Which fuels are primarily used during aerobic metabolism?

Aerobic metabolism primarily utilizes glucose and fatty acids as its main fuel sources. When engaging in prolonged, steady-state exercise, the body relies heavily on these substrates because they can be broken down in the presence of oxygen to produce ATP, the energy currency of the cell.

In the context of the options presented, glycogen, which is the stored form of glucose in muscles and the liver, is indeed a critical fuel source during aerobic activity. It allows the body to sustain energy over longer periods. Phosphocreatine, while important for replenishing ATP in short bursts of intense exercise, does not play a primary role in aerobic metabolism. Instead, it is mainly utilized in anaerobic situations, which are characterized by quick, high-intensity efforts where oxygen availability is limited.

Thus, focusing on glycogen makes sense when discussing fuels during aerobic metabolism, as it ties directly into how the body efficiently generates energy during extended physical activities.