The onset of muscle fatigue has hampered many athletes from achieving their maximum potential. Lactic acid buildup is a byproduct of anaerobic metabolism. Under normal activity levels, the body mostly relies on aerobic metabolism and hence lactate (another name for lactic acid) buildup is not a major concern. However, with increased activity levels, specifically, when the metabolism switches from aerobic (oxidative) to anaerobic (glycolytic), as in power activities performed at high heart rates, lactate levels quickly build up, which, if not cleared from muscles, cause fatigue and a burning sensation.
But how quickly lactic acid is cleared and how quickly a person feels this fatigue is also influenced by your genetics, especially the MCT1 gene. This article provides insights into how individual differences effects the lactic acid clearance rate and muscle fatigue.
During short term power (anaerobic) exercise, our body uses substances such as ATP and creatine phosphate (CP) within the first 7 seconds to produce energy. This signals the body to start glycolysis, a process to utilize the glycogen (stored glucose) to produce energy. When glycogen is broken down to release energy, which allows the muscle movement to continue. During this process, a substance called lactic acid is formed. Small amounts of lactic acid operate as a temporary energy source, thus helping you avoid fatigue during a workout. However, a buildup of lactic acid during a workout can create burning sensations in the muscle & limits the muscle contraction, resulting in muscle fatigue. For this reason, it may be desirable to reduce lactic acid build up in the muscles. However, if you are a bodybuilder, lactic acid buildup has been shown to be highly anabolic- meaning, good for muscle building. Body builders routinely workout to feel the “burn” in their muscles.
Monocarboxylate transporters (MCT) regulates the transport of lactate and many other substances and removes lactic acid from the muscles. MCT1 gene influences the amount of MCT you produce. The more you produce, the quicker is the clearance rate, thus the delay in the onset of muscle fatigue. Individuals with faster version have shown to produce higher levels of MCT, making them more suitable for endurance based exercises than individuals with slower versions producing lower levels of MCT.
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