Which process is most commonly associated with muscle fatigue?

The process most commonly associated with muscle fatigue is lactic acid fermentation. When muscles exert themselves during intense physical activity, they may not receive enough oxygen to sustain aerobic respiration. In such cases, cells switch to anaerobic metabolism, specifically lactic acid fermentation, to generate ATP rapidly. This process occurs when pyruvate, produced from glycolysis, is converted into lactic acid.

The accumulation of lactic acid in the muscle cells is responsible for the sensation of fatigue and soreness. It leads to a decrease in pH within the muscle, disrupting the function of proteins and enzymes essential for muscle contraction. As this buildup continues during prolonged exercise, it can contribute to decreased performance and an increased feeling of tiredness.

Other processes, such as aerobic respiration and glycolysis, primarily provide energy when oxygen is adequately available, while alcoholic fermentation is not relevant to muscle metabolism. Therefore, lactic acid fermentation is directly linked to the experience of muscle fatigue during anaerobic conditions.