The Lactic Acid Myth

Under normal resting or non-strenuous conditions, the body’s energy is provided mainly through the aerobic energy system. However, when the demand for ATP outpaces the aerobic system’s output it must be generated anaerobically. The glycolytic (intermediate/lactic) energy system is one of the anaerobic means that allows the body to keep functioning as demands of workloads intensify.

The glycolytic energy system primarily uses blood glucose and muscle glycogen to create ATP via glycolysis. When this happens anaerobically it results in the production of lactic acid, a substance commonly misunderstood as a toxin or waste product that makes muscles burn and causes delayed onset muscle soreness (DOMS).

Lactic acid is not the reason for muscle discomfort or failure. Contrarily, its production can delay fatigue. When lactic acid is broken down into lactate, it then can be turned into pyruvate and thrown back into the Krebs cycle and fuel tissues that rely heavily on the oxidative process such as cardiac and type I muscle.

So, what causes the burning sensation in the muscles? Upon the formation of lactate, lactic acid must donate a hydrogen ion which will enter the bloodstream. As more lactate is produced more hydrogen ions accumulate in the blood. It is this accumulation of hydrogen that has been hypothesized to create muscle burning and discomfort. Just as burning cannot be attributed directly to lactic acid neither can DOMS. Soreness experienced the day or two after a training session is linked primarily to the breakdown and damage suffered by the muscle tissue, not lingering lactic acid.

The glycolytic system is commonly misunderstood by coaches and athlete alike. It serves to be an intermediary between the aerobic and anaerobic-alactic systems, help prolong intense activity, and aid in fueling aerobic tissues. Without lactic acid athletes would not be able to maintain workloads beyond the reach of aerobic capabilities.