Pro Lactate

Lactate accumulation has been thought to cause muscle fatigue and adverse affects during exercise but there is enough evidence to dispute this point. According to the Point:Counterpoint article, lactic acid accumulation is not the cause of muscle fatigue, it is due to the issues in the excitation-contraction coupling. Increase in K+ causes fatigue by depolarizing the fibers and interfering with the Na+ channels.  As metabolites increase such as ADP and Mg2+ and ATP and glucose decrease, muscles fatigue as well. EC coupling is also not affected by the pH changes that come along with lactate accumulation, in fact the lower pH actually releases more Ca2+. McArdle’s disease also stands as an example of how lactate is unrelated to muscle fatigue because these patients are unable to produce lactic acid, yet they fatigue much faster. This provides evidence that the muscle fatigue is indeed caused by other factors and metabolites, not lactic acid. Fast twitch glycolytic fibers also express a specific monocarboxylate transporter that produces a high amount of lactic acid, whereas they could have a different isoform that does not produce as much acid. It must be beneficial for these muscles to have this increased lactate production.


Not only is lactic acid not responsible for muscle fatigue, it also has separate benefits that make lactic acid accumulation beneficial. An article I read titled, “Effect of Lactate Accumulation during Exercise-induced Muscle Fatigue on the Sensorimotor Cortex” used eleven healthy men and a handgrip muscle fatigue exercise to record rates of lactate accumulation and consequent brain activity flow. They found that as the muscles began to fatigue lactate did accumulate in the muscles, but there was also a strong positive correlation with signals to the sensorimotor cortex. Brain activity and signaling could be affected by lactate levels, meaning that without the build up of lactate the sensorimotor pathways could be altered. Lactic acid definitely increases with increased exercise, but there is not enough evidence to say that lactic acid causes muscle fatigue and it is actually likely correlated with pathways that are beneficial for the muscles.

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