Teach me about glycogen

Rae6503

and why it is important in the fitness world.

Yes, I know I could look it up myself but I am supposed to be working.

infamousmk

I tried to scan the wiki for a general overview, but it's way sciencey. Pretty sure I'd be the one asking you to explain it.

geri1955

Im bored and I was interested to know what the heck it was tooo!! So I googles it for you!! Here it is::::



Glycogen is stored glucose. After eating, the body takes the glucose it needs to function for movement and brain power and stores the rest as glycogen in the liver and muscles, to be used at a time when it is needed. This is called glycogenesis. When you begin to workout the body uses it glycogen stores, but the body is smart. It knows it cannot fully deplete its glycogen stores or it will have nothing to use for quick energy (imagine not being able to walk or run because your body has no energy to move).
After a few hours without refueling by food consumption, the body's glycogen stores are exhausted and yet the nervous system continues to demand it. Lower glycogen stores result in sluggish mental and physical reactions, making it difficult to concentrate and respond to emergencies.

Read more: Why Does a Body Need Glycogen? | eHow.com http://www.ehow.com/about_4601012_why-does-body-need-glycogen.html#ixzz1bLXkpLHc

LabRat529

Glycogen is a starch produced mostly in the liver and muscles by chaining molecules of glucose together. When blood sugar rises, the pancreas secretes insulin, and insulin stimulates the movement of blood-sugar (glucose) into the liver, muscles, and other cells, to be used as glucose or stored as glycogen. When blood sugar drops, glucagon is released by the pancreas, and glucagon stimulates the break-down of glycogen and the production of glucose. This glucose is released back into the blood stream to be used as energy.

In terms of exercise... I can only talk about basic human physiology. I just don't know all the ins and outs of human nutrition and exercise science, so... I could be preaching something that's not quite accurate. But anyway

When you exercise, you burn up the glucose that's in your blood stream, triggering the break-down of glycogen and release of glucose from the liver and muscles, which raises your blood glucose and helps you continue on with your exercise. Eventually, you can deplete your glycogen stores. Marathon runners talk about 'hitting the wall' and from what I've read, that wall is the depletion of glycogen and is rather painful (not pain "ouch", but pain as in muscles burn and you're really tired) because your body has to scramble for an alternative energy source to keep you on your feet.

So glycogen is good, especially if you are doing something that requires endurance.

But there's another side to all this- and that's the insulin/glucagon side of things. And this is where things get a little murky for me, because the science isn't cut-and-dry. Prevailing theories change and I'm just not sure what's 'new' and most accurate. What I do know is this: Insulin stimulates the conversion of glucose to glycogen, but it also stimulates the synthesis of fat, which is stored in adipose tissues. You hear a lot about low glycemic diets, and the logic there is that you want a slow release of glucose from the gut into the blood-stream. The slow release avoids spikes in blood glucose levels, which keeps insulin levels from spiking, which promotes glycogen storage but not fat storage.

The other thing I know is that exercise makes your body more sensitive to insulin and glucose levels. You become more efficient at using them, better at storing that glycogen. This is one of the reasons exercise is soooooo important for the type II diabetic. Type II diabetics are insulin resistant... their bodies can't move glucose from the blood to their cells, so blood sugar levels rise. But muscle contraction causes sugar-absorbing proteins to move to the surface of the cell with or without insulin, and those proteins move the sugar from your blood into your cells so that you can actually use it.

And that's about all I know about that

Oh... except brain glucose.

Rae6503

Remember, brains are overrated...

That helps a lot! But I'm curious as to out they related to weight lifting and then cardio after weight lifting I guess.

solpwr

If you really want to learn about sports nutrition, I have a great site for you:

http://btc.montana.edu/olympics/default.htm

LabRat529

Remember, brains are overrated...

That helps a lot! But I'm curious as to out they related to weight lifting and then cardio after weight lifting I guess.

I don't know I wish I did, but beyond the basics... I just don't know.

moniquelessard

http://www.youtube.com/watch?v=h0Qqer8rFkA

Glycogen is stored energy. When you work out it's used as fuel for your workout. Carbs are important to restore glycogen.

LabRat529

So I didn't find much with a pubmed query of "glycogen weight lifting", but I did find some.

I think the answer is... weight lifting depletes glycogen stores just like any other exercise. When you add cardio to the routine (as in do something cardio after weight lifting), you're going to deplete those stores even faster. The more depleted your glycogen stores, the more recovery time you need between weight lifting sessions to perform at your best.

Here's a review: http://www.ncbi.nlm.nih.gov/pubmed/12580676

I just read the abstract, but it seemed useful.

I was originally thinking that there might be a difference between weights and cardio in terms of store useage, but now I don't think so.

jerelallday

Hey there-- what is it that you were wanting to know about glycogen, anything specific? In general, glycogen is stored in several places and is basically how your body stores sugar to use as energy. You have muscle glycogen, glycogen in the liver, etc. When exercising... let's say you're doing strength training and you're doing a set of... 25 chest presses at a light weight (near failure @ 22-24), which is a good rep range for muscle endurance / fat loss, then your body burns energy in this way:

First 5-10 seconds, your body uses ATP for energy
Approx 10-15 seconds, your body uses ADP + Creatine for energy,
After that, glycogen is used, then after glycogen is depleted, fat stores are used for energy

Numbers may be slightly off, but in general that's how it works. Your body stores about 300-400 calories worth of glycogen in your liver, something to keep in mind when thinking about duration of cardio / exercise.

Hope that helps! I'm a trainer so I reference this stuff almost daily

jerelallday

If you are going for body fat recuction, you generally want to save your glycogen for weight lifting, as the conversion of using fat for energy is a slower process. 10 minutes of a warm up, weights, then however much energy you have left for lower intensity cardio... once you deplete glycogen stores, you don't need to "run hard" to burn fat after your weight session, keeping your heart rate somewhere around 125-140 is pretty sufficient. Sometimes the heart rate won't come down that low right away, meaning you had a pretty exhausting lifting segment, even just a cooldown of 5 minutes at a walking speed will help reduce lactic acid buildup and allow your heart rate some time to recover.

madisonsteelex

Whatever glucose(sugars and carbs) you have consumed that your body doesn't need gets converted into glycogen and stored in the liver for later use, but if there is too much it can get stored as fat. It is a form of energy. Your body needs sugars and carbs to run.

Lift_hard_eat_big

What's your opinion on fasted cardio? Such as cardio first thing in the morning without eating to deplete glycogen reserves faster and shift to burning fat sooner.

Rae6503

I just see the term thrown about a lot and really had no idea what it was...