What is the primary method of ATP synthesis during prolonged, moderate activity?

The primary method of ATP synthesis during prolonged, moderate activity is aerobic metabolism. This process occurs in the mitochondria of cells and utilizes oxygen to convert carbohydrates, fats, and, to a lesser extent, proteins into ATP. During extended periods of exercise, the body relies on aerobic metabolism because it efficiently produces a larger amount of ATP compared to anaerobic pathways, as it can sustain energy production for hours, making it ideal for endurance activities.

Aerobic metabolism supports the energy demands of moderate-intensity exercise such as running, cycling, or swimming, where oxygen is readily available. It is characterized by a steady state of energy supply, allowing the body to perform consistently over a long duration.

In contrast, anaerobic metabolism is predominant during high-intensity, short-duration activities, as it does not require oxygen but results in quicker fatigue due to lactic acid buildup. The breakdown of phosphocreatine is more relevant for very short bursts of high-intensity activity and acts as an immediate but short-lived source of energy. Similarly, the ATP-CP system is involved in rapid energy production during short, intense efforts, but its capacity is limited and cannot sustain prolonged activity. Thus, aerobic metabolism is the most suitable system for extended, moderate-intensity exercise, making