Anaerobic glycolysis and lactate production

Glucose metabolization in the absence of oxygen

When the physical stimulus exceeds the brief capacity of the phosphagen system, usually extending over a period of between thirty seconds and two minutes, the body's physiology shifts to anaerobic glycolysis.

This metabolic framework is responsible for meticulously breaking down the glucose circulating in the bloodstream, as well as the glycogen previously deposited in the muscle matrix, with the firm purpose of forging new ATP.

Analogous to the alactic pathway, this chemical fractionation is carried out without the participation of oxygen, making it the ideal tool to meet high intensity and medium duration demands, such as an intense four hundred meter run.

Despite being considerably more agile than the respiratory system, its level of efficiency is low, managing to synthesize a limited amount of net energy for each degraded molecule.

Tissue pyruvate and lactate generation

During the violent intracellular breakdown of sugars, the immediate chemical by-product that emerges is called pyruvate.

Because the energy demand of training is so pressing that the cardiorespiratory system is unable to supply sufficient oxygen to the zone, this pyruvate is unable to enter the efficient aerobic cycle.

Consequently, it is forced to transform itself rapidly into lactate molecules, an event that is closely accompanied by the release of numerous hydrogen ions.

It is the ferocious accumulation of these hydrogen ions in particular, and not of lactate itself, that plummets the internal pH of the fibers, triggering a profoundly acidic cellular environment.

This dreaded acidosis generates the classic crippling burn that forces the athlete to slow down drastically, acting as a natural lifeline against major tears.

Metabolic Recycling of Lactic Acid

Contrary to the great dogmas of the past that demonized lactic acid as a mere toxic waste product, contemporary research has shown that it is an exceptionally valuable energy substrate.

As soon as the intensity of exercise decreases or an active recovery phase begins, the accumulated lactate leaves the fatigued fibers and enters the general circulation.

Through the bloodstream, it is directed to structures such as the myocardium and the liver; in the latter, by means of a formidable process called gluconeogenesis, lactate is reversed and transformed back into pure glucose.

This brand new recycled glucose can be stored as a hepatic reserve or, alternatively, dispatched back to the muscles to continue propelling the effort, evidencing dazzling organic logistics.

Summary

The glycolytic pathway is intensely activated during sustained efforts of submaximal intensity. To maintain physical performance, the body rapidly breaks down its intracellular sugar reserves without requiring the presence of oxygen in the tissue.

This rapid metabolic degradation generates pyruvate which is eventually transformed into lactate molecules. The simultaneous accumulation of acid ions causes a drastic drop in cellular pH, giving rise to the well-known sensation of burning and muscle fatigue.

Far from being a useless biological waste, this compound is recycled in a highly efficient manner. As the intensity of the effort decreases, the liver transforms these elements back into useful fuel to prolong the sports activity.