Does muscle soreness really come from “lactic acid accumulation”?

   After climbing several floors in a row, there is a soreness in the thigh. Is this lactic acid accumulating? On the second day after exercise, the muscles are so painful as soon as they are strained. Why has the lactic acid not gone?
   Muscle contraction produces “lactate” instead of “lactic acid”. The
   traditional concept believes that when human muscles contract, sugar breaks down to produce lactic acid. The lactic acid is immediately decomposed into lactate and hydrogen ions, resulting in acidification of the environment, which makes the muscles sore and weak. . However, a scientist put forward another point of view in 1983, and was affirmed by more researchers after 2004: that is, the word “lactic acid” itself is not accurate, because no studies have confirmed that muscle contraction produces lactic acid, which is not produced when sugar is broken down. Lactic acid, but “lactate”, this decomposition process not only does not directly produce acid, it may also consume a hydrogen ion to alkalinize the cell.
   In addition, muscles do acidify during exercise, but the source of hydrogen ions is still under debate. At present, most people believe that lactic acid is not a direct source. The hydrogen ions may mainly come from ATP (adenosine triphosphate, which is the most direct source of energy in the body). ) Hydrolysis process. Although muscle soreness and weakness do occur at the same time as the increase in lactate levels during exercise, and the degree is related, the causal relationship cannot be determined. In fact, muscle aches and fatigue are accompanied by other physiological changes, such as acidification and decreased ATP levels.
  Lactate alone does not cause muscle soreness
   in addition to theoretical analysis, the actual test results do not support the lactate during exercise causes muscle soreness argument alone. In a 2014 study, researchers directly injected lactate into the palm muscles of humans and found that even if the concentration of the solution is significantly higher than the level that can be achieved by exercise, it will not cause significant pain. The other two common metabolites ATP and hydrogen ions during muscle contraction will hardly cause pain when injected alone, but injection of these three substances at the same time will cause significant muscle pain.
   It is currently believed that among all metabolites, the three main substances that cause muscle pain are lactate, ATP and hydrogen ions. When the three exist alone or when only the two are superimposed, the effect is weaker, but when the three appear at the same time, there will be a synergistic effect that enhances each other and a signal that significantly enhances pain.
   In addition, there are many substances that increase in concentration during muscle contraction and may increase pain, including bradykinin, potassium, and a variety of cytokines.
   The next day soreness sport has nothing to do with lactate
   As for the movement of people the next day muscle soreness, lactate relationships with smaller, since early in the movement just ended, lactate was metabolized.
   For this soreness that begins 6 hours to 12 hours after exercise and reaches its peak at 48 hours to 72 hours, researchers still have not ascertained the mechanism. It is currently believed that it is mainly related to skeletal muscle mechanical damage and inflammation, rather than Caused by lactate.