IFPA Trainer Practice Exam

Which energy system is primarily utilized during high-intensity exercise?

1. Krebs Cycle

2. Lactic acid system

3. ATP-CP

4. Ketosis

The correct answer is: ATP-CP

During high-intensity exercise, the body primarily relies on the ATP-CP energy system, also known as the phosphagen system. This system provides immediate energy through the breakdown of adenosine triphosphate (ATP) and creatine phosphate (CP) stored in the muscles. The ATP-CP system is particularly effective during short bursts of intense activity, such as sprinting or weightlifting, lasting about 10 seconds or less. The reason this system is preferred during high-intensity efforts is due to its speed and efficiency. It allows for rapid energy production without the need for oxygen, making it ideal for activities that require quick, explosive movements. Other systems, while important, do not provide energy as rapidly as the ATP-CP system during such intense demands. For instance, the lactic acid system, though it kicks in quickly after the ATP-CP stores are depleted, primarily supports activities in a slightly longer duration (up to about 2 minutes) and produces lactic acid as a byproduct, which can lead to fatigue. The Krebs Cycle is part of aerobic metabolism and operates primarily during lower intensity, longer-duration activities, and ketosis is a metabolic state that occurs when carbohydrate intake is very low, which is less relevant for immediate energy