Which specific muscle adaptation occurs with regular exercise to counteract fatigue?

Regular exercise leads to a range of adaptations in muscle tissue, one of which is an increased ability to break down lactic acid. During intense exercise, muscles may produce lactic acid, which can contribute to fatigue. An adaptation to regular physical activity includes enhancing the muscles’ capacity to produce enzymes that metabolize lactic acid, thereby reducing its accumulation and the associated fatigue. This allows for longer-duration performance without the onset of fatigue that occurs due to lactic acid buildup.

The other choices do not align with the context of improving muscular endurance or counteracting fatigue. For instance, increasing muscle fiber size typically enhances strength but does not specifically address fatigue. Decreasing the number of mitochondria would negatively impact aerobic energy production, making fatigue more likely, not less. Finally, a reduction in blood flow would impair the delivery of oxygen and nutrients necessary for sustained muscle function, which would also contribute to increased levels of fatigue rather than counteracting it. Thus, the ability to increase lactic acid breakdown through adaptations is crucial for improving performance and reducing fatigue during exercise.