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Lactic Acid; Friend or Foe?

Lactic Acid; Friend or Foe?

LACTIC ACID DOES NOT CONTRIBUTE TO MUSCLE FATIGUE

In recent years, the argument of whether or not lactic acid contributes to muscle fatigue, has become a focal point of discussion in exercise physiology. We have to start from the beginning and fully understand what fatigue and lactic acid are. Fatigue can be defined as extreme tiredness resulting from mental or physical exertion or illness (Surenkok, O. 2008), whereas Lactate is produced when muscle glycogen or glucose is broken down to produce ATP (Patlar, S 2017).

A 1924 research study, conducted by Nobel Laureate A.V. Hill and his associates, concluded that in prolonged exercise activities, fatigue resulted from lactic acid accumulation in the muscles. Sullivan et al. (2009)suggested that, when intense exercise occurred, a lack of oxygen supply to the muscles caused an individual to use their anaerobic energy system. It was later thought that the anaerobic system produced lactic acid, lowering pH and resulting in fatigue (Hill, Long, and Lupton, 1924). This crucial piece of evidence is still highly respected in the modern exercise physiology society. It has played a vital role in understanding muscular fatigue in most athletic activities. However, a 1995 study (Pate, et al, 1995) introduced a contrasting opinion. It was theorized that high levels of lactic acid do not interfere with muscular contractions, where body temperatures are within ‘normal’ range (Surenkok, O 2008). As a result of this new evidence, we find ourselves at the present day argument of whether or not lactic acid contributes to muscle fatigue. This article will present and agree with the argument, that lactic acid does not promote muscle fatigue.

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Recently, muscle physiologists have conducted studies concluding that induced acidosis has limited effects on muscle contractile function at body temperatures (Patlar, S 2017). Acidosis can be defined as an excessively acidic condition of the body fluids or tissues (Black, M. 2017).The body temperatures in this study ranged between 28 degrees Celsius and 37 degrees Celsius. The study conducted by Shalayel, M (2010) has encouraged us to reassess whether Hydrogen ions (H+) are not hazardous but rather ergogenic. An ergogenic aid in this case is anything that gives you a physical edge while exercising or competing (Perciavalle, V 2015). This physical edge comes in the form of lactic acid. “But how” do you say? It comes back to why we produce lactic acid or lactate. The anaerobic glycolysis system is commonly referred to as the “Lactic Acid system”. It is through this system that lactic acid exists in the body along side H+. As previously mentioned, lactate is produced when muscle glycogen or glucose is broken down to produce ATP. This process occurs during moderately high exercise intensities, where the glycogen is broken down into pyruvate (Black, M. 2017).The majority of the pyruvate is broken down to generate more ATP. The lactic acid synthesis cycle can be capitalized on through specific anaerobic training. Benefits of anaerobic training include an increased ability to clear lactate from the blood, and an increased efficiency use lactic acid to create energy.

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There are few associative indicators that may suggest that lactic acid is a potential cause of fatigue. However, these ‘indicators’ are unable to prove of the effect of lactic acid on muscles and the cause of lactic acid. There are several factors that explain why the muscles in the human body fatigue. The decline of force in a muscle, causing fatigue, is associated with the decline of ATP levels (Patlar, S 2017). This regression is a result of lactate produced in high intensity efforts, not receiving enough oxygen to break down. This in turn means the lactate is unable to build more ATP, and essentially energy to support the body’s efforts (Shalayel, M 2010). Another factor of fatigue is an individual’s muscles. The individual’s muscles may not have enough strength to produce a desired amount of force for the expected duration of exercise (Surenkok, O 2008). Central nervous fatigue (CNF) can also occur, resulting in muscle exhaustion. CNF is associated with changes in the function of neurotransmitters with the central nervous system(Sullivan. 2009).This can affect muscle function and exercise performance in many ways. It can occur in healthy individuals after a prolonged period of exercise at moderate to high intensities.

A definition of lactic acid was not provided at the beginning of the article for an important reason. Lactic acid can be defined as many things. However, in conclusion to this article it is defined as not a muscles foe but a muscles fuel. If well trained, lactic acid can be beneficial enough to push an athlete from getting bronze in an 800m final to winning gold. The information provided throughout this article, should allow you to fully understand why the definition given will not be found on any google search.

Justin Sanseviero

References:

  • Black, M., Jones, A., Blackwell, J., Bailey, S., Wylie, L., McDonagh, S., Thompson, C., Kelly, J., Sumners, P., Mileva, K., Bowtell, J. and Vanhatalo, A. (2017). Muscle metabolic and neuromuscular determinants of fatigue during cycling in different exercise intensity domains. Journal of Applied Physiology, 122(3), pp.446-459.
  • Lactic acid concentration in the blood during muscular work. (2009). Acta Medica Scandinavica, 68(S24), pp.25-39.
  • Patlar, S., Baltaci, A., Mogulkoc, R. and Gunay, M. (2017). Effect of Vitamin C Supplementation on Lipid Peroxidation and Lactate Levels in Individuals Performing Exhaustion Exercise. Annals of Applied Sport Science, 5(2), pp.21-27.
  • Perciavalle, V., Alagona, G., De Maria, G., Rapisarda, G., Costanzo, E., Perciavalle, V. and Coco, M. (2015). Somatosensory evoked potentials and blood lactate levels. Neurological Sciences, 36(9), pp.1597-1601.
  • Shalayel, M. and Ahmed, S. (2010). Lactic acid – the innocent culprit of muscle fatigue. Sudan Journal of Medical Sciences, 5(2).
  • Sullivan, Å., Nord, C. and Evengård, B. (2009). Effect of supplement with lactic-acid producing bacteria on fatigue and physical activity in patients with chronic fatigue syndrome. Nutrition Journal, 8(1).
  • Surenkok, O., Kin-Isler, A., Aytar, A. and Gültekin, Z. (2008). Effect of Trunk-Muscle Fatigue and Lactic Acid Accumulation on Balance in Healthy Subjects. Journal of Sport Rehabilitation, 17(4), pp.380-386.

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