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Genes and sport: what research shows about strength, endurance and talent
In twin studies, about half of the differences in strength and endurance between people trace back to genes; for competitive athlete status, heritability was 66%. The best-known examples are ACTN3, whose functioning variant is more common in elite sprinters, and ACE, whose I variant is more common in endurance athletes. But no gene decides on its own: performance is teamwork among many genes, and training determines how much of it becomes visible. For your work, this means genes show tendencies in adults – they are not a talent test and not a prediction.
The longer the distance, the more common the variant
Researchers in London studied 91 British runners of Olympic standard – using a simple mouthwash from which they extracted DNA. They were interested in the ACE gene. It holds the blueprint for an enzyme that helps regulate blood pressure and blood flow. One of its variants, the I variant, goes along with lower ACE levels.
The result reads like a staircase: the longer the race distance, the more common the I variant. Among sprinters running up to 200 m, it made up 35% of all ACE gene copies; over 400 to 3,000 m, 53%; and from 5,000 m upward, 62%. In 404 athletes from 19 other sports, where endurance is not necessarily decisive, the share sat right at the level of the comparison group: 50% versus 49% (Myerson et al., Journal of Applied Physiology, 1999).
That is exactly what makes the study so exciting: the variant clusters where the discipline demands endurance. The same research group had previously linked the I variant to better endurance in high-altitude mountaineers and British Army recruits (Montgomery et al., Nature, 1998). And among 64 Australian national-team rowers, the I variant was also more common than in the general population (Gayagay et al., Human Genetics, 1998).
What twins reveal about performance
How much of athletic performance lies in our genes overall? Research answers this question with twins. Identical twins share all of their genetic material, fraternal twins about half. By comparing how similar the pairs are, researchers can estimate what share of the differences traces back to genes.
In the British TwinsUK registry, 4,488 adult female twins reported whether they had ever competed in sports. Those who had competed at county or national level counted as elite athletes. The heritability of this athlete status was 66% (De Moor et al., Twin Research and Human Genetics, 2007). Two meta-analyses show what this looks like for individual traits:
| Trait | Heritability in studies | Source |
|---|---|---|
| Muscle strength (average of 58 measurements) | 52% | Zempo et al., Scandinavian Journal of Medicine & Science in Sports, 2017 |
| Grip strength | 56% | Zempo et al., 2017 |
| Jumping ability | 55% | Zempo et al., 2017 |
| VO2max, absolute | 68% | Miyamoto-Mikami et al., Scandinavian Journal of Medicine & Science in Sports, 2018 |
| VO2max per kilogram of body weight | 56% | Miyamoto-Mikami et al., 2018 |
| Endurance performance | 53% | Miyamoto-Mikami et al., 2018 |
| VO2max gain through training | up to 47% | Bouchard et al., Journal of Applied Physiology, 1999 |
An important point for conversations with your clients: heritability describes how much of the differences between people in a group traces back to genes. It does not mean that 68% of your VO2max is fixed. And one detail is encouraging: for muscle strength, heritability decreased with age, while the influence of the environment grew. Over the years, more and more is in our own hands. How differently people respond to the same endurance training is shown by the HERITAGE study – explained in detail in Genetics in training.
Even whether people exercise regularly at all has a genetic side. In an analysis of 37,051 twin pairs from seven countries, the heritability of leisure-time exercise participation ranged from 48% to 71%. The researchers suspect, among other things, genes that influence how much exercise lifts mood right away and how easy it feels (Stubbe et al., PLoS One, 2006). For your gym, that is a valuable thought: someone who struggles with training is not necessarily lacking willpower. They may simply need a way in that brings them joy sooner.
ACTN3: the best-known sports gene
About 18% of healthy people of European descent produce no trace of a particular muscle protein: alpha-actinin-3 (North et al., Nature Genetics, 1999; Yang et al., American Journal of Human Genetics, 2003). It acts as a strut in the fast muscle fibers that generate power in a flash when you sprint, jump or lift heavy. People who carry two impaired copies of the ACTN3 gene do not produce it; a related protein steps in, and everyday life goes on completely normally.
