AFAA Personal Trainer Certification Practice Exam

What occurs at the anaerobic threshold during exercise?

1. Lactic acid begins to decrease

2. Muscle cells rely more on aerobic processes

3. Lactic acid begins to accumulate

4. Fat is burned for energy

The correct answer is: Lactic acid begins to accumulate

At the anaerobic threshold during exercise, the body transitions from primarily using aerobic energy production to relying more on anaerobic processes. This shift leads to an accumulation of lactic acid in the muscle cells. The anaerobic threshold represents the point during increasing intensity of exercise at which the oxygen demand surpasses the oxygen supply, prompting the body to utilize anaerobic glycolysis for energy. As a result, lactic acid is produced as a byproduct when glucose is broken down without sufficient oxygen. The accumulation of lactic acid is significant because it is often associated with fatigue and a decrease in exercise performance. Understanding this concept is crucial for personal trainers when designing workouts and monitoring clients' training intensities, especially in endurance training or high-intensity interval training where managing the anaerobic threshold can impact performance outcomes.