Long duration, steady-state aerobic activity is primarily fueled by what substrate?

Long duration, steady-state aerobic activity relies primarily on fat as the main substrate for energy production. During such activities, the body requires a continuous supply of energy over an extended period, which is best provided by fat.

As exercise duration increases, the body increases its reliance on fat oxidation while carbohydrates become less dominant. This is because fat stores in the body are abundant and can provide a sustained source of energy for aerobic metabolism when oxygen is available. This process is more efficient for longer, moderate-intensity activities, where the demand for immediate fuel is met through a combination of both fat and carbohydrates, but fat is the primary fuel source as the activity extends.

Carbohydrates do play a crucial role, especially during high-intensity activities where energy demands are immediate, and protein is not typically used as a primary energy substrate during aerobic exercise. Carbon dioxide, on the other hand, is a waste product of metabolism and does not serve as an energy fuel. Therefore, fat stands out as the principal source during long-duration, steady-state aerobic exercise.