How does the body adapt to prolonged endurance training in terms of metabolism?

The body adapts to prolonged endurance training primarily through increased mitochondrial efficiency. As an individual engages in regular endurance activities, such as running, cycling, or swimming, there is a significant increase in the number and size of mitochondria in muscle cells. These organelles are essential for aerobic metabolism, as they are responsible for producing ATP through oxidative phosphorylation.

With enhanced mitochondrial density and efficiency, the body improves its ability to utilize oxygen and oxidize substrates such as fats and carbohydrates for energy. This allows trained athletes to sustain prolonged exercise at higher intensities while using fuel sources more effectively. Additionally, improved mitochondrial function enables better energy production with less lactate buildup, enhancing stamina and overall exercise performance. This adaptation plays a crucial role in endurance athletes' ability to maintain exercise over longer periods.

The other options do not accurately reflect the adaptations associated with prolonged endurance training. For instance, hormone levels typically do not decrease in a way that negatively impacts performance; rather, the body may enhance hormonal responses to support training demands. Fat oxidation generally increases, allowing the body to utilize fat as a primary energy source during extended activities. Glycogen storage does not decrease but rather can improve following consistent training, as the muscles and liver adapt to store more glycogen for energy availability.