Which energy system predominates during sustained, lower-intensity exercise?

The aerobic energy system predominates during sustained, lower-intensity exercise because it relies on oxygen to convert carbohydrates and fats into energy. This system is capable of producing a larger amount of ATP (adenosine triphosphate), which is the energy currency of the body, over an extended period of time. During lower-intensity exercise, such as jogging or swimming at a steady pace, the body can efficiently utilize the aerobic pathways for energy production, enabling prolonged activity without quickly depleting energy stores.

In contrast, the anaerobic energy system, including the phosphagen and glycolytic systems, tends to be more predominant during high-intensity, short-duration efforts. These systems operate without the need for oxygen and can provide instant energy but are limited in their capacity to sustain prolonged exercise. Consequently, as exercise intensity decreases, the body shifts towards the aerobic system, optimizing energy production for longer-lasting activities.