The Effect of Our Genes on Athletic Performance

Can talent be predicted with a tube of blood or saliva?

Athletic performance is the combined product of many factors, including training, nutrition, sleep, recovery, age, sex, motivation and, of course, genetics. Today, many tests are sold online saying “learn your child’s sporting talent from their genes.” But is it really possible to tell which sport we will succeed in with a tube of saliva or a single blood test? The short answer: No. Genes certainly play an important role in athletic performance, but it is not possible to “read” that contribution for individuals using today’s tests. In this article, we discuss how decisive genetics is in sport, what commercially available tests really offer, which genetic tests are actually used in sport, and why different data should be assessed together rather than relying on a single test.

How important is genetics in sport?

There is no question that genetics has an important place in athletic performance. The strongest data on this come from twin and family studies:

• Being an athlete: In twin studies, approximately 66% of the variation in whether someone is an athlete is explained by genetic factors.
• Aerobic capacity: In the HERITAGE study examining families, the maximum amount of oxygen the body can use (VO2max) was found to be approximately 50% heritable.
• Response to training: In the same study, at most 47% of the variation in response to the same training program was explained by genetics. In other words, of two people following the same program, one may improve greatly and the other only slightly.
• Muscle strength: Heritability varies between 30% and 83% depending on the muscle and type of contraction.

However, there is a very important distinction here: High heritability does not mean that predictions can be made for individuals through genetic testing. This is because the effect does not come from a single “athlete gene,” but from the sum of hundreds of genetic differences, each contributing very little, and their interactions with the environment.

How many genetic markers are known today?

The “239 genes” mentioned in our earlier article was based on Human Gene Map studies published in the 2000s, covering not only athletic performance but also health-related physical fitness characteristics. According to a comprehensive review published in 2023, the current picture is as follows:

• Associated with being an athlete, 251 genetic differences (polymorphisms) have been identified.
• Of these, only 128 (%51) could be confirmed in at least two studies; among these 128, 29 also have studies that failed to confirm them.
• Only 13 of these markers were found using modern methods scanning the entire genome. The remainder come from studies examining individual candidate genes with low reproducibility.

The fundamental problem is that there are very few elite athletes worldwide, while genetic studies need thousands or even tens of thousands of people for reliable results. Therefore, most of our current knowledge comes from small studies that are difficult to replicate. We also discussed how genetic tests should generally be assessed in our article on DNA-based tests for nutrition ; similar problems apply here too.

The best-known “sports genes”

The table shows that even the best-known genes are not strong enough to be translated into a personalized recommendation. ACTN3 and ACE are genes included in most commercially available tests; an international expert group describes the individual predictive value of these two markers as “virtually zero.”

What do commercially available genetic tests promise and deliver?

Direct-to-consumer sports genetics tests are generally performed using saliva or an inner-cheek swab and promise to tell whether a person is a “power or endurance” athlete, which training type they will benefit from most, their injury susceptibility or which diet is suitable. But what does science say?

Few studies investigate the benefit of planning training by genotype. In two small studies conducted in 2016 involving a total of 67 people, those undertaking training “suited” to their genotype were reported to improve more in jumping and aerobic tests; however, the studies were small and their methods were criticized. There is currently no strong evidence supporting genotype-based training planning. A meta-analysis in 2025 covering 42 studies and 41 thousand people also concluded that the ACTN3 gene is not a reliable predictive marker for any sport.

Genetic tests actually used in sport

It cannot be said that genetic tests have no place in sport, but their area of use is not talent prediction; it is health, safety and competition eligibility:

• Sickle cell trait: The NCAA, which governs university athletes in the United States, has required athletes to undergo sickle cell trait screening (or provide a document accepting responsibility) since 2010. The practice began after the death of a university American football player during training in 2006 led to a lawsuit settled in 2009; the American Society of Hematology criticized this mandatory screening as medically unfounded.
• Participation in the female category: From 1 September 2025, World Athletics requires athletes competing in the female category to undergo a once-in-a-lifetime SRY gene test (cheek swab or blood); it was first applied at the September 2025 Tokyo World Championships. World Boxing has also applied similar genetic screening since 2025.
• Inherited heart diseases: According to the European Association of Preventive Cardiology’s 2022 position statement, genetic testing in athletes should be performed when clinical assessment raises suspicion of an inherited heart disease or when there is a known genetic change in the family; routine genetic testing is not recommended in athletes without findings or family history.
• Gene doping is prohibited: The World Anti-Doping Agency (WADA) keeps all methods capable of changing genes or gene expression on its prohibited list.

How widespread are the market and use?

• Among athletes: In surveys of elite athletes in the United Kingdom, 10-17% of athletes and 8-11% of support staff reported using genetic tests. Although most users said they found the test “useful,” this reflects personal perception rather than a contribution to performance. Low awareness, high cost and weak evidence were listed as the main barriers.
• Market size: We could not find reliable market-size data specific to sports genetics. For the nutritional genetics (nutrigenomics) market, commercial reports estimate that in 2025 it is approximately 613 million dollars and in 2035 approximately 3 billion dollars; it should be recalled that such reports are not independent scientific sources.
• Prices: An international company’s sports DNA test sells for 199 dollars. In Türkiye, according to a health guide website, prices in 2024 were approximately 4.000 to 15.000 TL.

