without the body resorting to breaking down protein? I could be way off here but I thought the body went to it's stores when it needs to fuel activity and doesn't immediately use what's digesting at the moment?
Muscle glycogen levels may be adequate for a fasted early morning run if you're eating a high carb diet but liver glycogen stores will be low following your overnight fast. If liver glycogen stores fall too low hypoglycemia develops and you will be forced to end your run prematurely due to central fatigue. Underperform due to central fatigue (or any other reason) on a regular basis and muscles will start to atrophy as you lose any adaptations to training you might have made.
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Old 08-14-2010, 08:05 AM   #14
Steven Low
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Basically,

1. Eat enough.
2. Up protein if still muscle wasting
3. BCAAs may help

Not that hard..
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Old 08-14-2010, 06:09 PM   #15
Randy Gurley
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Point taken on what to do to avoid muscle loss. I usually don't IF most of the days on weekends anyways so I'll start to eat something before morning cardio. I do have a question about what Darryl wrote about liver glycogen. I haven't done a search here for this, but say someone has eaten and has full liver and muscle glycogen stores, and goes running at say, 70% VO2 Max. At what percentage does liver glycogen delete, my understanding is that a lot of muscle glycogen is used due to the exercising muscles, but unable to find the rate of depletion for the liver. From reading other sites, it seems the liver holds around 70-100 grams, so 280-400 calories worth. Running at an intensity burning 50% carbs/50% fat, if muscle and liver depleted at the same rate, you would have to run 1.5 to 2 hours to deplete a full liver. I found a very large study today that went into detail of exercise induced hypoglycemia and about all the hormones involved, and lots of other things, I still haven't finished reading it yet.
Again, this is just for my knowledge, I find the study of the body very interesting, and can't seem to get enough. If I need to do a search as this subject has already been discussed, tell me.
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Old 08-14-2010, 10:17 PM   #16
Derek Weaver
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I may very well be wrong, but I thought liver glycogen was primarily used to fuel the brain? Once glycogen stores were depleted the brain, and other tissues, could switch to ketones for fuel?
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Old 08-15-2010, 02:15 PM   #17
Jarod Barker
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Hey Randy, does your sweat smell like ammonia? I don't know if this is true, but I once asked my boxing coach why my sweat smells like ammonia, and he said that it comes from when your body is burning muscle for energy. Like I said, I don't know how true that is, but if it is true, maybe you could balance your muscle loss and training by taking time off and eating more when your sweat smells like ammonia, and going hard when it's fine.

On a side note, BMac is a strong dude, and he runs quite often, so it may require some tweaking and effort, but I think it is possible to train for long distance with very minimal muscle loss.
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Old 08-16-2010, 04:05 AM   #18
Darryl Shaw
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Quote:
Originally Posted by Randy Gurley View Post
Point taken on what to do to avoid muscle loss. I usually don't IF most of the days on weekends anyways so I'll start to eat something before morning cardio. I do have a question about what Darryl wrote about liver glycogen. I haven't done a search here for this, but say someone has eaten and has full liver and muscle glycogen stores, and goes running at say, 70% VO2 Max. At what percentage does liver glycogen delete, my understanding is that a lot of muscle glycogen is used due to the exercising muscles, but unable to find the rate of depletion for the liver. From reading other sites, it seems the liver holds around 70-100 grams, so 280-400 calories worth. Running at an intensity burning 50% carbs/50% fat, if muscle and liver depleted at the same rate, you would have to run 1.5 to 2 hours to deplete a full liver. I found a very large study today that went into detail of exercise induced hypoglycemia and about all the hormones involved, and lots of other things, I still haven't finished reading it yet.
Again, this is just for my knowledge, I find the study of the body very interesting, and can't seem to get enough. If I need to do a search as this subject has already been discussed, tell me.
At rest liver glycogen is used at a rate of ~10g/hour and during exercise ~60g/hour. If you've done some serious carb loading you might have ~130g of liver glycogen available so at best you can run at a good pace for a little over two hours before hypoglycemia develops forcing you to slow down and eventually stop. In practice that means that if they don't take on board CHO during a marathon an average runner might make it to somewhere around the 20 mile mark before they're forced to quit.

Edit: I think this might interest you -

http://www.marathontraining.com/articles/art_39th.htm
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Old 08-16-2010, 05:40 AM   #19
Darryl Shaw
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Quote:
Originally Posted by Derek Weaver View Post
I may very well be wrong, but I thought liver glycogen was primarily used to fuel the brain?
Correct, liver glycogen is used primarily to fuel the brain and CNS.

Quote:
Once glycogen stores were depleted the brain, and other tissues, could switch to ketones for fuel?
It can take up to a week for your brain to switch over to using ketones as fuel so in the short term you're dependent on gluconeogenesis to keep your blood glucose stable. Unfortunately free glucose can't be produced fast enough by gluconeogenesis to keep up with demand during intense exercise so if glycogen stores run out during a marathon your only options are slow down significantly, which is only going to delay the inevitable, or quit.
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Old 08-20-2010, 03:35 AM   #20
Darryl Shaw
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I found an interesting review article from Tarnopolsky that addresses some of the questions that have been raised in this thread -

Quote:
Protein requirements for endurance athletes.

Tarnopolsky M.

Abstract


Acute endurance exercise results in the oxidation of several amino acids. The total amount of amino acid oxidation during endurance exercise amounts to only 1-6% of the total energy cost of exercise. The branched chain amino acid, leucine, has been most often studied in relation to endurance exercise. Leucine is oxidized by the enzyme, branched-chain oxo-acid dehydrogenase (BCOAD). BCOAD is relatively inactive at rest ( approximately 4-7%) and is activated at the onset of exercise by dephosphorylation (to about 25%). After a period of endurance exercise training, the activation of BCOAD and amino acid oxidation are attenuated, however the total amount of BCOAD enzyme is up-regulated. A low energy and/or carbohydrate intake will increase amino acid oxidation and total protein requirements. With adequate energy and carbohydrate intake, low to moderate intensity endurance activity has little impact on dietary protein requirements and 1.0 gPRO/kg/d is sufficient. The only situation where dietary protein requirements exceed those for relatively sedentary individuals is in top sport athletes where the maximal requirement is approximately 1.6 gPRO/kg/d. Although most endurance athletes get enough protein to support any increased requirements, those with low energy or carbohydrate intakes may require nutritional advice to optimize dietary protein intake.
http://img2.tapuz.co.il/forums/1_102825767.pdf

Note: I'm going to post this abstract and link in a thread of their own as I'm sure this question will come up again sooner or later.
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