NSCF Certified Personal Trainer Practice Exam

The correct answer is glucose. Glucose is the only energy substrate that can be metabolized both aerobically and anaerobically to produce ATP.

In aerobic metabolism, glucose undergoes glycolysis, followed by the citric acid cycle (Krebs cycle) and oxidative phosphorylation, where a significant amount of ATP is produced in the presence of oxygen. This process is efficient and can yield a high amount of ATP, making it the preferred method of energy production during prolonged, moderate to high-intensity exercise.

In anaerobic conditions, such as during short bursts of intense activity, glucose can still be metabolized through glycolysis, but it leads to the formation of lactate instead of proceeding into the Krebs cycle. This anaerobic glycolysis allows for the quick production of ATP when oxygen supply is limited.

Glycogen is a storage form of glucose and is broken down into glucose before it can be used for energy. It cannot independently be metabolized; it must first convert to glucose. Fatty acids primarily undergo aerobic metabolism, requiring oxygen for breakdown, and are not suitable for anaerobic energy production. Amino acids can be used for energy but primarily serve other functions such as protein synthesis and are processed differently, making them less efficient for ATP