Lactate begins to accumulate when the intensity of exercise is increased, usually throughout short duration and high intensity exercise. Blood Lactate builds up above resting levels where the clearance of Lactate can no longer keep up with the production of Lactate. This is the breaking point where levels are known to rise.
Even at rest, Lactate continues to develop and be removed from tissues such as muscles, intestines and red blood cells. Some of the Lactate can find its way into the blood stream; this is the balance of energy of Lactate in the blood and what has been removed.
When oxygen is available during moderate intensity exercise, lactate in the muscles and blood start to increase. Lactic Acid is formed when glycolysis (this is the energy which is produced immediately to maintain intense exercise) takes place, with or without oxygen. The presence of Lactate does not mean oxygen has been deprived and is not a waste product.
Lactate in the blood is used for energy by the heart and brain; they are Slow Twitch Muscle Fibres and prefer Lactate to be used as their energy source. It also allows metabolism of carbohydrates in an individual’s diet to continue through gylcolysis (energy). Lactate is good at clearing itself from the blood but must be converted into pyruvate (also energy produced from the metabolism of carbohydrates) before it is used as an energy source.
75% of Lactate produced is used as aerobic energy. A common mistake many people make is that Blood Lactate has a negative effect on muscle performance! This is incorrect. The Negative performance from an athlete is due to the increase of Hydrogen ions. When Lactic Acid separates, it forms Lactate and Hydrogen ions; this causes an increase in acidity known as Acidosis (a painful effect on muscle contraction).
Blood Lactate levels are at their highest about five minutes after exercising; assuming that the finished exercise was due to exhaustion from acidosis. The return to Resting Lactate levels occur within an hour of light exercise as this help with clearance.