Which one of the following statements concerning metabolic m

Which one of the following statements concerning metabolic mechanisms of muscle fatigue is incorrect?

                  a.     Inorganic phosphate, resulting from net creatine phosphate hydrolysis, accumulates to high levels during high intensity exercise.

            b.     Lactic acid accumulation, resulting from aerobic glycolysis, severely limits lower-intensity exercise.

            c.         Glycogen depletion is not a limiting factor in the duration of lower-intensity exercise.

            d.         Depletion of the adipose tissue lipid supply is the most significant limitation to high-intensity exercise.

            e.         Fast-twitch fiber types are better able to derive ATP from glycogen use while slow-twitch fibers are better able to derive ATP from fatty acid use.

Solution

The answer is B part because

Lactic acid fatigue only occurs during high intensity training. The acid will lower the pH of the muscle from a resting value of approximately 7.1 to as low as 6.4. At a pH of 6.9 the function of the glycolytic enzyme phosphofructokinase is inhibited, slowing glycolytic ATP production. At pH of 6.4, all glycogen breakdown is inhibited. Moreover, H+ from lactic acid interferes with calcium binding to Troponin C and the subsequent shift of tropomyosin, preventing the actin-myosin crossbridges and thus decreasing contractile force3. More on fatigue will follow in a later article.

Meanwhile, to prevent muscle shut down, the lactate, acid, and pyruvate are transported out of the cells passively. But, the transfer and conversion is not fast enough to prevent the lactic acid buildup. Lactic acid shuts down the muscle in approximately 30 seconds of maximum intensity exercise