What does the aerobic energy system primarily utilize?

The aerobic energy system primarily utilizes carbohydrates and fats to produce energy during prolonged, lower-intensity activities. This system is activated when oxygen is available and is crucial for endurance activities, as it generates adenosine triphosphate (ATP) through processes such as aerobic glycolysis and the Krebs cycle.

In the presence of oxygen, glucose is broken down via aerobic glycolysis, and fatty acids are oxidized for energy, which allows sustained physical activity over longer periods. This energy system is particularly important for athletes participating in endurance sports such as running, swimming, and cycling, where maintaining a steady energy supply is essential.

Although proteins can also be used as an energy source, they are typically not a primary fuel unless carbohydrate and fat stores are low, making carbohydrates and fats the predominant substrates in the aerobic energy system.