If pyruvate does not break down, it usually turns into lactate. When pyruvate is produced, the muscle cell will try to use it for aerobic energy. However, if the cell does not have the capacity to use all the pyruvate produced, it will be changed chemically to lactate. Some cells have a large capacity to use pyruvate for aerobic energy while others have very little. With training, many cells can adapt to use more pyruvate and, thus, produce less lactate. Lactate is present in our system at rest and as we go about our every day activities, although at low levels. However, as exercise or work activity increases in intensity, large amounts of pyruvate are produced very quickly. Because pyruvate can be produced quickly, not all of it may be used for aerobic energy. The surplus pyruvate will turn into lactate. This is why lactate is such a significant marker for training. When it is produced, it is a sign that aerobic energy is limited during the activity. There is a different reason why more lactate is produced as exercise intensity increases. As exercise increases, extra muscle fibers will be recruited. These fibers are used infrequently at rest or in light activity. Fast twitch fibers are not very good at turning pyruvate into aerobic energy. Hence, a lot of this pyruvate turns into lactate.
Lactate is a major metabolic intermediate. Its fate depends on the conditions of the cell. ...Show more