Lactic acid, we've all felt it now let's learn more about it.
Lactic acid is a metabolic byproduct of the process known as glycolysis, which is the breakdown of glucose to produce energy and occurs during intense exercise when the body's demand for energy exceeds the supply of oxygen. During intense exercise, the muscles require a large amount of energy in a short amount of time. When the oxygen supply is not sufficient to meet this demand, the body turns to anaerobic metabolism to generate energy. In this process, glucose is broken down into pyruvate, a process that also produces lactic acid as a byproduct.
The accumulation of lactic acid in the muscles can cause a decrease in muscle pH, resulting in a decrease in muscle function and a burning sensation. This is why lactic acid build-up is often associated with the feeling of fatigue during intense exercise.
However, the body has ways of coping with the lactic acid build-up. The liver can convert lactic acid into glucose through a process called gluconeogenesis. The muscles can also remove lactic acid through the blood stream and transport it to the liver for conversion into glucose.
It is important to note that lactic acid build-up is not necessarily a bad thing and can even have positive effects on the body. Studies have shown that lactic acid can stimulate the release of growth hormone, which can aid in muscle recovery and growth (1).
Now, let's dive into the burning sensation that many people feel during exercise. This sensation is commonly attributed to the presence of lactic acid in the muscles, but research has shown that lactic acid is not directly responsible for the burning sensation. Instead, it is believed that the burning sensation is caused by the accumulation of hydrogen ions in the muscle tissue, which occurs alongside the production of lactate.
During high-intensity exercise, the body produces lactate faster than it can clear it from the muscles. As a result, the lactate accumulates in the muscle tissue, causing the pH of the muscle tissue to decrease and become more acidic. This acidic environment activates pain receptors in the muscle tissue, which leads to the burning sensation that many people experience during intense exercise.
So, why does the body struggle to clear lactate from the muscles during high-intensity exercise? One theory is that the body's ability to clear lactate is limited by the availability of oxygen. During high-intensity exercise, oxygen delivery to the muscles is reduced, which impairs the body's ability to use lactate as a fuel source and slows down the removal of lactate from the muscles.
Another theory is that lactate clearance is limited by the availability of transporters that move lactate out of the muscle tissue and into the bloodstream. These transporters can become overwhelmed during high-intensity exercise, leading to an accumulation of lactate in the muscle tissue.
Hope this helps you to better understand your body next time your training hard and feeling that burning sensation in your muscles.
Yours in health,
Coach Ry
References:
Kravitz, L. (n.d.). Lactic acid: Friend or foe? IDEA Fitness Journal, 14(1), 18-2.
Brooks, G. A., Fahey, T. D., & Baldwin, K. M. (2020). Exercise Physiology: Human Bioenergetics and Its Applications. New York: McGraw-Hill Education.
Gladden, L. B. (2004). Lactate metabolism: a new paradigm for the third millennium. The Journal of Physiology, 558(1), 5-30.
Jentjens, R., & Jeukendrup, A. (2003). Determinants of post-exercise glycogen synthesis during short-term recovery. Sports Medicine, 33(2), 117-144.
Kiens, B., & Richter, E. A. (1999). Skeletal muscle metabolism during exercise. Physiological Reviews, 79(3), 965-1011.
Linnarsson, D., Sahlin, K., & Tonkonogi, M. (2007). The effect of different protocols of muscle acidification on muscle metabolism and force production. Acta Physiologica, 191(1), 59-66.
Sahlin, K., & Harris, R. C. (2000). The regulation of muscle glycogenolysis and its effects on muscle performance. Sports Medicine, 30(1), 1-14.
Zoladz, J. A., Pilis, W., Majerczak, J., Duda, K., & Dzienis-Straczkowska, J. (2008). Lactic acid and exercise. Journal of Physiology and Pharmacology, 59(6), 9-21.
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