How are some runners able to explode off the blocks while others remain at the back of the pack? And why might some people be better at distance running, swimming, or biking while others quickly run out of steam.

Many genetic and non-genetic factors determine whether a person might be fast and powerful or have the stamina to be steady over a long distance. AncestryDNA^® + Traits can tell you if your DNA makes you more—or less—likely to be a sprinter or an endurance athlete.

Is There a Gene for Sprinting?

The gene ACTN3, known commonly as the sprinter gene, is one of many genes that may explain some of this variation in athletic ability. This gene can have a large impact on a person’s fast-twitch muscles. In some people, the ACTN3 gene makes a protein that helps the fast-twitch fibers be their most powerful for high-intensity physical activities. This is why it's often called the sprinter gene, or the “gene for speed."

While slow-twitch muscle fibers help with endurance (think marathon running), your fast-twitch muscle fibers are what help you have high-intensity bursts of speed or power (think weightlifting). There are a number of genes that can contribute to a person having a higher proportion of fast-twitch muscles.

Is There Only One Gene for Sprinting?

The ACTN3 gene is one of hundreds of genes that can play a role in athletic performance. It’s 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. That means there are a lot more factors than just this one gene that affect sprinting ability.

AncestryDNA® scientists look at over 15,000 DNA markers to predict your sprinting ability. These DNA markers may reside in genes that play a role in features other than just sprinting— like height, bone structure, muscle performance, heart rate, and how efficiently your body uses oxygen. In this way, many genetic factors go into making an athlete.

Does Everyone Have a Sprinter Gene?

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. A person 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 mutation in the DNA sequence.

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 biological parent, 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.

What Else Influences Sprinting and Endurance Fitness?

The maximum amount of oxygen your body can use during exercise, VO2 max, also plays a role in fitness, primarily for long-distance sports activities. The higher your VO2 max, the better endurance you'll have. But just as athletes can work on strength training, you can still increase your VO2 max when your training program includes regular workouts at the gym, on a trail, or in the pool, for example.

Many non-genetic factors also influence your sprinting or endurance fitness ability. It matters for example, whether your training plan includes access to coaching and resources. So does the amount of effort you’ve put into training. While the genes for speed may offer an advantage in certain types of sport performance, it’s likely all elite sprinters have a similar advantage. And people who will never become elite athletes also have these genes. Ultimately, the training and effort will factor more into athletic success than genes alone.

Interesting Facts About the Sprinter Gene

How do you explain families of talented runners? It's likely a combination of genetics plus environmental and behavioral factors, i.e., lifestyle. For example, families and communities that live at high elevations tend to have increased lung capacity compared to lower-elevation communities. So can living in a city with a top-notch running program, or parents making a habit of running with their kids.

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 country’s culture.

What does your DNA say about whether you’re more of a sprinter or a long-distance runner? fitness? An AncestryDNA^® Traits kit can tell whether you’re more or less likely to carry the genes for endurance activities like long-distance running, biking, or swimming. If you already have your AncestryDNA results, then check out your traits results with an Ancestry subscription.

References

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Guth, Lisa M, and Stephen M Roth. “Genetic Influence on Athletic Performance.” Current Opinion in Pediatrics. December 2013. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3993978/.

“Is Athletic Performance Determined by Genetics?” MedlinePlus. U.S. National Library of Medicine. https://medlineplus.gov/genetics/understanding/traits/athleticperformance/.

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/.

Moir, Hannah J, Rachael Kemp, et al. “Genes and Elite Marathon Running Performance: A Systematic Review.” Journal of Sports Science & Medicine, August 1, 2019. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6683622/.

Penney, Stacey. “Fast-Twitch vs. Slow-Twitch Muscle Fiber Types + Training Tips.” NASM. https://blog.nasm.org/fitness/fast-twitch-vs-slow-twitch.

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.

Ross, Robert, Steven N. Blair, et al. “Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement From the American Heart Association.” Circulation. American Heart Association, November 21, 2016. https://www.ahajournals.org/doi/full/10.1161/CIR.0000000000000461.

“Single Nucleotide Variant: 11-66328095 - T-C (GRCh37).” gnomAD browser. Accessed August 11, 2023. https://gnomad.broadinstitute.org/variant/11-66328095-T-C?dataset=gnomad_r2_1.

Yang, Nan, Daniel G. MacArthur, et al. “ACTN3 Genotype Is Associated with Human Elite Athletic Performance.” AJHG, September 1, 2003. https://www.cell.com/ajhg/fulltext/S0002-9297(07)62024-2.