Muscle glycogen accumulation after endurance exercise in trained and untrained individuals is a paper written about a study that measured the glycogen accumulation in the tissues of muscles of trained and untrained people after they performed strenuous exercise. The purpose of this study was to determine if a group of trained individuals was more capable at excelling at strenuous exercises in comparison to a group of untrained individuals. The scientists conducting the test hypothesized that trained individuals would be able to exercise longer and recuperate faster. The test also attempts to show that the reason for this ability would be a higher amount of glycogen present in the bodies of trained individuals, and the ability to resynthesize it faster.
Glycogen to energy and back again
In order for your body to work, especially during physical activities, it needs an energy source. What your body uses as one of its energy source is a molecule called glucose. The cells of your body break down glucose through a process called glycolysis. In glycolysis energy is transferred from bonds in the glucose molecule to phosphate bonds in ATP and GTP, and hydrogen bonds in NADH and FADH. Your body then uses the ATP produced to power cellular processes. It’s all a matter of energy transfer.
How does this relate to Glycogen?
Glucose is a monosaccharide, in other words a sugar. The formula for glucose is C6H12O6. Glycogen is simply a branched polymer of glucose.
Glycogen is found mostly in the liver and muscles. However, it is broken down differently in each. In the liver a hormone called glucagon breaks down the glycogen into glucose. This hormone is dependent on your blood sugar level. When your blood sugar level is low Glucagon is secreted and proceeds to break down the glycogen into glucose. Now the glucose is able to enter the blood and restore blood sugar levels to normal. In the muscles, muscle contractions stimulate the breakdown of glycogen. Thus, when you're exercising, in essence contracting your muscles, you are stimulating the breakdown of glycogen. The more you exercise, the more glycogen you break down. This allows the muscles to have the needed glucose, or energy, to continue exercising. Unfortunately your body does not have and endless supply of glycogen and you can eventually run out of "fuel."
After exercising your body needs to replenish its supply of glycogen. For this your body uses the glucose that is in your blood stream. This glucose can come from the glucose broken down from the glycogen in your liver or from glucose broken down from the food you eat. However, the only way that the glucose in the blood stream can enter the cells where they are needed is via glucose transporters. GLUT-4 is the transporter referred to in this experiment. GLUT-4 allows the glucose to enter into a cell so that it can be used in that cell. GLUT-4 is believed to be source for the limiting rate for glucose uptake in the cell....