Final answer:
Lactic acid fermentation does not produce enough ATP to support the energy needs of our muscle cells over a long period of time.
Step-by-step explanation:
Lactic acid fermentation, which occurs when there is not enough oxygen available, produces a small amount of ATP to support the energy needs of muscle cells for short bursts of high-intensity activity. However, it cannot sustain muscle activity for a long period of time. Glycolysis, the initial step of lactic acid fermentation, yields only a net gain of two ATP molecules per molecule of glucose, which is not sufficient to meet the prolonged energy demands of muscles.