How are some runners able to explode off the blocks while others remain at the back of the pack? Many genetic and non-genetic factors determine how fast and powerful a person will be. The gene ACTN3, known commonly as the sprinter gene, may explain some of this variation in sprinting ability. An AncestryDNA® Traits test can tell you if you have a working copy of this gene.
What Is the Sprinter Gene?
While slow-twitch muscle fibers help with endurance (think marathon running), your fast-twitch muscle fibers are what help you have bursts of speed. For example, sprinters use fast-twitch muscles. In some people, the ACTN3 gene makes a protein that helps the fast-twitch fibers be their most powerful. This is why it's often called the sprinter gene, or the “gene for speed."
Everyone has two copies of the ACTN3 gene. The working copy (which makes the protein) is called 577R. The non-working one (which doesn't make protein) is called 577X. People can have two working or two non-working, or one of each. The difference between the working and non-working version of the gene is caused by a single difference in the DNA sequence.
Are Athletes Born or Made?
From height and weight to bone structure and how efficiently your body uses oxygen, many genetic factors go into making an athlete. Whether they have access to coaching and resources matters, too. So does the amount of effort they put into their sport.
That said, studies of elite sprinters have found that nearly all of them have at least one working copy of ACTN3. So while the gene for speed may offer an advantage, likely all elite sprinters will have that same advantage. And people who will never become elite athletes also have the gene. So ultimately, the training and effort will factor more into athletic success than genes alone.
Sprinter Gene and Genetics
The ACTN3 gene is one of hundreds of genes that can play a role in athletic performance, and is one of the most studied and best supported by science. Surprisingly, despite its association with elite sprinters, the majority of people in the world have at least one functioning copy of the sprinter gene.
The ACTN3 gene's effect on fast-twitch muscles is what's called an "additive" effect, which means having more copies of the gene has a greater effect on you. So if you got two "R" copies (the working one), one from each of your biological parents, you'd likely be a better sprinter than if you got just one copy from only one parent.
Of course, if neither parent has a working copy of this gene, you won't have one either. That's the case for about 18 percent of people worldwide.
Interesting Facts About the Sprinter Gene
What happens if you lack the protein that amplifies the fast-twitch muscles? In short, nothing. Lack of the sprinter gene doesn't cause any muscle damage, or even preclude athletic success. But researchers continue to study whether ACTN3's ability to make protein might be related to injury risk or how fast the body heals from injury.
There's also no evidence that sprinters from Jamaica (the land of Usain Bolt) fare better in track events due to the sprinter gene. While Jamaica's top sprinters are likely to have a working copy of the gene, so are top sprinters from every country. Jamaica has dominated track events because running is a huge part of the culture.
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MacArthur, Daniel. “The Gene for Jamaican Sprinting Success? No, Not Really.” Wired, October 4, 2008. https://www.wired.com/2008/10/the-gene-for-jamaican-sprinting-success-no-not-really/.
Pickering, Craig, and John Kiely. “ACTN3: More than Just a Gene for Speed.” Frontiers in Physiology, December 18, 2017. https://www.frontiersin.org/articles/10.3389/fphys.2017.01080/full#B74.
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