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When the oxygen supply is insufficient to fulfil the needs of the working muscles during high-intensity exercise, the body frequently turns to anaerobic metabolism to generate energy quickly. Lactate, often known as lactic acid, is an important component in this process. Here’s how it works during intense exercise:

 

  1. Energy Production: When the need for energy exceeds the capacity of aerobic metabolism (oxygen-dependent metabolism), the body uses anaerobic glycolysis to generate energy. In anaerobic glycolysis, glucose is broken down into pyruvate, which is then transformed into lactate. This mechanism produces ATP (adenosine triphosphate), the primary energy currency of cells, allowing muscles to contract even without oxygen. Reported by (Melkonian & Schury, 2023)

 

  1. NAD+ Regeneration: The conversion of pyruvate to lactate is critical for regenerating NAD+ (nicotinamide adenine dinucleotide), which is required to maintain the glycolytic process. During glycolysis, NAD+ is momentarily converted into NADH. By converting pyruvate to lactate, NADH is oxidised back into NAD+, allowing glycolysis to continue and providing a consistent supply of ATP for muscular contraction. (Hopp et al., 2019). 

 

  1. pH buffering: Contrary to popular belief, lactate does not produce muscle exhaustion or acidosis. Instead, it serves to buffer pH levels in the muscle. During intensive exercise, hydrogen ions (H+) accumulate in muscle cells, causing a pH drop and the development of muscular exhaustion. Lactate works as a buffer by binding to excess hydrogen ions, lowering acidity in muscle cells and delaying exhaustion. (Kemp et al., 2006)

 

  1. Energy Substrate: Lactate can function as an energy substrate by itself. It can be transferred to other tissues, including the heart, liver, and even muscles, where it can be oxidised and utilised to generate energy. This procedure, known as the lactate shuttle, permits lactate produced in one muscle group to be used by other tissues with greater oxidative ability. Researched by (Brooks, 2020)

 

Overall, lactate serves a variety of functions during high-intensity exercise, including being a major component of anaerobic metabolism, aiding in NAD+ regeneration, buffering pH levels in the muscle, and acting as an energy substrate for other tissues.

 

Reference:

  1. Brooks G. A. (2020). Lactate as a fulcrum of metabolism. Redox biology, 35, 101454. https://doi.org/10.1016/j.redox.2020.101454.



  1. Hopp, A.K. et al., (2019). Regulation of Glucose Metabolism by NAD+ and ADP-Ribosylation. Cells, 8(8), 890. https://doi.org/10.3390/cells8080890.



  1. Kemp, G., Böning, D., Beneke, R. & Maassen, N. 2006. Explaining pH Change in Exercising Muscle: Lactic acid, Proton Consumption, and Buffering vs. Strong Ion Difference. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 291(1):R235–R237. DOI: 10.1152/ajpregu.00662.2005.

 

  1.  Melkonian, E.A. & Schury, M.P. 2023. Biochemistry, Anaerobic Glycolysis. Available at: https://www.ncbi.nlm.nih.gov/books/NBK546695/.

 

 

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