Glycogen window - the essay on glycogen

Glycogen is the molecule built up from small rings of glucose (see the picture). It's structure is highly branched, which left a lot of space inbetween, and this space needs to be filled up with water. Glycogen reserves are located in the liver, holding 25% of it and the resting 75% is in the muscles.

 

Total amount of glycogen, which the body can produce and store is around 500g in average (meaning untrained) person. With the increase of muscle mass in bodybuilders or athletes, this reserve can add up to 1100g. To imagine this, take for example 1 kg loaf of white bread. That would be something over 500g of complex carbohydrates, which would be the exact amount of glycogen created from eating that whole loaf.

 

Supposing you eat that loaf on 3-4 times during the whole day. Your body needed to cover the energy for that day, and the night that follows. So when you wake up in the mornig, out of those 500g, you can have something less then half left. Plus, if you add up some exercise during the day, the demand of your body for carbohydrates will be even bigger. So here's where the phrase glycogen window start to pick up a proper meaning.

 

Glycogen window metaphorically means eating a lots of carbs and still not having enough of them for the body to process. It's like you would throw them out of window, literally. They disappear somewhere in your stomach, and get soaked into your muscles. That, of course, under the condition that you trained to stimulate growth, and provided sufficient rest for recuperation and restoring all used up nutrients.

 

Muscle growth is not facilitated only by storing extra glycogen. As mentioned earlier, additional mass contain a lots of water, as it's estimated to count 2-3g of water as an addition to every gram of glycogen itself. Plus, after training, muscles stock up on extra fats, and extra creatine phosphate to cover the energy. All together looks as pure muscle on the outside, because all those substances are inside of muscle, or around muscle fibres.

 

Otherwise, after reaching the adulthood, the number of muscle fibres stays the same for the rest of the life for everybody. Muscles are getting bigger only by storing the extra energy. And the volume can be added right into the muscle cells or fibres, or around them in so-called sarcoplasm, as an extra storage.

 

 This flow diagram shows the pathways from glucose to glycogen and back. The whole process take place in the liver cells. Glucose from blood enter liver cells and gets phosphorylated twice before start stacking them into branches of glycogen. The process of creating glycogen out of glucose is called glycogenesis, and the opposite process of breaking it down back to glucose is called glycogenolysis.