Blood and Excerise Type II muscle fibers oxidize lactate at a very fast rates. When muscle contraction produces a significant amount of lactate, it is then released into the central circulation of the blood, and within seconds it is made available to that muscle for energy. Therefore, 75% of the lactate produced from high intensity exercise is made available for energy production in type II muscle fibers. The remaining 25% of lactic acid is used for energy in the heart, the make up of liver glycogen, and the supply of energy to inactive muscles. A good example of this would be a runner who is exceeding his or her planned race