Certified Sports Nutritionist from the International Society of Sports Nutrition (CISSN) Practice Exam

In a 1500 m run, which typically lasts between 4 to 8 minutes for well-trained athletes, the primary fuel source is glycogen and some fat oxidation. During this duration, the body primarily relies on carbohydrates because they can be quickly metabolized to provide energy necessary for sustained high-intensity exercise. Glycogen, stored in muscles and the liver, is the preferred energy source since it can be rapidly converted to glucose, which feeds into the energy pathways needed for energetic tasks like running.

While some fat oxidation occurs, especially as the duration of exercise extends, the intensity of a 1500 m run generally makes carbohydrates the dominant fuel source. This is due to the demand for quick energy and the necessity of maintaining a higher pace throughout the run. The contribution of fat becomes less significant during high-intensity efforts that require rapid ATP production.

The other options do not serve as primary fuel sources for this distance and intensity:

- ATP reserves provide immediate but very limited energy and are depleted quickly; they cannot sustain effort for the 1500 m distance.

- Fat oxidation becomes more prominent in endurance events of longer duration and lower intensity but is not the main contributor in a 1500 m run.

- Protein breakdown is generally not a significant