Is Athleticism Genetic?

By: Nick Soleyn, Editor in Chief

“All fools are poets; this the Prefect feels; and he is merely guilty of a non distributio medii in thence inferring that all poets are fools.” -Edgar Allen Poe, The Purloined Letter.

Watch any group of youth athletes, and it’s clear that not all kids show up to play with the same innate abilities. Most kids will play at about the same level, a few will be off chasing butterflies, but then a few others will stand out. They are faster, stronger, and have better control over their movements. These outliers seem physically “gifted,” possibly having won the genetic lottery for good sports genes.

Whether we like it or not, genetics plays a role in sports performance. Successful athletes at the highest levels tend to be physically capable in ways that most of us are not. They also tend to be dedicated and hard-working and to have significantly more hours of practice and training under their belts than most others. At the professional or Olympic levels, there’s a synergy between the athlete’s physical potential, trained competence, and the specific sport—a confluence of factors, some far outside of the athlete’s control, contributing to success. It starts (but does not end) with the right genes.

What Genes Do for Us?

There is a difference between the blueprint and the physical expressions of that blueprint in the way that people are built. From the earliest indications of life, a person’s body starts developing and growing through a process of cell differentiation. One’s genotype—the makeup of their gene variants or alleles—helps determine what a bunch of homogenous cells will turn into. Cells divide and organize themselves according to this general blueprint, collecting together in the right places to become organs and tissues, forming the basic structure. Unspecialized cells become specialized in a process called differentiation. Some become muscles, some became blood cells, some neurons, and so on. As development continues, cells take on a particular role in the body, allowing for development along a narrower functional path.

There has been a lot of hype about the gene ACTN3, which encodes the protein alpha-actinin-3. Alpha-actinin-3 is one of the main structural components of the smallest functional unit in skeletal muscle. The protein is only seen in Type II or “fast-twitch” muscle fibers, and its deficiency has been tentatively linked to declining physical strength as we age. (See, e.g., Fernández-Araque, et. al. 2021.) Studies relating a certain polymorphism of the ACTN3 gene have led to this often being called “The Speed Gene.” This started with researchers discovering a dearth of the gene that leads to an alpha-actinin-3 deficiency in Olympic level sprinters (the XX genotype). The first of these studies discovered a widely varied prevalence of the XX genotype with different ethnicities and a rare to non-existent prevalence in high-level sprinters. Whereas 18% of the Australian population had the XX genotype, “5 out of 107 sprinters were XX, and zero of the 32 sprinters who had gone to the Olympics were XX.” (Epstein, 2013).

Since then, ACTN3 has been tied to athletic development and performance in various ways, including adaptation to exercise and recovery, strength, and protection from eccentric training-induced muscle damage and sports injury. (Kiely, 2017.) Researchers continue to identify and study other genes that have some association with performance, but the more they find, the more complex the task of identifying markers for performance becomes. “There are 200 genes we are cataloging as having some positive association with fitness-related performance… and there are 20,000 genes in the genome, so we’re scratching the surface in relation to those studied.” (Lite, 2008.)

Predicting Sports Performance

If the target is elite sports performance, however, having the right genes is akin to aiming at that target with multitudinous distractions: environment, upbringing, motivation, opportunity; food availability, development, avoidance of injury. There are so many branching paths that take the nascent athlete from Point A to Point B in their career, and sports performance is too complex for us to understand the mechanisms by which genes might affect it. At best, researchers are limited to observations at certain levels of performance and loose extrapolations to the role that any given person’s genetic makeup plays in his or her ultimate success.

Genetics aren’t destiny. The right genes are a threshold to athletic greatness that most of us cannot cross. And, yes, there is a kind of grim determinism in that thought, but the rarity of elite athletes is something we knew already?

It’s true that a person’s performance is capped by their genetic endowment. You cannot express physical capabilities beyond your genetic limits. Some companies sell at-home gene testing, targeting parents of children under age 9. When kids “don’t have the physical maturity and motor skills to do well…. That’s where the genetic test can come in [handy] for looking for early indicators of talent in performance areas.” (Lite, 2008.)

The idea of genetic testing being predictive is a logical fallacy based on the research being done. If all Olympic sprinters carry a certain gene type, that does not mean that a child with the same gene type can or will be an Olympian. That’s similar to saying that because “All fools are poets” it must then follow that “all poets are fools.” As Poe pointed out in The Purloined Letter, this is a fallacy of logic non distributio medii or the undistributed middle.

Some argue that genetic testing as part of a determinative for sports performance is unethical. (See, Camporesi, 2016.) As one author writes, “It’s just hype as far as I can see… If you want to see if someone is going to be a good sprinter, watch them. An educated observer can tell you more than a genetic test.” (Collier, 2012) (quoting McNamee).) These critics argue that sports, for children especially, have much more to do with their own physical and social development than with the ability to win at the highest levels. Changing that goal may be harmful to their development, supplanting the more basic physical development and social interaction either by pushing them toward their genetic potential for greatness or reigning in a child’s desire for competitive athletics out of the belief that they are not built for one kind of sport or another.

The role of genetics in sports is a fascinating area of study. It gives insights into human performance and may help us learn more about training and sports. But as far as predictive power for sports, it is limited. Most people never get close to their genetic potential. Sports and training are far more important than winning at the highest levels. Gene testing might only tell us that out of the two hundred and sixty-five million kids playing soccer only a fraction of a percent will ever become a professional (0.0004% according to a large FIFA study in 2006). But we already knew that.

References

Ana Fernández-Araque, Andrea Giaquinta-Aranda, Jose Andrés Rodríguez-Díez, Silvia Carretero-Molinero, Jorge López-López, and Zoraida Verde, “Muscular Strength and Quality of Life in Older Adults: The Role of ACTN3 R577X Polymorphism,” Int. J. Environ. Res. Public Health, 18, 1055. https:// doi.org/10.3390/ijerph18031055 (2021)

Camporesi, McNamee, “Ethics, genetic testing, and athletic talent: children’s best interests, and the right to an open (athletic) future,” Physiol Genomics 48: 191–195 (2016)

Collier, “Genetic tests for athletic ability: Science or snake oil?” CMAJ. Jan 10; 184(1): E43–E44 (2012) (quoting McNamee)

David Epstein, “The Sports Gene” (2013)

Jordan Lite, “Can Genes Predict Athletic Performance?” Scientific American (2008)

Pickering Kiely, “ACTN3: More than Just a Gene for Speed” Front Physiol., 8: 1080 (2017)