where does the glycogen come from?

[Poncho]

say i work my legs.

does the glycogen come solely from the muscles in my legs?

or from the muscles in my entire body?

or MOSTLY from the muscles in my legs?

how does that work?

i was reading about energy systems here:

http://www.abcbodybuilding.com/musclefibers.php

[Buffysboy]

Muslces don't store that much glycogen, most of it comes from the liver.

[President Wilson]

The human body stores approximately 400 grams of glycogen in muscle tissue and 100 in the liver for an average weight individual.
Of course this increases with training.

Where does glycogen come from?

When you consume carbohydrates your body breaks them down into single glucose units in the small intestine. These are then absorbed into the blood, which stimulates the pancreas to release insulin. Insulin signals muscle tissue to transport take the glucose up and to increase the rate at which glycogen is formed.

So what is glycogen? Its a branching chain of glucose units. When your muscles contract they break down glycogen back into the glucose units again, and these are processed to form ATP our primary energy currency.

The use of muscle glycogen vs. liver glycogen is dependent on the intensity and duration of exercise. During intense weight training most of muscular contraction is powered by muscle glycogen and not liver glycogen, but this varies with aerobic exercise. Heres a breakdown

At 25 % V02 max intensity you use about 8 % carbs, almost all of which come from the liver

at 65 % (moderate intensity) you use about 50 % carbs, with 80 % of this coming from intramuscular glycogen stores.

at 85 % (high intensity) 75 % if the fuel comes from carbs, with nearly all of these comming from intramuscular glycogen.

Heres a summary of this

http://www.abcbodybuilding.com/cardiolayman.php

[Poncho]

thank you for that insightful response. it was *just* what i was looking for.

[adenine]

Thanks for the explanation Pres.


I've been wondering the same thing for quite some time.

[dave12345]

[ QUOTE ]
The human body stores approximately 400 grams of glycogen in muscle tissue and 100 in the liver for an average weight individual.
Of course this increases with training.

Where does glycogen come from?

When you consume carbohydrates your body breaks them down into single glucose units in the small intestine. These are then absorbed into the blood, which stimulates the pancreas to release insulin. Insulin signals muscle tissue to transport take the glucose up and to increase the rate at which glycogen is formed.

So what is glycogen? Its a branching chain of glucose units. When your muscles contract they break down glycogen back into the glucose units again, and these are processed to form ATP our primary energy currency.

The use of muscle glycogen vs. liver glycogen is dependent on the intensity and duration of exercise. During intense weight training most of muscular contraction is powered by muscle glycogen and not liver glycogen, but this varies with aerobic exercise. Heres a breakdown

At 25 % V02 max intensity you use about 8 % carbs, almost all of which come from the liver

at 65 % (moderate intensity) you use about 50 % carbs, with 80 % of this coming from intramuscular glycogen stores.

at 85 % (high intensity) 75 % if the fuel comes from carbs, with nearly all of these comming from intramuscular glycogen.

Heres a summary of this

http://www.abcbodybuilding.com/cardiolayman.php

[/ QUOTE ]

great response! follow up question:

so let's say people do cardio on a stair stepper. im assumming at optimum intensity, they will burn both fat and glycogen. what about the fat and glycogen of muscles that aren't really involved in the cardio activity? like let's say forearms.

can the body go to different areas to pick up fat for energy? like getting fat from your forearms to power the cardio that involves only your legs?

what abuot glycogen? can the body use glycogen from like your biceps if the glycogen ran out of your triceps?

[Zeppelin_Child]

Spot reduction does not exist, so I believe that fat is used from all over, but glycogen is restreicted. I'm not positive on that, so could some one confirm?

This is a little off topic, but I've been wondering it for quite some time:

Granted your body uses few carbs throughout the day, but if you were to eat no fructose on a low carb diet, would your liver simply empty out? Or is there a mechanism for refilling the liver without fructose? Also, is fat used as energy in times of little activity? Or does sugar in the blood from foods and your liver take care of that?

Thanks for any help you guys can give!

[DirtbagDan]

[ QUOTE ]

what abuot glycogen? can the body use glycogen from like your biceps if the glycogen ran out of your triceps?

[/ QUOTE ]

Your muscles have alot of glycogen in them, and it is pretty much impossible to completely deplete your muscles of glycogen. If we could do that, then we wouldn't even be able to use said muscle at all (let alone with weights) due to zero muscle fuel. It's possible to burn a ton of glycogen, but not ALL of it.

The only way you could probably do that is if you went on a super long term zero carb diet (we're talking months of going zero carb here). Not low carb, ZERO carb. And do this while training at the gym. Again, you also have to consider the fact that with no glycogen coming from carbs in your diet, your body will turn on itself to replenish glycogen stores. Your body will break down muscle tissue, carry it to the liver, and through a complex process called gluconogenesis, will turn the broken down muscle into blood sugar for use as glycogen.

So, the answer to your question is a simple no. When (or better yet, IF) you deplete any given muscle of glycogen, your body will simply chew up muscle from another area of your body to replace glycogen. This is why prolonged periods of exercise (more than an hour's worth) is not good and becomes catabolic.

[dashforce]

While I don't know much about the possibility of "zero" glycogen, I know that "glycogen depletion" (though I'm sure that's a relative term) can be easily achieved in a relatively short time period (depending on exercise volume and intensity). 2 weeks no problem.

Gluconeogenesis is a process designed to provide glucose for the brain when in a hypoglycemic state; excluding cases of obesity/insulin resistance, I'm not sure that gluconeogensis could be responsible for any meaningful quantity of glycogenesis.

Glycogen depleted states are actually not always correlated to increased catabolism; as a matter of fact, the following paper seems to provide evidence that VLC diets (which result in glycogen depletion -- although as I admitted, I'm not sure that this necessarily indicates 0 mmol/kg glycogen content) are actually LESS catabolic to LBM than an isocaloric, but higher carb diet.

http://www.nutritionandmetabolism.co...3-7075-3-9.pdf

Also, even at 0 mmol/kg glycogen (which may not be physiologically possible), a muscle would still be able to use fat as a substrate for energy. That's why proper "fat adaptation" can support high intensity training even in the face of "glycogen depletion."