Did you know DNA affects your use of lactate for energy?

Exercise, lactate and the MCT1 gene

What do Micheal Phelps, Usain Bolt, Christy Ren and Evgeny Tishchenco have in common? Aside from being Olympians, they excel in sports that require either athletic speed or power, like swimming, sprinting, speed skating and boxing. All these sports depend on an ability to generate bursts of energy. While making energy usually requires oxygen, the energy demand when Phelps completes the 100m butterfly in 49 seconds or when Bolt crosses the finish line in under 10 seconds is so high that it’s nearly impossible for their muscles to get enough oxygen. Instead these athletes rely on what is known as anaerobic respiration, a process that can power muscles without oxygen.

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Sprinters like Bolt and Phelps use a type of muscle known as ‘fast-twitch’ fibres, and these muscles use anaerobic respiration. These anaerobic reactions result in increased proton release (causing increased acidity and that painful stinging sensation in your muscles during intense exercise) and the generation of lactate from the breakdown of sugars. Lactate helps to reduce the acidic environment by combining with the excess protons to convert into lactic acid. In the short-term, lactate (or lactic acid) is harmless because it’s quickly broken down when oxygen returns to your muscles. However, it can cause permanent damage if oxygen deprivation lasts for more than a few minutes. Endurance athletes also have some oxygen-starved muscles, but their bodies have adapted to use lactate as an alternative energy source instead. When Mo Farrah runs the 5000m race, lactate in his blood gets shuttled to ‘slow-twitch’ muscles with plenty of oxygen, so it can be broken down. This means controlling lactate levels is key to the performance of these athletes, and centres around the function of a single gene, MCT1, which is involved in lactase transport.

The MCT1 gene gives instructions for a transporter protein found mostly on the surface of slow-twitch muscle cells and certain fast-twitch muscle cells. This transporter protein binds to lactate on the outside of the cell and brings it inside. People with a version of MCT1, called rs1049434, are not as efficient at this process. They typically have higher levels of lactate in their blood and tend to clear lactate more slowly following exercise. As one would expect, endurance athletes, like rowers, who rely on lactate clearance and utilization by slow-twitch muscles rarely have this version of the gene. Surprisingly, it is more frequent among swimmers and sprint/power athletes. Why a sprint athlete or a swimmer would benefit from high lactate levels in their blood remains to be seen.

Based on emerging research studying the relationship between genes and exercise, it certainly seems that some athletes are born for power sports, while others are inherently suited for endurance. However, if you happen to inherit the less effective version of MCT1 and have your heart set on becoming a marathoner, there’s no need to despair, regular training can actually increase the levels of the MCT1 transporter. Without doubt, professional athletes are built from perseverance and personal sacrifice, yet modern genetics can perhaps give us a hint as to just how much of a sacrifice we will need to make to master the sport of our choice.

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