Instead of fortune-telling with one test: an integrated athlete profile

Athletic performance is a complex characteristic produced by many factors acting together. Genetics is only one of these factors and currently the least readable. By contrast, data that can be measured directly and monitored over time provide much more information:

• Performance tests: VO2max, lactate threshold, sprint and jump tests directly measure a person’s current capacity. While genetic testing tries to estimate “predisposition,” performance testing directly shows the result.
• Training load monitoring: The international consensus report published in 2017 describes monitoring training load through both external indicators (duration, distance, speed) and internal indicators (heart rate, perceived exertion) as a fundamental tool for preventing injuries and improving performance.
• Sleep and recovery: Data such as sleep duration and quality, resting heart rate and heart rate variability can be monitored using wearable devices.
• Blood values: Iron stores, vitamin D and general health screening reveal correctable problems that may affect performance.
• Nutrition and fluids: Factors such as energy and protein intake, fluid balance and caffeine use also directly affect performance. Nutrition and performance in sport are discussed in detail in a separate article.
• Psychology and motivation: Determination, coping with stress and enthusiasm for sport may be as decisive for success as genetics. The importance of being willing to exercise was discussed in our earlier article.

Assessing these data together and over time, rather than individually, provides much more realistic and applicable guidance for an athlete or someone exercising. Perhaps genetic data may become a small part of this integrated profile in the future, but for now this layer’s contribution is uncertain.

Epigenetics: genes are not destiny

Exercise does not change our genes, but it changes how they work. In 2012, Cell Metabolismpublished a study showing that even a single exercise session changed chemical marks (DNA methylation) in regulatory regions of certain genes in skeletal muscle. Regular exercise is known to influence the activity of genes related to energy metabolism, insulin sensitivity and muscle adaptation. We explained how biological age is measured through epigenetic marks in this article .

This information says the exact opposite of the “fatalistic” view offered by genetic tests: Whatever genes we are born with, regular exercise improves both our performance and our health. We discussed the effect of regular physical activity on lifespan in “Exercise and extend your life” our article.

Should I have genetic testing?

• For talent identification or choosing a sport, do not have genetic testing; these tests are particularly not recommended for children.
• If the family has a history of sudden death at a young age, fainting or heart disease, have a cardiology assessment before starting sport; medical genetic testing and genetic counseling may be considered if necessary.
• If you have decided to have testing, ask which genes are examined, the laboratory’s quality certifications, how your data will be stored and with whom results will be shared.
• If you want to improve your performance, performance tests, training load monitoring, adequate sleep, proper nutrition and a coach’s observations provide much more guidance than a genetic test.
• Exercise timing and regularity also matter; the best time of day to exercise is discussed in our article.

Frequently asked questions

Can genetic testing tell which sport my child will succeed in?

No. International consensus reports explicitly state that genetic tests have no place in identifying talent and children should not be subjected to these tests. Your child’s interests, enjoyable activities and opportunities to try different sports provide much more guidance.

My ACTN3 test showed XX; can I not sprint?

You can. Although the XX genotype is rarer among elite sprinters, this gene’s contribution to sprint performance is very small. Training, technique and many other factors are far more decisive. Approximately 18% of Europeans have the XX genotype.

Does genetic testing help personalize my training?

Current evidence does not support this. Studies investigating training by genotype are small and controversial. The best way to see how you respond to training is to measure performance regularly and monitor your training load.

When is genetic testing really necessary in athletes?

Medical genetic testing and genetic counseling are considered when there is a family history of sudden death at a young age or inherited heart disease, or when examination and investigations raise suspicion of an inherited disease. These tests’ quality standards are very different from sports genetics tests; we discussed good practice in medical genetic testing in this article .

Is it genetic that athletes’ children also become good athletes?

Partly. Genetic predisposition matters, but children in athletic families also have environmental advantages such as starting sport early, access to good coaches and facilities, family support and motivation. Separating genetic and environmental effects is not easy.

Are my genetic data safe?

This is a question everyone having a test should ask. Genetic data are permanent and concern not only you but also your relatives. Before testing, learn where and for how long data will be stored, with whom they may be shared and whether you can request their deletion.

Glossary

Heritability

The proportion showing how much variation in a trait within a population is explained by genetic differences. It does not show the genetic contribution in an individual.

Polymorphism

Small differences in DNA sequence commonly occurring between individuals.

Genotype

The combination of two copies a person carries in a particular gene region (for example, RR, RX or XX for ACTN3).

VO2max

The maximum amount of oxygen the body can use during exercise; a measure of aerobic capacity.

Direct-to-consumer test

A test sold directly to consumers online or through a store without a physician’s order.

Epigenetics

Chemical regulation determining when and how much genes work without changing the DNA sequence.

SRY gene

The gene located on the Y chromosome that initiates male development.