Which of the following statements about lactic acid is true?

Lactic acid is a byproduct of anaerobic respiration, which occurs when the body exercises intensely and the oxygen supply is insufficient for a significant aerobic metabolism. When lactic acid accumulates in the muscles, it can lead to muscle fatigue, causing discomfort and reducing the muscles’ ability to perform optimally. This fatigue occurs because the body is unable to clear the lactic acid quickly enough, leading to a buildup that interferes with muscle function.

The other options do not hold true in the same context. For instance, lactic acid is not produced during aerobic respiration, nor does it directly aid in muscle recovery, and it is not a type of energy source. Understanding the role of lactic acid in physical performance and its effect on fatigue helps athletes manage their training and recovery effectively.