College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What energy system is primarily used by marathon runners?

1. Phosphagen system

2. Fast glycolytic system

3. Slow oxidative system

4. Intermediate glycolytic system

The correct answer is: Slow oxidative system

Marathon runners primarily rely on the slow oxidative energy system, also known as aerobic metabolism. This system is crucial for endurance activities that last for prolonged periods, such as running a marathon. It efficiently uses oxygen to break down carbohydrates and fats, providing a sustained energy supply that is necessary for the continuous, long-duration effort encountered in marathon running. The slow oxidative fibers, also referred to as Type I muscle fibers, are characterized by their high fatigue resistance, allowing marathon runners to maintain a steady pace over a significant distance. These fibers enable a more efficient energy release from fatty acids and glucose in the presence of oxygen, making this system the most effective choice for the demands of a marathon. In contrast, the phosphagen system is utilized for short, explosive bursts of energy lasting only a few seconds, making it unsuitable for marathon running. The fast glycolytic system is more applicable to short-duration, high-intensity efforts, while the intermediate glycolytic system is typically employed in moderate-duration efforts but does not match the efficiency needed for the extended duration of a marathon. Thus, the slow oxidative system stands out as the primary energy source for marathon runners.