You’re running the 400m, and your legs begin to burn from lactate as you reach the 300m mark. Lactate is a chemical produced by the body that is commonly associated with fatigue and a burning sensation in your muscles that indicates a lack of oxygen. Its produced as a byproduct of anaerobic glycolysis, a process that generates Adenosine triphosphate (ATP) less efficiently than aerobic respiration, which occurs when oxygen is in short supply. It has been regarded as metabolic “waste” and villainized for a long time, but this turns out to be a commonly held misconception: lactate actually serves as an important source of fuel for the body, along with glucose.
While it is true that high levels of lactate can be found in your muscles during intense exercise sessions, it is not the cause of your muscle pain. A research paper published in the Cell Metabolism magazine confirms that there is no evidence that the accumulation of lactate in the muscles causes fatigue (Brooks 761). The real culprit for the burning sensation in your muscles is the accumulation of H+ ions, which is also a byproduct formed during anaerobic glycolysis. The production of too many H+ ions can result in acidosis, or the lowering of the pH in your muscles; this phenomenon causes muscle fatigue and impairs their effective function (Woodward and Debold 1).
Furthermore, an article from UC Berkeley News asserts that lactate is an essential fuel that is favored by skeletal muscles, the heart, and the brain and is not a simply harmful waste product (Sanders). Lactate and H+ ions are constantly being cleared out by your muscles and redirected to other systems and tissues that can use lactate as a valuable energy source with the help of monocarboxylate transport proteins (MCTs) (Sanders; Brooks 759). Lactate can be easily converted into either glucose or pyruvate and used to generate energy through cellular respiration in these other cells, with the H+ ions being released as a byproduct as water vapor. In addition to playing a vital role as a fuel source, lactate levels can also be measured during intense exercise to determine an individual’s fitness ability, since people who can more efficiently transport or shuttle around lactate can perform more intense exercise for longer durations of time and fatigue more slowly (“Lactate Profile”).
The discovery of this “lactic shuttle” mechanism is also important when considering advancements in cancer treatment methods, since it plays a vital role in delivering energy and fuels to all kinds of cells. By blocking the functioning of essential MCTs in tumor cells, their utilization of lactate as a fuel can potentially be hindered, which consequently puts a halt to cancerous tumor growth (Brooks 776). It’s important to understand the mechanisms behind the lactate because it provides your body with a valuable source of energy, can give you a reliable indicator of your performance condition, and has important health implications. The next time you have an intense training session and begin to feel the burn in your muscles, don’t pin the blame on lactate, because it’s giving you the fuel you need to get through the workout. Good luck and enjoy exercising!
References:
Brooks, George A. “The Science and Translation of Lactate Shuttle Theory.” Cell Metabolism, vol. 27, no. 4, Apr. 2018, pp. 757-85, https://doi.org/10.1016/j.cmet.2018.03.008. Accessed 30 Dec. 2024.
“Lactate Profile.” UC Davis Health Sports Medicine, health.ucdavis.edu/sports-medicine/resources/lactate#:~:text=However%2C%20since%20heart%20rate%2C%20speed,and%20compared%20to%20subsequent%20tests. Accessed 30 Dec. 2024.
Sanders, Robert. “Far from toxic, lactate rivals glucose as body’s major fuel after a carbohydrate meal.” UC Berkeley News, 14 May 2024, news.berkeley.edu/2024/05/14/far-from-toxic-lactate-rivals-glucose-as-body-s-major-fuel-after-a-carbohydrate-meal/#:~:text=Levels%20of%20lactate%20began%20rising,30%20minutes%20after%20glucose%20ingestion. Accessed 30 Dec. 2024.
Woodward, Mike, and Edward P. Debold. “Acidosis and Phosphate Directly Reduce Myosin’s Force-Generating Capacity through Distinct Molecular Mechanisms.” Frontiers in Physiology, vol. 9, 10 July 2018, https://doi.org/10.3389/fphys.2018.00862. Accessed 30 Dec. 2024.