As a specialist in the field of exercise physiology, I can provide a detailed explanation of what happens to muscle glycogen during exercise.

Muscle glycogen is a form of stored energy found within muscle cells. It is essentially a long chain of glucose molecules that are bound together. When the body is at rest, it primarily uses fats and carbohydrates as its main sources of energy. However, during exercise, the body's demand for energy increases, and it turns to muscle glycogen to meet this demand.

The process begins with the activation of the sympathetic nervous system, which is triggered by the onset of exercise. This system releases hormones such as adrenaline and noradrenaline, which in turn stimulate the breakdown of glycogen into glucose. This process is known as glycogenolysis.

The released glucose enters the bloodstream and is transported to the working muscles. Once in the muscle cells, the glucose undergoes a series of chemical reactions known as glycolysis. During glycolysis, glucose is broken down into two molecules of pyruvate, which can then be further metabolized to produce ATP (adenosine triphosphate), the body's primary energy currency.

In addition to glycogenolysis, the body also increases the rate of gluconeogenesis during exercise. This is the process by which the liver and, to a lesser extent, the kidneys synthesize glucose from non-carbohydrate sources such as amino acids and glycerol. This newly synthesized glucose is then released into the bloodstream to further support energy demands during exercise.

As exercise continues, muscle glycogen stores begin to deplete. This depletion can lead to a decrease in performance and, eventually, fatigue. The rate at which glycogen is used depends on several factors, including the intensity and duration of the exercise, the individual's fitness level, and their diet.

It's important to note that the body also has a finite capacity to store glycogen. For example, the average person can store approximately 350 to 400 grams of glycogen in their muscles. Once these stores are depleted, the body must rely more heavily on fats for energy, which can be a less efficient process and may contribute to feelings of fatigue.

To summarize, during exercise, muscle glycogen is broken down into glucose to meet the increased energy demands of the body. This process is essential for maintaining performance and preventing fatigue. However, the finite storage capacity of glycogen means that it is a limited resource that must be managed carefully, particularly during prolonged or high-intensity exercise.

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The increased heart rate increases the rate of blood flow around the body. The increased rate and depth of breathing increases the rate of gaseous exchange in the lungs. The muscles store glucose as glycogen. This can then be converted back to glucose for use during exercise.read more >>