About Lactic Acid
Lactic acid does not exist as an acid in the body. When the “lactic acid” concentration is measured in the blood, another form, called “lactate”, is determined. Lactate and lactic acid have different physiological effects.
Stiffness after a strenuous event comes mostly from damage to the muscle, not an accumulation of lactic acid or lactic acid crystals in the muscle.
Lactate does not acidify the blood. Lactate is an important fuel, used by the muscles during prolonged exercise. Lactate released from the muscle is converted to glucose in the liver. Then used as a source of energy.
Thus, it actually helps delay a possible lowering of blood glucose concentration, a condition called hypoglycemia, which may cause a runner to feel weak and fatigued.

Lactic Acid Lactate-ion