In sport, it leaves a mark: elite sprinters carry the functioning R variant significantly more often than comparison groups (Yang et al., 2003). A meta-analysis summarizing the research on ACTN3 and ACE confirms both genes: the RR variant of ACTN3 was more common in power athletes (odds ratio 1.21), and the II variant of ACE in endurance athletes (odds ratio 1.35). Put simply, the odds of carrying this variant were about one-fifth and about one-third higher, respectively, in the athlete groups (Ma et al., PLoS One, 2013).
What ACTN3 means for strength gains and how caffeine strategy fits in is explained in the gene story Power, endurance and the ACTN3 gene and the article Sports and performance nutrition in the nutrigenetics guide.
An orchestra, not a soloist
Think of genes as an orchestra. Every instrument plays its part; none carries the piece alone. An elegant calculation from the UK shows this: the researchers selected 23 gene variants that had been linked to endurance performance and asked how likely it is that a single person in the world carries the favorable form of all 23. The answer: 0.0005%. In a simulated population of one million people, 99% also differed by no more than seven of these genotypes from the typical profile (Williams & Folland, Journal of Physiology, 2008).
Two conclusions follow. First: practically nobody has the perfect athlete genome – everyone carries their own mix of favorable and less favorable variants. Second: most people are genetically closer to one another than you might think. What makes the difference then is what you steer in the gym. How Novogenia chooses from the multitude of possible genes is shown in The performance analysis.
Nature and training: two sides of the same coin
Are champions born or made? A review weighed training and genetics against each other and came to a clear conclusion: deliberate training is essential for elite performance, and genes set the individual boundaries. Training is the process through which genetic potential is realized (Tucker & Collins, British Journal of Sports Medicine, 2012).
For your work, that is a powerful message. Everyone brings their own orchestra; training is the conductor. It decides which instruments get loud and which stay in the background. Genes show you where a person’s strengths lie and where the road is a bit longer. Everyone has to walk it themselves – and that is exactly where you come in. What this looks like in practice is described in Personalizing training with genetic data.
A tendency, not a talent test: where the line runs
As fascinating as sport genetics is, it delivers tendencies, not verdicts. That leads to three clear boundaries in practice:
- No talent test for children: Sport genetics researchers agree that children and young athletes should not be exposed to genetic tests to define their training or to select talent (Webborn et al., British Journal of Sports Medicine, 2015). More in Clubs and teams.
- No prediction of injuries: A genetic analysis does not predict whether someone will get injured. Pain and complaints belong with a physician or a physiotherapist.
- No diagnosis: The performance analysis is a lifestyle analysis. It describes predispositions for training, recovery and nutrition – not diseases.
At Novogenia, a gene is only included in the analysis if at least three independent studies support the effect. The genetic traits are therefore well documented; the recommendations we derive from them are logical conclusions, not scientifically proven. This honesty makes the results credible in conversation.
What this means for your gym and your coaching
- Explain results as tendencies: “Your genes lean toward endurance” rather than “You are not a sprinter.”
- Set priorities, exclude nothing: someone leaning toward endurance still trains strength – and vice versa.
- Measure progress against the person’s own history, not against others.
- Use genes as a conversation starter about recovery and nutrition (Recovery, Sports nutrition by genetic profile).
- Test adults, not children for talent selection.
- Refer pain, injuries or illness to a physician or physiotherapist.
Frequently asked questions
How much of athletic performance is genetic?
Is there a sports gene?
What does it mean not to produce alpha-actinin-3?
Can a genetic analysis identify talent?
Does the result change over a lifetime?
Related: Genetics in training: performance and recovery · Power, endurance and the ACTN3 gene · Genes are not destiny: how genes and lifestyle work together
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Request a project →Performance analysisNote: This guide is general information for businesses and professionals and does not replace medical or legal advice. The genetic traits determined in a genetic analysis are well documented (each gene included is backed by at least three independent studies); recommendations derived from them are logical conclusions, not scientifically proven. Regulations can change; errors and changes excepted.