Which of the following statements is true regarding muscle fatigue?

The statement that muscle fatigue is caused by the accumulation of lactic acid is accurate. During intense physical activity, especially in anaerobic conditions—when the oxygen supply is limited—muscles rely on glycolysis, a process that breaks down glucose for energy. This process results in the production of lactic acid as a byproduct.

As lactic acid builds up in the muscle tissue, it can disrupt the pH balance, leading to a state of fatigue and a temporary decrease in muscle performance. This is why individuals might experience muscle soreness or a burning sensation during high-intensity exercises.

Other factors can contribute to muscle fatigue, such as the depletion of energy stores and neurochemical changes in the muscles and nervous system, but the accumulation of lactic acid is a significant and well-recognized element of this phenomenon.

In contrast, muscle fatigue does not primarily occur during the relaxation phase, nor is it predominantly driven by dehydration, although dehydration can contribute to fatigue in certain conditions. Additionally, muscle fatigue does not lead to increased muscle strength; rather, it typically signifies a temporary decline in performance and the need for recovery.